Staphylococcus aureus and MRSA nasal carriage in general population

Assessment of Staphylococcus aureus [S. aureus] and MRSA nasal carriage in our general population. Cross-sectional analytical study. A private Pathology Laboratory in Lahore city from January 2002 to December 2003. Nasal swabs were obtained from the apparently healthy persons accompanying the patients attending the laboratory. These swabs were inoculated on blood and mannitol salt agar plates and incubated at 37°C. The isolate[s] were identified as S. aureus on the basis of colony morphology, Gram staining, catalase and coagulase tests. Sensitivity to Oxacillin was determined using standard Kirby Bauer technique. Nasal swabs from 1660 subjects from the community were studied. Out of these samples, a total of 246 [14.82%] samples were positive for growth of S. aureus [nasal carriers of S. aureus]. Out of 246 S. aureus isolates, 48 [19.51%] isolates were methicillin resistant S. aureus [MRSA]. Nasal carriage was higher in males [15.47%] as compared to females [13.26%], in urban areas [16.99%] as compared to rural areas [11.32%] and in the year 2002 [16.02%] as compared to year 2003 [13.08%]. However, the difference was significant only for the urban vs. rural comparison [p<0.05]. MRSA isolates were also significantly higher among S. aureus isolates from the nasal cavities of urban subjects [22.98%] as compared to rural ones [11.11%]. Maximum nasal carriage was present in the age group upto 9 years [20.23%] with decrease in the age groups 10-19, 20-29 and 30-39 years followed by small rise in the older subjects. The nasal S. aureus carriage as well as methicillin resistance among these isolates are more common in urban community