EVALUATION OF METHODS FOR THE DETECTION OF NASAL CARRIAGE OF STAPHYLOCOCCUS-AUREUS

In the present study we investigate the optimal methodology for determ ination of the nasal carriage rate of Staphylococcus aureus. Tests wer e performed on 91 healthy laboratory staff. The reproducibility of dif ferent sampling, transportation, storage and culture methods was exami ned. We compared sterile dry cotton wool swabs with sterile dry cotton wool swabs impregnated with charcoal and 5% blood agar plates with ma nnitol salt agar plates after different incubation periods. Finally, w e investigated the detection rate for S. aureus following direct plati ng compared to storage in Stuart's transport medium for 7 days. There were no differences in isolation rates from the right or left nostril using either cotton or charcoal swabs. Charcoal swabs gave an increase d isolation rate as compared to cotton swabs, and incubation in broth enrichment medium containing 6.5% NaCl also increased the isolation ra te. Storage in Stuart's transport medium for 7 days gave an increase i n isolation rate as compared to direct plating on blood agar. With man nitol salt agar plates the increase in isolation rate when incubation was performed for from 2 to 4, 2 to 7, and 4 to 7 days was 5.9%, 16.7% , and 11.5%, respectively. For the detection of S. aureus nasal carrie rs we find the use of charcoal swabs and Stuart's transport medium com bined with cultivation on mannitol salt agar for 7 days to be the opti mal method.