Frequency of class 1 integron and multidrug resistance pattern among isolates of Staphylococcus aureus from hospitalized patients and environmental samples in an intensive care unit in Tahran, Iran

The aim of this study was to investigate the presence of class 1 integrons and their association with antimicrobial resistance profiles among Staphylococcus aureus (S. aureus) isolates from environment, staffs and hospitalized patients at an intensive care unit (ICU) in a hospital in Tehran, Iran. A total of 410 clinical, environmental and personnel samples were examined for S. aureus infections and contamination. Susceptibility of these isolates to 15 antibiotics and minimum inhibitory concentrations (MIC) of oxacillin were determined by disk diffusion and micro dilution methods, respectively. Class 1 integrons (int1) were determined among the extracted DNA and purified plasmid samples by PCR. In this study, 32.2% of the clinical specimens including respectively 27% and 19.3% of the environmental and personnel samples were positive for S. aureus. A total of 90.6%, 68% and 46% of the clinical, environmental and personnel samples showed oxacillin resistance phenotype, respectively. In addition, all of the clinical and 33.3% of the environmental isolates showed multidrug resistance (MDR) phenotype. Highest resistance rates for the clinical isolates were related to ampicillin and erythromycin (96.5%), penicillin and kanamycin (93.5%), and gentamicin (90.5%); and these rates for the environmental samples were related to penicillin (72%), ampicillin (68%), and erythromycin (66%); and also for the personnel samples were related to penicillin and ampicillin (73%) and erythromycin (61.5%). Integron class one was found among 32.3% of the clinical, 67.7% of the environmental and all of the oxacillin resistance isolates (100%). Nose and hands of the ICU nurses and staffs seems as main sources of the infections. Our results also established the presence of class 1 integron in these isolates, especially among the isolates with oxacillin resistant phenotype.