Importance of food handlers as a source of enterotoxigenic staphylococci.

The incidence of staphylococci in the nasal fossae of 300 food handlers working within the province of León (Spain) was studied. Sampling was carried out using a swabbing technique. For the quantitative estimation of staphylococci, a direct plating method and an enrichment procedure (MPN) were used simultaneously. Gram positive cocci that fermented glucose and were sensitive to lysostaphin (1 unit/ml) were found to be present in the noses of 201 food handlers (67%). Eighty three of them (27.6%) were carriers of coagulase positive staphylococci and 118 (39.3%) of coagulase negative staphylococci. The carriage rate of coagulase negative staphylococci was slightly higher in winter but carriers of coagulase positive strains were more frequently found during warmer months. Coagulase positive staphylococci appeared to be more often carried by males. In all instances, positive nasal cultures gave 10 or more colonies per sample. The majority of food handlers carrying coagulase negative staphylococci (64.4%) yielded counts between 10(3)-10(5) CFU per swab. Thirty four (40.9%) of the nasal carriers of coagulase positive staphylococci yielded more than 10(4) CFU per sample. The higher counts corresponded to this latter group. Preliminary enrichment did not increase the number of nasal carriers detected. Although a good correlation was observed between the results of direct plating and the MPN procedure (r = 0.87 +/- 0.04), the MPN technique gave lower counts. Thirty six (12%) individuals carried enterotoxigenic staphylococci. The incidence among carriers of coagulase positive strains was 43.4%. The enterotoxin types produced were: A (12 strains), B (8 strains), C (7 strains), D (2 strains), E (2 strains), A + D (4 strains) and B + C (1 strain). Most of the food handlers who harbored enterotoxigenic strains gave high nasal counts.