Antibiotic Susceptibility and mecA Frequency in Staphylococcus epidermidis, Isolated From Intensive Care Unit Patients

BACKGROUND: Coagulase-negative staphylococci (CoNS), especially Staphylococcus epidermidis, are considered as normal flora of human epithelia and also important opportunistic pathogens for nosocomial infections. S. epidermidis can also act as a reservoir for mecA, responsible for high-level resistance to methicillin and transferring it to S. aureus. OBJECTIVES: The aim of this study was to determine the prevalence of S. epidermidis as well as antibiotic susceptibility pattern and mecA prevalence in S. epidermidis isolated from intensive care unit (ICU) patients. MATERIALS AND METHODS: A cross-sectional study was conducted from September 2010 to September 2011 and 184 coagulase-negative staphylococci were collected from different clinical samples in three hospitals. S. epidermidis was identified by conventional bacteriological tests. Antibiotic susceptibility testing was performed using disk diffusion method. Frequency of mecA was detected by specific PCR. RESULTS: Frequency of S. epidermidis was 34.8%, the most susceptibility was seen to linezolid and vancomycin, and the least susceptibility was seen to tetracycline.Majority of the S. epidermidis isolates carried mecA (92.2%). The most common resistant pattern was trimethoprim-sulfamethoxazole, tetracycline, erythromycin, and methicillin resistance, found in 23.4% of the isolates, followed by resistance to methicillin as the second-most common resistant pattern, observed in 20.3% of the isolates. CONCLUSIONS: Frequency of S. epidermidis was significantly lower, compared to other studies. Presence rate of mecA and susceptibility to linezolid and vancomycin did not show significant differences with other investigations, while resistant to trimethoprim-sulfamethoxazole was significantly lower compared to other investigations, and resistance to tetracycline was significantly higher in comparison to other investigations. Presence of methicillin-resistant S. epidermidis in ICU patients, especially in individuals with compromised immune systems, may cause infection and would be more complicated in the case of antibiotic resistance.