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

Antimicrobial resistance of community and hospital acquired staphylococcus aureus isolates to oxacillin and glycopeptides

To determine sensitivity pattern of Staphylococcus aureus isolates from the community and hospitals to methicillin, glycopeptides and other antimicrobial agents. Design: Descriptive study. Place and Duration of Study: Private Pathology Laboratory in Lahore from January 2001 to April 2002. Subjects and A total of 714 Staphylococcus aureus [S.aureus] isolates from the community and hospital were tested. Community acquired S.aureus strains [n=434] were isolated from specimens like pus from boils/pimples and nasal swabs of patients with asthma attending a local allergy clinic. The hospital acquired S.aureus [n=280] were isolated from specimens like pus from wounds/discharging sinuses, ear swabs, blood and urine. All the isolates were subjected to sensitivity test against Oxacillin, Vancomycin, Teicoplanin, Penicillin, Imipenem, Cefipime and other anti-staphylococcal agents by standard Kirby-Bauer disk diffusion method. Beta lactamase production by all the isolates was also determined by acidimetric test. Significantly higher number of hospital acquired S.aureus isolates [p<0.01] were beta lactamase producing [96.07%] as compared to community acquired [81.79%]. Methicillin [Oxacillin] resistance was also higher among hospital strains [31.1%] as compared to community ones [14.1%]. No isolate from the community showed resistance to glycopeptides. While 0.3% and 0.7% of all S.aureus isolates were interpreted as resistant to Vancomycin and Teicoplanin respectively as there was no zone of inhibition. The resistance to these drugs was a bit higher among the MRSA [1.1% and 2.3% respectively]. More than 90% of nosocomial MRSA strains were sensitive to Ofloxacin and Fucidic Acid. Resistance to Erythromycin, Lincomycin and Gentamicin was 70.1, 33.3 and 39.1% in that order. In general resistance to different antimicrobial was lower among S.aureus strains of community origin as compared to those of hospital origin. Methicillin and multiple drug resistance is quite a significant problem in nosocomial as well as community acquired S.aureus strains. Moreover, it appears that resistance to glycopeptides has also emerged in our nosocomial S. aureus strains. Microbiology laboratories should make efforts not only to regularly screen S.aureus isolates for sensitivity to glycopeptides but also to determine MIC of the isolates