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

Abstract

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.

Molecular Characterization of Methicillin-Resistant Enterotoxin-Producing Staphylococcus aureus Isolated From Samosa and Falafel in Iran

“…22 Researchers have reported relatively high levels of contamination of ready-to-eat and street foods with S. aureus. 23,24 However, in some studies, low contamination rates of street foods have been reported. 25 Differences between our results and those obtained in other studies may be due to the studied food types (samosa and falafel) since poor personal hygiene habits in hand-processed foods may be associated with S. aureus contamination.…”

“…In some studies on sea, it was reported as the most prevalent enterotoxin encoding gene 9,29 ; however, in some other studies on sec and sed genes, prominent enterotoxin genes were found. 23,30 Differences in the distribution of enterotoxin encoding genes could be due to the ecological origins and geographical varieties of S. aureus isolated from foods, livestock, and humans. 31 In our study, tst gene was also detected in 12.5% of the samples, suggesting that contamination could occur through food handling by carriers of TSST-positive S. aureus.…”

“…In most studies, S. aureus isolates were resistant to beta-lactam antibiotics group. 23,39 Arbitrary consumption of antibiotics, especially in street food workers, can lead to an increase in antibioticresistant strains.…”