Journal
VETERINARY WORLD
Volume 13, Issue 7, Pages 1448-1456Publisher
VETERINARY WORLD
DOI: 10.14202/vetworld.2020.1448-1456
Keywords
bacteria; dairy goats; Kenya; subclinical mastitis; beta-lactam resistance
Funding
- Institute of Basic Sciences, Technology and Innovation, Pan-African University (PAUSTI)
- Jomo Kenyatta University of Agriculture and Technology (JKUAT)
- Grand Challenges Africa program [GCA/AMR/rnd2/079]
- Bill and Melinda Gates Foundation (BMGF)
- The African Academy of Sciences
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Aim: This study determined the resistance pattern to beta-lactam antibiotics of bacteria isolated from goats with subclinical mastitis in Thika subcounty, Kenya. We also administered a questionnaire to assess the risk factors associated with the occurrence of resistance to commonly used antibiotics. Materials and Methods: We collected milk samples from 110 lactating dairy goats in Thika subcounty to screen for subclinical mastitis using the California mastitis test. Bacterial isolation and identification were performed according to colony morphology, the hemolytic pattern on sheep blood agar, lactose fermentation on MacConkey plates, Gram staining, and standard biochemical tests. The antibiotic susceptibility of the isolates was determined by the agar disk diffusion method using penicillin G, cephalexin, cefoxitin, and cefotaxime antibiotic disks. The double-disk synergy test using amoxicillin-clavulanic acid was employed as a confirmatory test for extended-spectrum beta-lactamase (ESBL) production. Fisher's exact test was used to determine the risk factors associated with the occurrence of antibiotic resistance (p <= 0.05 was considered significant). Results: Of the 110 dairy goats sampled, 72.7% (80) were positive for subclinical mastitis. Isolation and identification of the bacteria from the positive samples yielded 149 bacteria isolates, including Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter spp., Yersinia spp., coagulase-negative staphylococci, and Escherichia coli. A high percentage (76.5%, 114/149) of the bacterial isolates was resistant to at least one of the tested antibiotics. At least 56/106 isolates (52.8%) showing cross-resistance to the beta-lactam antibiotics were resistant to all four of the tested antibiotics, while only one isolate was resistant to three antibiotics (penicillin G, cephalexin, and cefoxitin). The double-disk synergy test confirmed that none of the isolates possessed ESBLs. Pre- and post-milking practices (p=0.0336) were found to be significantly associated with the occurrence of antibiotic resistance. Conclusion: A large proportion of the goats in our study cohort were infected with beta-lactam-resistant bacteria associated with subclinical mastitis. Because the identified bacteria are of zoonotic importance, further studies should be undertaken to determine the transmission dynamics between humans and livestock and to identify novel intervention strategies.
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