Enterotoxigenicity of Staphylococcus aureus Strains Isolated from Nigerian Ready-to-Eat Foods

Abstract

The incidence of enterotoxin production by Staphylococcus aureus strains isolated from five Nigerian ready-to-eat products, i.e., roasted beef, dried beef, dried fish, fried fish and fried chicken, was investigated. Ninety-seven (39.1%) strains of 248 tested elaborated staphylococcal enterotoxins A(SEA), B(SEB), C(SEC), D(SED) or E(SEE). SED was most frequently produced as 43(17.3%) strains produced it, representing 44.3% of all enterotoxigenic strains. SEA and SEE were elaborated by 31(12.5%) and 29(11.7%) strains, respectively. Nineteen (7.7%) isolates produced SEB and the incidence of SEC was lowest, with only 12(4.8%) strains positive. Six (50.0%) of the SEC-producers were dried beef isolates. Of the three food sources (beef, fish and chicken) investigated, there was no significant difference (P>0.05, X2) between the incidence of enteroxigenicity of isolates, although beef isolates demonstrated the highest incidence (43.3%) followed by fish products (37.0%) and chicken product (36.0%). Regardless of source, roast beef isolates were the most frequently toxic (55.2%), whereas dried fish isolates were least frequently enterotoxigenic (34.5%). Multiple enterotoxin production most frequently encountered were types ADE, AD and BD which were produced by 6, 5 and 3 strains, respectively. It was concluded that the five ready-to-eat products investigated may pose a health hazard from the view point of staphylococcal intoxication due to the high incidence of enterotoxin production by isolates. SED appears to pose the greatest risk of this hazard to consumers of these products in this environment.