Prevalence, Risk Factors and Antimicrobial Resistance Profiles of Mastitis-Causing Bacteria Isolated from Dairy Goats in Mukurwe-ini Sub County, Nyeri County, Kenya

Abstract

Bovine mastitis continues to be a cause of economic losses in the dairy industry and remains a major public health hazard globally. Though dairy goat farming in the study area has realized tremendous growth in the recent years, there is limited region-specific data on the prevalence, associated risk factors, and antimicrobial resistance (AMR) profiles of mastitis-causing pathogens in the dairy goats. This knowledge gap hinders the development of targeted control strategies and prudent antimicrobial use policies tailored to the local context. Therefore, this study seeks to determine the prevalence, risk factors, and AMR patterns of mastitis-causing bacteria isolated from dairy goats in Mukurwe-ini Sub County, thereby contributing to informed interventions for mastitis control and antimicrobial stewardship. In this cross sectional study, farm level data on risk factors for mastitis was obtained from 56 farmers using semi-structured questionnaires. A total of 189 goat milk samples were collected from the farms. The goat’s udder was observed for signs of clinical mastitis and the California Mastitis Test (CMT) used to test the milk for presence of sub-clinical mastitis. All milk samples were then cultured for morphological identification of bacteria using culture and standard identification methods. The bacteria species were further confirmed by MALDI-ToF technique. The isolated bacteria were tested for antibiotic sensitivity to eight commonly used antibiotics namely; Cefuroxime (30µg), Cefotaxime (30µg), Amoxicillin and Clavulanic acid (10µg), Oxacillin (10µg), Azithromycin (15µg, Meropenem (10µg), Ciprofloxacin (10µg) and Nitrofurantoin (300µg) using the Kirby- Bauer disc diffusion test. The presence of antibiotic resistance genes (mecA, and blaTEM) was determined using polymerase chain reaction (PCR) method. The prevalence of clinical mastitis was 1.1% (2/189) while that of sub-clinical mastitis was 84.7% (160/189). Higher (p<0.05) prevalence of mastitis was observed in goats whose houses were cleaned fortnightly and in cases where farmers used same towel to dry different does’ udders during the milking process. Thirteen (13) different bacterial species were isolated from the milk samples and identified by MALDI-ToF, and these included S. aureus (21.16%), Coagulase- negative Staphylococci (19.58%), E. coli (17.46%), Pseudomonas spp. (13.76%), Enterobacter spp. (10.05%), K. oxytoca (5.82%), E. vulneris (1.59%), Proteus vulgaris (1.59%), Raoutella ornithinolytica (1.59%), Stenotrophomonas maltophilia (1.05%), Pantoea agglomerans (1.05%), Serratia marcescens (1.05%) and Cedeceas spp. (0.53%). Majority (97.5%) of S. aureus were resistant to Oxacillin and were 100% sensitive to Ciprofloxacin. The Coagulase-negative Staphylococcus isolates were 100% resistant to Oxacillin and 100% sensitive to Ciprofloxacin. Most (93.9%) E. coli isolates were resistant to Oxacillin, 69.7% were sensitive to Ciprofloxacin, and 87.9% were sensitive to both Amoxicillin/Clavulanic acid and Meropenem. The antimicrobial resistant genes detected in S. aureus and E. coli were mecA (66.67%, 0%), and blaTEM (20%, 78.26%), respectively. In conclusion, the study showed that most of the does were affected by subclinical mastitis with the main causative bacteria being Staphylococci spp. and coliforms. Farmers need to be trained on improved control of mastitis by adoption of good milking practices and use of CMT kit for early detection of mastitis. Occurrence of multidrug resistance by key mastitis - causing pathogens was shown to be prevalent and therefore there is need for development of intervention strategies.