Emergence of integron borne PER-1 mediated extended spectrum cephalosporin resistance among nosocomial isolates of Gram-negative bacilli.

ABSTRACT

Background & objectives: Pseudomonas extended resistant (PER) enzymes are rare type of extended-spectrum beta lactamases (ESBLs) that confer third generation cephalosporin resistance. These are often integron borne and laterally transmitted. The aim of the present study was to investigate the emergence of integron borne cephalosporin resistant PER-1 gene in diverse incompatibility (Inc) group plasmids among gram-negative bacteria. Methods: a total of 613 consecutive, non-duplicate, Gram-negative bacteria of Enterobacteriaceae family and non-fermenting Gram-negative bacteria were isolated from different clinical specimens during a period of 18 months. For amplification and detection of blaPER, multiplex PCR was done. For understanding the genetic environment of blaPER-1, integrase gene PCR and cassette PCR (59 be) was performed. Gene transferability experiment was carried out and PCR based replicon typing was performed for incompatibility group typing of plasmids using 18 pairs of primers. An inhibitor based method was used for phenotypic detection of intrinsic resistance. Results: Multiplex PCR and sequencing confirmed that 45 isolates were harbouring blaPER-1. Both class 1 and class 2 integrons were observed among them. Integrase and cassette PCR (59 be) PCR results confirmed that the resistant determinant was located within class 1 integron. Transformation and conjugation experiments revealed that PER-1 was laterally transferable and disseminated through diverse Inc plasmid type. Efflux pump mediated carbapenem resistance was observed in all isolates. All isolates belonged to heterogenous groups. Interpretation & conclusions: This study demonstrates the dissemination of cephalosporins resistant, integron borne blaPER-1 in hospital setting in this part of the country and emphasizes on the rational use of third generation cephalosporins to slow down the expansion of this rare type of ESBL gene.