Dataset Information

Combination of Amino Acid Substitutions Leading to CTX-M-15-Mediated Resistance to the Ceftazidime-Avibactam Combination.

ABSTRACT: Single amino acid substitutions in the ? loop of KPC ?-lactamases are known to lead to resistance to the ceftazidime-avibactam combination. Here, we investigate this mechanism of resistance in CTX-M enzymes, which are the most widely spread extended-spectrum ?-lactamases worldwide. Nine single amino acid polymorphisms were identified in the ? loop of the 172 CTX-M sequences present in the Lahey database of ?-lactamases. The corresponding modifications were introduced in CTX-M-15 by site-directed mutagenesis. None of the nine substitutions was associated with ceftazidime-avibactam resistance in Escherichia coli TOP10. However, two substitutions led to 4-fold (P167S) and 16-fold (L169Q) increases in the MIC of ceftazidime. We determined whether these substitutions favor the in vitro selection of mutants resistant to ceftazidime-avibactam. The selection provided mutants for the L169Q substitution but not for the P167S substitution or for the parental enzyme CTX-M-15. Resistance to the drug combination (MIC of ceftazidime, 16 ?g/ml in the presence of 4 ?g/ml of avibactam) resulted from the acquisition of the S130G substitution by CTX-M-15 L169Q. Purified CTX-M-15 with the two substitutions, L169Q and S130G, was only partially inhibited by avibactam at concentrations as high as 50,000 ?M but retained ceftazidime hydrolysis activity with partially compensatory decreases in kcat and Km These results indicate that emergence of resistance to the ceftazidime-avibactam combination requires more than one mutation in most CTX-M-encoding genes. Acquisition of resistance could be restricted to rare variants harboring predisposing polymorphisms such as Q at position 169 detected in a single naturally occurring CTX-M enzyme (CTX-M-93).

SUBMITTER: Compain F

PROVIDER: S-EPMC6125495 | biostudies-literature | 2018 Sep

REPOSITORIES: biostudies-literature

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Combination of Amino Acid Substitutions Leading to CTX-M-15-Mediated Resistance to the Ceftazidime-Avibactam Combination.

Compain Fabrice F Dorchène Delphine D Arthur Michel M

Antimicrobial agents and chemotherapy 20180827 9

Single amino acid substitutions in the Ω loop of KPC β-lactamases are known to lead to resistance to the ceftazidime-avibactam combination. Here, we investigate this mechanism of resistance in CTX-M enzymes, which are the most widely spread extended-spectrum β-lactamases worldwide. Nine single amino acid polymorphisms were identified in the Ω loop of the 172 CTX-M sequences present in the Lahey database of β-lactamases. The corresponding modifications were introduced in CTX-M-15 by site-directed ...[more]

PMID: 29941650

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Project description:Objective: To systematically review and compare the efficacy and posttreatment resistance of ceftazidime-avibactam therapy and ceftazidime-avibactam-based combination therapy in patients with Gram-negative pathogens. Methods: PubMed, Embase, Web of Science, CNKI, and Wanfang Data databases were searched from their inception up to March 31, 2021, to obtain studies on ceftazidime-avibactam therapy versus ceftazidime-avibactam-based combination therapy in patients with carbapenem-resistant Gram-negative pathogens. The primary outcome was mortality rate, and the second outcomes were microbiologically negative, clinical success, and the development of resistance after ceftazidime-avibactam treatment. Results: Seventeen studies representing 1,435 patients (837 received ceftazidime-avibactam-based combination therapy and 598 received ceftazidime-avibactam therapy) were included in the meta-analysis. The results of the meta-analysis showed that no statistically significant difference was found on mortality rate (Petos odds ratio (OR) = 1.03, 95% confidence interval (CI) 0.79-1.34), microbiologically negative (OR = 0.99, 95% CI 0.54-1.81), and clinical success (OR =0.95, 95% CI 0.64-1.39) between ceftazidime-avibactam-based combination therapy and ceftazidime-avibactam therapy. Although there was no difference in posttreatment resistance of ceftazidime-avibactam (OR = 0.65, 95% CI 0.34-1.26) in all included studies, a trend favoring the combination therapy was found (according to the pooled three studies, OR = 0.18, 95% CI 0.04-0.78). Conclusions: The current evidence suggests that ceftazidime-avibactam-based combination therapy may not have beneficial effects on mortality, microbiologically negative, and clinical success to patients with carbapenem-resistant Gram-negative pathogens. A trend of posttreatment resistance occurred more likely in ceftazidime-avibactam therapy than the combination therapy. Due to the limited number of studies that can be included, additional high-quality studies are needed to verify the above conclusions.

Project description:Infections due to carbapenemase-producing Gram-negative pathogens are associated with limited treatment options and consequently lead to increased mortality and morbidity. In response, combinations of existing ?-lactams and novel ?-lactamase inhibitors, such as ceftazidime-avibactam (CAZ-AVI), have been developed as alternative treatment options. To understand the development of resistance and evolutionary trajectories under CAZ-AVI exposure, we studied the effects of ceftazidime (CAZ) and CAZ-AVI on the carbapenemase OXA-48 and the epidemic OXA-48 plasmid in Escherichia coli Exposure of CAZ and CAZ-AVI resulted in single (P68A) and double (P68A,Y211S) amino acid substitutions in OXA-48, respectively. The antimicrobial susceptibility data and enzyme kinetics showed that the P68A substitution was responsible for an increased activity toward CAZ, whereas P68A,Y211S led to a decrease in the inhibitory activity of AVI. X-ray crystallography and molecular modeling of the mutants demonstrated increased flexibility within the active site, which could explain the elevated CAZ hydrolysis and reduced inhibitory activity of AVI. Interestingly, these substitutions resulted in collateral effects compromising the activity of OXA-48 toward carbapenems and penicillins. Moreover, exposure to CAZ-AVI selected for mutations within the OXA-48-encoding plasmid that severely reduced fitness in the absence of antimicrobial selection. These evolutionary trade-offs may contribute to limit the evolution of OXA-48-mediated CAZ and CAZ-AVI resistance, as well as potentially resensitize isolates toward other therapeutic alternatives.IMPORTANCE The recent introduction of novel ?-lactam/?-lactamase inhibitor combinations like ceftazidime-avibactam has increased our ability to treat infections caused by multidrug-resistant Gram-negative bacteria, including carbapenemase-producing Enterobacterales However, the increasing number of cases of reported resistance to ceftazidime-avibactam is a concern. OXA-48 is a carbapenemase that has no significant effect on ceftazidime, but is inhibited by avibactam. Since isolates with OXA-48 frequently harbor extended-spectrum ?-lactamases that are inhibited by avibactam, it is likely that ceftazidime-avibactam will be used to treat infections caused by OXA-48-producing Enterobacterales. Our data show that exposure to ceftazidime-avibactam can lead to changes in OXA-48, resulting in increased ability to hydrolyze ceftazidime and withstand the inhibitory effect of avibactam. Thus, resistance toward ceftazidime-avibactam among OXA-48-producing Enterobacterales should be monitored. Interestingly, the compromising effect of the amino acid substitutions in OXA-48 on other ?-lactams and the effect of ceftazidime-avibactam exposure on the epidemic OXA-48 plasmid indicate that the evolution of ceftazidime-avibactam resistance comes with collateral effects.

Dataset Information

Combination of Amino Acid Substitutions Leading to CTX-M-15-Mediated Resistance to the Ceftazidime-Avibactam Combination.

Publications

Combination of Amino Acid Substitutions Leading to CTX-M-15-Mediated Resistance to the Ceftazidime-Avibactam Combination.

Similar Datasets

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