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Xu Y, Zheng Z, Ye L, Chan EWC, Chen S. Identification and Genetic Characterization of Conjugative Plasmids Encoding Coresistance to Ciprofloxacin and Cephalosporin in Foodborne Vibrio spp. Microbiol Spectr 2023; 11:e0103223. [PMID: 37395663 PMCID: PMC10434038 DOI: 10.1128/spectrum.01032-23] [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: 03/15/2023] [Accepted: 06/12/2023] [Indexed: 07/04/2023] Open
Abstract
Plasmid-mediated quinolone resistance (PMQR) determinants, such as qnrVC genes, have been widely reported in Vibrio spp. while other types of PMQR genes were rarely reported in these bacteria. This study characterized the phenotypic and genotypic features of foodborne Vibrio spp. carrying qnrS, a key PMQR gene in Enterobacteriaceae. Among a total of 1,811 foodborne Vibrio isolates tested, 34 (1.88%) were found to harbor the qnrS gene. The allele qnrS2 was the most prevalent, but coexistence with other qnr alleles was common. Missense mutations in the quinolone resistance-determining region (QRDR) of the gyrA and parC genes were only found in 11 of the 34 qnrS-bearing isolates. Antimicrobial susceptibility tests showed that all 34 qnrS-bearing isolates were resistant to ampicillin and that a high percentage also exhibited resistance to cefotaxime, ceftriaxone, and trimethoprim-sulfamethoxazole. Genetic analysis showed that these phenotypes were attributed to a diverse range of resistance elements that the qnrS-bearing isolates harbored. The qnrS2 gene could be found in both the chromosome and plasmids; the plasmid-borne qnrS2 genes could be found on both conjugative and nonconjugative plasmids. pAQU-type qnrS2-bearing conjugative plasmids were able to mediate expression of phenotypic resistance to both ciprofloxacin and cephalosporins. Transmission of this plasmid among Vibrio spp. would speed up the emergence of multidrug-resistant (MDR) pathogens that are resistant to the most important antibiotics used in treatment of Vibrio infections, suggesting that close monitoring of emergence and dissemination of MDR Vibrio spp. in both food samples and clinical settings is necessary. IMPORTANCE Vibrio spp. used to be very susceptible to antibiotics. However, resistance to clinically important antibiotics, such as cephalosporins and fluoroquinolones, among clinically isolated Vibrio strains is increasingly common. In this study, we found that plasmid-mediated quinolone resistance (PMQR) genes, such as qnrS, that have not been previously reported in Vibrio spp. can now be detected in food isolates. The qnrS2 gene alone could mediate expression of ciprofloxacin resistance in Vibrio spp.; importantly, this gene could be found in both the chromosome and plasmids. The plasmids that harbor the qnrS2 gene could be both conjugative and nonconjugative, among which the pAQU-type qnrS2-bearing conjugative plasmids were able to mediate expression of resistance to both ciprofloxacin and cephalosporins. Transmission of this plasmid among Vibrio spp. would accelerate the emergence of multidrug-resistant pathogens.
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Affiliation(s)
- Yating Xu
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- City University of Hong Kong Chengdu Research Institute, Chengdu, People’s Republic of China
| | - Zhiwei Zheng
- Shenzhen Key Laboratory for Food Biological Safety Control, Food Safety and Technology Research Centre, The Hong Kong PolyU Shenzhen Research Institute, Shenzhen, People’s Republic of China
- State Key Laboratory of Chirosciences and the Department of Food Science and Nutrition, The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | - Lianwei Ye
- Department of Infectious Diseases and Public Health, Jockey Club College of Veterinary Medicine and Life Sciences, City University of Hong Kong, Kowloon, Hong Kong
- State Key Laboratory of Chirosciences and the Department of Food Science and Nutrition, The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | - Edward Wai-Chi Chan
- State Key Laboratory of Chirosciences and the Department of Food Science and Nutrition, The Hong Kong Polytechnic University, Kowloon, Hong Kong
| | - Sheng Chen
- City University of Hong Kong Chengdu Research Institute, Chengdu, People’s Republic of China
- Shenzhen Key Laboratory for Food Biological Safety Control, Food Safety and Technology Research Centre, The Hong Kong PolyU Shenzhen Research Institute, Shenzhen, People’s Republic of China
- State Key Laboratory of Chirosciences and the Department of Food Science and Nutrition, The Hong Kong Polytechnic University, Kowloon, Hong Kong
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Nohejl T, Valcek A, Papousek I, Palkovicova J, Wailan AM, Pratova H, Minoia M, Dolejska M. Genomic analysis of qnr-harbouring IncX plasmids and their transferability within different hosts under induced stress. BMC Microbiol 2022; 22:136. [PMID: 35590235 PMCID: PMC9118779 DOI: 10.1186/s12866-022-02546-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Accepted: 04/27/2022] [Indexed: 11/26/2022] Open
Abstract
Background Conjugative plasmids play a major role in the dissemination of antibiotic resistance genes. Knowledge of the plasmid characteristics and behaviour can allow development of control strategies. Here we focus on the IncX group of plasmids carrying genes conferring quinolone resistance (PMQR), reporting their transfer and persistence within host bacteria of various genotypes under distinct conditions and levels of induced stress in form of temperature change and various concentrations of ciprofloxacin supplementation. Methods Complete nucleotide sequences were determined for eight qnr-carrying IncX-type plasmids, of IncX1 (3), IncX2 (3) and a hybrid IncX1-2 (2) types, recovered from Escherichia coli of various origins. This data was compared with further complete sequences of IncX1 and IncX2 plasmids carrying qnr genes (n = 41) retrieved from GenBank and phylogenetic tree was constructed. Representatives of IncX1 (pHP2) and IncX2 (p194) and their qnrS knockout mutants, were studied for influence of induced stress and genetic background on conjugative transfer and maintenance. Results A high level of IncX core-genome similarity was found in plasmids of animal, environmental and clinical origin. Significant differences were found between the individual IncX plasmids, with IncX1 subgroup plasmids showing higher conjugative transfer rates than IncX2 plasmids. Knockout of qnr modified transfer frequency of both plasmids. Two stresses applied simultaneously were needed to affect transfer rate of wildtype plasmids, whereas a single stress was sufficient to affect the IncX ΔqnrS plasmids. The conjugative transfer was shown to be biased towards the host phylogenetic proximity. A long-term cultivation experiment pointed out the persistence of IncX plasmids in the antibiotic-free environment. Conclusions The study indicated the stimulating effect of ciprofloxacin supplementation on the plasmid transfer that can be nullified by the carriage of a single PMQR gene. The findings present the significant properties and behaviour of IncX plasmids carrying antibiotic resistance genes that are likely to play a role in their dissemination and stability in bacterial populations. Supplementary Information The online version contains supplementary material available at 10.1186/s12866-022-02546-6.
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Affiliation(s)
- Tomas Nohejl
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic.,CEITEC, University of Veterinary Sciences Brno, Brno, Czech Republic
| | - Adam Valcek
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic.,CEITEC, University of Veterinary Sciences Brno, Brno, Czech Republic.,Faculty of Medicine, Biomedical Center, Charles University, Pilsen, Czech Republic
| | - Ivo Papousek
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic
| | - Jana Palkovicova
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic.,CEITEC, University of Veterinary Sciences Brno, Brno, Czech Republic
| | - Alexander M Wailan
- Parasites and Microbes, Wellcome Trust Sanger Institute, Wellcome Genome Campus, Hinxton, CB10 1SA, UK
| | - Hana Pratova
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic.,CEITEC, University of Veterinary Sciences Brno, Brno, Czech Republic
| | - Marco Minoia
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic.,CEITEC, University of Veterinary Sciences Brno, Brno, Czech Republic
| | - Monika Dolejska
- Department of Biology and Wildlife Diseases, Faculty of Veterinary Hygiene and Ecology, University of Veterinary Sciences Brno, Brno, Czech Republic. .,CEITEC, University of Veterinary Sciences Brno, Brno, Czech Republic. .,Faculty of Medicine, Biomedical Center, Charles University, Pilsen, Czech Republic. .,Department of Clinical Microbiology and Immunology, Institute of Laboratory Medicine, The University Hospital Brno, Brno, Czech Republic.
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Moreno-Mingorance A, Espinal P, Rodriguez V, Goterris L, Fàbrega A, Serra-Pladevall J, Barberà MJ, Alberny M, Martín-González H, Cornejo-Sánchez T, Armas M, Mir-Cros A, Raventós A, Viñado B, Pumarola T, Larrosa MN, González-López JJ. Circulation of multi-drug-resistant Shigella sonnei and Shigella flexneri among men who have sex with men in Barcelona, Spain, 2015-2019. Int J Antimicrob Agents 2021; 58:106378. [PMID: 34157402 DOI: 10.1016/j.ijantimicag.2021.106378] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2021] [Revised: 05/20/2021] [Accepted: 06/13/2021] [Indexed: 01/08/2023]
Abstract
BACKGROUND In high-income countries, shigellosis is mainly found in travellers to high-risk regions or in men who have sex with men (MSM). This study investigated the genomic characteristics and the features of antimicrobial resistance of MSM-associated Shigella flexneri and Shigella sonnei circulating in Barcelona, Spain, elucidating their connectivity with contemporaneous Shigella spp. from other countries. METHODS Antimicrobial susceptibility, whole-genome sequencing, genomic characterization and phylogenetic analysis were performed in MSM-associated Shigella spp. recovered from 2015 to 2019. Reference genomes of MSM-associated Shigella spp. were included for contextualization and to determine their connection with international outbreaks. RESULTS In total, 44 S. flexneri and 26 S. sonnei were identified among MSM. Overall, 80% showed resistance to azithromycin, 65.7% showed resistance to trimethoprim-sulphamethoxazole and 32.8% showed resistance to ciprofloxacin; 27.1% were resistant to all three antimicrobials. mphA and/or ermB, and qnrS and mutations in the quinolone resistance determining regions were found in the azithromycin- and ciprofloxacin-resistant isolates, respectively. Additionally, two isolates carried blaCTX-M-27. Single-nucleotide-polymorphism-based analysis revealed that the isolates were organized into different lineages, most of which were closely related to dominant MSM-associated lineages described previously in the UK and Australia. CONCLUSIONS This study investigated the circulation of lineages of S. flexneri and S. sonnei among MSM in Spain that were mainly resistant to first-/second-line oral treatments, and closely related to dominant MSM-associated lineages described previously in the UK and Australia. These data reinforce the urgent need for the implementation of public health measures focusing on the early detection and prevention of transmission of this emerging pathogen, which is contributing to the antimicrobial resistance crisis in sexually transmitted infections.
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Affiliation(s)
- Albert Moreno-Mingorance
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Paula Espinal
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain
| | - Virginia Rodriguez
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - Lidia Goterris
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - Anna Fàbrega
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - Judit Serra-Pladevall
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - M Jesús Barberà
- Drassanes-Vall d'Hebron Sexually Transmitted Infections Unit, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - Mireia Alberny
- Primary Healthcare Division, Catalan Institute of Health, Barcelona, Spain
| | - Héctor Martín-González
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain
| | - Thais Cornejo-Sánchez
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain
| | - Mayuli Armas
- Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - Alba Mir-Cros
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Alex Raventós
- Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain
| | - Belén Viñado
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - Tomàs Pumarola
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain
| | - M Nieves Larrosa
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain.
| | - Juan José González-López
- Vall d'Hebron Institut de Recerca, Vall d'Hebron Hospital Universitari, Vall d'Hebron Barcelona Hospital Campus, Barcelona, Spain; Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Barcelona, Spain; Department of Clinical Microbiology, Vall d'Hebron Hospital Universitari, Barcelona, Spain.
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Wang P, Hu L, Hao Z. Palmatine Is a Plasmid-Mediated Quinolone Resistance (PMQR) Inhibitor That Restores the Activity of Ciprofloxacin Against QnrS and AAC(6')-Ib-cr-Producing Escherichia coli. Infect Drug Resist 2020; 13:749-759. [PMID: 32210589 PMCID: PMC7069587 DOI: 10.2147/idr.s242304] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 02/13/2020] [Indexed: 12/12/2022] Open
Abstract
Purpose The emergence of plasmid-mediated quinolone resistance (PMQR) is a global challenge in the treatment of clinical disease in both humans and animals and is exacerbated by the presence of different PMQR genes existing in the same bacterial strain. Here, we discovered that a natural isoquinoline alkaloid palmatine extracted from traditional Chinese medicinal plants effectively inhibited the activity of PMQR proteins QnrS and AAC(6′)-Ib-cr. Methods In total 120 clinical ciprofloxacin-resistant Escherichia coli (E. coli) were screened for the presence of qnrS and aac(6ʹ)-Ib-cr by PCR. Recombinant E. coli that produced QnrS or AAC(6ʹ)-Ib-cr proteins were constructed and the correct expression was confirmed by MALDI/TOF MS analysis and SDS-PAGE. A minimal inhibitory concentration (MICs) assay, growth curve assay and time-kill assay were conducted to evaluate the in vitro antibacterial activity of palmatine and the combination of palmatine and ciprofloxacin. Cytotoxicity assays and mouse thigh infection model were used to evaluate the in vivo synergies. Molecular docking, gyrase supercoiling assay and acetylation assay were used to clarify the mechanism of action. Results Palmatine effectively restored the activity of ciprofloxacin against qnrS and aac(6ʹ)-Ib-cr-positive E. coli strains in a synergistic manner in vitro. In addition, the combined therapy significantly reduced the bacterial burden in a mouse thigh infection model. Molecular docking revealed that palmatine bound at the functional large loop B of QnrS and Trp102Arg and Asp179Tyr in the binding pocket of AAC(6′)-Ib-cr. Furthermore, interaction analysis confirmed that palmatine reduced the gyrase protective effect of QnrS and the acetylation effect of AAC(6′)-Ib-cr. Conclusion Our findings suggest that palmatine is a potential efficacious compound to restore PMQR-mediated ciprofloxacin resistance and warrants further preclinical evaluations.
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Affiliation(s)
- Peng Wang
- Agricultural Bio-Pharmaceutical Laboratory, Qingdao Agricultural University, Qingdao 266109, People's Republic of China
| | - Longfei Hu
- Agricultural Bio-Pharmaceutical Laboratory, Qingdao Agricultural University, Qingdao 266109, People's Republic of China
| | - Zhihui Hao
- National Centre for Veterinary Drug Safety Evaluation, College of Veterinary Medicine, China Agricultural University, Beijing 100089, People's Republic of China
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Nisa I, Qasim M, Yasin N, Ullah R, Ali A. Shigella flexneri: an emerging pathogen. Folia Microbiol (Praha) 2020; 65:275-291. [PMID: 32026288 DOI: 10.1007/s12223-020-00773-w] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 01/16/2020] [Indexed: 12/19/2022]
Abstract
Shigella flexneri is a leading etiologic agent of diarrhea in low socioeconomic countries. Notably, various serotypes in S. flexneri are reported from different regions of the world. The precise approximations of illness and death owing to shigellosis are missing in low socioeconomic countries, although it is widespread in different regions. The inadequate statistics available reveal S. flexneri to be a significant food and waterborne pathogen. All over the world, different antibiotic-resistant strains of S. flexneri serotypes have been emerged especially multidrug-resistant strains. Recently, increased resistance was observed in cephalosporins (3rd generation), azithromycin, and fluoroquinolones. There is a need for a continuous surveillance study on antibiotic resistance that will be helpful in the update of the antibiogram. The shigellosis burden can be reduced by adopting preventive measures like delivery of safe drinking water, suitable sanitation, and development of an effective and inexpensive multivalent vaccine. This review attempts to provide the recent findings of S. flexneri related to epidemiology and the emergence of multidrug resistance.
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Affiliation(s)
- Iqbal Nisa
- Department of Microbiology, Kohat University of Science and Technology, Kohat, Pakistan.
| | - Muhammad Qasim
- Department of Microbiology, Kohat University of Science and Technology, Kohat, Pakistan
| | - Nusrat Yasin
- Department of Microbiology, Kohat University of Science and Technology, Kohat, Pakistan
| | - Rafi Ullah
- Bacteriology Laboratory Center of Microbiology and Bacteriology (CMB) Veterinary Research Institute, Peshawar, Pakistan
| | - Anwar Ali
- Bacteriology Laboratory Center of Microbiology and Bacteriology (CMB) Veterinary Research Institute, Peshawar, Pakistan
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Ranjbar R, Farahani A. Shigella: Antibiotic-Resistance Mechanisms And New Horizons For Treatment. Infect Drug Resist 2019; 12:3137-3167. [PMID: 31632102 PMCID: PMC6789722 DOI: 10.2147/idr.s219755] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Accepted: 08/28/2019] [Indexed: 12/17/2022] Open
Abstract
Shigella spp. are a common cause of diarrheal disease and have remained an important pathogen responsible for increased rates of morbidity and mortality caused by dysentery each year around the globe. Antibiotic treatment of Shigella infections plays an essential role in reducing prevalence and death rates of the disease. However, treatment of these infections remains a challenge, due to the global rise in broad-spectrum resistance to many antibiotics. Drug resistance in Shigella spp. can result from many mechanisms, such as decrease in cellular permeability, extrusion of drugs by active efflux pumps, and overexpression of drug-modifying and -inactivating enzymes or target modification by mutation. Therefore, there is an increasing need for identification and evolution of alternative therapeutic strategies presenting innovative avenues against Shigella infections, as well as paying further attention to this infection. The current review focuses on various antibiotic-resistance mechanisms of Shigella spp. with a particular emphasis on epidemiology and new mechanisms of resistance and their acquisition, and also discusses the status of novel strategies for treatment of Shigella infection and vaccine candidates currently under evaluation in preclinical or clinical phases.
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Affiliation(s)
- Reza Ranjbar
- Molecular Biology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Abbas Farahani
- Molecular Biology Research Center, Systems Biology and Poisonings Institute, Baqiyatallah University of Medical Sciences, Tehran, Iran
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Zhang WX, Chen HY, Tu LH, Xi MF, Chen M, Zhang J. Fluoroquinolone Resistance Mechanisms in Shigella Isolates in Shanghai, China, Between 2010 and 2015. Microb Drug Resist 2018; 25:212-218. [PMID: 30307807 DOI: 10.1089/mdr.2018.0113] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES This study aimed to investigate the antimicrobial susceptibility of Shigella isolated in Shanghai, China and to determine the genetic basis of its resistance to fluoroquinolones. MATERIALS AND METHODS A total of 402 strains of Shigella, including 145 Shigella flexneri and 257 Shigella sonnei isolates, were analyzed. The Kirby-Bauer disk diffusion method was used to determine the susceptibility of the strains to 13 antimicrobials. Minimum inhibitory concentration of ciprofloxacin was determined by E-test. Mutations within the quinolone resistance-determining regions (QRDRs) of gyrA and parC and in the plasmid-mediated quinolone resistance (PMQR) genes, including qnrA, qnrB, qnrS, and aac (6')-Ib-cr, were detected by polymerase chain reaction. All the products were then sequenced. RESULTS Most of the Shigella isolates were found to be resistant to nalidixic acid (96.4%), streptomycin (96.4%), ampicillin (86.2%), tetracycline (79.8%), and sulfamethoxazole/trimethoprim (80.6%). S. flexneri isolates showed a significantly higher resistance to cefepime (33.6%), ciprofloxacin (54.2%), norfloxacin (34.1%), and levofloxacin (12.1%) compared with that observed for the S. sonnei strains (χ2 analysis, p < 0.05). Three mutations (Ser83, Asp87, and His211) in gyrA and one mutation (Ser80) in parC were detected. Of 257 S. sonnei isolates, 11.7% possessed gyrA mutations and 2% had parC mutations. Of 145 S. flexneri isolates, 98.6% possessed gyrA mutations and 97.9% had parC mutations. The plasmid-mediated resistance genes of qnrS and aac (6')-Ib-cr were detected among 17 strains (4.2%). CONCLUSIONS The mutation percentage within the QRDR of S. flexneri was as high as 98.6 in gyrA and 97.9 in parC. The significant abundance of mutations within QRDRs conferred high levels of fluoroquinolone resistance. Moreover, the PMQR genes, particularly qnrS, played an important role in the decreased susceptibility of Shigella to fluoroquinolones.
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Affiliation(s)
- Wen-Xia Zhang
- 1 Department of Clinical Laboratory, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine , Shanghai, China
| | - Hong-You Chen
- 2 Laboratory of Bacterial, Shanghai Center for Disease Control and Prevention , Shanghai, China
| | - Li-Hong Tu
- 2 Laboratory of Bacterial, Shanghai Center for Disease Control and Prevention , Shanghai, China
| | - Man-Fang Xi
- 2 Laboratory of Bacterial, Shanghai Center for Disease Control and Prevention , Shanghai, China
| | - Min Chen
- 2 Laboratory of Bacterial, Shanghai Center for Disease Control and Prevention , Shanghai, China
| | - Jue Zhang
- 1 Department of Clinical Laboratory, Shuguang Hospital Affiliated to Shanghai University of Traditional Chinese Medicine , Shanghai, China
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