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English J, Newberry F, Hoyles L, Patrick S, Stewart L. Genomic analyses of Bacteroides fragilis: subdivisions I and II represent distinct species. J Med Microbiol 2023; 72. [PMID: 37910167 DOI: 10.1099/jmm.0.001768] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2023] Open
Abstract
Introduction. Bacteroides fragilis is a Gram-negative anaerobe that is a member of the human gastrointestinal microbiota and is frequently found as an extra-intestinal opportunistic pathogen. B. fragilis comprises two distinct groups - divisions I and II - characterized by the presence/absence of genes [cepA and ccrA (cfiA), respectively] that confer resistance to β-lactam antibiotics by either serine or metallo-β-lactamase production. No large-scale analyses of publicly available B. fragilis sequence data have been undertaken, and the resistome of the species remains poorly defined.Hypothesis/Gap Statement. Reclassification of divisions I and II B. fragilis as two distinct species has been proposed but additional evidence is required.Aims. To investigate the genomic diversity of GenBank B. fragilis genomes and establish the prevalence of division I and II strains among publicly available B. fragilis genomes, and to generate further evidence to demonstrate that B. fragilis division I and II strains represent distinct genomospecies.Methodology. High-quality (n=377) genomes listed as B. fragilis in GenBank were included in pangenome and functional analyses. Genome data were also subject to resistome profiling using The Comprehensive Antibiotic Resistance Database.Results. Average nucleotide identity and phylogenetic analyses showed B. fragilis divisions I and II represent distinct species: B. fragilis sensu stricto (n=275 genomes) and B. fragilis A (n=102 genomes; Genome Taxonomy Database designation), respectively. Exploration of the pangenome of B. fragilis sensu stricto and B. fragilis A revealed separation of the two species at the core and accessory gene levels.Conclusion. The findings indicate that B. fragilis A, previously referred to as division II B. fragilis, is an individual species and distinct from B. fragilis sensu stricto. The B. fragilis pangenome analysis supported previous genomic, phylogenetic and resistome screening analyses collectively reinforcing that divisions I and II are two separate species. In addition, it was confirmed that differences in the accessory genes of B. fragilis divisions I and II are primarily associated with carbohydrate metabolism and suggest that differences other than antimicrobial resistance could also be used to distinguish between these two species.
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Affiliation(s)
- Jamie English
- Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, UK
| | - Fiona Newberry
- Department of Biosciences, School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Lesley Hoyles
- Department of Biosciences, School of Science and Technology, Nottingham Trent University, Nottingham, UK
| | - Sheila Patrick
- Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, UK
- Wellcome Wolfson Institute for Experimental Medicine, School of Medicine, Dentistry and Biomedical Sciences, Queen's University Belfast, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Linda Stewart
- Institute for Global Food Security, School of Biological Sciences, Queen's University, Belfast, UK
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Ashraf MV, Pant S, Khan MAH, Shah AA, Siddiqui S, Jeridi M, Alhamdi HWS, Ahmad S. Phytochemicals as Antimicrobials: Prospecting Himalayan Medicinal Plants as Source of Alternate Medicine to Combat Antimicrobial Resistance. Pharmaceuticals (Basel) 2023; 16:881. [PMID: 37375828 DOI: 10.3390/ph16060881] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2023] [Revised: 06/10/2023] [Accepted: 06/12/2023] [Indexed: 06/29/2023] Open
Abstract
Among all available antimicrobials, antibiotics hold a prime position in the treatment of infectious diseases. However, the emergence of antimicrobial resistance (AMR) has posed a serious threat to the effectiveness of antibiotics, resulting in increased morbidity, mortality, and escalation in healthcare costs causing a global health crisis. The overuse and misuse of antibiotics in global healthcare setups have accelerated the development and spread of AMR, leading to the emergence of multidrug-resistant (MDR) pathogens, which further limits treatment options. This creates a critical need to explore alternative approaches to combat bacterial infections. Phytochemicals have gained attention as a potential source of alternative medicine to address the challenge of AMR. Phytochemicals are structurally and functionally diverse and have multitarget antimicrobial effects, disrupting essential cellular activities. Given the promising results of plant-based antimicrobials, coupled with the slow discovery of novel antibiotics, it has become highly imperative to explore the vast repository of phytocompounds to overcome the looming catastrophe of AMR. This review summarizes the emergence of AMR towards existing antibiotics and potent phytochemicals having antimicrobial activities, along with a comprehensive overview of 123 Himalayan medicinal plants reported to possess antimicrobial phytocompounds, thus compiling the existing information that will help researchers in the exploration of phytochemicals to combat AMR.
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Affiliation(s)
- Mohammad Vikas Ashraf
- Department of Biotechnology, School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri 185 234, India
| | - Shreekar Pant
- Centre for Biodiversity Studies, School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri 185 234, India
| | - M A Hannan Khan
- Department of Zoology, School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri 185 234, India
| | - Ali Asghar Shah
- Department of Zoology, School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri 185 234, India
| | - Sazada Siddiqui
- Department of Biology, College of Science, King Khalid University, Abha 61413, Saudi Arabia
| | - Mouna Jeridi
- Department of Biology, College of Science, King Khalid University, Abha 61413, Saudi Arabia
| | | | - Shoeb Ahmad
- Department of Biotechnology, School of Biosciences and Biotechnology, Baba Ghulam Shah Badshah University, Rajouri 185 234, India
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3
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Kumar H, Williford EE, Blake KS, Virgin-Downey B, Dantas G, Wencewicz TA, Tolia NH. Structure of anhydrotetracycline-bound Tet(X6) reveals the mechanism for inhibition of type 1 tetracycline destructases. Commun Biol 2023; 6:423. [PMID: 37062778 PMCID: PMC10106456 DOI: 10.1038/s42003-023-04792-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2022] [Accepted: 03/31/2023] [Indexed: 04/18/2023] Open
Abstract
Inactivation of tetracycline antibiotics by tetracycline destructases (TDases) remains a clinical and agricultural threat. TDases can be classified as type 1 Tet(X)-like TDases and type 2 soil-derived TDases. Type 1 TDases are widely identified in clinical pathogens. A combination therapy of tetracycline and a TDase inhibitor is much needed to rescue the clinical efficacy of tetracyclines. Anhydrotetracycline is a pan-TDase inhibitor that inhibits both type 1 and type 2 TDases. Here, we present structural, biochemical, and phenotypic evidence that anhydrotetracycline binds in a substrate-like orientation and competitively inhibits the type 1 TDase Tet(X6) to rescue tetracycline antibiotic activity as a sacrificial substrate. Anhydrotetracycline interacting residues of Tet(X6) are conserved within type 1 TDases, indicating a conserved binding mode and mechanism of inhibition. This mode of binding and inhibition is distinct from anhydrotetracycline's inhibition of type 2 TDases. This study forms the framework for development of next-generation therapies to counteract enzymatic tetracycline resistance.
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Affiliation(s)
- Hirdesh Kumar
- Host-pathogen interaction and structural vaccinology section (HPISV), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, USA
| | - Emily E Williford
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA
| | - Kevin S Blake
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO, USA
| | - Brett Virgin-Downey
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA
| | - Gautam Dantas
- The Edison Family Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, MO, USA.
- Department of Pathology and Immunology, Division of Laboratory and Genomic Medicine, Washington University School of Medicine, St. Louis, MO, USA.
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, USA.
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA.
- Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, USA.
| | - Timothy A Wencewicz
- Department of Chemistry, Washington University in St. Louis, One Brookings Drive, St. Louis, MO, 63130, USA.
| | - Niraj H Tolia
- Host-pathogen interaction and structural vaccinology section (HPISV), National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health (NIH), Bethesda, MD, USA.
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4
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Cheng Y, Li Y, Yu R, Ma M, Yang M, Si H. Identification of Novel tet(X3) Variants Resistant To Tigecycline in Acinetobacter Species. Microbiol Spectr 2022; 10:e0133322. [PMID: 36409072 PMCID: PMC9784759 DOI: 10.1128/spectrum.01333-22] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Accepted: 11/01/2022] [Indexed: 11/23/2022] Open
Abstract
The emergence of the tet(X) gene is a severe challenge to global public health security, as clinical tigecycline resistance shows a rapidly rising trend. In this research, we identified two tigecycline-resistant Acinetobacter sp. strains containing seven novel tet(X3) variants recovered from fecal samples from Chinese farms. The seven Tet(X3) variants showed 15.4% to 99.7% amino acid identity with Tet(X3). By expressing tet(X3.7) and tet(X3.9), the tigecycline MIC values for Escherichia coli JM109 increased 64-fold (from 0.13 to 8 mg/L). However, the other tet(X3) variants did not have a significant change in the MIC of tigecycline. We found that the 26th amino acid site of Tet(X3.7) changed from proline to serine, and the 25th amino acid site of Tet(X3.9) changed from glycine to alanine, which reduced the MIC of tigecycline by 2-fold [the MIC of tet(X3) to tigecycline was 16 mg/L] but did not affect its expression to tigecycline. The tet(X3) variants surrounded by mobile genetic elements appeared in the structure of gene clusters with tandem repeat sequences and were adjacent to the site-specific recombinase-encoding gene xerD. Therefore, there is a risk of horizontal transfer of resistant genes. Our study reports seven novel tet(X3) variants; the continuing emergence of tigecycline variants makes continuous monitoring of resistance to tigecycline even more critical. IMPORTANCE Although it is illegal to use tigecycline and carbapenems to treat bacterial infections in animals, we can still isolate bacteria containing both mobile resistance genes from animals, and tet(X) is currently an essential factor in degrading tigecycline. Here, we characterized two multidrug-resistant Acinetobacter sp. strains that contained vital resistance genes, such as sul2, a blaOXA-164-like gene, floR, tetM, and multiple novel tet(X3) variants with different tandem structures. It is of paramount significance that their mechanism may transfer to other Gram-negative pathogens, even if their tandem structures have no cumulative effect on tigecycline resistance.
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Affiliation(s)
- Yumeng Cheng
- College of Animal Science and Technology, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Yakun Li
- College of Life Science and Technology, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Runhao Yu
- College of Veterinary Medicine, Henan Agricultural University, Zhengzhou, China
| | - Mingxiang Ma
- College of Animal Science and Technology, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Meng Yang
- College of Animal Science and Technology, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
| | - Hongbin Si
- College of Animal Science and Technology, State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, Guangxi University, Nanning, China
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Functional and phylogenetic analysis of TetX variants to design a new classification system. Commun Biol 2022; 5:522. [PMID: 35641548 PMCID: PMC9156754 DOI: 10.1038/s42003-022-03465-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 05/09/2022] [Indexed: 11/08/2022] Open
Abstract
Recently, many TetX variants such as Tet(X3~14) were reported to confer resistance to tigecycline which is a last-resort antibiotic used to treat infections caused by multidrug-resistant bacteria. In this study, we identified essential residues including 329, 339, 340, 350, and 351 in TetX variants that mediated the evolution of the tigecycline-inactive Tet(X2) enzyme to the active forms of Tet(X3) and Tet(X4). Based on their amino acid sequences and functional features, we classified TetX variants into TetX-A class, TetX-B class and TetX-C class. We further found that TetX-A class variants originated from Bacteroidetes, with some variants further evolving to TetX-C class and acquired by Enterobacteriaceae. On the other hand, our data showed that some variants genes belonging to TetX-A class evolved directly to TetX-B class, which was further transmitted to Acinetobacter spp. This new classification system may facilitate better clinical management of patients infected by TetX-producing strains.
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Hu X, Wu C, Shi H, Xu W, Hu B, Lou L. Potential threat of antibiotics resistance genes in bioleaching of heavy metals from sediment. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 814:152750. [PMID: 34979232 DOI: 10.1016/j.scitotenv.2021.152750] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 12/22/2021] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
Bioleaching is considered a promising technology for remediating heavy metals pollution in sediments. During bioleaching, the pressure from the metals bioleached is more likely to cause the spread of antibiotic resistance genes (ARGs). The changes in abundance of ARGs in two typical heavy metal bioleaching treatments using indigenous bacteria or functional bacteria agent were compared in this study. Results showed that both treatments successfully bioleached heavy metals, with a higher removal ratio of Cu with functional bacteria agent. The absolute abundances of most ARGs decreased by one log unit after bioleaching, particularly tetR (p = 0.02) and tetX (p = 0.04), and intI1 decreased from 106 to 104 copies/g. As for the relative abundance, ARGs in the non-agent treatment increased from 3.90 × 10-4 to 1.67 × 10-3 copies/16S rRNA gene copies (p = 0.01), and in the treatment with agent, it reached 6.65 × 10-2 copies/16S rRNA gene copies, and intI1 relative abundance was maintained at 10-3 copies/16S rRNA gene copies. The relative abundance of ARGs associated with efflux pump mechanism and ribosomal protection mechanism increased the most. The co-occurrence network indicated that Cu bioleached was the environmental factor determining the distribution of ARGs, Firmicutes might be the potential hosts of ARGs. Compared to bioleaching with indigenous bacteria, the addition of functional bacteria agent engendered a decrease in microbial alpha diversity and an increase in the amount of Cu bioleached, resulting in a higher relative abundance of ARGs. Heavy metal pollution can be effectively removed from sediments using the two bioleaching treatments, however, the risk of ARGs propagation posed by those procedures should be considered, especially the treatment with functional bacteria agents. In the future, an economical and efficient green technology that simultaneously reduces both the absolute abundance and relative abundance of ARGs should be developed.
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Affiliation(s)
- Xinyi Hu
- Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, People's Republic of China
| | - Chuncheng Wu
- Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, People's Republic of China
| | - Hongyu Shi
- Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, People's Republic of China
| | - Weijian Xu
- Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, People's Republic of China
| | - Baolan Hu
- Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, People's Republic of China; Key Laboratory of Water Pollution Control and Environmental Safety of Zhejiang Province, 310020, People's Republic of China
| | - Liping Lou
- Department of Environmental Engineering, Zhejiang University, Hangzhou 310029, People's Republic of China; Key Laboratory of Water Pollution Control and Environmental Safety of Zhejiang Province, 310020, People's Republic of China.
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7
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Yapicier OŞ, Ozturk D, Kaya M. Genotypic and phenotypic tetracycline-based properties of Trueperella pyogenes isolates from bovine samples. VETERINARY RESEARCH FORUM : AN INTERNATIONAL QUARTERLY JOURNAL 2022; 13:469-474. [PMID: 36686870 PMCID: PMC9840790 DOI: 10.30466/vrf.2021.138938.3090] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 03/01/2021] [Indexed: 01/24/2023]
Abstract
The purpose of this study was to investigate the tetracycline resistance in Trueperella pyogenes isolates from bovine samples in Burdur, Turkiye, and assess 16 tetracycline-resistance genes distribution among the isolates. Forty-nine T. pyogenes isolates were phenotypically characterized for anti-microbial resistance to doxycycline, oxytetracycline and tetracycline by disc diffusion method. Presence of tetracycline genes of T. pyogenes was investigated by multiplex and singleplex polymerase chain reaction. Our results indicated that 87.80% and 42.86% of the isolates were resistant to tetracycline and oxytetracycline, respectively, and the rate of resistance to doxycycline was 6.12%. Total of 21 (42.85%) were carrying tetracycline-resistance genes and tet(A) was present in 12 (24.49%) isolates; whereas, the tet(W) gene was identified in 9 (18.37%) and 2 (4.08%) of the isolates carried both tet(A) and tet(W), respectively. The study indicated antibiotic resistance patterns of tetracycline agents and links to the tet-genes among T. pyogenes were detected. It makes it worthwhile that this is the first report for detection of tet(A) gene in T. pyogenes.
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Affiliation(s)
- Ozlem Şahan Yapicier
- Bacteriological Diagnostic Laboratory, Veterinary Control Central Research Institute, Republic of Turkiye Ministry of Agriculture and Forestry, Ankara, Turkiye;,Correspondence Ozlem Sahan Yapicier. DVM, PhD, Bacteriological Diagnostic Laboratory, Veterinary Control Central Research Institute, Republic of Turkiye Ministry of Agriculture and Forestry, Ankara, Turkiye , E-mail:
| | - Dilek Ozturk
- Department of Microbiology, Faculty of Veterinary Medicine, Mehmet Akif Ersoy University, Burdur, Turkiye.
| | - Mehmet Kaya
- Department of Microbiology, Faculty of Veterinary Medicine, Mehmet Akif Ersoy University, Burdur, Turkiye.
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8
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Wang X, Han C, Lan B, Wang C, Zhu G. Antibiotic resistance genes on the Qinghai-Tibet Plateau above an elevation of 5,000 m. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:4508-4518. [PMID: 34414535 DOI: 10.1007/s11356-021-16007-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/20/2021] [Accepted: 08/13/2021] [Indexed: 06/13/2023]
Abstract
Antibiotic resistance genes (ARGs) widely occur in both anthropogenic and remote environments. Several studies have investigated the distribution of antibiotic resistance in natural environments. However, the occurrence and diversity of ARGs in remote environments at high elevations have not yet been well elucidated. Abundance, diversity, as well as influencing factors of ARGs in different ecosystems on the Qinghai-Tibet Plateau beyond elevation 5,000 m were explored, using high-throughput quantitative PCR. Totally, 197 ARGs and 12 mobile genetic elements (MGEs) were determined with abundances ranging from 3.75 × 106 to 2.39 × 107 and from 2.21 × 104 to 1.62 × 106 copies g-1, respectively. Both the absolute and relative abundances of ARGs in farmland were lower than those in wetland and grassland. The diversity and dominant resistance mechanism of ARG profiles showed obvious differences among these ecosystems. Bacterial communities and MGEs significantly correlated with ARG profiles, while physico-chemical factors showed little impact. The high abundance and strong positive correlation between integron intI-1 and ARGs suggested a high potential horizontal ARG transfer. Based on the results, the Qinghai-Tibet Plateau can be regarded as a considerable ARG gene pool. This study provides insights into the provenance of ARGs at high elevations.
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Affiliation(s)
- Xiaomin Wang
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Chang Han
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Bangrui Lan
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
- University of Chinese Academy of Sciences, Beijing, 100049, China
| | - Cheng Wang
- South China Sea Institution, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou, 510006, China
| | - Guibing Zhu
- Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China.
- University of Chinese Academy of Sciences, Beijing, 100049, China.
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An Outbreak of tet(X6)-Carrying Tigecycline-Resistant Acinetobacter baumannii Isolates with a New Capsular Type at a Hospital in Taiwan. Antibiotics (Basel) 2021; 10:antibiotics10101239. [PMID: 34680819 PMCID: PMC8532604 DOI: 10.3390/antibiotics10101239] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 10/06/2021] [Accepted: 10/08/2021] [Indexed: 11/21/2022] Open
Abstract
Dissemination of multidrug-resistant, particularly tigecycline-resistant, Acinetobacter baumannii is of critical importance, as tigecycline is considered a last-line antibiotic. Acquisition of tet(X), a tigecycline-inactivating enzyme mostly found in strains of animal origin, imparts tigecycline resistance to A. baumannii. Herein, we investigated the presence of tet(X) variants among 228 tigecycline-non-susceptible A. baumannii isolates from patients at a Taiwanese hospital via polymerase chain reaction using a newly designed universal primer pair. Seven strains (3%) carrying tet(X)-like genes were subjected to whole genome sequencing, revealing high DNA identity. Phylogenetic analysis based on the PFGE profile clustered the seven strains in a clade, which were thus considered outbreak strains. These strains, which were found to co-harbor the chromosome-encoded tet(X6) and the plasmid-encoded blaOXA-72 genes, showed a distinct genotype with an uncommon sequence type (Oxford ST793/Pasteur ST723) and a new capsular type (KL129). In conclusion, we identified an outbreak clone co-carrying tet(X6) and blaOXA-72 among a group of clinical A. baumannii isolates in Taiwan. To the best of our knowledge, this is the first description of tet(X6) in humans and the first report of a tet(X)-like gene in Taiwan. These findings identify the risk for the spread of tet(X6)-carrying tigecycline- and carbapenem-resistant A. baumannii in human healthcare settings.
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Hobson C, Chan AN, Wright GD. The Antibiotic Resistome: A Guide for the Discovery of Natural Products as Antimicrobial Agents. Chem Rev 2021; 121:3464-3494. [PMID: 33606500 DOI: 10.1021/acs.chemrev.0c01214] [Citation(s) in RCA: 82] [Impact Index Per Article: 27.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The use of life-saving antibiotics has long been plagued by the ability of pathogenic bacteria to acquire and develop an array of antibiotic resistance mechanisms. The sum of these resistance mechanisms, the antibiotic resistome, is a formidable threat to antibiotic discovery, development, and use. The study and understanding of the molecular mechanisms in the resistome provide the basis for traditional approaches to combat resistance, including semisynthetic modification of naturally occurring antibiotic scaffolds, the development of adjuvant therapies that overcome resistance mechanisms, and the total synthesis of new antibiotics and their analogues. Using two major classes of antibiotics, the aminoglycosides and tetracyclines as case studies, we review the success and limitations of these strategies when used to combat the many forms of resistance that have emerged toward natural product-based antibiotics specifically. Furthermore, we discuss the use of the resistome as a guide for the genomics-driven discovery of novel antimicrobials, which are essential to combat the growing number of emerging pathogens that are resistant to even the newest approved therapies.
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Affiliation(s)
- Christian Hobson
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
| | - Andrew N Chan
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
| | - Gerard D Wright
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4L8, Canada
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11
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Fang LX, Chen C, Cui CY, Li XP, Zhang Y, Liao XP, Sun J, Liu YH. Emerging High-Level Tigecycline Resistance: Novel Tetracycline Destructases Spread via the Mobile Tet(X). Bioessays 2020; 42:e2000014. [PMID: 32567703 DOI: 10.1002/bies.202000014] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 04/18/2020] [Indexed: 12/20/2022]
Abstract
Antibiotic resistance in bacteria has become a great threat to global public health. Tigecycline is a next-generation tetracycline that is the final line of defense against severe infections by pan-drug-resistant bacterial pathogens. Unfortunately, this last-resort antibiotic has been challenged by the recent emergence of the mobile Tet(X) orthologs that can confer high-level tigecycline resistance. As it is reviewed here, these novel tetracycline destructases represent a growing threat to the next-generation tetracyclines, and a basic framework for understanding the molecular epidemiology and resistance mechanisms of them is presented. However, further large-scale epidemiological and functional studies are urgently needed to better understand the prevalence and dissemination of these newly discovered Tet(X) orthologs among Gram-negative bacteria in both human and veterinary medicine.
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Affiliation(s)
- Liang-Xing Fang
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China.,Laboratory of Veterinary Pharmacology, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, China
| | - Chong Chen
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China
| | - Chao-Yue Cui
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China
| | - Xing-Ping Li
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China
| | - Yan Zhang
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China
| | - Xiao-Ping Liao
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China.,Laboratory of Veterinary Pharmacology, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, China
| | - Jian Sun
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China.,Laboratory of Veterinary Pharmacology, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, China
| | - Ya-Hong Liu
- National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University, Guangzhou, 510642, China.,Laboratory of Veterinary Pharmacology, College of Veterinary Medicine, South China Agricultural University, Guangzhou, 510642, China.,Guangdong Provincial Key Laboratory of Veterinary Pharmaceutics Development and Safety Evaluation, South China Agricultural University, Guangzhou, 510642, China
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Shi Y, Tian Z, Gillings MR, Zhang Y, Zhang H, Huyan J, Yang M. Novel Transposon Tn 6433 Variants Accelerate the Dissemination of tet(E) in Aeromonas in an Aerobic Biofilm Reactor under Oxytetracycline Stresses. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:6781-6791. [PMID: 32384241 DOI: 10.1021/acs.est.0c01272] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Little is known about the mechanisms that disseminate antibiotic resistance genes (ARGs) in wastewater microbial communities under antibiotic stress. The role of horizontal transfer mechanisms in dissemination of ARGs in an aerobic biofilm reactor under incremental oxytetracycline doses from 0 to 50 mg/L was studied. Aeromonas strains were the most common culturable bacteria in the reactor, with tet(E) as the most prevalent ARGs (73.3%) being possibly responsible for the oxytetracycline resistance phenotype. Genomic sequencing demonstrated that tet(E) was mainly carried by a Tn3 family transposon named Tn6433, whose incidence increased from 14.6% to 75.0% across the treatments. Tn6433 carrying tet(E) was initially detected in Aeromonas chromosomes at an oxytetracycline dose of 1 mg/L but subsequently detected on plasmids pAeca1-a variants (pAeca1-a, pAeca1-b, and pAeme6) and pAeca2 under higher oxytetracycline stress. The core region of the Tn6433-tet(E) structure was highly conserved, consisting of a transposition and resolution module, a class 1 integron, core passenger genes, and a Tn1722/Tn501-like transposon. Such a structure was found on both the chromosome and plasmids, suggesting that Tn6433 mediated the transposition of tet(E) from the chromosome to plasmid pAeca2 under increasing stresses. Bacteria carrying the transferable plasmid pAeca1-a were dominant in high antibiotic treatments, suggesting that Tn6433 disseminated tet(E), conferring selective advantages to recipients of this ARG.
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Affiliation(s)
- Yanhong Shi
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- School of the Environment and Safety Engineering, Jiangsu University, Zhenjiang 212013, China
| | - Zhe Tian
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- University of the Chinese Academy of Sciences, 19A Yu-Quan Road, Beijing 100049, China
| | - Michael R Gillings
- Department of Biological Sciences, Macquarie University, Sydney, New South Wales 2109, Australia
| | - Yu Zhang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- University of the Chinese Academy of Sciences, 19A Yu-Quan Road, Beijing 100049, China
| | - Hong Zhang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Jiaoqi Huyan
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- University of the Chinese Academy of Sciences, 19A Yu-Quan Road, Beijing 100049, China
| | - Min Yang
- State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
- University of the Chinese Academy of Sciences, 19A Yu-Quan Road, Beijing 100049, China
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13
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Gasparrini AJ, Markley JL, Kumar H, Wang B, Fang L, Irum S, Symister CT, Wallace M, Burnham CAD, Andleeb S, Tolia NH, Wencewicz TA, Dantas G. Tetracycline-inactivating enzymes from environmental, human commensal, and pathogenic bacteria cause broad-spectrum tetracycline resistance. Commun Biol 2020; 3:241. [PMID: 32415166 PMCID: PMC7229144 DOI: 10.1038/s42003-020-0966-5] [Citation(s) in RCA: 83] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 04/17/2020] [Indexed: 12/19/2022] Open
Abstract
Tetracycline resistance by antibiotic inactivation was first identified in commensal organisms but has since been reported in environmental and pathogenic microbes. Here, we identify and characterize an expanded pool of tet(X)-like genes in environmental and human commensal metagenomes via inactivation by antibiotic selection of metagenomic libraries. These genes formed two distinct clades according to habitat of origin, and resistance phenotypes were similarly correlated. Each gene isolated from the human gut encodes resistance to all tetracyclines tested, including eravacycline and omadacycline. We report a biochemical and structural characterization of one enzyme, Tet(X7). Further, we identify Tet(X7) in a clinical Pseudomonas aeruginosa isolate and demonstrate its contribution to tetracycline resistance. Lastly, we show anhydrotetracycline and semi-synthetic analogues inhibit Tet(X7) to prevent enzymatic tetracycline degradation and increase tetracycline efficacy against strains expressing tet(X7). This work improves our understanding of resistance by tetracycline-inactivation and provides the foundation for an inhibition-based strategy for countering resistance.
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Affiliation(s)
- Andrew J Gasparrini
- The Edison Family Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Jana L Markley
- Department of Chemistry, Washington University, St. Louis, MO, 63130, USA
| | - Hirdesh Kumar
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Bin Wang
- The Edison Family Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Luting Fang
- Department of Chemistry, Washington University, St. Louis, MO, 63130, USA
| | - Sidra Irum
- The Edison Family Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Atta ur Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan
| | - Chanez T Symister
- Department of Chemistry, Washington University, St. Louis, MO, 63130, USA
| | - Meghan Wallace
- Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Carey-Ann D Burnham
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Department of Pediatrics, Washington University School of Medicine, St. Louis, MO, 63110, USA.,Department of Medicine, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Saadia Andleeb
- Atta ur Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, Pakistan
| | - Niraj H Tolia
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Laboratory of Malaria Immunology and Vaccinology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
| | | | - Gautam Dantas
- The Edison Family Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO, 63110, USA. .,Department of Biomedical Engineering, Washington University, St. Louis, MO, 63130, USA.
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14
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Development of a Multiplex Real-Time PCR Assay for Rapid Detection of Tigecycline Resistance Gene tet(X) Variants from Bacterial, Fecal, and Environmental Samples. Antimicrob Agents Chemother 2020; 64:AAC.02292-19. [PMID: 32041710 DOI: 10.1128/aac.02292-19] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2019] [Accepted: 01/20/2020] [Indexed: 11/20/2022] Open
Abstract
We developed a multiplex real-time SYBR green-based PCR assay for rapid detection of tet(X) and its variants, including tet(X1) and tet(X2) and high-level tigecycline resistance genes tet(X3), tet(X4), and tet(X5). We showed that the real-time PCR assay developed had high linearity (R 2 ≥ 0.996), sensitivity (low detection limit), and specificity (only the target gene could be amplified significantly) and further evaluated it using bacterial, fecal, and environmental samples.
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15
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Molecules that Inhibit Bacterial Resistance Enzymes. Molecules 2018; 24:molecules24010043. [PMID: 30583527 PMCID: PMC6337270 DOI: 10.3390/molecules24010043] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Revised: 12/18/2018] [Accepted: 12/19/2018] [Indexed: 12/14/2022] Open
Abstract
Antibiotic resistance mediated by bacterial enzymes constitutes an unmet clinical challenge for public health, particularly for those currently used antibiotics that are recognized as "last-resort" defense against multidrug-resistant (MDR) bacteria. Inhibitors of resistance enzymes offer an alternative strategy to counter this threat. The combination of inhibitors and antibiotics could effectively prolong the lifespan of clinically relevant antibiotics and minimize the impact and emergence of resistance. In this review, we first provide a brief overview of antibiotic resistance mechanism by bacterial secreted enzymes. Furthermore, we summarize the potential inhibitors that sabotage these resistance pathways and restore the bactericidal activity of inactive antibiotics. Finally, the faced challenges and an outlook for the development of more effective and safer resistance enzyme inhibitors are discussed.
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16
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Markley JL, Wencewicz TA. Tetracycline-Inactivating Enzymes. Front Microbiol 2018; 9:1058. [PMID: 29899733 PMCID: PMC5988894 DOI: 10.3389/fmicb.2018.01058] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2018] [Accepted: 05/04/2018] [Indexed: 12/25/2022] Open
Abstract
Tetracyclines have been foundational antibacterial agents for more than 70 years. Renewed interest in tetracycline antibiotics is being driven by advancements in tetracycline synthesis and strategic scaffold modifications designed to overcome established clinical resistance mechanisms including efflux and ribosome protection. Emerging new resistance mechanisms, including enzymatic antibiotic inactivation, threaten recent progress on bringing these next-generation tetracyclines to the clinic. Here we review the current state of knowledge on the structure, mechanism, and inhibition of tetracycline-inactivating enzymes.
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Affiliation(s)
- Jana L Markley
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO, United States
| | - Timothy A Wencewicz
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO, United States
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17
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High Levels of Intrinsic Tetracycline Resistance in Mycobacterium abscessus Are Conferred by a Tetracycline-Modifying Monooxygenase. Antimicrob Agents Chemother 2018; 62:AAC.00119-18. [PMID: 29632012 DOI: 10.1128/aac.00119-18] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2018] [Accepted: 03/27/2018] [Indexed: 11/20/2022] Open
Abstract
Tetracyclines have been one of the most successful classes of antibiotics. However, its extensive use has led to the emergence of widespread drug resistance, resulting in discontinuation of use against several bacterial infections. Prominent resistance mechanisms include drug efflux and the use of ribosome protection proteins. Infrequently, tetracyclines can be inactivated by the TetX class of enzymes, also referred to as tetracycline destructases. Low levels of tolerance to tetracycline in Mycobacterium smegmatis and Mycobacterium tuberculosis have been previously attributed to the WhiB7-dependent TetV/Tap efflux pump. However, Mycobacterium abscessus is ∼500-fold more resistant to tetracycline than M. smegmatis and M. tuberculosis In this report, we show that this high level of resistance to tetracycline and doxycycline in M. abscessus is conferred by a WhiB7-independent tetracycline-inactivating monooxygenase, MabTetX (MAB_1496c). The presence of sublethal doses of tetracycline and doxycycline results in a >200-fold induction of MabTetX, and an isogenic deletion strain is highly sensitive to both antibiotics. Further, purified MabTetX can rapidly monooxygenate both antibiotics. We also demonstrate that expression of MabTetX is repressed by MabTetRx, by binding to an inverted repeat sequence upstream of MabTetRx; the presence of either antibiotic relieves this repression. Moreover, anhydrotetracycline (ATc) can effectively inhibit MabTetX activity in vitro and decreases the MICs of both tetracycline and doxycycline in vivo Finally, we show that tigecycline, a glycylcycline tetracycline, not only is a poor substrate of MabTetX but also is incapable of inducing the expression of MabTetX. This is therefore the first demonstration of a tetracycline-inactivating enzyme in mycobacteria. It (i) elucidates the mechanism of tetracycline resistance in M. abscessus, (ii) demonstrates the use of an inhibitor that can potentially reclaim the use of tetracycline and doxycycline, and (iii) identifies two sequential bottlenecks-MabTetX and MabTetRx-for acquiring resistance to tigecycline, thereby reiterating its use against M. abscessus.
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18
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Abstract
Ever since antibiotics were introduced into human and veterinary medicine to treat and prevent bacterial infections there has been a steady selection and increase in the frequency of antibiotic resistant bacteria. To be able to reduce the rate of resistance evolution, we need to understand how various biotic and abiotic factors interact to drive the complex processes of resistance emergence and transmission. We describe several of the fundamental factors that underlay resistance evolution, including rates and niches of emergence and persistence of resistant bacteria, time- and space-gradients of various selective agents, and rates and routes of transmission of resistant bacteria between humans, animals and other environments. Furthermore, we discuss the options available to reduce the rate of resistance evolution and/ or transmission and their advantages and disadvantages.
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19
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Li T, Shan M, He J, Wang X, Wang S, Tian M, Qi J, Luo T, Shi Y, Ding C, Yu S. Riemerella anatipestifer M949_0459 gene is responsible for the bacterial resistance to tigecycline. Oncotarget 2017; 8:96615-96626. [PMID: 29228556 PMCID: PMC5722508 DOI: 10.18632/oncotarget.19633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Accepted: 06/29/2017] [Indexed: 02/06/2023] Open
Abstract
Based on its important role in last-line therapeutics against multidrug-resistant bacteria, tigecycline has been increasingly important in treating infections. However, mounting reports on tigecycline-resistant bacterial strains isolated from different sources are of concern, and molecular mechanisms regarding tigecycline resistance are poorly understood. Riemerella anatipestifer is a Gram-negative, non-motile, non-spore-forming, rod-shaped bacterium, which causes fibrinous pericarditis, perihepatitis, and meningitis in infected ducks. We previously constructed a random transposon mutant library using Riemerella anatipestifer strain CH3, in present study, we described that Riemerella anatipestifer M949_0459 gene is responsible for the bacterial resistance to tigecycline. Using the minimum inhibitory concentration assay, a mutant strain showed significantly increased (about six-fold) tigecycline susceptibility. Subsequently, the knocked-down gene was identified as M949_0459, a putative flavin adenine dinucleotide-dependent oxidoreductase. To confirm the resistance function, M949_0459 gene was overexpressed in Escherichia coli strain BL21, and the minimum inhibitory concentration analysis showed that the gene product conferred resistance to tigecycline. Additionally, expression of the M949_0459 gene under treatment with tigecycline was measured with quantitative real-time PCR. Results showed that the mRNA expression of M949_0459 gene was elevated under tigecycline treatment with dose range of 1-10 mg/L, and peaked at 4 mg/L. Moreover, two kinds of efflux pump inhibitors, carbonyl cyanide m-chlorophenyl hydrazone and phenylalanine arginyl β-naphthylamide were tested, which showed no function on tigecycline resistance in the strain CH3. Our results may provide insights into molecular mechanisms for chemotherapy in combating Riemerella anatipestifer infections.
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Affiliation(s)
- Tao Li
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Min Shan
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China.,College of Animal Science and Technology, Guangxi University, Guangxi, China
| | - Jing He
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Xiaolan Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Shaohui Wang
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Mingxing Tian
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Jingjing Qi
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Tingrong Luo
- College of Animal Science and Technology, Guangxi University, Guangxi, China
| | - Yonghong Shi
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Chan Ding
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
| | - Shengqing Yu
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
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20
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Park J, Gasparrini AJ, Reck MR, Symister CT, Elliott JL, Vogel JP, Wencewicz TA, Dantas G, Tolia NH. Plasticity, dynamics, and inhibition of emerging tetracycline resistance enzymes. Nat Chem Biol 2017; 13:730-736. [PMID: 28481346 PMCID: PMC5478473 DOI: 10.1038/nchembio.2376] [Citation(s) in RCA: 75] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Accepted: 02/08/2017] [Indexed: 12/18/2022]
Abstract
While tetracyclines are an important class of antibiotics in agriculture and the clinic, their efficacy is threatened by increasing resistance. Resistance to tetracyclines can occur through efflux, ribosomal protection, or enzymatic inactivation. Surprisingly, tetracycline enzymatic inactivation has remained largely unexplored despite providing the distinct advantage of antibiotic clearance. The tetracycline destructases are a recently-discovered family of tetracycline-inactivating flavoenzymes from pathogens and soil metagenomes with a high potential for broad dissemination. Here, we show tetracycline destructases accommodate tetracycline-class antibiotics in diverse and novel orientations for catalysis, and antibiotic binding drives unprecedented structural dynamics facilitating tetracycline inactivation. We identify a key inhibitor binding mode that locks the flavin adenine dinucleotide cofactor in an inactive state, functionally rescuing tetracycline activity. Our results reveal the potential of a novel tetracycline/tetracycline destructase inhibitor combination therapy strategy to overcome resistance by enzymatic inactivation and restore the use of an important class of antibiotics.
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Affiliation(s)
- Jooyoung Park
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Andrew J Gasparrini
- Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Margaret R Reck
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Chanez T Symister
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Jennifer L Elliott
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Joseph P Vogel
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA
| | - Timothy A Wencewicz
- Department of Chemistry, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Gautam Dantas
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.,Center for Genome Sciences and Systems Biology, Washington University School of Medicine, St. Louis, Missouri, USA.,Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, Missouri, USA.,Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
| | - Niraj H Tolia
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri, USA.,Department of Biochemistry and Molecular Biophysics, Washington University School of Medicine, St. Louis, Missouri, USA
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21
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Low A, Ng C, He J. Identification of antibiotic resistant bacteria community and a GeoChip based study of resistome in urban watersheds. WATER RESEARCH 2016; 106:330-338. [PMID: 27750121 DOI: 10.1016/j.watres.2016.09.032] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 07/31/2016] [Accepted: 09/19/2016] [Indexed: 06/06/2023]
Abstract
Urban watersheds from point sources are potential reservoirs of antibiotic resistance genes (ARGs). However, few studies have investigated urban watersheds of non-point sources. To understand the type of ARGs and bacteria that might carry such genes, we investigated two non-point source urban watersheds with different land-use profiles. Antibiotic resistance levels of two watersheds (R1, R3) were examined using heterotrophic plate counts (HPC) as a culturing method to obtain counts of bacteria resistant to seven antibiotics belonging to different classes (erythromycin, kanamycin, lincomycin, norfloxacin, sulfanilamide, tetracycline and trimethoprim). From the HPC study, 239 antibiotic resistant bacteria were characterized for resistance to more antibiotics. Furthermore, ARGs and antimicrobial biosynthesis genes were identified using GeoChip version 5.0 to elucidate the resistomes of surface waters in watersheds R1 and R3. The HPC study showed that water samples from R1 had significantly higher counts of bacteria resistant to erythromycin, kanamycin, norfloxacin, sulfanilamide, tetracycline and trimethoprim than those from R3 (Analysis of Similarity (ANOSIM), R = 0.557, p < 0.01). Of the seven antibiotics tested, lincomycin and trimethoprim resistant bacteria are greater in abundances. The 239 antibiotic resistant isolates represent a subset of resistant bacterial populations, including bacteria not previously known for resistance. Majority of the isolates had resistance to ampicillin, vancomycin, lincomycin and trimethoprim. GeoChip revealed similar ARGs in both watersheds, but with significantly higher intensities for tetX and β-lactamase B genes in R1 than R3. The genes with the highest average normalized intensities in R1 and R3 were tetracycline (tet) and fosfomycin (fosA) resistance genes, respectively. The higher abundance of tetX genes in R1 is congruent with the higher abundance of tetracycline resistant HPC observed in R1 samples. Strong correlations (r ≥ 0.8) of efflux pumps with antimicrobial biosynthesis genes suggest that natural production of antimicrobials may act as a selective pressure of transporter proteins in the absence of antibiotics from anthropogenic sources. In conclusion, distinct antibiotic resistant bacteria phylotypes and a variety of ARGs were present in the non-point sources urban watersheds of different land-use profiles, suggesting that ARG risk assessments and monitoring studies need to include these types of watersheds.
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Affiliation(s)
- Adrian Low
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, 117576, Singapore.
| | - Charmaine Ng
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, 117576, Singapore.
| | - Jianzhong He
- Department of Civil and Environmental Engineering, National University of Singapore, Block E2-02-13, 1 Engineering Drive 3, 117576, Singapore.
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22
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Abstract
Tetracyclines possess many properties considered ideal for antibiotic drugs, including activity against Gram-positive and -negative pathogens, proven clinical safety, acceptable tolerability, and the availability of intravenous (IV) and oral formulations for most members of the class. As with all antibiotic classes, the antimicrobial activities of tetracyclines are subject to both class-specific and intrinsic antibiotic-resistance mechanisms. Since the discovery of the first tetracyclines more than 60 years ago, ongoing optimization of the core scaffold has produced tetracyclines in clinical use and development that are capable of thwarting many of these resistance mechanisms. New chemistry approaches have enabled the creation of synthetic derivatives with improved in vitro potency and in vivo efficacy, ensuring that the full potential of the class can be explored for use against current and emerging multidrug-resistant (MDR) pathogens, including carbapenem-resistant Enterobacteriaceae, MDR Acinetobacter species, and Pseudomonas aeruginosa.
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23
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Andersson D. Improving predictions of the risk of resistance development against new and old antibiotics. Clin Microbiol Infect 2015; 21:894-8. [DOI: 10.1016/j.cmi.2015.05.012] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2015] [Revised: 05/06/2015] [Accepted: 05/08/2015] [Indexed: 11/24/2022]
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24
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Forsberg KJ, Patel S, Wencewicz TA, Dantas G. The Tetracycline Destructases: A Novel Family of Tetracycline-Inactivating Enzymes. ACTA ACUST UNITED AC 2015; 22:888-97. [PMID: 26097034 DOI: 10.1016/j.chembiol.2015.05.017] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2015] [Revised: 05/05/2015] [Accepted: 05/17/2015] [Indexed: 10/23/2022]
Abstract
Enzymes capable of inactivating tetracycline are paradoxically rare compared with enzymes that inactivate other natural-product antibiotics. We describe a family of flavoenzymes, previously unrecognizable as resistance genes, which are capable of degrading tetracycline antibiotics. From soil functional metagenomic selections, we discovered nine genes that confer high-level tetracycline resistance by enzymatic inactivation. We also demonstrate that a tenth enzyme, an uncharacterized homolog in the human pathogen Legionella longbeachae, similarly inactivates tetracycline. These enzymes catalyze the oxidation of tetracyclines in vitro both by known mechanisms and via previously undescribed activity. Tetracycline-inactivation genes were identified in diverse soil types, encompass substantial sequence diversity, and are adjacent to genes implicated in horizontal gene transfer. Because tetracycline inactivation is scarcely observed in hospitals, these enzymes may fill an empty niche in pathogenic organisms, and should therefore be monitored for their dissemination potential into the clinic.
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Affiliation(s)
- Kevin J Forsberg
- Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO 63108, USA
| | - Sanket Patel
- Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO 63108, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63108, USA
| | - Timothy A Wencewicz
- Department of Chemistry, Washington University in St. Louis, St. Louis, MO 63130, USA.
| | - Gautam Dantas
- Center for Genome Sciences & Systems Biology, Washington University School of Medicine, St. Louis, MO 63108, USA; Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63108, USA; Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA.
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26
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Leski TA, Bangura U, Jimmy DH, Ansumana R, Lizewski SE, Stenger DA, Taitt CR, Vora GJ. Multidrug-resistant tet(X)-containing hospital isolates in Sierra Leone. Int J Antimicrob Agents 2013; 42:83-6. [PMID: 23688520 DOI: 10.1016/j.ijantimicag.2013.04.014] [Citation(s) in RCA: 77] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2012] [Revised: 04/01/2013] [Accepted: 04/09/2013] [Indexed: 11/26/2022]
Abstract
The tet(X) gene encodes a flavin-dependent monooxygenase that confers resistance to all clinically relevant tetracycline antibiotics including tigecycline. It has only previously been identified in environmental and non-human pathogenic bacteria. To investigate levels of multidrug resistance in Bo, Sierra Leone, a molecular epidemiological study was conducted using an antimicrobial resistance determinant microarray (ARDM), PCR and DNA sequencing. The study found that 21% of isolates from Mercy Hospital (Bo, Sierra Leone) were tet(X)-positive, all of which originated from urinary specimens. Use of molecular epidemiological surveillance tools has provided the first evidence of tet(X)-containing multidrug-resistant Gram-negative hospital isolates in a hospital in Sierra Leone.
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Affiliation(s)
- Tomasz A Leski
- Center for Bio/Molecular Science and Engineering, Naval Research Laboratory, Washington, DC, USA
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27
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Volkers G, Palm GJ, Weiss MS, Wright GD, Hinrichs W. Structural basis for a new tetracycline resistance mechanism relying on the TetX monooxygenase. FEBS Lett 2011; 585:1061-6. [PMID: 21402075 DOI: 10.1016/j.febslet.2011.03.012] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 03/04/2011] [Indexed: 11/30/2022]
Abstract
The flavin-dependent monooxygenase TetX confers resistance to all clinically relevant tetracyclines, including the recently approved, broad-spectrum antibiotic tigecycline (Tygacil®) which is a critical last-ditch defense against multidrug-resistant pathogens. TetX represents the first resistance mechanism against tigecycline, which circumvents both the tet-gene encoded resistances, relying on active efflux of tetracyclines, and ribosomal protection proteins. The alternative enzyme-based mechanism of TetX depends on regioselective hydroxylation of tetracycline antibiotics to 11a-hydroxy-tetracyclines. Here, we report the X-ray crystallographic structure determinations at 2.1Å resolution of native TetX from Bacteroides thetaiotaomicron and its complexes with tetracyclines. Our crystal structures explain the extremely versatile substrate diversity of the enzyme and provide a first step towards the rational design of novel tetracycline derivatives to counter TetX-based resistance prior to emerging clinical observations.
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Affiliation(s)
- Gesa Volkers
- Institut für Biochemie, Universität Greifswald, Greifswald, Germany
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Volkers G, Schuldt L, Palm GJ, Wright GD, Hinrichs W. Crystallization and preliminary X-ray crystallographic analysis of the tetracycline-degrading monooxygenase TetX2 from Bacteroides thetaiotaomicron. Acta Crystallogr Sect F Struct Biol Cryst Commun 2010; 66:611-4. [PMID: 20445272 PMCID: PMC2864705 DOI: 10.1107/s174430911001225x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2010] [Accepted: 03/31/2010] [Indexed: 11/10/2022]
Abstract
The flavin-dependent monooxygenase TetX2 from Bacteroides thetaiotaomicron confers resistance against tetracyclines in aerobically grown Escherichia coli. TetX2 modifies several tetracycline antibiotics by regioselective hydroxylation of the substrates to 11a-hydroxy-tetracyclines. X-ray diffraction data were collected from a native TetX2 crystal and a TetX2 crystal with incorporated selenomethionine to resolutions of 2.5 and 3.0 A, respectively. The native crystal belonged to the triclinic space group P1, with unit-cell parameters a = 68.55, b = 80.88, c = 87.53 A, alpha = 111.09, beta = 98.98, gamma = 93.38 degrees , whereas the selenomethionine-labelled TetX2 crystal belonged to the monoclinic space group P2(1), with unit-cell parameters a = 87.34, b = 68.66, c = 152.48 A, beta = 101.08 degrees .
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Affiliation(s)
- Gesa Volkers
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, D-17489 Greifswald, Germany.
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Vedantam G. Antimicrobial resistance in Bacteroides spp.: occurrence and dissemination. Future Microbiol 2009; 4:413-23. [PMID: 19416011 DOI: 10.2217/fmb.09.12] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Bacteroides spp. organisms, though important human commensals, are also opportunistic pathogens when they escape the colonic milieu. Resistance to multiple antibiotics has been increasing in Bacteroides spp. for decades, and is primarily due to horizontal gene transfer of a plethora of mobile elements. The mechanistic aspects of conjugation in Bacteroides spp. are only now being elucidated at a functional level. There appear to be key differences between Bacteroides spp. and non-Bacteroides spp. conjugation systems that may contribute to promiscuous gene transfer within and from this genus. This review summarizes the mechanisms of action and resistance of antibiotics used to treat Bacteroides spp. infections, and highlights current information on conjugation-based DNA exchange.
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Affiliation(s)
- Gayatri Vedantam
- Department of Veterinary Science & Microbiology, Building 90, Room 108A, 1117 E. Lowell Street, Tucson, AZ 85721, USA.
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Zakeri B, Wright GD. Chemical biology of tetracycline antibioticsThis paper is one of a selection of papers published in this Special Issue, entitled CSBMCB — Systems and Chemical Biology, and has undergone the Journal's usual peer review process. Biochem Cell Biol 2008; 86:124-36. [DOI: 10.1139/o08-002] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
For more than half a century, tetracycline antibiotics have been used to treat infectious disease. However, what once used to be a commonly prescribed family of antibiotics has now decreased in effectiveness due to wide-spread bacterial resistance. The chemical scaffold of the tetracyclines is a versatile and modifiable structure that is able to interact with many cellular targets. The recent availability of detailed molecular interactions between tetracycline and its cellular targets, along with an understanding of the tetracycline biosynthetic pathway, has provided us with a unique opportunity to usher in a new era of rational drug design. Herein we discuss recent findings that have clarified the mode of action and the biosynthetic pathway of tetracyclines and that have shed light on the chemical biology of tetracycline antibiotics.
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Affiliation(s)
- Bijan Zakeri
- Department of Biochemistry and Biomedical Sciences, DeGroote School of Medicine, McMaster University, 1200 Main St. W, Hamilton, ON L8N 3Z5, Canada
| | - Gerard D. Wright
- Department of Biochemistry and Biomedical Sciences, DeGroote School of Medicine, McMaster University, 1200 Main St. W, Hamilton, ON L8N 3Z5, Canada
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Moore IF, Hughes DW, Wright GD. Tigecycline Is Modified by the Flavin-Dependent Monooxygenase TetX. Biochemistry 2005; 44:11829-35. [PMID: 16128584 DOI: 10.1021/bi0506066] [Citation(s) in RCA: 138] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The clinical use of tetracycline antibiotics has decreased due to the emergence of efflux and ribosomal protection-based resistance mechanisms. Currently in phase III clinical trials, the glycylcycline derivative tigecycline (GAR-936) containing a 9-tert-butylglycylamido group is part of a new generation of tetracycline antibiotics developed during the 1990s. Tigecycline displays a broad spectrum of antibacterial activity and circumvents the efflux and ribosomal protection resistance mechanisms. The TetX protein is a flavin-dependent monooxygenase that modifies first and second generation tetracyclines and requires NADPH, Mg(2+), and O(2) for activity. We report that tigecycline is a substrate for TetX and that bacterial strains containing the tet(X) gene are resistant to tigecycline. The resistance is due to the modification of tigecycline by TetX to form 11a-hydroxytigecycline, which we have shown has a weakened ability to inhibit protein translation compared with tigecycline. We have explored the basis of this decreased ability to block translation and found that hydroxylation occurs in the region of the molecule important for coordinating magnesium. 11a-Hydroxytigecycline forms a weaker complex with magnesium than tigecycline; the crystal structure of tetracycline in complex with the ribosome has shown that magnesium coordination is critical for binding tetracycline. Although tet(X) has not been isolated from any clinically resistant strains, our report demonstrates the first enzymatic resistance mechanism to tigecycline and provides an alert for the surveillance of resistant strains that may contain tet(X).
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Affiliation(s)
- Ian F Moore
- Antimicrobial Research Centre, Department of Biochemistry and Biomedical Sciences, McMaster University, 1200 Main Street West, Hamilton, Ontario, L8N 3Z5, Canada
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Yang W, Moore IF, Koteva KP, Bareich DC, Hughes DW, Wright GD. TetX is a flavin-dependent monooxygenase conferring resistance to tetracycline antibiotics. J Biol Chem 2004; 279:52346-52. [PMID: 15452119 DOI: 10.1074/jbc.m409573200] [Citation(s) in RCA: 198] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The tetracycline antibiotics block microbial translation and constitute an important group of antimicrobial agents that find broad clinical utility. Resistance to this class of antibiotics is primarily the result of active efflux or ribosomal protection; however, a novel mechanism of resistance has been reported to be oxygen-dependent destruction of the drugs catalyzed by the enzyme TetX. Paradoxically, the tetX genes have been identified on transposable elements found in anaerobic bacteria of the genus Bacteroides. Overexpression of recombinant TetX in Escherichia coli followed by protein purification revealed a stoichiometric complex with flavin adenine dinucleotide. Reconstitution of in vitro enzyme activity demonstrated a broad tetracycline antibiotic spectrum and a requirement for molecular oxygen and NADPH in antibiotic degradation. The tetracycline products of TetX activity were unstable at neutral pH, but mass spectral and NMR characterization under acidic conditions supported initial monohydroxylation at position 11a followed by intramolecular cyclization and non-enzymatic breakdown to other undefined products. TetX is therefore a FAD-dependent monooxygenase. The enzyme not only catalyzed efficient degradation of a broad range of tetracycline analogues but also conferred resistance to these antibiotics in vivo. This is the first molecular characterization of an antibiotic-inactivating monooxygenase, the origins of which may lie in environmental bacteria.
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Affiliation(s)
- Wangrong Yang
- Antimicrobial Research Center, Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
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Ng LK, Martin I, Alfa M, Mulvey M. Multiplex PCR for the detection of tetracycline resistant genes. Mol Cell Probes 2001; 15:209-15. [PMID: 11513555 DOI: 10.1006/mcpr.2001.0363] [Citation(s) in RCA: 551] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Specific primer pairs were selected for the PCR amplification of 14 tetracycline resistant genes commonly found in Gram positive and Gram negative organisms. Combinations of primer pairs were used in multiplex PCR reactions to detect specific groups of tet genes as follows; Group I tet (B), tet (C), tet (D); Group II tet (A), tet (E), tet (G); Group III tet (K), tet (L), tet (M), tet (O), tet (S); Group IV tetA (P), tet (Q), tet (X). To test the multiplex PCR, Groups I and II were used on 25 clinical isolates of Salmonella enterica serovar Typhimurium DT104. Group III primers were used to investigate 19 clinical isolates of methicillin-resistant Staphylococcus aureus. Multiplex PCR should result in significant savings in terms of labour and cost in analysis of a large number of strains when compared with using an individual PCR for targeting each gene. It may also be a useful method to differentiate the types of tetracycline resistance when used as an additional marker for the purpose of outbreak investigation and surveillance.
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Affiliation(s)
- L K Ng
- National Microbiology Laboratory, Population and Public Health Branch, Winnipeg, MB, R3E 3R2, Canada.
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Barbosa TM, Scott KP, Flint HJ. Evidence for recent intergeneric transfer of a new tetracycline resistance gene, tet(W), isolated from Butyrivibrio fibrisolvens, and the occurrence of tet(O) in ruminal bacteria. Environ Microbiol 1999; 1:53-64. [PMID: 11207718 DOI: 10.1046/j.1462-2920.1999.00004.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
We have previously reported high-frequency transfer of tetracycline resistance between strains of the rumen anaerobic bacterium Butyrivibrio fibrisolvens. Donor strains were postulated to carry two TcR genes, one of which is transferred on a novel chromosomal element. It is shown here that coding sequences within the non-transmissible gene in B. fibrisolvens 1.230 are identical to those of the Streptococcus pneumoniae tet(O) gene. This provides the first evidence for genetic exchange between facultatively anaerobic bacteria and rumen obligate anaerobes. In contrast, the product of the transmissible TcR gene shares only 68% amino acid sequence identity with the TetO and TetM proteins and represents a new class of ribosome protection tetracycline resistance determinant, designated Tet W. The tet(W) coding region shows a higher DNA G + C content (53%) than other B. fibrisolvens genes or other ribosome protection-type tet genes, suggesting recent acquisition from a high G + C content genome. Tet(W) genes with almost identical sequences are also shown to be present in TcR strains of B. fibrisolvens from Australian sheep and in TcR strains of two other genera of rumen obligate anaerobes, Selenomonas ruminantium and Mitsuokella multiacidus. This provides compelling evidence for recent intergeneric transfer of resistance genes between ruminal bacteria. Tet(W) is not restricted to ruminal bacteria, as it was also present in a porcine strain of M. multiacidus.
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Affiliation(s)
- T M Barbosa
- Rowett Research Institute, Bucksburn, Aberdeen, UK
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35
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Scott KP, Barbosa TM, Forbes KJ, Flint HJ. High-frequency transfer of a naturally occurring chromosomal tetracycline resistance element in the ruminal anaerobe Butyrivibrio fibrisolvens. Appl Environ Microbiol 1997; 63:3405-11. [PMID: 9292992 PMCID: PMC168648 DOI: 10.1128/aem.63.9.3405-3411.1997] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Butyrivibrio fibrisolvens strains resistant to tetracycline were isolated from the bovine rumen. Two of three Tcr B. fibrisolvens tested were able to donate tetracycline resistance at frequencies ranging from 10(-7) to 10(-1) per donor cell in anaerobic filter matings to a rifampin-resistant mutant of the type strain of B.fibrisolvens, 2221R. The recipient strain 2221R exhibited rapid autoaggregation, which might be a factor in the high transfer rates observed. Tcr transconjugants of B. fibrisolvens 2221R were also capable of further transferring tetracycline resistance to a fusidic acid-resistant mutant, 2221F. Comparison of genomic DNAs by pulsed-field gel electrophoresis demonstrated altered band profiles in transconjugants, consistent with the acquisition of a large mobile chromosomal element. The transferable elements from the two B. fibrisolvens donors 1.23 and 1.230 (TnB123 and TnB1230, respectively) showed the same preferred insertion site in the B. fibrisolvens 2221R chromosome and are likely to be similar, or identical, elements. Hybridization experiments showed no close relationship between TnB1230 and int-xis regions from Tn916 or Tn5253. Although DNA from the B. fibrisolvens donor strains hybridized with probes carrying tet(M) or tet(O) sequences, transconjugants were found to have acquired a distinct band that hybridized only weakly with these probes, suggesting that a second, distantly related Tcr determinant had been transferred.
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Affiliation(s)
- K P Scott
- Rowett Research Institute, University of Aberdeen, United Kingdom
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36
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Lacroix JM, Walker CB. Detection and prevalence of the tetracycline resistance determinant Tet Q in the microbiota associated with adult periodontitis. ORAL MICROBIOLOGY AND IMMUNOLOGY 1996; 11:282-8. [PMID: 9002882 DOI: 10.1111/j.1399-302x.1996.tb00182.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Subgingival plaque samples were collected from 68 patients with a history of moderate to severe adult periodontitis and enumerated on Trypticase-soy blood agar plates, with and without tetracycline at 4 micrograms/ml. Each different colony morphotype was enumerated, and a representative colony was subcultured for identification and examined for the tetracycline resistance gene tet(Q) by polymerase chain reaction (PCR) amplification and DNA hybridization, using a fragment of tetA(Q)2 from Bacteroides fragilis 1126. PCR primers (5'-GGCTTCTACGACATCTATTA-3' and 5'-CATCAACATTTATCTCTCTG-3') were chosen to amplify a 755 bp region of tet(Q). The subgingival plaque samples were also tested by PCR. Approximately 12% of the total cultivable flora was resistant to tetracycline, and the percentage of the tetracycline-resistant cultivable flora with the tet(Q) gene varied greatly from one patient to another with a range from 0.0 to 67%. Half of the 68 subgingival plaque samples were positive or weakly positive for tet(Q) by PCR. Approximately 15% of the 210 isolates subcultured with resistance to tetracycline, (> or = 4 micrograms/ml) contained tet(Q), and 60% contained tet(M). All of the tet(Q)-resistant isolates were gram-negative anaerobic bacilli and included all of the Prevotella and Bacteroides isolates.
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Affiliation(s)
- J M Lacroix
- Periodontal Disease Research Center, College of Dentistry, University of Florida, Gainesville, USA
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37
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Olsvik B, Olsen I, Tenover FC. Detection of tet(M) and tet(O) using the polymerase chain reaction in bacteria isolated from patients with periodontal disease. ORAL MICROBIOLOGY AND IMMUNOLOGY 1995; 10:87-92. [PMID: 7675524 DOI: 10.1111/j.1399-302x.1995.tb00124.x] [Citation(s) in RCA: 75] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The polymerase chain reaction was used to examine 114 tetracycline-resistant anaerobic and facultative anaerobic bacterial isolates from patients with periodontal disease for the tet(M) and tet(O) genes. A 740-base-pair fragment of the tet(M) gene was amplified from 84 of 114 isolates, and a 519-base-pair fragment of the tet(O) gene was amplified from 13 streptococcal isolates. Six of 7 tetracycline-resistant isolates of Veillonella spp. and tetracycline-resistant isolates of Eubacterium spp. (n = 3), Eubacterium saburreum (n = 1), Streptococcus intermedius (n = 5) and Gemella morbillorum (n = 2) all harbored the tet(M) gene. The tet(M) and tet(O) negative as well as selected positive isolates were tested for the tet(K) and tet(L) genes using DNA probes. All isolates of Staphylococcus spp. (n = 11) hybridized with the tet(K) probe. None of the isolates tested hybridized with the probe for tet(L). This is the first report of the tet(M) gene in the facultative bacterium G. morbillorum and in E. saburreum.
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38
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Allen NE. Biochemical mechanisms of resistance to non-cell wall antibacterial agents. PROGRESS IN MEDICINAL CHEMISTRY 1995; 32:157-238. [PMID: 8577918 DOI: 10.1016/s0079-6468(08)70454-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Affiliation(s)
- N E Allen
- Infectious Disease Research, Eli Lilly and Company, Indianapolis, IN 46285, USA
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Tetracyclines — extending the atypical spectrum. Int J Antimicrob Agents 1993; 3 Suppl 1:S31-46. [DOI: 10.1016/0924-8579(93)90033-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/25/1993] [Indexed: 11/21/2022]
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Speer BS, Shoemaker NB, Salyers AA. Bacterial resistance to tetracycline: mechanisms, transfer, and clinical significance. Clin Microbiol Rev 1992; 5:387-99. [PMID: 1423217 PMCID: PMC358256 DOI: 10.1128/cmr.5.4.387] [Citation(s) in RCA: 286] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Tetracycline has been a widely used antibiotic because of its low toxicity and broad spectrum of activity. However, its clinical usefulness has been declining because of the appearance of an increasing number of tetracycline-resistant isolates of clinically important bacteria. Two types of resistance mechanisms predominate: tetracycline efflux and ribosomal protection. A third mechanism of resistance, tetracycline modification, has been identified, but its clinical relevance is still unclear. For some tetracycline resistance genes, expression is regulated. In efflux genes found in gram-negative enteric bacteria, regulation is via a repressor that interacts with tetracycline. Gram-positive efflux genes appear to be regulated by an attenuation mechanism. Recently it was reported that at least one of the ribosome protection genes is regulated by attenuation. Tetracycline resistance genes are often found on transmissible elements. Efflux resistance genes are generally found on plasmids, whereas genes involved in ribosome protection have been found on both plasmids and self-transmissible chromosomal elements (conjugative transposons). One class of conjugative transposon, originally found in streptococci, can transfer itself from streptococci to a variety of recipients, including other gram-positive bacteria, gram-negative bacteria, and mycoplasmas. Another class of conjugative transposons has been found in the Bacteroides group. An unusual feature of the Bacteroides elements is that their transfer is enhanced by preexposure to tetracycline. Thus, tetracycline has the double effect of selecting for recipients that acquire a resistance gene and stimulating transfer of the gene.
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Affiliation(s)
- B S Speer
- Keck Laboratories, California Institute of Technology, Pasadena 91125
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41
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Nikolich MP, Shoemaker NB, Salyers AA. A Bacteroides tetracycline resistance gene represents a new class of ribosome protection tetracycline resistance. Antimicrob Agents Chemother 1992; 36:1005-12. [PMID: 1339256 PMCID: PMC188826 DOI: 10.1128/aac.36.5.1005] [Citation(s) in RCA: 79] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
The ribosome protection type of tetracycline resistance (Tcr) has been found in a variety of bacterial species, but the only two classes described previously, Tet(M) and Tet(O), shared a high degree of amino acid sequence identity (greater than 75%). Thus, it appeared that this type of resistance emerged recently in evolution and spread among different species of bacteria by horizontal transmission. We obtained the DNA sequence of a Tcr gene from Bacteroides, a genus of gram-negative, obligately anaerobic bacteria that is phylogenetically distant from the diverse species in which tet(M) and tet(O) have been found. The Bacteroides Tcr gene defines a new class of ribosome protection resistance genes, Tet(Q), and has a deduced amino acid sequence that was only 40% identical to Tet(M) or Tet(O). Like tet(M) and tet(O), tet(Q) appears to have spread by horizontal transmission, but only within the Bacteroides group.
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Affiliation(s)
- M P Nikolich
- Department of Microbiology, University of Illinois, Urbana 61801
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Speer BS, Bedzyk L, Salyers AA. Evidence that a novel tetracycline resistance gene found on two Bacteroides transposons encodes an NADP-requiring oxidoreductase. J Bacteriol 1991; 173:176-83. [PMID: 1846135 PMCID: PMC207172 DOI: 10.1128/jb.173.1.176-183.1991] [Citation(s) in RCA: 138] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Two transposons, Tn4351 and Tn4400, which were originally isolated from the obligate anaerobe Bacteroides fragilis, carry a tetracycline resistance (Tcr) gene that confers resistance only on aerobically grown Escherichia coli. This aerobic Tcr gene, designated tetX, has been shown previously to act by chemically modifying tetracycline in a reaction that appears to require oxygen. We have now obtained the DNA sequence of tetX and 0.6 kb of its upstream region from Tn4400. Analysis of the DNA sequence of tetX revealed that this gene encoded a 43.7-kDa protein. The deduced amino acid sequence of the amino terminus of the protein had homology with a number of enzymes, all of which had in common a requirement for NAD(P). In an earlier study, we had observed that disrupted cells, unlike intact cells, could not carry out the alteration of tetracycline. We have now shown that if NADPH (1 mM) is added to the disrupted cell preparation, alteration of tetracycline occurs. Thus, TetX appears to be an NADP-requiring oxidoreductase. Tn4400 conferred a fivefold-lower level of tetracycline resistance than Tn4351. This finding appears to be due to a lower level of expression of the tetX on Tn4400, because the activity of a tetX-lacZ fusion from Tn4400 was 10-fold lower than that of the same fusion from Tn4351. A comparison of the sequence of the tetX region on Tn4351 with that on Tn4400 showed that the only difference between the upstream regions of the two transposons was a 4-base change 350 bp upstream of the start of the tetX coding region. The 4-base change difference creates a good consensus -35 region on Tn4351 that is not present on Tn4400 and could be creating an extra promoter.
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Affiliation(s)
- B S Speer
- Department of Microbiology, University of Illinois, Urbana 61801
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43
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Ives CL, Bott KF. Characterization of chromosomal DNA amplifications with associated tetracycline resistance in Bacillus subtilis. J Bacteriol 1990; 172:4936-44. [PMID: 1697573 PMCID: PMC213148 DOI: 10.1128/jb.172.9.4936-4944.1990] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Endogenous chromosomal DNA amplifications with associated tetracycline resistance (Tcr) in Bacillus subtilis were first described by C. R. Wilson and A. E. Morgan (J. Bacteriol. 163:445-453, 1985). We have confirmed and extended their results, and we show that fusion of protoplasts from Tcs B. subtilis 168 trpC2 with polyethylene glycol and regeneration on medium containing 20 micrograms of tetracycline per ml induces Tcr regenerants that contain amplified DNA. This phenomenon appeared to be recE dependent and requires the addition of polyethylene glycol. Along with three regenerants kindly provided by Wilson and Morgan (RAD1, RAD6, and RAD7), we characterized three strains (CLI20, CLI22, CLI30) isolated in this laboratory. All six contain an amplified region of DNA which was independently cloned on plasmid pCIS7. Integration of pCIS7 into the wild-type (Tcs) B. subtilis chromosome and amplification of the plasmid sequences generated a Tcr phenotype, even though the DNA on pCIS7 was cloned from Tcs B. subtilis KS162 (Ives and Bott, J. Bacteriol. 171:1801-1810, 1989). The amplified DNA also showed homology (through hybridization analysis) with pAM alpha 1 delta 1, a gram-positive Tcr plasmid, indicating that B. subtilis normally contains a silent integrated copy of the gene whose amplification confers Tcr. The amplifications were determined to lie between purA and gyrB on the B. subtilis chromosome, and the endpoints were mapped. RAD6 and CLI30 may share the same left-hand endpoint, but the other endpoints are different in each isolate. The amplified DNAs of RAD1, RAD6, CLI20, and CLI30 end near known DNA membrane binding sites. The number of amplified units of DNA was determined through dot blot analysis to do approximately 80 to 100 copies per cell, with corresponding increases in transcription of RAD1, RAD6, CLI20, CLI22, and CLI30.
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Affiliation(s)
- C L Ives
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599
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44
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Shoemaker NB, Salyers AA. A cryptic 65-kilobase-pair transposonlike element isolated from Bacteroides uniformis has homology with Bacteroides conjugal tetracycline resistance elements. J Bacteriol 1990; 172:1694-702. [PMID: 2156799 PMCID: PMC208658 DOI: 10.1128/jb.172.4.1694-1702.1990] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A 65-kilobase-pair element, XBU4422, which has some transposonlike characteristics but carries no known antibiotic resistance genes, has been isolated from Bacteroides uniformis 0061. XBU4422 was trapped on Bacteroides-Escherichia coli shuttle vectors during experiments in which one of the conjugal Bacteroides tetracycline resistance (Tcr) elements was being used to mobilize the shuttle vectors to Bacteroides recipients. Results of Southern hybridization experiments showed that XBU4422 is normally integrated in the B. uniformis 0061 chromosome and is found only in some strains. Insertion of XBU4422 in the shuttle vectors was site specific and orientation specific. Nonmobilizable vectors that had acquired XBU4422 became transmissible and could be transferred to Bacteroides or E. coli recipients. In B. uniformis transconjugants, the XBU4422 insertion in the vectors was usually intact, but XBU4422 was always lost in matings with E. coli, Bacteroides thetaiotaomicron, or B. ovatus. The loss of XBU4422 did not visibly alter the vector; in the case of E. coli, the loss of the insertion appeared to be RecA dependent. Although XBU4422 carried no antibiotic resistances, it shared regions of homology with six conjugal Bacteroides Tcr elements; this homology was strongest with the ends of XBU4422. Using a strain of B. thetaiotaomicron that contains no XBU4422-hybridizing sequences, we showed that the ends of XBU4422 were probably reacting with the ends of the Tcr elements. These results provide the first direct evidence that the Tcr elements, like XBU4422, are integrated in the chromosome and that insertion of the least some Tcr elements, such as TcrEmr DOT, is relatively site specific.
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Affiliation(s)
- N B Shoemaker
- Department of Microbiology, University of Illinois, Urbana 61801
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Abstract
Until recently, tetracycline efflux was thought to be the only mechanism of tetracycline resistance. As studies of tetracycline resistance have shifted to bacteria outside the Enterobacteriaceae, two other mechanisms of resistance have been discovered. The first is ribosomal protection, a type of resistance which is found in mycoplasmas, Gram-positive and Gram-negative bacteria and may be the most common type of tetracycline resistance in nature. The second is tetracycline modification, which has been found only in two strains of an obligate anaerobe (Bacteroides). Recent studies have also turned up such anomalies as a tetracycline efflux pump which does not confer resistance to tetracycline and a gene near the replication origin of a tetracycline-sensitive Bacillus strain which confers resistance when it is amplified.
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Affiliation(s)
- A A Salyers
- Department of Microbiology, University of Illinois, Urbana 61801
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Manavathu EK, Fernandez CL, Cooperman BS, Taylor DE. Molecular studies on the mechanism of tetracycline resistance mediated by Tet(O). Antimicrob Agents Chemother 1990; 34:71-7. [PMID: 2183711 PMCID: PMC171522 DOI: 10.1128/aac.34.1.71] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
The mechanism of resistance to tetracycline in Escherichia coli mediated by the Campylobacter jejuni-derived resistance determinant Tet(O) was investigated. The cloned Tet(O) protein had no detectable effect on the intracellular accumulation of tetracycline. The presence of Tet(O) markedly diminished the inhibitory effect of tetracycline on protein synthesis both in vivo and in vitro. Ribosomes prepared from tetracycline-resistant and susceptible E. coli cells bound almost identical amounts of radiolabeled tetracycline. Thus, a reduction in the binding of the antibiotic to its target site on the ribosome is not the primary mechanism of resistance. Poly(U)-directed polyphenylalanine synthesis revealed that an S-100 fraction prepared from tetracycline-resistant cells made the ribosomes prepared from susceptible cells considerably more resistant to the inhibitory action of tetracycline. The N-terminal portion (1 to 150 residues) of Tet(O) is highly homologous to the GTP-binding domain of elongation factor Tu and to elongation factor G, indicating that the Tet(O) protein has the potential to bind GTP. These data suggest that the Tet(O) protein could function either as a tetracycline-resistant analog of this elongation factor(s) or by modifying the target sites on the ribosomes in a catalytic fashion.
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Affiliation(s)
- E K Manavathu
- Department of Medical Microbiology, University of Alberta, Edmonton, Canada
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Speer BS, Salyers AA. A tetracycline efflux gene on Bacteroides transposon Tn4400 does not contribute to tetracycline resistance. J Bacteriol 1990; 172:292-8. [PMID: 2152904 PMCID: PMC208431 DOI: 10.1128/jb.172.1.292-298.1990] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Previously, we demonstrated that the Bacteroides transposon Tn4351, which confers tetracycline resistance only on aerobically grown Escherichia coli, carries a gene that codes for a tetracycline-inactivating enzyme (B. S. Speer and A. A. Salyers, J. Bacteriol. 170:1423-1429, 1988). However, Park et al. (B. H. Park, M. Hendricks, M. H. Malamy, F. P. Tally, and S. B. Levy, Antimicrob. Agents Chemother. 31:1739-1743, 1987) showed that E. coli carrying a closely related transposon, Tn4400, exhibits energy-dependent efflux of tetracycline as well as tetracycline-inactivating activity (B. H. Park and S. B. Levy, Antimicrob. Agents Chemother. 32:1797-1800, 1988). This result raised the question of whether efflux or inactivation or a combination of the two was necessary for resistance conferred by both transposons. We showed that cells carrying Tn4351 did not exhibit the clear-cut efflux activity seen with cells carrying Tn4400 but rather exhibited a tetracycline accumulation profile which could be explained solely on the basis of inactivation of tetracycline in the cytoplasm and rapid diffusion of altered tetracycline out of the cell. Additionally, we were able to clone the efflux and tetracycline-modifying genes of Tn4400 separately. The region carrying the efflux gene spanned one of the two regions in which Tn4400 differs from Tn4351. A clone containing the corresponding region of Tn4351 did not exhibit efflux. Thus, it appears that Tn4351 does not have the efflux gene and that efflux makes no contribution to the resistance conferred by Tn4351. The MIC for cells carrying the subclone from Tn4400 that contained only the gene for tetracycline inactivation was the same that for cells carrying both the inactivation and efflux genes. Cells carrying only the gene for tetracycline efflux were tetracycline sensitive. This was true even when the efflux gene was on a high-copy-number plasmid which increased the level of efflux to that associated with the Tcr gene on pBR328. These results indicate that efflux activity does not contribute significantly to the tetracycline resistance conferred by Tn4400.
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Affiliation(s)
- B S Speer
- Department of Microbiology, University of Illinois, Urbana 61801
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Ives CL, Bott KF. Cloned Bacillus subtilis chromosomal DNA mediates tetracycline resistance when present in multiple copies. J Bacteriol 1989; 171:1801-10. [PMID: 2539352 PMCID: PMC209825 DOI: 10.1128/jb.171.4.1801-1810.1989] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Plasmid pCIS7, containing 11.5 kilobases (kb) of Bacillus subtilis DNA, was isolated from a Tn917 transposon insertion in tetracycline-sensitive B. subtilis KS162. When integrated into the chromosome of B. subtilis 168, this plasmid conferred tetracycline resistance upon reiteration of the plasmid DNA sequences in the chromosome. Deletions and subclones of pCIS7 were constructed and introduced into an Escherichia coli in vitro transcription-translation system. A 72-kilodalton protein was localized to a 3.1-kb PstI-EcoRI fragment of the plasmid. Amplification of the 3.1-kb PstI-EcoRI fragment was required for expression of tetracycline resistance in B. subtilis 168. By hybridization to previously characterized clones, the 11.5-kb fragment was localized to the origin region of the chromosome. Through contour-clamped homogeneous electric field electrophoresis, this cluster of clones was shown to reside on a 200-kb NotI fragment bridging SfiI fragments of 150 and 250 kb and was oriented with respect to the purA and guaA loci, developing an accurate physical map of the region surrounding the origin of replication.
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Affiliation(s)
- C L Ives
- Department of Microbiology and Immunology, University of North Carolina, Chapel Hill 27599
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Smith KA, Salyers AA. Cell-associated pullulanase from Bacteroides thetaiotaomicron: cloning, characterization, and insertional mutagenesis to determine role in pullulan utilization. J Bacteriol 1989; 171:2116-23. [PMID: 2703467 PMCID: PMC209865 DOI: 10.1128/jb.171.4.2116-2123.1989] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
We have cloned a pullulanase gene from Bacteroides thetaiotaomicron. The pullulanase expressed from this clone in Escherichia coli was cell associated and soluble and had a molecular mass of 72 kilodaltons by gel filtration. Maxicell analysis of proteins coded by the cloned insert showed that a 71.6- to 73.2-kilodalton doublet was associated with pullulanase activity. Thus, the pullulanase is probably a monomer. The cloned pullulanase produced maltotriose as an end product of pullulan digestion. In B. thetaiotaomicron the pullulanase activity was cell associated. Approximately 80% of the activity was soluble, and 16 to 18% was membrane associated. The molecular mass of the soluble pullulanase was 77 kilodaltons by gel filtration. To determine whether the cloned pullulanase gene was essential for pullulan utilization, we used directed insertional mutagenesis to inactivate the B. thetaiotaomicron pullulanase gene. The pullulanase specific activity of the mutant was approximately 45% of that of wild-type B. thetaiotaomicron. However, the pullulanase-negative insertional mutant 95-1 was still able to grow on pullulan at a rate similar to that of wild-type B. thetaiotaomicron. Thus, there must be a second pullulanase in B. thetaiotaomicron.
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Affiliation(s)
- K A Smith
- Department of Microbiology, University of Illinois, Urbana 61801
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Jupeau-Vessières AN, Leroux YG, Scavizzi MR, el Manouni D, Gerbaud GR. Evidence for broken minocycline by NMR and HPLC techniques: a new additional resistance mechanism mediated by tetB determinant. Res Microbiol 1989; 140:207-19. [PMID: 2694246 DOI: 10.1016/0923-2508(89)90076-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
As demonstrated by microbiological assays, a decrease in the active minocycline level occurs in spent media from each Escherichia coli K12 recipient containing one of 10 different plasmids bearing tetB determinants. No such decrease was detected when tetA, C, D or E determinants were tested under the same conditions. Likewise, no decrease in tetracycline or doxycycline levels was detected when 20 plasmids bearing tetA to E determinants were tested. Studies carried out by nuclear magnetic resonance and high pressure liquid chromatography proved that minocycline is broken by a mechanism mediated by the tetB determinant. This new mechanism can be considered as additional to the active efflux of minocycline.
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Affiliation(s)
- A N Jupeau-Vessières
- Service de Bactériologie-Virologie, Centre Hospitalier Universitaire Avicenne, Université Paris Nord, Bobigny, France
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