PREVALENCE OF AMINOGLYCOSIDE MODIFYING ENZYMES GENES AMONG ISOLATES OF ENTEROCOCCUS FAECALIS AND ENTEROCOCCUS FAECIUM IN IRAN

Disks containing 120 µg of gentamicin were used to detect high-level gentamicin-resistant phenotype (HLGR) among isolates of Enterococcus faecalis (n = 79) and E. faecium (n = 35). These isolates were collected from three hospitals in Tehran during 2002–2004. The macrobroth dilution assay was then used to determine the minimum inhibitory concentration (MIC) of gentamicin. The susceptibility of isolates against amikacin, netilmicin, tobramycin, and kanamycin were also determined by Kirby-Bauer method. All isolates were subjected to polymerase chain reaction (PCR) assays targeting aminoglycoside modifying enzyme (AMEs) genes including aac(6 ′)-aph(2 ″), aph(2 ″)-Ib, aph(2 ″)-Ic, aph(2 ″)-Ia, aph(2 ″)-Id, aph(3 ′)-IIIa, and ant(4 ′)-Ia. Fifty-nine isolates (52%) showed HLGR phenotype. All isolates with HLGR phenotype and those showing 64 < MIC < 500 µg/ml contained aac(6 ′)-aph(2 ″). The aph(3 ′)-IIIa was found in 61% of the isolates with HLGR phenotypes and in 65% of isolates with MIC < 500. Coexistence of ...