Occurrence, isolation, and antimicrobial susceptibility profile of Staphylococcus aureus from raw cow milk and traditionally processed dairy products in Adama and DebreBerhan towns, Ethiopia
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Date
2023
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Addis Ababa University
Abstract
Staphylococcal foodborne intoxication is among the most known food-borne illness with global distribution. Particularly, S. aureus antimicrobial resistance has rapidly grown into a major worldwide health issue. This study was intended to determine the prevalence of S. aureus and its antimicrobial susceptibility profiles in raw milk and traditionally processed dairy products in Adama and DebereBerhan towns. A total of 421 samples (188 raw milk, 80 traditionally processed dairy products, 73 milkers’ hand swabs, 38 bucket swabs, and 42 bulk tank milk from collection centers) were sampled and analysed from December 2022 to May 2023. The samples were cultured to identify S. aureus following a standard microbiological procedure and using MALDI-TOF MS Bruker method. The antimicrobial susceptibility of the isolates was performed by a panel of 9 antimicrobials using the Kirby-Bauer disc diffusion technique. The association between the occurrence of S. aureus and potential risk factors was assessed using logistic regression. Resistance of the isolate to penicillin G and ampicillin were identified for the presence of blaZ gene using PCR. S. aureus was isolated from 32 (17.02%) of raw milk, 7(9.59%) of milkers’ hand swab, 9 (21.43%) of bulk tank milk from collection centre, 3 (7.89%) of bucket swabs, 2 (5%) of yoghurt and 1(2.5%) of cottage cheese. A significant difference with a higher rate of contamination with S. aureus was observed among samples (p =0.021). Out of 54 S. aureus isolates subjected to 9 antimicrobials, 53(98.15%) isolates were developed resistance to penicillin G and Ampicillin. Twenty-three (42.6%) of the isolates were developed resistance to Tetracycline and 7 (12.96%) of the isolates were developed resistance to Erythromycin. In addition to this, 3 (5.56%) of the isolates were developed resistance to Clindamycin. However, among the 21 isolates subjected to DNA amplification for detection of resistance gene, only a single (4.76%) isolate was positive for blaZ gene. In conclusion, this study showed that raw milk and other dairy products were highly contaminated with S. aureus. Most of the isolates developed multi-drug resistance, which is a serious public health risk for the dairy consumers of the study area. Additionally, there is a lack of agreement between the phenotypic and genotypic (blaZ gene) detection, and this necessitates additional research to determine the mechanism by which S. aureus develops resistance to β-lactam drugs particularly penicillin, and ampicillin.
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Keywords
Antimicrobial resistance, Dairy products, Milkers hand,, S. aureus, MALDI-TOF MS