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.
