Prevalence, source tracking and antimicrobial resistance of selected pathogenic bacteria in street vended foods sold in Kisumu city, Western Kenya

Abstract

The street food industry plays an important role in developing countries by meeting the food demand of the urban dwellers. There is an increase of food vending in Kisumu city due to poor economy and un-employment. Street foods are frequently associated with diarrheal diseases. The contribution of street-vended foods towards food borne infections is unknown in the city. Moreover, limited studies have been conducted in Kisumu city on pathogens associated with street-vended foods, potential sources and their resistance to commonly used antibiotics. Therefore, this study aimed at determining the prevalence, source tracking and antimicrobial resistance of selected pathogenic bacteria in street vended foods. This study adopted a cross sectional study design where quantitative approaches were employed. These approaches were used to investigate the prevalence, source tracking and antimicrobial resistance of selected microbes in street vended foods sold in the three open air markets within Kisumu city; Kondele, Kibuye and Oile. Systematic random sampling was used to select 62 street-vendors from whom food, water, soil and hand swabs samples were collected. Each market proportionately contributed to the sample size. A total of 248 samples were collected and analyzed using standard microbiological techniques for isolation and identification. The street-vended foods, water used for preparation of street-vended foods, swabs obtained from the vendors hands and soil from the vending environment were inoculated onto xylose lysine deoxycholate agar, hektoen agar and brilliant green agar for isolation of Salmonella and Shigella, Baird parker agar for Staphylococcus aureus, thiosulphate citrate bile salts agar for Vibrio cholera and violet red bile lactose agar for E.coli and Total Coliforms. This was followed by biochemical tests for identification using slide agglutination and homologous antisera. Eight antibiotics namely; ampicillin, amoxycillin, tetracycline, sulphamethoxazole, norfloxacin, nilidixic acid, erythromycin and chloramphenical were examined using standard disk diffusion method on Muller Hinton agar to determine antimicrobial resistance of the isolates. Microbial source tracking was carried out by swabbing of the vendors hands, testing of water used for food preparation and soil from the vending environment. Data was entered in Statistical Packages for Social Sciences (SPSS, version 19). Pearson correlation was performed to determine association between source and food contamination. Descriptive statistics were used to determine the prevalence and occurrences of pathogens in foods, hand swabs, soil, and water samples and to determine the antibiotic susceptibility levels. The data was then presented in tables and graphs. Results of this study demonstrated that the prevalence of enteric pathogens in street vended foods was; 74% Total Coliforms, 20% Staphylococcus aureus and 6% E.coli. Salmonella. Vibrio and Shigella were not isolated in any street food sampled. A further analysis by Pearsons’ correlation indicated that S. aureus isolated from the vendors hands and foods was significantly correlated (r2=0.076; p= 0.03). The study finding showed that antimicrobial resistance was observed in members of the Enterobacteriaceae and S.aureus isolates. Resistance to erythromycin was the most frequent (82.7%), sulfamethoxazole (43.2%), chloramphenicol (35.8%), amoxycillin and ampicillin (33.3%), tetracycline (22.2%) nalidixic acid (17.3%) and norfloxacin (16%). The results suggest that street-vended foods were contaminated with Total Coliforms, E.coli and S. aureus and these isolates exhibited some level of resistance to commonly used antibiotics. Therefore, regular testing and inspection of street-foods should be done by regulatory authorities. Health workers should carry out regular surveillance on resistance pattern of food borne pathogens.