Isolation, characterization and antibiotic susceptibility of staphylococcal isolates, with special reference to methicillin resistant Staphylococcus aureus, from anterior nares of health care workers in a tertiary health care centre.

Abstract

Background: Staphylococcus aureus (S.aureus) and its resistant form Methicillin resistant S. aureus (MRSA) is one of the most common nosocomial pathogen, causing a wide range of infections in humans. The anterior nares are the main ecological niche for S.aureus. Nasal carriage of S. aureus acts as an important reservoir of infection among the colonized health care workers and they transmit the infection to the community. The aim of the present study is to estimate nasal colonization of S.aureus (with special reference to MRSA) in health care workers (doctors and nursing staff) and its antibiotic susceptibility pattern.Methods: A descriptive study was planned in the Department of Microbiology, JLN Medical College, Ajmer (Rajasthan, India) after due approval from institutional ethics committee. A total of 170 health care workers of either sex and ages between 18 to 60 years were screened for S.aureus. Identification was done using standard microbiological techniques, by studying their morphology, colony and biochemical characteristics. MRSA was detected by cefoxitin disc diffusion test, oxacillin disc diffusion test, minimum inhibitory concentration (MIC) of oxacillin by E-test and oxacillin screen agar test. The observations were described in proportions and chi-squared test was used to find independence. Statistical significance was considered at 5%. Results: Among 170 samples, 159 (93.53%) samples (50 doctors and 109 nursing staff) had staphylococci colonization. Out of 159 isolates, 34(21.38%) isolates were S.aureus. Further, 8(5.03%) S. aureus isolates were resistant to both cefoxitin and oxacillin and had oxacillin MIC values ≥ 4 µg/ml and were considered MRSA. All the MRSA belonged to nursing staff [Males: 5.50% , Females :1.83%]. All S. aureus and MRSA isolates were found sensitive to linezolid. In addition, 0.63% MRSA was found vancomycin intermediate S. aureus (VISA) and all MRSA isolates were sensitive to mupirocin (minimum inhibitory concentration ≤ 4 µg/ml).Conclusion: Screening and treatment of health care workers colonized with MRSA should be an important component of hospital infection control policy. These measures will prevent spread of infection to patients and community and thereby reduce the morbidity, mortality and health care costs associated with nosocomial infections.