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Singh NS, Singhal N, Kumar M, Virdi JS. Exploring the genetic mechanisms underlying amoxicillin-clavulanate resistance in waterborne Escherichia coli. INFECTION GENETICS AND EVOLUTION 2021; 90:104767. [PMID: 33581330 DOI: 10.1016/j.meegid.2021.104767] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2020] [Revised: 01/22/2021] [Accepted: 02/08/2021] [Indexed: 11/28/2022]
Abstract
Escherichia coli is a human commensal and faecal indicator bacteria which is also the etiologic agent of several nosocomial- and community-acquired infections. Amoxicillin-clavulanate (AMC) is a widely prescribed β-lactam/β-lactamase inhibitor which is used against E. coli infections. Resistance to AMC in E. coli has been primarily attributed to point mutations in blaTEM-1 resulting in inhibitor-resistant TEM (IRT) β-lactamases. In this study, we have explored the reasons underlying AMC-resistance in waterborne E. coli. Most of the studies regarding IRT-producing E. coli have been conducted on clinical samples and studies exploring genetic mechanisms underlying AMC-resistance in aquatic E. coli are scarce. Since, blaTEM-1 and several antimicrobial resistance determinants are located on mobile genetic elements they can easily disseminate among other microbes inhabiting urban waterbodies. Thus, it is important to understand the underlying mechanisms to check the dissemination of AMC-resistance in other waterborne pathogens. Our results indicated that AMC-resistant E. coli were susceptible to other β-lactam/β-lactamase inhibitors like, ampicillin/sulbactam and piperacillin/tazobactam. Though, blaTEM-1 was present, none of the strains harbored point mutations which could qualify as IRT and only one strain harbored both blaTEM-1 and blaOXA-1. Hyperproduction of blaTEM-1, presence of plasimd-mediated ampC or promoter/attenuator mutations in the chromososmal ampC might not be related to IRT-like phenotype or AMC-resistance. This suggests that other mechanisms like, increased plasmid copy numbers or gene amplification or deficiency in the expression/function of porins might be responsible for AMC-resistance in waterborne E. coli.
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Affiliation(s)
- Nambram Somendro Singh
- Department of Microbiology, University of Delhi South Campus, New Delhi, India; Department of Biophysics, University of Delhi South Campus, New Delhi, India
| | - Neelja Singhal
- Department of Biophysics, University of Delhi South Campus, New Delhi, India.
| | - Manish Kumar
- Department of Biophysics, University of Delhi South Campus, New Delhi, India
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Hansen KH, Andreasen MR, Pedersen MS, Westh H, Jelsbak L, Schønning K. Resistance to piperacillin/tazobactam in Escherichia coli resulting from extensive IS26-associated gene amplification of blaTEM-1. J Antimicrob Chemother 2019; 74:3179-3183. [DOI: 10.1093/jac/dkz349] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2019] [Revised: 06/26/2019] [Accepted: 07/11/2019] [Indexed: 12/20/2022] Open
Abstract
Abstract
Background
bla TEM-1 encodes a narrow-spectrum β-lactamase that is inhibited by β-lactamase inhibitors and commonly present in Escherichia coli. Hyperproduction of blaTEM-1 may cause resistance to penicillin/β-lactamase inhibitor (P/BLI) combinations.
Objectives
To characterize EC78, an E. coli bloodstream isolate, resistant to P/BLI combinations, which contains extensive amplification of blaTEM-1 within the chromosome.
Methods
EC78 was sequenced using Illumina and Oxford Nanopore Technology (ONT) methodology. Configuration of blaTEM-1 amplification was probed using PCR. Expression of blaTEM-1 mRNA was determined using quantitative PCR and β-lactamase activity was determined spectrophotometrically in a nitrocefin conversion assay. Growth rate was assessed to determine fitness and stability of the gene amplification was assessed by passage in the absence of antibiotics.
Results
Illumina sequencing of EC78 identified blaTEM-1B as the only acquired β-lactamase preceded by the WT P3 promoter and present at a copy number of 182.6 with blaTEM-1B bracketed by IS26 elements. The chromosomal location of the IS26-blaTEM-1B amplification was confirmed by ONT sequencing. Hyperproduction of blaTEM-1 was confirmed by increased transcription of blaTEM-1 and β-lactamase activity and associated with a significant fitness cost; however, the array was maintained at a relatively high copy number for 150 generations. PCR screening for blaTEM amplification of isolates resistant to P/BLI combinations identified an additional strain containing an IS26-associated amplification of a blaTEM gene.
Conclusions
IS26-associated amplification of blaTEM can cause resistance to P/BLI combinations. This adaptive mechanism of resistance may be overlooked if simple methods of genotypic prediction (e.g. gene presence/absence) are used to predict antimicrobial susceptibility from sequencing data.
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Affiliation(s)
- Katrine Hartung Hansen
- Department of Clinical Microbiology 445, Hvidovre University Hospital, Hvidovre, Denmark
| | - Minna Rud Andreasen
- Department of Clinical Microbiology 445, Hvidovre University Hospital, Hvidovre, Denmark
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Martin Schou Pedersen
- Department of Clinical Microbiology 445, Hvidovre University Hospital, Hvidovre, Denmark
| | - Henrik Westh
- Department of Clinical Microbiology 445, Hvidovre University Hospital, Hvidovre, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Lotte Jelsbak
- Department of Science and Environment, Roskilde University, Roskilde, Denmark
| | - Kristian Schønning
- Department of Clinical Microbiology 445, Hvidovre University Hospital, Hvidovre, Denmark
- Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Activity of Ceftolozane-Tazobactam against Carbapenem-Resistant, Non-Carbapenemase-Producing Pseudomonas aeruginosa and Associated Resistance Mechanisms. Antimicrob Agents Chemother 2017; 62:AAC.01970-17. [PMID: 29133568 DOI: 10.1128/aac.01970-17] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/02/2017] [Indexed: 01/01/2023] Open
Abstract
Although carbapenems are effective for treating serious multidrug-resistant Pseudomonas aeruginosa infections, carbapenem-resistant P. aeruginosa (CRPA) is now being reported worldwide. Ceftolozane-tazobactam (C/T) demonstrates activity against many multidrug-resistant isolates. We evaluated the activity of C/T and compared its activity to that of ceftazidime-avibactam (C/A) using a well-characterized collection of non-carbapenemase-producing CRPA isolates. Forty-two non-carbapenemase-producing CRPA isolates from a previous study (J. Y. Lee and K. S. Ko, Int J Antimicrob Agents 40:168-172, 2012, https://doi.org/10.1016/j.ijantimicag.2012.04.004) were included. All had been previously shown to be negative for blaIMP, blaVIM, blaSPM, blaGIM, blaSIM, and blaKPC by PCR. In the prior study, expression of oprD, ampC, and several efflux pump genes had been defined by quantitative reverse transcription-PCR. Here, antimicrobial susceptibility was determined by broth microdilution according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Time-kill curve assays were performed using three C/T- and C/A-susceptible CRPA isolates. Among 42 non-carbapenemase-producing CRPA isolates, overall susceptibility to C/T was 95.2%, compared to 71.4%, 42.9%, 23.8%, 21.4%, and 2.4% for C/A, ceftazidime, piperacillin-tazobactam, cefepime, and meropenem, respectively. The C/T resistance rate was significantly lower than that of C/A among isolates showing decreased oprD and increased mexB expression (5.1% versus 25.6%, P = 0.025, and 4.3% versus 34.8%, P = 0.022, respectively). In time-kill curve studies, C/T was less bactericidal than C/A against an isolate with decreased oprD and increased ampC expression. C/T was active against 95.2% of non-carbapenemase-producing CRPA clinical isolates. No apparent correlation of C/T MIC values with specific mutation-driven resistance mechanisms was noted.
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Sy SKB, Zhuang L, Beaudoin ME, Kircher P, Tabosa MAM, Cavalcanti NCT, Grunwitz C, Pieper S, Schuck VJ, Nichols WW, Derendorf H. Potentiation of ceftazidime by avibactam against β-lactam-resistant Pseudomonas aeruginosa in an in vitro infection model. J Antimicrob Chemother 2017; 72:1109-1117. [PMID: 28077672 DOI: 10.1093/jac/dkw535] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2016] [Accepted: 11/11/2016] [Indexed: 12/15/2022] Open
Abstract
Objectives This study evaluated the in vitro pharmacodynamics of combinations of ceftazidime and the non-β-lactam β-lactamase inhibitor, avibactam, against ceftazidime-, piperacillin/tazobactam- and meropenem-multiresistant Pseudomonas aeruginosa by a quantitative time-kill method. Methods MICs of ceftazidime plus 0-16 mg/L avibactam were determined against eight isolates of P. aeruginosa . Single-compartment, 24 h time-kill kinetics were investigated for three isolates at 0-16 mg/L avibactam with ceftazidime at 0.25-4-fold the MIC as measured at the respective avibactam concentration. Ceftazidime and avibactam concentrations were measured by LC-MS/MS during the time-kill kinetic studies to evaluate drug degradation. Results Avibactam alone displayed no antimicrobial activity. MICs of ceftazidime decreased by 8-16-fold in the presence of avibactam at 4 mg/L. The changes in log 10 cfu/mL at both the 10 h and 24 h timepoints (versus 0 h) revealed bacterial killing at ≥1-fold MIC. Significantly higher concentrations of ceftazidime alone, as compared with those of ceftazidime in combination, were required to produce any given kill. Without avibactam, ceftazidime degradation was significant (defined as degradation t 1/2 < 24 h), with as little as 19% ± 18% of the original concentration remaining at 8 h for the most resistant strain. In combination with avibactam, ceftazidime degradation at ≥ 1-fold MIC was negligible. Conclusion The addition of avibactam protected ceftazidime from degradation in a dose-dependent manner and restored its cidal and static activity at concentrations in combination well below the MIC of ceftazidime alone.
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Affiliation(s)
- Sherwin K B Sy
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Luning Zhuang
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | | | - Philipp Kircher
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Maria A M Tabosa
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Noely C T Cavalcanti
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Christian Grunwitz
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | - Sebastian Pieper
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
| | | | | | - Hartmut Derendorf
- Department of Pharmaceutics, College of Pharmacy, University of Florida, Gainesville, FL, USA
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Sy SKB, Beaudoin ME, Zhuang L, Löblein KI, Lux C, Kissel M, Tremmel R, Frank C, Strasser S, Heuberger JAAC, Mulder MB, Schuck VJ, Derendorf H. In vitropharmacokinetics/pharmacodynamics of the combination of avibactam and aztreonam against MDR organisms. J Antimicrob Chemother 2016; 71:1866-80. [DOI: 10.1093/jac/dkw082] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Accepted: 02/21/2016] [Indexed: 11/12/2022] Open
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Bajaj P, Singh NS, Virdi JS. Escherichia coli β-Lactamases: What Really Matters. Front Microbiol 2016; 7:417. [PMID: 27065978 PMCID: PMC4811930 DOI: 10.3389/fmicb.2016.00417] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2016] [Accepted: 03/14/2016] [Indexed: 01/09/2023] Open
Abstract
Escherichia coli strains belonging to diverse pathotypes have increasingly been recognized as a major public health concern. The β-lactam antibiotics have been used successfully to treat infections caused by pathogenic E. coli. However, currently, the utility of β-lactams is being challenged severely by a large number of hydrolytic enzymes – the β-lactamases expressed by bacteria. The menace is further compounded by the highly flexible genome of E. coli, and propensity of resistance dissemination through horizontal gene transfer and clonal spread. Successful management of infections caused by such resistant strains requires an understanding of the diversity of β-lactamases, their unambiguous detection, and molecular mechanisms underlying their expression and spread with regard to the most relevant information about individual bacterial species. Thus, this review comprises first such effort in this direction for E. coli, a bacterial species known to be associated with production of diverse classes of β-lactamases. The review also highlights the role of commensal E. coli as a potential but under-estimated reservoir of β-lactamases-encoding genes.
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Affiliation(s)
- Priyanka Bajaj
- Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus New Delhi, India
| | - Nambram S Singh
- Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus New Delhi, India
| | - Jugsharan S Virdi
- Microbial Pathogenicity Laboratory, Department of Microbiology, University of Delhi South Campus New Delhi, India
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Combinatorial Pharmacodynamics of Ceftolozane-Tazobactam against Genotypically Defined β-Lactamase-Producing Escherichia coli: Insights into the Pharmacokinetics/Pharmacodynamics of β-Lactam-β-Lactamase Inhibitor Combinations. Antimicrob Agents Chemother 2016; 60:1967-73. [PMID: 26729494 DOI: 10.1128/aac.02635-15] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Accepted: 12/24/2015] [Indexed: 12/25/2022] Open
Abstract
Despite a dearth of new agents currently being developed to combat multidrug-resistant Gram-negative pathogens, the combination of ceftolozane and tazobactam was recently approved by the Food and Drug Administration to treat complicated intra-abdominal and urinary tract infections. To characterize the activity of the combination product, time-kill studies were conducted against 4 strains ofEscherichia colithat differed in the type of β-lactamase they expressed. The four investigational strains included 2805 (no β-lactamase), 2890 (AmpC β-lactamase), 2842 (CMY-10 β-lactamase), and 2807 (CTX-M-15 β-lactamase), with MICs to ceftolozane of 0.25, 4, 8, and >128 mg/liter with no tazobactam, and MICs of 0.25, 1, 4, and 8 mg/liter with 4 mg/liter tazobactam, respectively. All four strains were exposed to a 6 by 5 array of ceftolozane (0, 1, 4, 16, 64, and 256 mg/liter) and tazobactam (0, 1, 4, 16, and 64 mg/liter) over 48 h using starting inocula of 10(6)and 10(8)CFU/ml. While ceftolozane-tazobactam achieved bactericidal activity against all 4 strains, the concentrations of ceftolozane and tazobactam required for a ≥3-log reduction varied between the two starting inocula and the 4 strains. At both inocula, the Hill plots (R(2)> 0.882) of ceftolozane revealed significantly higher 50% effective concentrations (EC50s) at tazobactam concentrations of ≤4 mg/liter than those at concentrations of ≥16 mg/liter (P< 0.01). Moreover, the EC50s at 10(8)CFU/ml were 2.81 to 66.5 times greater than the EC50s at 10(6)CFU/ml (median, 10.7-fold increase;P= 0.002). These promising results indicate that ceftolozane-tazobactam achieves bactericidal activity against a wide range of β-lactamase-producingE. colistrains.
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Anthelmintic closantel enhances bacterial killing of polymyxin B against multidrug-resistant Acinetobacter baumannii. J Antibiot (Tokyo) 2015; 69:415-21. [PMID: 26669752 PMCID: PMC4911330 DOI: 10.1038/ja.2015.127] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Revised: 10/29/2015] [Accepted: 11/08/2015] [Indexed: 12/14/2022]
Abstract
Polymyxins, an old class of antibiotics, are currently used as the last resort for the treatment of multidrug-resistant (MDR) Acinetobacter baumannii. However, recent pharmacokinetic and pharmacodynamic data indicate that monotherapy can lead to the development of resistance. Novel approaches are urgently needed to preserve and improve the efficacy of this last-line class of antibiotics. This study examined the antimicrobial activity of novel combination of polymyxin B with anthelmintic closantel against A. baumannii. Closantel monotherapy (16 mg l(-1)) was ineffective against most tested A. baumannii isolates. However, closantel at 4-16 mg l(-1) with a clinically achievable concentration of polymyxin B (2 mg l(-1)) successfully inhibited the development of polymyxin resistance in polymyxin-susceptible isolates, and provided synergistic killing against polymyxin-resistant isolates (MIC ⩾4 mg l(-1)). Our findings suggest that the combination of polymyxin B with closantel could be potentially useful for the treatment of MDR, including polymyxin-resistant, A. baumannii infections. The repositioning of non-antibiotic drugs to treat bacterial infections may significantly expedite discovery of new treatment options for bacterial 'superbugs'.
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Keepers TR, Gomez M, Celeri C, Nichols WW, Krause KM. Bactericidal activity, absence of serum effect, and time-kill kinetics of ceftazidime-avibactam against β-lactamase-producing Enterobacteriaceae and Pseudomonas aeruginosa. Antimicrob Agents Chemother 2014; 58:5297-305. [PMID: 24957838 PMCID: PMC4135815 DOI: 10.1128/aac.02894-14] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2014] [Accepted: 06/17/2014] [Indexed: 01/31/2023] Open
Abstract
Avibactam, a non-β-lactam β-lactamase inhibitor with activity against extended-spectrum β-lactamases (ESBLs), KPC, AmpC, and some OXA enzymes, extends the antibacterial activity of ceftazidime against most ceftazidime-resistant organisms producing these enzymes. In this study, the bactericidal activity of ceftazidime-avibactam against 18 Pseudomonas aeruginosa isolates and 15 Enterobacteriaceae isolates, including wild-type isolates and ESBL, KPC, and/or AmpC producers, was evaluated. Ceftazidime-avibactam MICs (0.016 to 32 μg/ml) were lower than those for ceftazidime alone (0.06 to ≥256 μg/ml) against all isolates except for 2 P. aeruginosa isolates (1 blaVIM-positive isolate and 1 blaOXA-23-positive isolate). The minimum bactericidal concentration/MIC ratios of ceftazidime-avibactam were ≤4 for all isolates, indicating bactericidal activity. Human serum and human serum albumin had a minimal effect on ceftazidime-avibactam MICs. Ceftazidime-avibactam time-kill kinetics were evaluated at low MIC multiples and showed time-dependent reductions in the number of CFU/ml from 0 to 6 h for all strains tested. A ≥3-log10 decrease in the number of CFU/ml was observed at 6 h for all Enterobacteriaceae, and a 2-log10 reduction in the number of CFU/ml was observed at 6 h for 3 of the 6 P. aeruginosa isolates. Regrowth was noted at 24 h for some of the isolates tested in time-kill assays. These data demonstrate the potent bactericidal activity of ceftazidime-avibactam and support the continued clinical development of ceftazidime-avibactam as a new treatment option for infections caused by Enterobacteriaceae and P. aeruginosa, including isolates resistant to ceftazidime by mechanisms dependent on avibactam-sensitive β-lactamases.
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Lee J, Oh CE, Choi EH, Lee HJ. The impact of the increased use of piperacillin/tazobactam on the selection of antibiotic resistance among invasive Escherichia coli and Klebsiella pneumoniae isolates. Int J Infect Dis 2013; 17:e638-43. [PMID: 23523562 DOI: 10.1016/j.ijid.2013.01.030] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Revised: 01/08/2013] [Accepted: 01/25/2013] [Indexed: 11/26/2022] Open
Abstract
OBJECTIVES Increasing antimicrobial resistance is related to the selective pressure exerted by antibiotic usage. This study evaluated the impact of the increased use of piperacillin/tazobactam (TZP) on the selection of antibiotic resistance. METHODS From 1999 to 2010, Escherichia coli and Klebsiella pneumoniae invasive isolates obtained from hospitalized Korean children were analyzed in antibiotic susceptibility tests and subjected to characterization of the β-lactamase types. Antibiotic consumption data were also analyzed. RESULTS Between January 1999 and December 2010, 409 invasive isolates of E. coli (n=170) and K. pneumoniae (n=239) were obtained. A rebound of extended-spectrum β-lactamase (ESBL) prevalence with an increase in total antibiotics was noted. Non-susceptibility to TZP was determined in 7.6% of E. coli isolates and 20.9% of K. pneumoniae isolates. Despite the increase in TZP usage, the overall prevalence of TZP resistance did not significantly increase over time, especially in E. coli. The mechanisms for TZP resistance included the presence of AmpC producers, possible TEM-1 hyperproducers, and multiple β-lactamases in individual organisms of a given isolate. CONCLUSIONS Replacement of only the antibiotic class appears to be insufficient to control antibiotic resistance, and continued efforts to decrease overall antibiotic pressure are needed, especially in highly endemic situations.
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Affiliation(s)
- Jina Lee
- Department of Pediatrics, Seoul National University Bundang Hospital, Seongnam, Korea
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Firnberg E, Ostermeier M. PFunkel: efficient, expansive, user-defined mutagenesis. PLoS One 2012; 7:e52031. [PMID: 23284860 PMCID: PMC3524131 DOI: 10.1371/journal.pone.0052031] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Accepted: 11/12/2012] [Indexed: 12/24/2022] Open
Abstract
We introduce PFunkel, a versatile method for extensive, researcher-defined DNA mutagenesis using a ssDNA or dsDNA template. Once the template DNA is prepared, the method can be completed in a single day in a single tube, and requires no intermediate DNA purification or sub-cloning. PFunkel can be used for site-directed mutagenesis at an efficiency approaching 100%. More importantly, PFunkel allows researchers the unparalleled ability to efficiently construct user-defined libraries. We demonstrate the creation of a library with site-saturation at four distal sites simultaneously at 70% efficiency. We also employ PFunkel to create a comprehensive codon mutagenesis library of the TEM-1 ß-lactamase gene. We designed this library to contain 18,081 members, one for each possible codon substitution in the gene (287 positions in TEM-1 x 63 possible codon substitutions). Deep sequencing revealed that ∼97% of the designed single codon substitutions are present in the library. From such a library we identified 18 previously unreported adaptive mutations that each confer resistance to the ß-lactamase inhibitor tazobactam. Three of these mutations confer resistance equal to or higher than that of the most resistant reported TEM-1 allele and have the potential to emerge clinically.
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Affiliation(s)
- Elad Firnberg
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Baltimore, MD, USA
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