Bacteriological Quality, Associated Factors and Antibiotic Susceptibility Pattern of the Isolates of Raw Cow’s Milk Collected from Cafeterias in Adama Town, Oromia Region, Ethiopia

Abstract

Milk contains abundant water and nutrients with nearly neutral pH which makes it good media for the growth of microorganisms. Consuming quality deteriorated milk is hazardous to health. The aim of this study was to determine bacteriological quality, associated factors and antibiotic susceptibility pattern of targeted isolates of raw cow’s milk from Adama town cafeterias, Oromia Region, Ethiopia from March 23-June 06/2017. A cross-sectional study on 115 raw cow’s milk samples collected from randomly selected cafeterias was conducted. Questionnaires were employed to survey handling practices. About 10-15 mL milk samples collected and transported in an ice box below 5°C to Oromia Regional laboratory in Adama town for bacteriological analysis. Serially diluted sample inoculated in duplicate on to Nutrient Agar and Eoisin Methylene Blue Agar for total and coliform bacteria counts respectively. Colony with metallic sheen on Eoisin Methylene Blue Agar was presumptively assumed as Escherichia coli and streaked onto same media to get pure isolates after which were confirmed by biochemical tests. Mannitol Salt Agar and Salmonella–Shigella Agar selective media were also used for the cultivation of Staphylococcus aureus and Salmonella spp respectively. Data were entered into EPI data version 7 and exported to SPSS version 22 computer soft ware and interpreted using descriptive statistics. Also Pearson chi square test used to see the association of the potential factors with bacterial milk contamination. The mean± standard error of total bacterial and coliform counts was 6.600±0.144 and 4.957±0.104Log10 CFU/mL respectively. About 7.8% (n=6) E. coli and 23.5% (n=27) S. aureus were isolated but none sample were positive for Salmonella spp. Antibiotic sensitivity test was done for all E. coli and Staphylococcus aureus isolates by the Kirby-Bauer’s disk diffusion technique as modified by the Clinical and Laboratory Standard Institute. All isolates of E. coli were highly resistant to ampicillin but sensitive to amoxicillin-clavulanic acid, cotrimoxazole, gentamicin, tetracycline, ciprofloxacin, chloramphenicol, cefoxitin, and ceftriaxone. Most of the S. aureus isolates were resistant to one or more antibiotics tested. Most resistance was observed for ampicillin and tetracycline, while 100% sensitivity was recorded for ciprofloxacin. About 25.9% were resistant to three or more antibiotics (multidrug xvii resistant). About 71.3 % samples of raw whole milk collected and analyzed for their bacteriological quality were substandard in terms of their total bacterial counts. Of the total samples analyze about 67% were positive for coliforms and all had total coliform counts above tolerable limit. The poor bacteriological quality is perhaps attributable to lack of good producing practices during milking and mishandling practices during post milking. Therefore, adequate sanitary measures and strict monitoring and quality control measures should be in place at all levels from production to consumption to assure delivery of safe and quality of raw whole milk to various stakeholders