High-Level Aminoglycoside Resistance and β-Lactamase Production in Enterococci at a Tertiary Care Hospital in India

Enterococci, a family of important opportunistic pathogens, exhibits intrinsic resistance to a number of antimicrobial agents in addition to acquired multidrug resistance. The present study was conducted to determine whether enterococci at a tertiary care hospital in India exhibit high-level aminoglycoside resistance and beta-lactamase production. Enterococci were isolated from various clinical specimens and identified phenotypically. High-level resistance (HLR) to gentamicin, kanamycin, and streptomycin was determined by disc diffusion tests. beta-lactamase production was detected using three methods: iodometric, acidometric, and chromogenic beta-lactamase assays. Among the 86 enterococci isolated, 34 were found to have HLR to one or more aminoglycosides; HLR to kanamycin was most common. Vancomycin resistance was present in four of the isolates. Only one enterococcus produced beta-lactamase, and it was sensitive to ampicillin on routine disc diffusion testing. beta-lactamase production among enterococci, though not very common, may be missed on routine susceptibility testing. Frequent occurrence of HLR to kanamycin makes amikacin a poor choice for inclusion in combination therapy with cell wall-active agents.