Iranian Journal of Medical Sciences

Document Type: Original Article(s)



Background: Enterococci faecalis are predominating species of Enterococci causing nosocomial infections. Acquisition of resistance to antibacterial agents, and ability to transfer the resistant genes made them clinically important. This study was performed to determine the frequency of isolation of different species of Enterococci, and the antibacterial resistance pattern of the isolated species. Methods: Enterococcal species were isolated from clinical samples. In vitro susceptibility of the isolates to 10 antibacterial agents was tested by standard methods and β-lactamase production was detected using starch-iodide method. Results: 100 Enterococci were isolated from 585 different clinical samples. 73% of the isolates were E. faecalis, 13% E. faecium and 14% which were not identified as either one, were regarded as other enterococcal species. Highest rate of resistance (98% or more) was found for oxacillin and penicillin while vancomycin and chloramphenicol were among the most active agents. Resistance to antibacterial agents was more common for E. faecium and β-lactamase production was found in 81% of the isolates. Conclusion: E. faecalis was the dominant species, with the higher rate of β-lactamase production. E. faecium was more resistant to antibacterial agents as compared to other isolates. 80% of the isolates had multiple drug resistance phenotypes (MDR). Low-level resistance to vancomycin (intermediate reaction in disk diffusion method, minimum inhibitory concentrations range ≥4-16 µg/ml) and presence of MDR isolates is very important and should be considered as an danger alarm for serious enterococcal infections.Iran J Med Sci 2005; 30(2): 68-72. Keywords ● Enterococci ● antibacterial resistance ● beta-lactamase