Screening Kulfi for Staphylococcal Enterotoxins with the Thermonuclease Test

Forty kulfi samples collected from local push-cart vendors and restaurants were screened for thermonuclease and staphylococcal enterotoxins. Viable staphylococcal counts were also determined in these samples. Thermonuclease was detected in four kulfi samples. The incidence was, however, more (15%) in samples from push-cart vendors as compared to those from restaurants (5%). Enterotoxins were also detected in thermonuclease-positive samples. The incidence of enterotoxins A and B was 10%. Enterotoxins C and D were not detected in the samples. Of 81 isolates of staphylococci obtained from kulfi samples, seven exhibited thermonuclease, coagulase and enterotoxin production. Ten percent of thermonuclease-positive isolates came from kulfi samples collected from push-cart vendors as compared to 6.5% from restaurant samples. The incidence of enterotoxin A producing staphylococci was 8% and 3.2% in samples from push-cart vendors and restaurants, respectively. One of the coagulase-positive isolates from restaurant samples failed to produce either thermonuclease or enterotoxins.