Determination of antibiotic resistance and enterotoxigenic potential of Staphylococcus aureus strains isolated from foods sold by street vendors in Gaborone, Botswana

Staphylococcus aureus is one of the causes of foodborne diseases worldwide. Staphylococcal food poisoning ensues after ingestion of contaminated food and results in symptoms of gastroenteritis such as vomiting, abdominal cramps and diarrhea. The present paper aims to isolate Staphylococcus aureus from foods sold by street vendors in Gaborone, Botswana, and to determine its enterotoxigenic potential and antibiotic resistance profile. One hundred eight food samples comprising starch, meat, salads and vegetables portions were collected from these vendors and tested for the presence of S. aureus. Identification of Staphylococcus aureus to the species level was performed using the Vitek 2 automated identification and susceptibility testing system (BioMerieux, Marcy-I’Etoile, France). Enterotoxins were detected by the Reversed Passive Latex Agglutination method (SET-RPLA). Results showed that 49 (45%) of the samples tested positive for Staphylococcus aureus . The organism was isolated at higher frequencies in vegetables and starchy foods (34.7%) than in meats (30.6%). These differences in isolation rates however, were not statistically significant (p> 0.05). Staphylococcus aureus isolates were found to be resistant to penicillin G (52.4%), tetracycline (38.1%), methicillin (26.2%) and vancomycin (11.9%). Four Staphylococcal enterotoxin types A-D, were detected among the isolates. Staphylococcal enterotoxin D was the most prevalent (52.9%), while enterotoxin C was produced by the least number of isolates (5.9%). Of note, five isolates simultaneously expressed two or more enterotoxin types in varying combinations. The present study underscores a potential risk of staphylococcal food poisoning and transmission of methicillin resistant S. aueus strains for consumers of street vended food products in Gaborone, Botswana especially in the absence of a quality assurance regulatory framework. As a mitigating factor, sensitization of street food vendors on the importance of food and personal hygiene is strongly recommended.