Phenotypic & molecular characterization of AmpC β-lactamases among Escherichia coli, Klebsiella spp. & Enterobacter spp. from five Indian Medical Centers.
Plasmid mediated Amp C phenotype was confirmed in 114 of the 312 (36.5%) cefoxitin resistant isolates with 255 (81.7%) showing multidrug resistance. Susceptibility to tigecycline was highest (99%) followed by imipenem, meropenem (97%), ertapenem (89%), amikacin (85%), and piperacillin-tazobactam (74.6%). Levofloxacin resistance was 82 per cent. ESBL co carriage was observed among 92 per cent of Amp C producers. Among 114 Amp C producers, 48 could be assigned a genotype, this included CIT- FOX (n=25), EBC (n=10), FOX (n = 4), CIT (n=3), EBC-ACC (n=2) and one each of DHA, EBC-DHA, FOX -DHA and FOX-EBC-DHA. Interpretation &
Conclusions:
Overall, AmpC phenotypes were found in 12.5 per cent isolates, multidrug resistance and ESBL co-carriage among them was high suggesting plasmid mediated spread. The study results have implications in rational antimicrobial therapy and continued surveillance of mechanisms of resistance among nosocomial pathogens.