Prevalence, susceptibility patterns and risk factors associated with staphylococcus aureus presence in marketed milk and milk products within Nairobi City County, Kenya
Macharia, John Macharia
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Staphylococcus aureus is a major food-borne pathogen that poses a serious threat to public health. In Kenya, with the continuous water shortage, proper sanitary conditions are not sufficiently met and hence pre-disposing the community to S. aureus infections. One of the difficulties of controlling S. aureus food poisoning is that food can contain a very high population of the bacteria without being noticeably identified. It has been suggested that food-borne diseases represent one of the most widespread and overwhelming public health problems in poor resource settings. The increasing rate of multidrug resistant S. aureus has continued to pose a challenge to the pharmaceutical firms and patients management. The aim of this study was therefore to determine the presence of S. aureus in milk and milk products, antimicrobial susceptibility patterns and factors associated with food contamination. A total of 334 samples were collected for analysis in the laboratories. A loop-full of each sample was streaked directly on MacConkey agar and Blood agar. Suspected isolates were subcultured in Mannitol salt agar which was used as an indicator media. Sensitivity test was accomplished using Muller-Hinton agar. Biochemical tests; Catalase test and Coagulase test were used as confirmatory tests for S. aureus. To determine antimicrobial susceptibility, panels of selected antibiotics commonly used in empirical treatment of S aureus infections were obtained from different classes. The antibiotics were Penicillin G, Erythromycin, Vancomycin, Chloramphenicol, Tetracycline, Gentamycin, Methicillin and Ciprofloxacin. From all the 54 samples of raw milk analyzed, 35 (64.81%) samples were contaminated by S aureus. In pasteurized milk, out of 112 samples, 23 (20.54%) samples were contaminated while in yoghurt, out of 112 samples, 12 (10.71%) samples were contaminated. In ice cream, out of 56 samples, 2 (3.57%) were contaminated. All isolates were found to be 100 % sensitive to Tetracycline, Ciprofloxacin, Erythromycin and Methicillin. Resistance to Penicillin G was occasionally observed across the different sources of milk and milk products. From the milk outlets selling raw milk within the study area, regular opening of the containers to sell milk pre-disposed the milk to hand contamination and consequently greater risks of contamination by environmental contaminants. Out of 120 respondents interviewed, an average of 84 (70%) claimed to be aware of the health risks associated with milk. Of the respondents, 28 (23%) claimed to be aware of diseases associated with consumption of contaminated milk. Most of them claimed to have encountered stomach disorders and diarrhea while others claimed to have experienced body rashes, severe headache and vomiting. On average, 8 (9%) of the respondents claimed to have contracted a disease as a result of drinking contaminated milk within the last one year. It was established that 118 (98%) of food handlers did not receive any formal training regarding food hygiene. Information generated from the study provides a basis upon which formulation of better policies regarding raw milk and milk products can be based on. In addition, given the imminent risks of infection and resistance involved, the relevant authorities should adopt severe inspection measures in order to regulate or prohibit the informal sale of milk.