Microbiology Research Journal International

The purpose of this study was to determine the mechanisms of third generation cephalosporins resistance among blood isolates of Klebsiella pneumoniae and Escherichia coli. A total of 549 isolates, Klebsiella pneumoniae (n=369) and Escherichia coli (n=180) were included. Antibiotic susceptibility pattern, phenotypic and genotypic detection of ESBL and AmpC production were carried out. The genetic environment surrounding bla_CTX-M gene was assessed for insertion sequences. The plasmid-mediated quinolone resistance (PMQR) and integron carriage rate of ESBL producers were studied. The clonality was assessed by pulsed-field gel electrophoresis.  Also, the plasmids bearing the ESBL, AmpC genes were studied by incompatibility typing and conjugation assay. By phenotypic tests, K. pneumoniae (79.8%) and E. coli (74.1%) were ESBL producers. Similarly, K. pneumoniae (70.5%) and E. coli (76.8%) were AmpC producers. By PCR, K. pneumoniae (68%) and E. coli (62%) carried ESBL genes. bla_{CTX-M- 15} was the prevalent type (98.1%). The linkage of ISEcp1 with bla_CTX-M-15 gene was found in 92.5% of the bla_CTX-M-15 genes. bla_CMY-2 was present in 57% isolates. PFGE showed no clonal relatedness however; replicon typing revealed that ESBL genes were carried on 5 different replicon types, IncA/C being the commonest type present in this region. Also, PMQR was found in 19.3% of the ESBL producers. As high as 21.5% of class 2 integron was noted for first time from this region. A high prevalence of ESBL and AmpC genes was noticed. The clonal diversity, transferability of bla_CTX-M plasmids suggest a higher incidence and wider distribution of ESBL and AmpC producing bacteria existing in the South India.