Single or in Combination Antimicrobial Resistance Mechanisms of Klebsiella pneumoniae Contribute to Varied Susceptibility to Different Carbapenems

Yu-Kuo Tsai,Ci-Hong Liou,Chang-Phone Fung,L Kristopher Siu,Jung-Chung Lin,José A Bengoechea

doi:10.1371/journal.pone.0079640

Abstract

Resistance to carbapenems has been documented by the production of carbapenemase or the loss of porins combined with extended-spectrum β-lactamases or AmpC β-lactamases. However, no complete comparisons have been made regarding the contributions of each resistance mechanism towards carbapenem resistance. In this study, we genetically engineered mutants of Klebsiella pneumoniae with individual and combined resistance mechanisms, and then compared each resistance mechanism in response to ertapenem, imipenem, meropenem, doripenem and other antibiotics. Among the four studied carbapenems, ertapenem was the least active against the loss of porins, cephalosporinases and carbapenemases. In addition to the production of KPC-2 or NDM-1 alone, resistance to all four carbapenems could also be conferred by the loss of two major porins, OmpK35 and OmpK36, combined with CTX-M-15 or DHA-1 with its regulator AmpR. Because the loss of OmpK35/36 alone or the loss of a single porin combined with bla CTX-M-15 or bla DHA-1-ampR expression was only sufficient for ertapenem resistance, our results suggest that carbapenems other than ertapenem should still be effective against these strains and laboratory testing for non-susceptibility to other carbapenems should improve the accurate identification of these isolates.

Highlights

The increasing prevalence of extended-spectrum βlactamases (ESBLs) and plasmid-mediated AmpC βlactamases in Enterobacteriaceae is a critical concern for scientists trying to develop treatments against bacterial infections
Because E. coli J53 does not retain the blaKPC-2-carrying plasmids of clinical K. pneumoniae for any period of time [11], the blaKPC-2-carrying plasmid was directly transferred to the K. pneumoniae strains NVT2001S, ΔompK35, ΔompK36 and ΔompK35/36 by filter conjugation [10]
The β-lactamases detected in the clinical plasmids are shown in Table 1, while blaCTX-M-15, blaSHV-12, blaDHA-1-ampR, blaKPC-2 or blaNDM-1 was found in each of the five clinical plasmids

Summary

Introduction

The increasing prevalence of extended-spectrum βlactamases (ESBLs) and plasmid-mediated AmpC βlactamases in Enterobacteriaceae is a critical concern for scientists trying to develop treatments against bacterial infections. TEM-, SHV- and CTX-M-type ESBLs and CMY- and DHA-type AmpC β-lactamases are commonly found in multidrug-resistant Enterobacteriaceae [1,2,3,4]. Carbapenem-resistant Enterobacteriaceae have recently been reported worldwide. In Klebsiella pneumoniae, numerous reports have confirmed carbapenem resistance by ESBLs or AmpC β-lactamases combined with the loss of outer membrane porins OmpK35 and/or OmpK36 [5,6,7], or by carbapenemases alone [8]. The mechanisms of carbapenem resistance were mainly detected from clinical isolates with individual or combined genetic alterations. We created mutants with individual or combined resistance mechanisms from a susceptible clinical K. pneumoniae isolate and studied each resistance mechanism in response to these four carbapenems

Methods

Results

Conclusion