Emergence and dissemination of Enterobacteriaceae with plasmid-mediated CMY-6 and CTX-M-15 beta-lactamases in community in North-India

A collection of 88 Escherichia coli and 22 Klebsiella pneumoniae strains previously studied for the carriage of bla CTX₋M₋₁₅ were screened for the presence of bla ampC using multiplex PCR, and analysed for antibiotic resistance and co-carriage of bla ampC and bla CTX₋M₋₁₅. Cefoxitin resistance was noticed in total of 41.8% isolates. Concomitant resistance to third and fourth generation cephalosporins, aztreonam, gentamicin, trimethoprim and ciprofloxacin was noted. A total of 20% (22/110) isolates (14.5% E. coli and 5.5% K. pneumoniae) carried plasmidic bla ampC of the CIT-family. Sequencing of the representative isolates revealed CMY-6 AmpC-beta-lactamase. Simultaneous occurrence of bla ampC and bla CTX₋M was noticed in 77.3% (17/22) isolates. Plasmid analysis of the selected isolates showed the presence of a single plasmid of ca. ~23 kb. Curing and transconjugation experiments provided evidence of carriage of bla CMY and bla CTX₋M on same plasmid. RAPD typing revealed the presence of bla CMY and bla CTX₋M in a wider range of strains of E. coli and K. pneumoniae.