A Survey of Methicillin-Resistance Staphylococcus aureus Isolated from Patients Hospitalized in the ICU, NICU and Surgical Departments of Tehran University of Medical Sciences Hospitals

Background and Aim: Staphylococcus aureus is an important pathogen that causes various infections. The presence of some pathogenic factors in this bacterium helps the bacteria to survive in response to the immune system and antimicrobial treatments. Efforts to treat infections caused by these strains have resulted in resistance to most antibiotics, especially methicillin and vancomycin resistance, during recent years. Therefore, the consequences of infections caused by this bacterium can be serious. In this study we aimed to survey methicillin- resistance Staphylococcus aureus isolated from patients hospitalized in the ICU, NICU and surgical departments of Tehran University of Medical Sciences hospitals. Material and Method: 430 clinical samples of the patients were collected and identified as Staphylococcus aureus by phenotype and biotype tests. MRSA isolates were first screened by showing resistance to cefoxitin by disc diffusion method and finally confirmed by examining the mecA gene by PCR. The microbial resistance pattern of MRSA was also measured by disk diffusion method. Investigating the presence of a vancomycin resistance gene in isolated MRSA occurred by PCR. Results: Out of 430 clinical samples, 117 (27.20%) Staphylococcus aureus were isolated of which 42 (35.89%) were identified as MRSA. The most MRSA obtained from the ICU department with 25 cases (59.52%). The majority of patients infected with MRSA belonged to the age group of 40-65 years. The mecA gene was detected in all MRSA. The entire MRSA was 100% sensitive to vancomycin and linezolid, and 100% resistance to cloxacillin. Molecular detection of vanA gene in isolated MRSA showed 2 (4.76%) of them contained vanA gene. Conclusion: The high prevalence of MRSA and its antibiotic resistance pattern to vancomycin and other antibiotic families can lead to treatment failures, uncontrolled nosocomial infections, and mortality. Although the PCR-based detection method is superior to other conventional techniques, a combination of these methods can provide diagnostic accuracy.