blaCTX-M, blaTEM, and blaSHV in Enterobacteriaceae from North-Indian tertiary hospital: high occurrence of combination genes

ObjectiveTo delineate the frequency of occurrence of blaCTX-M, blaTEM, and blaSHV in Enterobacteriaceae from North-Indian tertiary hospital.MethodsA random collection of a subset of 45 Escherichia coli (E. coli) and 28 Klebsiella pneumoniae (K. pneumoniae) that was resistant to a third generation cephalosporin and obtained during 2007–2008 was selected for detailed screening for blaCTX-M, blaTEM, and blaSHV by monoplex PCRs. The isolates demonstrating the presence of blaCTX-M alleles were characterized for the specific CTX-M-genogroup by using a multiplex PCR.ResultsResistance to cefoperazone, ceftazidime, ceftriaxone, cefotaxime, cefoxitin and piperacillin was 100% each in K. pneumoniae isolates, whereas these resistance-rates for E. coli isolates were 93.1%, 83.8%, 91.9%, 93.6%, 97.3% and 97.1%, respectively. Concomitant resistance to aminoglycosides, quinolones and aztreonam was also noticed. Presence of any of the bla genes (blaCTX-M, blaTEM, and blaSHV) was noticed in a total of 28 (38.4%) isolates of the 73 isolates studied. Many isolates demonstrated occurrence of these genes in various combinations. blaCTX-M, blaTEM, and blaSHV were noticed in 28.8%, 10.9% and 13.7% isolates, respectively. Multiplex PCR in blaCTX-M harboring isolates demonstrated the presence of CTX-M-Genogroup-1 and sequencing for the specific CTX-M-type revealed presence of CTX-M-15 type. RAPD typing showed wide diversity in isolates.ConclusionsThis is amongst the premier report describing the simultaneous occurrence of blaTEM, blaSHV, and blaampC in Indian Enterobacteriaceae and that wider dissemination of these genes, as demonstrated by diversity of isolates, raises concern and emphasizes a need for extensive search for the presence of these gene pools in Indian subcontinent.