Characteristics of Nosocomial MRSA in Assir Central Hospital, Abha, Kingdom of Saudi Arabia

The objective of this study is to determine the characteristics of nosocomial methicillin-resistant and sensitive Staphylococcus aureus (MRSA & MSSA) and their minimum inhibitory concentration (MIC) to vancomycin and oxacillin. Over a six-month period a study of Staphylococcus aureusisolates from clinical specimens of patients with nosocomial infections in Assir Central Hospital (ACH), Abha, Saudi Arabia, between September 2003 and February 2004, was carried out. Isolation and identification of Staphylococcus aureus was performed using standard microbiological methods. MIC to vancomycin and oxacillin was carried out using the E-test strips. Eighty-five Staphylococcus aureus isolates were identified. These were made up of 39 (45.9%) MRSA and 46 (54.1%) MSSA. The MIC to oxacillin showed that 37/39 (94.9%) MRSA had MIC >256 µg/ml and only 2/39 (5.1%) had MIC of 4 and 32 µg/ml. Thirty of forty six (65.2%) of the MSSA had MIC < 0.50 µg/ml and 16/46 (34.8%) had MIC of between 0.50 -2 µg/ml. All the 85 isolates were fully sensitive to vancomycin (MIC breakpoint < 4 µg/ml). There is even distribution of sensitivity pattern to vancomycin among MRSA and MSSA isolates. 31/39 (79.5%) of MRSA had MIC of 2 µg/ml while 34/46(74.0%) of MSSA had MIC of 2 µg/ml. The prevalence of MRSA in nosocomial infections in ACH is 45.9%. Thirty-seven out of thirty-nine (94.9%) of the MRSA strains show high resistance to oxacillin (MIC > 256 µg/ml). The use of oxacillin-related drugs to treat nosocomial Staphylococcal infections in ACH should be reviewed and infection control practices should be intensified so as to stem any future increase in MRSA prevalence in the hospital.
Key words: MRSA, Characteristics, MICs, Vancomycin, Oxacillin.Afr. J. Clin. Exper. Microbiol. 2005; 6(2): 163-166

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