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d'Udekem d'Acoz O, Hue F, Ye T, Wang L, Leroux M, Rajngewerc L, Tran T, Phan K, Ramirez MS, Reisner W, Tolmasky ME, Reyes-Lamothe R. Dynamics and quantitative contribution of the aminoglycoside 6'- N-acetyltransferase type Ib to amikacin resistance. mSphere 2024; 9:e0078923. [PMID: 38353533 DOI: 10.1128/msphere.00789-23] [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: 12/18/2023] [Accepted: 01/09/2024] [Indexed: 02/27/2024] Open
Abstract
Aminoglycosides are essential components in the available armamentarium to treat bacterial infections. The surge and rapid dissemination of resistance genes strongly reduce their efficiency, compromising public health. Among the multitude of modifying enzymes that confer resistance to aminoglycosides, the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib] is the most prevalent and relevant in the clinical setting as it can inactivate numerous aminoglycosides, such as amikacin. Although the mechanism of action, structure, and biochemical properties of the AAC(6')-Ib protein have been extensively studied, the contribution of the intracellular milieu to its activity remains unclear. In this work, we used a fluorescent-based system to quantify the number of AAC(6')-Ib per cell in Escherichia coli, and we modulated this copy number with the CRISPR interference method. These tools were then used to correlate enzyme concentrations with amikacin resistance levels. Our results show that resistance to amikacin increases linearly with a higher concentration of AAC(6')-Ib until it reaches a plateau at a specific protein concentration. In vivo imaging of this protein shows that it diffuses freely within the cytoplasm of the cell, but it tends to form inclusion bodies at higher concentrations in rich culture media. Addition of a chelating agent completely dissolves these aggregates and partially prevents the plateau in the resistance level, suggesting that AAC(6')-Ib aggregation lowers resistance to amikacin. These results provide the first step in understanding the cellular impact of each AAC(6')-Ib molecule on aminoglycoside resistance. They also highlight the importance of studying its dynamic behavior within the cell.IMPORTANCEAntibiotic resistance is a growing threat to human health. Understanding antibiotic resistance mechanisms can serve as foundation for developing innovative treatment strategies to counter this threat. While numerous studies clarified the genetics and dissemination of resistance genes and explored biochemical and structural features of resistance enzymes, their molecular dynamics and individual contribution to resistance within the cellular context remain unknown. Here, we examined this relationship modulating expression levels of aminoglycoside 6'-N-acetyltransferase type Ib, an enzyme of clinical relevance. We show a linear correlation between copy number of the enzyme per cell and amikacin resistance levels up to a threshold where resistance plateaus. We propose that at concentrations below the threshold, the enzyme diffuses freely in the cytoplasm but aggregates at the cell poles at concentrations over the threshold. This research opens promising avenues for studying enzyme solubility's impact on resistance, creating opportunities for future approaches to counter resistance.
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Affiliation(s)
| | - Fong Hue
- Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
| | - Tianyi Ye
- Department of Biology, McGill University, Montréal, Québec, Canada
| | - Louise Wang
- Department of Biology, McGill University, Montréal, Québec, Canada
| | - Maxime Leroux
- Department of Biology, McGill University, Montréal, Québec, Canada
| | - Lucila Rajngewerc
- Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
| | - Tung Tran
- Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
| | - Kimberly Phan
- Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
| | - Maria S Ramirez
- Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
| | - Walter Reisner
- Department of Physics, McGill University, Montréal, Québec, Canada
| | - Marcelo E Tolmasky
- Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, California, USA
- Department of Biological Science, California State University Fullerton, Fullerton, California, USA
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d'Acoz OD, Hue F, Ye T, Wang L, Leroux M, Rajngewerc L, Tran T, Phan K, Ramirez MS, Reisner W, Tolmasky ME, Reyes-Lamothe R. Dynamics and quantitative contribution of the aminoglycoside 6'- N-acetyltransferase type Ib [AAC(6')-Ib] to amikacin resistance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.05.556435. [PMID: 38168340 PMCID: PMC10760054 DOI: 10.1101/2023.09.05.556435] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Aminoglycosides are essential components in the available armamentarium to treat bacterial infections. The surge and rapid dissemination of resistance genes strongly reduce their efficiency, compromising public health. Among the multitude of modifying enzymes that confer resistance to aminoglycosides, the aminoglycoside acetyltransferase AAC(6')-Ib is the most prevalent and relevant in the clinical setting as it can inactivate numerous aminoglycosides, such as amikacin. Although the mechanism of action, structure, and biochemical properties of the AAC(6')-Ib protein have been extensively studied, the contribution of the intracellular milieu to its activity remains unclear. In this work, we used a fluorescent-based system to quantify the number of AAC(6')-Ib per cell in Escherichia coli, and we modulated this copy number with the CRISPR interference method. These tools were then used to correlate enzyme concentrations with amikacin resistance levels. Our results show that resistance to amikacin increases linearly with a higher concentration of AAC(6')-Ib until it reaches a plateau at a specific protein concentration. In vivo imaging of this protein shows that it diffuses freely within the cytoplasm of the cell, but it tends to form inclusion bodies at higher concentrations in rich culture media. Addition of a chelating agent completely dissolves these aggregates and partially prevents the plateau in the resistance level, suggesting that AAC(6')-Ib aggregation lowers resistance to amikacin. These results provide the first step in understanding the cellular impact of each AAC(6')-Ib molecule on aminoglycoside resistance. They also highlight the importance of studying its dynamic behavior within the cell.
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Affiliation(s)
- Ophélie d'Udekem d'Acoz
- Department of Biology, McGill University, 3649 Sir William Osler, Montréal, Québec, H3G 0B1, Canada
| | - Fong Hue
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, California
| | - Tianyi Ye
- Department of Biology, McGill University, 3649 Sir William Osler, Montréal, Québec, H3G 0B1, Canada
| | - Louise Wang
- Department of Biology, McGill University, 3649 Sir William Osler, Montréal, Québec, H3G 0B1, Canada
| | - Maxime Leroux
- Department of Biology, McGill University, 3649 Sir William Osler, Montréal, Québec, H3G 0B1, Canada
| | - Lucila Rajngewerc
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, California
| | - Tung Tran
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, California
| | - Kimberly Phan
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, California
| | - Maria S Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, California
| | - Walter Reisner
- Department of Physics, McGill University, 3600 rue université, Montréal, Québec, H3A 2T8, Canada
| | - Marcelo E Tolmasky
- Center for Applied Biotechnology Studies, Department of Biological Science, California State University Fullerton, Fullerton, California
| | - Rodrigo Reyes-Lamothe
- Department of Biology, McGill University, 3649 Sir William Osler, Montréal, Québec, H3G 0B1, Canada
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Rajput MI, Verma NK. Identification of critical residues of O-antigen-modifying O-acetyltransferase B (OacB) of Shigella flexneri. BMC Mol Cell Biol 2022; 23:16. [PMID: 35331134 PMCID: PMC8952252 DOI: 10.1186/s12860-022-00415-8] [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: 06/23/2021] [Accepted: 03/09/2022] [Indexed: 11/25/2022] Open
Abstract
Background Shigellosis is an acute gastrointestinal disease caused primarily by the bacterium Shigella flexneri. Upon ingestion, S. flexneri initiates a serotype-specific immune response that targets the O-antigen of the pathogen’s lipopolysaccharide. O-antigen subunits are modified by the addition of chemical moieties, which give rise to new serotypes of S. flexneri. Nineteen different serotypes of S. flexneri have been recognized. A recently identified O-antigen-modifying enzyme, O-acetyltransferase B (OacB), which adds an acetyl residue at either position 3 or 4 of RhamnoseIII (3/4-O-acetylation) in serotypes 1a, 1b, 2a, 5a, 7a, Y, and 6 and position 6 of N- acetylglucosamine (6-O-acetylation) in serotypes 2a, 3a, Y and Yv of the O-antigen subunits. Critical residues in other proteins involved in O-antigen modifications such as glucosyltransferases (Gtrs) and acetyltransferase (Oac) of S. flexneri have been identified, whereas identification of important amino acids in OacB function is yet to be determined. Results Hydrophobicity analysis showed that OacB is a transmembrane protein with 11 transmembrane segments, 12 loops, and periplasmic N- and cytoplasmic C- termini. Bioinformatics analyses revealed that OacB contains acetyltransferase-3 domain and several conserved residues. Using site-directed mutagenesis, selected amino acids were mutated to alanine to elucidate their role in the mechanism of action of OacB. Seven amino acids R47, H58, F98, W71, R116, R119, and S146 were found critical for the OacB function. Conclusion In the absence of a three-dimensional structure of the serotype converting enzyme, O-acetyltransferase B (OacB), a clear role of important residues in the mechanism of action is precluded. Therefore, in this study, using site-directed mutagenesis, seven residues critical to the function of OacB were identified. The lack of agglutination of cell expressing mutant OacB in the presence of the antiserum indicated the functional role of the corresponding residues. Hence, this study provides significant information about key residues in OacB which might be involved in forming the catalytic sites of this O-antigen modifying enzyme of S. flexneri. Supplementary Information The online version contains supplementary material available at 10.1186/s12860-022-00415-8.
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Affiliation(s)
- Munazza I Rajput
- Division of Biomedical Science and Biochemistry, Research School of Biology, The Australian National University, Bldg.134, Linnaeus Way, Canberra, ACT, 2601, Australia
| | - Naresh K Verma
- Division of Biomedical Science and Biochemistry, Research School of Biology, The Australian National University, Bldg.134, Linnaeus Way, Canberra, ACT, 2601, Australia.
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Ramirez MS, Iriarte A, Reyes-Lamothe R, Sherratt DJ, Tolmasky ME. Small Klebsiella pneumoniae Plasmids: Neglected Contributors to Antibiotic Resistance. Front Microbiol 2019; 10:2182. [PMID: 31616398 PMCID: PMC6764390 DOI: 10.3389/fmicb.2019.02182] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2019] [Accepted: 09/05/2019] [Indexed: 12/15/2022] Open
Abstract
Klebsiella pneumoniae is the causative agent of community- and, more commonly, hospital-acquired infections. Infections caused by this bacterium have recently become more dangerous due to the acquisition of multiresistance to antibiotics and the rise of hypervirulent variants. Plasmids usually carry genes coding for resistance to antibiotics or virulence factors, and the recent sequence of complete K. pneumoniae genomes showed that most strains harbor many of them. Unlike large plasmids, small, usually high copy number plasmids, did not attract much attention. However, these plasmids may include genes coding for specialized functions, such as antibiotic resistance, that can be expressed at high levels due to gene dosage effect. These genes may be part of mobile elements that not only facilitate their dissemination but also participate in plasmid evolution. Furthermore, high copy number plasmids may also play a role in evolution by allowing coexistence of mutated and non-mutated versions of a gene, which helps to circumvent the constraints imposed by trade-offs after certain genes mutate. Most K. pneumoniae plasmids 25-kb or smaller replicate by the ColE1-type mechanism and many of them are mobilizable. The transposon Tn1331 and derivatives were found in a high percentage of these plasmids. Another transposon that was found in representatives of this group is the bla KPC-containing Tn4401. Common resistance determinants found in these plasmids were aac(6')-Ib and genes coding for β-lactamases including carbapenemases.
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Affiliation(s)
- Maria S. Ramirez
- Center for Applied Biotechnology Studies, Department of Biological Sciences, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States
| | - Andrés Iriarte
- Laboratorio de Biología Computacional, Departamento de Desarrollo Biotecnológico, Facultad de Medicina, Universidad de la República de Uruguay, Montevideo, Uruguay
| | | | - David J. Sherratt
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
| | - Marcelo E. Tolmasky
- Center for Applied Biotechnology Studies, Department of Biological Sciences, College of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, CA, United States
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
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Insights into the Function of the N-Acetyltransferase SatA That Detoxifies Streptothricin in Bacillus subtilis and Bacillus anthracis. Appl Environ Microbiol 2019; 85:AEM.03029-18. [PMID: 30658980 DOI: 10.1128/aem.03029-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 01/09/2019] [Indexed: 11/20/2022] Open
Abstract
Acylation of epsilon amino groups of lysyl side chains is a widespread modification of proteins and small molecules in cells of all three domains of life. Recently, we showed that Bacillus subtilis and Bacillus anthracis encode the GCN5-related N-acetyltransferase (GNAT) SatA that can acetylate and inactivate streptothricin, which is a broad-spectrum antibiotic produced by actinomycetes in the soil. To determine functionally relevant residues of B. subtilis SatA (BsSatA), a mutational screen was performed, highlighting the importance of a conserved area near the C terminus. Upon inspection of the crystal structure of the B. anthracis Ames SatA (BaSatA; PDB entry 3PP9), this area appears to form a pocket with multiple conserved aromatic residues; we hypothesized this region contains the streptothricin-binding site. Chemical and site-directed mutagenesis was used to introduce missense mutations into satA, and the functionality of the variants was assessed using a heterologous host (Salmonella enterica). Results of isothermal titration calorimetry experiments showed that residue Y164 of BaSatA was important for binding streptothricin. Results of size exclusion chromatography analyses showed that residue D160 was important for dimerization. Together, these data advance our understanding of how SatA interacts with streptothricin.IMPORTANCE This work provides insights into how an abundant antibiotic found in soil is bound to the enzyme that inactivates it. This work identifies residues for the binding of the antibiotic and probes the contributions of substituting side chains for those in the native protein, providing information regarding hydrophobicity, size, and flexibility of the antibiotic binding site.
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Smith CA, Bhattacharya M, Toth M, Stewart NK, Vakulenko SB. Aminoglycoside resistance profile and structural architecture of the aminoglycoside acetyltransferase AAC(6')-Im. MICROBIAL CELL 2017; 4:402-410. [PMID: 29234669 PMCID: PMC5722643 DOI: 10.15698/mic2017.12.602] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Aminoglycoside 6'-acetyltransferase-Im (AAC(6')-Im) is the closest monofunctional homolog of the AAC(6')-Ie acetyltransferase of the bifunctional enzyme AAC(6')-Ie/APH(2")-Ia. The AAC(6')-Im acetyltransferase confers 4- to 64-fold higher MICs to 4,6-disubstituted aminoglycosides and the 4,5-disubstituted aminoglycoside neomycin than AAC(6')-Ie, yet unlike AAC(6')-Ie, the AAC(6')-Im enzyme does not confer resistance to the atypical aminoglycoside fortimicin. The structure of the kanamycin A complex of AAC(6')-Im shows that the substrate binds in a shallow positively-charged pocket, with the N6' amino group positioned appropriately for an efficient nucleophilic attack on an acetyl-CoA cofactor. The AAC(6')-Ie enzyme binds kanamycin A in a sufficiently different manner to position the N6' group less efficiently, thereby reducing the activity of this enzyme towards the 4,6-disubstituted aminoglycosides. Conversely, docking studies with fortimicin in both acetyltransferases suggest that the atypical aminoglycoside might bind less productively in AAC(6')-Im, thus explaining the lack of resistance to this molecule.
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Affiliation(s)
- Clyde A Smith
- Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, Menlo Park, CA 94025, USA
| | - Monolekha Bhattacharya
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Marta Toth
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Nichole K Stewart
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Sergei B Vakulenko
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
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7
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Paiva MC, Reis MP, Costa PS, Dias MF, Bleicher L, Scholte LLS, Nardi RMD, Nascimento AMA. Identification of new bacteria harboring qnrS and aac(6')-Ib/cr and mutations possibly involved in fluoroquinolone resistance in raw sewage and activated sludge samples from a full-scale WWTP. WATER RESEARCH 2017; 110:27-37. [PMID: 27984803 DOI: 10.1016/j.watres.2016.11.056] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/22/2016] [Accepted: 11/23/2016] [Indexed: 06/06/2023]
Abstract
Wastewater treatment plants (WWTPs) harbor bacteria and antimicrobial resistance genes, favoring gene exchange events and resistance dissemination. Here, a culture-based and metagenomic survey of qnrA, qnrB, qnrS, and aac(6')-Ib genes from raw sewage (RS) and activated sludge (AS) of a full-scale municipal WWTP was performed. A total of 96 bacterial isolates were recovered from nalidixic acid-enrichment cultures. Bacteria harboring the aac(6')-Ib gene predominated in RS, whereas qnrS-positive isolates were specific to AS. Novel qnrS- and aac(6')-Ib-cr positive species were identified: Morganella morganii, Providencia rettgeri, and Pseudomonas guangdongensis (qnrS), and Alcaligenes faecalis and P. rettgeri (aac(6')-Ib-cr). Analysis of qnrS and aac(6')-Ib sequences from isolates and clone libraries suggested that the diversity of qnrS is wider than that of aac(6')-Ib. A large number of amino acid mutations were observed in the QnrS and AAC(6')-Ib proteins at previously undetected positions, whose structural implications are not clear. An accumulation of mutations at the C72, Q73, L74, A75 and M76 positions of QnrS, and D181 of AAC(6')-Ib might be important for resistance. These findings add significant information on bacteria harboring qnrS and aac(6')-Ib genes, and the presence of novel mutations that may eventually emerge in clinical isolates.
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Affiliation(s)
- Magna C Paiva
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil; Campus Dona Lindu, Universidade Federal de São João del Rei, Divinópolis, Minas Gerais, Brazil
| | - Mariana P Reis
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Patrícia S Costa
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Marcela F Dias
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Lucas Bleicher
- Departamento de Bioquímica e Imunologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Larissa L S Scholte
- Centro de Pesquisas René Rachou - FIOCRUZ, Belo Horizonte, Minas Gerais, Brazil
| | - Regina M D Nardi
- Departamento de Microbiologia, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Andréa M A Nascimento
- Departamento de Biologia Geral, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
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Stogios PJ, Kuhn ML, Evdokimova E, Law M, Courvalin P, Savchenko A. Structural and Biochemical Characterization of Acinetobacter spp. Aminoglycoside Acetyltransferases Highlights Functional and Evolutionary Variation among Antibiotic Resistance Enzymes. ACS Infect Dis 2017; 3:132-143. [PMID: 27785912 DOI: 10.1021/acsinfecdis.6b00058] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Modification of aminoglycosides by N-acetyltransferases (AACs) is one of the major mechanisms of resistance to these antibiotics in human bacterial pathogens. More than 50 enzymes belonging to the AAC(6') subfamily have been identified in Gram-negative and Gram-positive clinical isolates. Our understanding of the molecular function and evolutionary origin of these resistance enzymes remains incomplete. Here we report the structural and enzymatic characterization of AAC(6')-Ig and AAC(6')-Ih from Acinetobacter spp. The crystal structure of AAC(6')-Ig in complex with tobramycin revealed a large substrate-binding cleft remaining partially unoccupied by the substrate, which is in stark contrast with the previously characterized AAC(6')-Ib enzyme. Enzymatic analysis indicated that AAC(6')-Ig and -Ih possess a broad specificity against aminoglycosides but with significantly lower turnover rates as compared to other AAC(6') enzymes. Structure- and function-informed phylogenetic analysis of AAC(6') enzymes led to identification of at least three distinct subfamilies varying in oligomeric state, active site composition, and drug recognition mode. Our data support the concept of AAC(6') functionality originating through convergent evolution from diverse Gcn5-related-N-acetyltransferase (GNAT) ancestral enzymes, with AAC(6')-Ig and -Ih representing enzymes that may still retain ancestral nonresistance functions in the cell as provided by their particular active site properties.
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Affiliation(s)
- Peter J. Stogios
- Department of Chemical
Engineering and Applied Chemistry, University of Toronto, 200 College
Street, Toronto, Ontario M5G 1L6, Canada
| | - Misty L. Kuhn
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, United States
| | - Elena Evdokimova
- Department of Chemical
Engineering and Applied Chemistry, University of Toronto, 200 College
Street, Toronto, Ontario M5G 1L6, Canada
| | - Melissa Law
- Department of Chemistry and Biochemistry, San Francisco State University, San Francisco, California 94132, United States
| | - Patrice Courvalin
- Institut Pasteur, Unité des Agents Antibactériens, 25 rue du Docteur Roux, 75724 Cedex 15 Paris, France
| | - Alexei Savchenko
- Department of Chemical
Engineering and Applied Chemistry, University of Toronto, 200 College
Street, Toronto, Ontario M5G 1L6, Canada
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9
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Guérin F. Infections à Enterobacter cloacae complex : résistance aux antibiotiques et traitement. ACTA ACUST UNITED AC 2015. [DOI: 10.1016/j.antinf.2015.03.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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10
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Increased prevalence of aminoglycoside resistance in clinical isolates of Escherichia coli and Klebsiella spp. in Norway is associated with the acquisition of AAC(3)-II and AAC(6′)-Ib. Diagn Microbiol Infect Dis 2014; 78:66-9. [DOI: 10.1016/j.diagmicrobio.2013.10.001] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2013] [Revised: 09/17/2013] [Accepted: 10/02/2013] [Indexed: 11/19/2022]
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Ramirez MS, Nikolaidis N, Tolmasky ME. Rise and dissemination of aminoglycoside resistance: the aac(6')-Ib paradigm. Front Microbiol 2013; 4:121. [PMID: 23730301 PMCID: PMC3656343 DOI: 10.3389/fmicb.2013.00121] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 04/29/2013] [Indexed: 11/21/2022] Open
Abstract
Enzymatic modification is a prevalent mechanism by which bacteria defeat the action of antibiotics. Aminoglycosides are often inactivated by aminoglycoside modifying enzymes encoded by genes present in the chromosome, plasmids, and other genetic elements. The AAC(6′)-Ib (aminoglycoside 6′-N-acetyltransferase type Ib) is an enzyme of clinical importance found in a wide variety of gram-negative pathogens. The AAC(6′)-Ib enzyme is of interest not only because of his ubiquity but also because of other characteristics, it presents significant microheterogeneity at the N-termini and the aac(6′)-Ib gene is often present in integrons, transposons, plasmids, genomic islands, and other genetic structures. Excluding the highly heterogeneous N-termini, there are 45 non-identical AAC(6′)-Ib related entries in the NCBI database, 32 of which have identical name in spite of not having identical amino acid sequence. While some variants conserved similar properties, others show dramatic differences in specificity, including the case of AAC(6′)-Ib-cr that mediates acetylation of ciprofloxacin representing a rare case where a resistance enzyme acquires the ability to utilize an antibiotic of a different class as substrate. Efforts to utilize antisense technologies to turn off expression of the gene or to identify enzymatic inhibitors to induce phenotypic conversion to susceptibility are under way.
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Affiliation(s)
- María S Ramirez
- Department of Biological Science, Center for Applied Biotechnology Studies, College of Natural Sciences and Mathematics, California State University Fullerton Fullerton, CA, USA
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12
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Romanowska J, Reuter N, Trylska J. Comparing aminoglycoside binding sites in bacterial ribosomal RNA and aminoglycoside modifying enzymes. Proteins 2012; 81:63-80. [PMID: 22907688 DOI: 10.1002/prot.24163] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 08/02/2012] [Accepted: 08/09/2012] [Indexed: 11/10/2022]
Abstract
Aminoglycoside antibiotics are used against severe bacterial infections. They bind to the bacterial ribosomal RNA and interfere with the translation process. However, bacteria produce aminoglycoside modifying enzymes (AME) to resist aminoglycoside actions. AMEs form a variable group and yet they specifically recognize and efficiently bind aminoglycosides, which are also diverse in terms of total net charge and the number of pseudo-sugar rings. Here, we present the results of 25 molecular dynamics simulations of three AME representatives and aminoglycoside ribosomal RNA binding site, unliganded and complexed with an aminoglycoside, kanamycin A. A comparison of the aminoglycoside binding sites in these different receptors revealed that the enzymes efficiently mimic the nucleic acid environment of the ribosomal RNA binding cleft. Although internal dynamics of AMEs and their interaction patterns with aminoglycosides differ, the energetical analysis showed that the most favorable sites are virtually the same in the enzymes and RNA. The most copied interactions were of electrostatic nature, but stacking was also replicated in one AME:kanamycin complex. In addition, we found that some water-mediated interactions were very stable in the simulations of the complexes. We show that our simulations reproduce well findings from NMR or X-ray structural studies, as well as results from directed mutagenesis. The outcomes of our analyses provide new insight into aminoglycoside resistance mechanism that is related to the enzymatic modification of these drugs.
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Affiliation(s)
- Julia Romanowska
- Department of Biophysics, Faculty of Physics, University of Warsaw, Hoża 69, 00-681 Warsaw, Poland.
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13
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Vong K, Auclair K. Understanding and overcoming aminoglycoside resistance caused by N-6'-acetyltransferase. MEDCHEMCOMM 2012; 3:397-407. [PMID: 28018574 PMCID: PMC5179255 DOI: 10.1039/c2md00253a] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Aminoglycosides occupy a special niche amongst antibiotics in part because of their broad spectrum of action. Bacterial resistance is however menacing to render these drugs obsolete. A significant amount of work has been devoted to understand and overcome aminoglycoside resistance. This mini-review will discuss aminoglycoside-modifying enzymes (AMEs), with a special emphasis on the efforts to comprehend and block resistance caused by aminoglycoside 6'-N-acetyltransferase (AAC(6')).
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Affiliation(s)
- Kenward Vong
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Québec, Canada H3A 2K6
| | - Karine Auclair
- Department of Chemistry, McGill University, 801 Sherbrooke Street West, Montréal, Québec, Canada H3A 2K6
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14
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Kim SY, Park YJ, Yu JK, Kim YS. Aminoglycoside susceptibility profiles of Enterobacter cloacae isolates harboring the aac(6')-Ib gene. Korean J Lab Med 2011; 31:279-81. [PMID: 22016682 PMCID: PMC3190007 DOI: 10.3343/kjlm.2011.31.4.279] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2011] [Revised: 04/17/2011] [Accepted: 06/24/2011] [Indexed: 11/30/2022] Open
Abstract
The aminoglycoside 6'-N-acetyltransferases of type Ib (aac(6')-Ib) gene confers resistance to amikacin, tobramycin, kanamycin, and netilmicin but not gentamicin. However, some isolates harboring this gene show reduced susceptibility to amikacin. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recommends a revision of the phenotypic description for isolates harboring the aac(6')-Ib gene. In this study, we determined the aminoglycoside susceptibility profiles of 58 AAC(6')-Ib-producing Enterobacter cloacae isolates. On the basis of the CLSI and EUCAST breakpoints, a large proportion (84.5% and 55.2%, respectively) of these 58 isolates were found to be susceptible to amikacin. However, among the isolates that were shown to be anikacin-susceptible according to the CLSI and EUCAST breakpoints, only 30.6% and 18.8% isolates, respectively, could be considered to have intermediate resistance on the basis of the EUCAST expert rules. Further studies should be conducted to determine the aminoglycoside susceptibility profiles of aac(6')-Ib-harboring isolates from various geographic regions and to monitor the therapeutic efficacy of amikacin in infections caused by these isolates.
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Affiliation(s)
- Soo-Young Kim
- Department of Laboratory Medicine, College of Medicine, The Catholic University of Korea, St. Vincent's Hospital, Suwon, Korea
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15
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Abstract
Aminoglycosides have been an essential component of the armamentarium in the treatment of life-threatening infections. Unfortunately, their efficacy has been reduced by the surge and dissemination of resistance. In some cases the levels of resistance reached the point that rendered them virtually useless. Among many known mechanisms of resistance to aminoglycosides, enzymatic modification is the most prevalent in the clinical setting. Aminoglycoside modifying enzymes catalyze the modification at different -OH or -NH₂ groups of the 2-deoxystreptamine nucleus or the sugar moieties and can be nucleotidyltransferases, phosphotransferases, or acetyltransferases. The number of aminoglycoside modifying enzymes identified to date as well as the genetic environments where the coding genes are located is impressive and there is virtually no bacteria that is unable to support enzymatic resistance to aminoglycosides. Aside from the development of new aminoglycosides refractory to as many as possible modifying enzymes there are currently two main strategies being pursued to overcome the action of aminoglycoside modifying enzymes. Their successful development would extend the useful life of existing antibiotics that have proven effective in the treatment of infections. These strategies consist of the development of inhibitors of the enzymatic action or of the expression of the modifying enzymes.
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16
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Wu Y, Li H, Li J, Huang ZH. Detection of Pseudomonas aeruginosa carried a new array of gene cassettes within class 1 integron isolated from a teaching hospital in Nanjing, China. J Microbiol 2008; 46:687-91. [PMID: 19107398 DOI: 10.1007/s12275-008-0021-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2008] [Accepted: 09/03/2008] [Indexed: 11/27/2022]
Abstract
We report here novel array of gene cassettes found in single variable region of class 1 integron disseminated in Pseudomonas aeruginosa isolated from a teaching hospital in Nanjing, Jiangsu Province, China. 29 of 47 (61%) P. aeruginosa strains were confirmed haboured class 1 integron, and all the positive strains have the same variable region confirmed by PCR and RFLP methods. The variable region contained an unreported order of four gene cassettes aac(6')-II-aadA13-cmlA8-oxa-10. Of those, cmlA8 gene was a variant of cmlA5 encoding non-enzymatic protein which putatively confer resistance to chloramphenicol. Susceptibility testing revealed multidrug-resistant mechanisms were involved in the class 1 integron positive clinical isolates. And the class 1 integron located on an about 15 kb transferable plasmid was certified by conjugation experiment and plasmid DNA analysis. The macro restriction profile indicated those clinical strains were clonally related.
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Affiliation(s)
- Yuan Wu
- The Department of Infectious Diseases, the First Affiliated Hospital with Nanjing Medical University, Nanjing, Jiangsu Province, 210029, P. R. China
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17
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Vetting MW, Park CH, Hegde SS, Jacoby GA, Hooper DC, Blanchard JS. Mechanistic and structural analysis of aminoglycoside N-acetyltransferase AAC(6')-Ib and its bifunctional, fluoroquinolone-active AAC(6')-Ib-cr variant. Biochemistry 2008; 47:9825-35. [PMID: 18710261 DOI: 10.1021/bi800664x] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Enzymatic modification of aminoglycoside antibiotics mediated by regioselective aminoglycoside N-acetyltransferases is the predominant cause of bacterial resistance to aminoglycosides. A recently discovered bifunctional aminoglycoside acetyltransferase (AAC(6')-Ib variant, AAC(6')-Ib-cr) has been shown to catalyze the acetylation of fluoroquinolones as well as aminoglycosides. We have expressed and purified AAC(6')-Ib-wt and its bifunctional variant AAC(6')-Ib-cr in Escherichia coli and characterized their kinetic and chemical mechanism. Initial velocity and dead-end inhibition studies support an ordered sequential mechanism for the enzyme(s). The three-dimensional structure of AAC(6')-Ib-wt was determined in various complexes with donor and acceptor ligands to resolutions greater than 2.2 A. Observation of the direct, and optimally positioned, interaction between the 6'-NH 2 and Asp115 suggests that Asp115 acts as a general base to accept a proton in the reaction. The structure of AAC(6')-Ib-wt permits the construction of a molecular model of the interactions of fluoroquinolones with the AAC(6')-Ib-cr variant. The model suggests that a major contribution to the fluoroquinolone acetylation activity comes from the Asp179Tyr mutation, where Tyr179 makes pi-stacking interactions with the quinolone ring facilitating quinolone binding. The model also suggests that fluoroquinolones and aminoglycosides have different binding modes. On the basis of kinetic properties, the pH dependence of the kinetic parameters, and structural information, we propose an acid/base-assisted reaction catalyzed by AAC(6')-Ib-wt and the AAC(6')-Ib-cr variant involving a ternary complex.
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Affiliation(s)
- Matthew W Vetting
- Department of Biochemistry, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461, USA
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18
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Sekiguchi JI, Asagi T, Miyoshi-Akiyama T, Fujino T, Kobayashi I, Morita K, Kikuchi Y, Kuratsuji T, Kirikae T. Multidrug-resistant Pseudomonas aeruginosa strain that caused an outbreak in a neurosurgery ward and its aac(6')-Iae gene cassette encoding a novel aminoglycoside acetyltransferase. Antimicrob Agents Chemother 2005; 49:3734-42. [PMID: 16127047 PMCID: PMC1195402 DOI: 10.1128/aac.49.9.3734-3742.2005] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We characterized multidrug-resistant Pseudomonas aeruginosa strains isolated from patients involved in an outbreak of catheter-associated urinary tract infections that occurred in a neurosurgery ward of a hospital in Sendai, Japan. Pulsed-field gel electrophoresis of SpeI-, XbaI-, or HpaI-digested genomic DNAs from the isolates revealed that clonal expansion of a P. aeruginosa strain designated IMCJ2.S1 had occurred in the ward. This strain possessed broad-spectrum resistance to aminoglycosides, beta-lactams, fluoroquinolones, tetracyclines, sulfonamides, and chlorhexidine. Strain IMCJ2.S1 showed a level of resistance to some kinds of disinfectants similar to that of a control strain of P. aeruginosa, ATCC 27853. IMCJ2.S1 contained a novel class 1 integron, In113, in the chromosome but not on a plasmid. In113 contains an array of three gene cassettes of bla(IMP-1), a novel aminoglycoside resistance gene, and the aadA1 gene. The aminoglycoside resistance gene, designated aac(6')-Iae, encoded a 183-amino-acid protein that shared 57.1% identity with AAC(6')-Iq. Recombinant AAC(6')-Iae protein showed aminoglycoside 6'-N-acetyltransferase activity by thin-layer chromatography. Escherichia coli expressing exogenous aac(6')-Iae showed resistance to amikacin, dibekacin, isepamicin, kanamycin, netilmicin, sisomicin, and tobramycin but not to arbekacin, gentamicins, or streptomycin. Alterations of gyrA and parC at the amino acid sequence level were detected in IMCJ2.S1, suggesting that such mutations confer the resistance to fluoroquinolones observed for this strain. These results indicate that P. aeruginosa IMCJ2.S1 has developed multidrug resistance by acquiring resistance determinants, including a novel member of the aac(6')-I family and mutations in drug resistance genes.
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Affiliation(s)
- Jun-ichiro Sekiguchi
- Department of Infectious Diseases, Research Institute, International Medical Center of Japan, 1-21-1 Toyama, Shinjuku, Tokyo 162-8655, Japan
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19
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Pourreza A, Witherspoon M, Fox J, Newmark J, Bui D, Tolmasky ME. Mutagenesis analysis of a conserved region involved in acetyl coenzyme A binding in the aminoglycoside 6'-N-acetyltransferase type Ib encoded by plasmid pJHCMW1. Antimicrob Agents Chemother 2005; 49:2979-82. [PMID: 15980378 PMCID: PMC1168681 DOI: 10.1128/aac.49.7.2979-2982.2005] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Alanine scanning of motif A in the pJHCMW1-encoded aminoglycoside 6'-N-acetyltransferase type Ib identified amino acids important for the ability of the enzyme to confer wild-type levels of resistance to kanamycin and amikacin. The replacement of two amino acids, D117 or L120, with alanine residues resulted in complete loss of the resistance phenotype.
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Affiliation(s)
- Atousa Pourreza
- Department of Biological Science, School of Natural Sciences and Mathematics, California State University Fullerton, Fullerton, California 92834-6850, USA
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20
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Riesenfeld CS, Goodman RM, Handelsman J. Uncultured soil bacteria are a reservoir of new antibiotic resistance genes. Environ Microbiol 2004; 6:981-9. [PMID: 15305923 DOI: 10.1111/j.1462-2920.2004.00664.x] [Citation(s) in RCA: 287] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Antibiotic resistance genes are typically isolated by cloning from cultured bacteria or by polymerase chain reaction (PCR) amplification from environmental samples. These methods do not access the potential reservoir of undiscovered antibiotic resistance genes harboured by soil bacteria because most soil bacteria are not cultured readily, and PCR detection of antibiotic resistance genes depends on primers that are based on known genes. To explore this reservoir, we isolated DNA directly from soil samples, cloned the DNA and selected for clones that expressed antibiotic resistance in Escherichia coli. We constructed four libraries that collectively contain 4.1 gigabases of cloned soil DNA. From these and two previously reported libraries, we identified nine clones expressing resistance to aminoglycoside antibiotics and one expressing tetracycline resistance. Based on the predicted amino acid sequences of the resistance genes, the resistance mechanisms include efflux of tetracycline and inactivation of aminoglycoside antibiotics by phosphorylation and acetylation. With one exception, all the sequences are considerably different from previously reported sequences. The results indicate that soil bacteria are a reservoir of antibiotic resistance genes with greater genetic diversity than previously accounted for, and that the diversity can be surveyed by a culture-independent method.
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21
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Doi Y, Wachino JI, Yamane K, Shibata N, Yagi T, Shibayama K, Kato H, Arakawa Y. Spread of novel aminoglycoside resistance gene aac(6')-Iad among Acinetobacter clinical isolates in Japan. Antimicrob Agents Chemother 2004; 48:2075-80. [PMID: 15155202 PMCID: PMC415623 DOI: 10.1128/aac.48.6.2075-2080.2004] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
A novel aminoglycoside resistance gene, aac(6')-Iad, encoding aminoglycoside 6'-N-acetyltransferase, was identified in Acinetobacter genospecies 3 strain A-51. The gene encoded a 144-amino-acid protein, which shared modest identity (up to 36.7%) with some of the aminoglycoside 6'-N-acetyltransferases. The results of high-pressure liquid chromatography assays confirmed that the protein is a functional aminoglycoside 6'-N-acetyltransferase. The enzyme conferred resistance to amikacin, tobramycin, sisomicin, and isepamicin but not to gentamicin. The prevalence of this gene among Acinetobacter clinical isolates in Japan was then investigated. Of 264 Acinetobacter sp. strains isolated from geographically diverse areas in Japan in 2002, 16 were not susceptible to amikacin, and aac(6')-Iad was detected in 7. Five of the producers of aminoglycoside 6'-N-acetyltransferase type Iad were identified as Acinetobacter baumannii, and two were identified as Acinetobacter genospecies 3. These results suggest that aac(6')-Iad plays a substantial role in amikacin resistance among Acinetobacter spp. in Japan.
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Affiliation(s)
- Yohei Doi
- Department of Bacterial Pathogenesis and Infection Control, National Institute of Infectious Diseases, 4-7-1, Gakuen, Musashi-Murayama, Tokyo 208-0011, Japan
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22
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Sarno R, Ha H, Weinsetel N, Tolmasky ME. Inhibition of aminoglycoside 6'-N-acetyltransferase type Ib-mediated amikacin resistance by antisense oligodeoxynucleotides. Antimicrob Agents Chemother 2004; 47:3296-304. [PMID: 14506044 PMCID: PMC201158 DOI: 10.1128/aac.47.10.3296-3304.2003] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Amikacin has been very useful in the treatment of infections caused by multiresistant bacteria because it is refractory to the actions of most modifying enzymes. However, the spread of AAC(6')-I-type acetyltransferases, enzymes capable of catalyzing inactivation of amikacin, has rendered this antibiotic all but useless in some parts of the world. The aminoglycoside 6'-N-acetyltransferase type Ib, which is coded for by the aac(6')-Ib gene, mediates resistance to amikacin and other aminoglycosides. RNase H mapping and computer prediction of the secondary structure led to the identification of five regions accessible for interaction with antisense oligodeoxynucleotides in the aac(6')-Ib mRNA. Oligodeoxynucleotides targeting these regions could bind to native mRNA with different efficiencies and mediated RNase H digestion. Selected oligodeoxynucleotides inhibited AAC(6')-Ib synthesis in cell-free coupled transcription-translation assays. After their introduction into an Escherichia coli strain harboring aac(6')-Ib by electroporation, some of these oligodeoxynucleotides decreased the level of resistance to amikacin. Our results indicate that use of antisense compounds could be a viable strategy to preserve the efficacies of existing antibiotics to which bacteria are becoming increasingly resistant.
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MESH Headings
- Acetyltransferases/antagonists & inhibitors
- Acetyltransferases/genetics
- Acetyltransferases/metabolism
- Amikacin/pharmacology
- Base Sequence
- Binding Sites
- Cell-Free System
- Colony Count, Microbial
- Drug Resistance, Multiple, Bacterial/drug effects
- Drug Resistance, Multiple, Bacterial/genetics
- Drug Resistance, Multiple, Bacterial/physiology
- Enzyme Inhibitors/pharmacology
- Escherichia coli/drug effects
- Escherichia coli/genetics
- Molecular Sequence Data
- Nucleic Acid Conformation
- Oligonucleotides, Antisense/genetics
- Oligonucleotides, Antisense/metabolism
- Oligonucleotides, Antisense/pharmacology
- Protein Biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Ribonuclease H/metabolism
- Transcription, Genetic
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Affiliation(s)
- Renee Sarno
- Department of Biological Science, College of Natural Science and Mathematics, California State University Fullerton, Fullerton, California 92834-6850, USA
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23
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Dery KJ, Søballe B, Witherspoon MSL, Bui D, Koch R, Sherratt DJ, Tolmasky ME. The aminoglycoside 6'-N-acetyltransferase type Ib encoded by Tn1331 is evenly distributed within the cell's cytoplasm. Antimicrob Agents Chemother 2003; 47:2897-902. [PMID: 12936992 PMCID: PMC182613 DOI: 10.1128/aac.47.9.2897-2902.2003] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The multiresistance transposon Tn1331, which mediates resistance to several aminoglycosides and beta-lactams, includes the aac(6')-Ib, aadA1, bla(OXA-9), and bla(TEM-1) genes. The nucleotide sequence of aac(6')-Ib includes a region identical to that of the bla(TEM-1) gene. This region encompasses the promoter and the initiation codon followed by 15 nucleotides. Since there were three possible translation initiation sites, the amino acid sequence at the N terminus of the aminoglycoside 6'-N-acetyltransferase type Ib [AAC(6')-Ib] was determined and was found to be SIQHF. This result indicated that aac(6')-Ib includes a translational fusion: the first five amino acids of the leader peptide of the TEM beta-lactamase are fused to the rest of the AAC(6')-Ib protein. This gene fusion could have formed during the genesis of Tn1331 as a consequence of the generation of a 520-nucleotide duplication (M. E. Tolmasky, Plasmid 24:218-226, 1990). An identical gene isolated from a Serratia marcescens strain has been previously described (G. Tran van Nhieu and E. Collatz, J. Bacteriol. 169:5708-5714, 1987). Extraction of the periplasmic proteins of E. coli harboring aac(6')-Ib by spheroplast formation showed that most of the AAC(6')-Ib protein is present in the cytoplasm. A genetic fusion to phoA confirmed these results. AAC(6')-Ib was shown to be evenly distributed inside the cell's cytoplasm by fluorescent microscopy with an AAC(6')-Ib-cyan fluorescent protein fusion.
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Affiliation(s)
- Ken J Dery
- Department of Biological Science, College of Natural Science and Mathematics, California State University Fullerton, Fullerton, California 92834-6850, USA
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24
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Correia M, Boavida F, Grosso F, Salgado MJ, Lito LM, Cristino JM, Mendo S, Duarte A. Molecular characterization of a new class 3 integron in Klebsiella pneumoniae. Antimicrob Agents Chemother 2003; 47:2838-43. [PMID: 12936982 PMCID: PMC182612 DOI: 10.1128/aac.47.9.2838-2843.2003] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Klebsiella pneumoniae FFUL 22K was isolated in April 1999 from the urine of an intensive care unit patient in Portugal. The strain showed an extended-spectrum cephalosporin resistance profile. A typical synergistic effect between cefotaxime or cefepime and clavulanic acid was observed. An Escherichia coli transformant displayed a similar resistance phenotype and harbored a ca. 9.4-kb plasmid (p22K9). Cloning experiments revealed that the extended-spectrum beta-lactamase was encoded by bla(GES-1), previously described in class 1 integrons from K. pneumoniae ORI-1 and Pseudomonas aeruginosa Pa695. Further sequence analysis demonstrated that the bla(GES-1) gene cassette was located on a new class 3 integron. The integron was 2863 bp long and consisted of an intI3 integrase gene, an attI3 recombination site, two promoter regions, and two gene cassettes. The IntI3 integrase was 98.8% identical to that of Serratia marcescens AK9373. The bla(GES-1) gene cassette was inserted at the attI3 site. The second gene cassette was the result of a fusion event between bla(OXA-10)-type and aac(6')-Ib gene cassettes and conferred resistance to kanamycin. This is the second class 3 integron reported and the first time that the bla(GES-1) gene cassette has been found on an integron belonging to this class, highlighting the considerable heterogeneity of their genetic environment and the spread of gene cassettes among different classes of integrons.
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Affiliation(s)
- Mário Correia
- Laboratory of Microbiology, Faculty of Pharmacy, University of Lisbon, Lisbon, Portugal
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25
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Boehr DD, Jenkins SI, Wright GD. The molecular basis of the expansive substrate specificity of the antibiotic resistance enzyme aminoglycoside acetyltransferase-6'-aminoglycoside phosphotransferase-2". The role of ASP-99 as an active site base important for acetyl transfer. J Biol Chem 2003; 278:12873-80. [PMID: 12566434 DOI: 10.1074/jbc.m211680200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The most frequent determinant of aminoglycoside antibiotic resistance in Gram-positive bacterial pathogens is a bifunctional enzyme, aminoglycoside acetyltransferase-6'-aminoglycoside phosphotransferase-2" (AAC(6')- aminoglycoside phosphotransferase-2", capable of modifying a wide selection of clinically relevant antibiotics through its acetyltransferase and kinase activities. The aminoglycoside acetyltransferase domain of the enzyme, AAC(6')-Ie, is the only member of the large AAC(6') subclass known to modify fortimicin A and catalyze O-acetylation. We have demonstrated through solvent isotope, pH, and site-directed mutagenesis effects that Asp-99 is responsible for the distinct abilities of AAC(6')-Ie. Moreover, we have demonstrated that small planar molecules such as 1-(bromomethyl)phenanthrene can inactivate the enzyme through covalent modification of this residue. Thus, Asp-99 acts as an active site base in the molecular mechanism of AAC(6')-Ie. The prominent role of this residue in aminoglycoside modification can be exploited as an anchoring site for the development of compounds capable of reversing antibiotic resistance in vivo.
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Affiliation(s)
- David D Boehr
- Antimicrobial Research Centre, Department of Biochemistry, McMaster University, Hamilton, Ontario L8N 3Z5, Canada
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26
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Casin I, Hanau-Berçot B, Podglajen I, Vahaboglu H, Collatz E. Salmonella enterica serovar Typhimurium bla(PER-1)-carrying plasmid pSTI1 encodes an extended-spectrum aminoglycoside 6'-N-acetyltransferase of type Ib. Antimicrob Agents Chemother 2003; 47:697-703. [PMID: 12543680 PMCID: PMC151738 DOI: 10.1128/aac.47.2.697-703.2003] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We have studied the aminoglycoside resistance gene, which confers high levels of resistance to both amikacin and gentamicin, that is carried by plasmid pSTI1 in the PER-1 beta-lactamase-producing strain of Salmonella enterica serovar Typhimurium previously isolated in Turkey. This gene, called aac(6')-Ib(11), was found in a class 1 integron and codes for a protein of 188 amino acids, a fusion product between the N-terminal moiety (8 amino acids) of the signal peptide of the beta-lactamase OXA-1 and the acetyltransferase. The gene lacked a plausible Shine-Dalgarno (SD) sequence and was located 45 nucleotides downstream from a small open reading frame, ORF-18, with a coding capacity of 18 amino acids and a properly spaced SD sequence likely to direct the initiation of aac(6')-Ib(11) translation. AAC(6')-Ib(11) had Leu118 and Ser119 as opposed to Gln and Leu or Gln and Ser, respectively, which were observed in all previously described enzymes of this type. We have evaluated the effect of Leu or Gln at position 118 by site-directed mutagenesis of aac(6')-Ib(11) and two other acetyltransferase gene variants, aac(6')-Ib(7) and -Ib(8), which naturally encode Gln118. Our results show that the combination of Leu118 and Ser119 confers an extended-spectrum aminoglycoside resistance, with the MICs of all aminoglycosides in clinical use, including gentamicin, being two to eight times higher for strains with Leu118 and Ser119 than for those with Gln118 and Ser119.
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Affiliation(s)
- Isabelle Casin
- Service de Microbiologie, Hôpital Saint-Louis, INSERM EMI-U 0004-LRMA, Université Paris VI, France.
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27
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Sarno R, McGillivary G, Sherratt DJ, Actis LA, Tolmasky ME. Complete nucleotide sequence of Klebsiella pneumoniae multiresistance plasmid pJHCMW1. Antimicrob Agents Chemother 2002; 46:3422-7. [PMID: 12384346 PMCID: PMC128720 DOI: 10.1128/aac.46.11.3422-3427.2002] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The multiresistance plasmid pJHCMW1, harbored by a clinical Klebsiella pneumoniae strain isolated from a neonate with meningitis, was sequenced. A circular sequence of 11,354 bp was generated, of which 7,993 bp make up Tn1331, a transposon including the antibiotic resistance genes aac(6')-Ib, aadA1, bla(OXA-9), and bla(TEM-1). The gene aac(6')-Ib is included in a gene cassette, and both aadA1 and bla(OXA-9) are included in a single-gene cassette that may have arisen as a consequence of a recombination event involving two integrons. The pJHCMW1 plasmid replicates through a ColE1-like RNA-regulated mechanism, includes a functional oriT, and two loci with similarity to XerCD site-specific recombination target sites involved in plasmid stabilization by the resolution of multimers. One of these two loci, mwr, is active and has been the subject of previous studies, and the other, dxs, is not functional but binds the recombinase XerD with low affinity. Two additional open reading frames were identified, one with low similarity to two hypothetical membrane proteins from Mycobacterium tuberculosis and Mycobacterium leprae and the other with low similarity to psiB, a gene encoding a function that facilitates the establishment of the transferring plasmid in the recipient bacterial cell during the process of conjugation.
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Affiliation(s)
- Renee Sarno
- Department of Biological Science, Institute of Molecular Biology and Nutrition, College of Natural Science and Mathematics, California State University Fullerton, Fullerton, California 92834-6850, USA
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