Isolation and Characterization of Staphylococcus aureus From Food of Bovine Origin in Mekelle, Tigray, Ethiopia

Background: Among Food-borne diseases, S. aureus is a leading cause of gastroenteritis resulting from the consumption of contaminated food. Objectives: The study aimed to isolate and characterize S. aureus from raw milk, yogurt and meat and determine its antibiotic sensitivity pattern. Materials and Methods: A cross-sectional study was conducted from December 2014 to June 2015 in Mekelle. A total of 284 samples were collected purposively. Enumeration of total viable bacteria count (TVBC), bacteriological isolation and identification, antimicrobial susceptibility testing, as well as PCR amplification of fem A and mec A genes were performed. Chi-square (χ2) and one way ANOVA tests were used for analysis. Results: Overall TVBC mean was found to be 1.29x108cfu/ml/g. The highest TVBC (1.38x108cfu/ml) was from the yogurt sample and the lowest (1.26x108cfu/g) was from meat. The overall prevalence of coagulase positive S. aureus (CoPS) was 39.1% (111) and of the smaples, 51(56.04%), 38(26.20%) and 22(45.83%) were isolated from meat, raw milk, and yogurt, respectively. There was a statistically significant difference (p<0.05) among the different sample types and sources in the prevalence of S. aureus. Almost half of the CoPS isolates were sensitive to Tetracycline, Gentamycin, and Kanamycin, but resistant to Amoxicillin (96.9%) and Penicillin G (93.8%). Moreover, 93.75% of the isolates developed multidrug resistance. All isolates carried the fem A gene and among these isolates, 12 (37.5%) carried mec A gene. Conclusion: The present study revealed that foods of bovine origin of the study area are found to be having less bacteriological quality, high prevalence of CoPS and development of drug resistance.