The sensitivity of automated culture of Staphylococcus aureus from flocked swabs versus that of manual culture of fiber swabs was prospectively compared using nasal swabs from 867 patients. Automated culture from flocked swabs significantly increased the detection rate, by 13.1% for direct culture and 10.2% for enrichment culture.

Culturing of pharyngeal swabs for Neisseria meningitidis is an important clinical and epidemiological tool. Routine methods include direct plating onto solid medium or later plating in the laboratory. A comparison of these methods used with 490 high school students found a significantly higher carriage rate with direct plating (11.8 versus 6.1%; P < 0.001).Pharyngeal carriage of Neisseria meningitidis is common in the general population, with rates of 20 to 30% in young adults (2, 3). Immediate plating of cotton swabs onto solid culture medium at the site of swabbing (direct plating) is commonly used in epidemiological studies to measure carriage rates (2). An accepted alternative method is to place the swabs in transport medium and send them to the laboratory for plating (3). In clinical practice in the United Kingdom, laboratory plating is usual, as reflected in the Public Health Laboratory Service standard operating procedure for culture of pharyngeal swabs. The assumption is that prompt (i.e., often overnight) transport under appropriate conditions will not significantly affect the rate of isolation of N. meningitidis.Nasopharyngeal swabs were collected in autumn 1999 from sixth-form students in the Plymouth area of southwest England as part of a United Kingdom multicenter study of meningococcal carriage. Other study centers were in Manchester, Oxford, Nottingham, London, Glasgow, Cardiff, and Bangor. The study protocol allowed either direct plating or transport in Amies medium for laboratory plating, with the latter method being used in Plymouth. The estimated interval between specimen collection and inoculation of plates ranged between 5 and 7 h. An interim analysis, after swabs were taken from 906 students, showed an unexpectedly low meningococcal carriage rate of 6.1% (55 of 906). This contrasted sharply with results from other centers, where direct plating was mostly used and where carriage rates ranged from 10 to 23%. The culture medium used was GCVCAT. This is a modified New York City medium, containing vancomycin, trimethoprim, and amphotericin B. Quality control of the medium revealed no inhibition of meningococcal growth, and the swab collection technique was satisfactory.We set out to compare meningococcal isolation rates obtained with direct and laboratory plating. Pharyngeal swabs from 490 students were plated on-site and then placed in transport medium for plating at the laboratory. The carriage rate from direct plating was 11.8% (58 of 490), whereas the rate obtained from laboratory plating was 6.1% (30 of 490) ( Table 1). This difference was highly statistically significant using McNemar's test (P Ͻ 0.001). The carriage rate from laboratory plating during the comparative study (6.1%) was the same as the rate before the study (6.1%), suggesting that the difference was unlikely to be due to loss of organisms from the plate. Swabs were taken from students in many of the same schools for direct plating a year later. For schools in which swabs were laboratory plated in the first year and directly...

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