Genetic characteristics of plasmid-mediated extended-spectrum ß-lactamases (CTX-M) and its coexistencewith carbapenemases (NDM-1) in clinical Gramnegative bacteria

Abstract

Infections caused by extended-spectrum ß-lactamase (ESBL) and carbapenemaseproducing Gramnegative bacteria are an emerging global health problem. For the present study, the clinical isolates (n=58) were collected from two diagnostic centers in Tamil Nadu, India. The bacterial isolates were screened for cefotaxime and meropenem resistance. Further, the presence of ESBL resistant gene <em>CTX-M</em> and carbapenem-resistant genes <em>bla</em>_NDM-1,<em>bla</em>_OXA-48, <em>bla</em>_IMP, <em>bla</em>_VIM, <em>bla</em>_KPC and integrons were studied. Transconjugation studies and DNA fingerprinting was performed. A total of 58 clinical isolates that included <em>Escherichia coli</em> (n=33), <em>Klebsiella pneumoniae</em> (n=8),<em>Pseudomonas aeruginosa</em> (n=6),<em>Enterobacter cloacae</em> (n=6) and <em>Proteus mirabilis</em> (n=5) were analyzed.MIC results showed that 77.6% (45/58) and 36.2% (21/58) of the clinical isolates were resistant to cefotaxime and meropenem, respectively. The <em>bla</em>_CTX-M was present in 34 isolates, the presence of <em>bla</em>_NDM-1 in 6 isolates and the <em>bla</em>_OXA-48 in 2 isolates. Class 1 integrons were found in 22 isolates and class 2 in 5 isolates. Conjugation studies revealed that 9 CTX-M positive <em>E. coli </em> strains were able to transfer resistance <em>via</em> plasmids to susceptible <em>E. coli</em> AB1157.This study documented the presence of <em>E. coli </em> strains to harbour both CTX-M and NDM-1 gene determinants and plasmid-associated ESBLs were transferable in some <em>E. coli</em> strains.