Bovine mastitis continues to be a leading cause of heavy economic losses in the dairy industry and a public health hazard globally. This cross-sectional study investigated the prevalence, etiologies of clinical and subclinical mastitis, and associated predisposing factors in Embu and Kajiado counties in Kenya. A semistructured questionnaire was administered to 154 smallholder dairy farmers to collect data on management practices, animal factors, and disease history. A total of 395 dairy cows were initially screened for subclinical mastitis using the California mastitis test (CMT), and milk samples were aseptically collected. Both CMT positive and CMT negative samples were analyzed using conventional bacteriological isolation and identification procedures. In the present study, the overall prevalence of mastitis based on CMT and clinical examination was 80% (316/395), out of which 6.8% (27/395) was clinical mastitis, while 73.1% (289/395) was subclinical mastitis. Based on culture, the overall prevalence of clinical and subclinical mastitis was 51.6% (815/1580), 74.4% (294/395), and 76.6% (118/154) at the quarter, cow, and farm level, respectively. From the 1574 milk samples analyzed by cultured, 1016 bacteria were yielded. The predominant bacteria were coagulase-negative Staphylococcus (CNS), 42.8% (435/1016), and in decreasing order, Streptococcus species, 22.2% (226/1016), Staphylococcus aureus, 15.7% (160/1016), and Pseudomonas aeruginosa, 5.1% (52/1016), and the least was Enterobacter species, 0.7% (7/1016), while 23.7% of the sample yielded no bacterial growth. Risk factor analysis revealed that milking mastitic cows last (p=0.002), using a clean udder drying towel for each cow (p=0.033) and previous history of mastitis (p=0.046) were significantly associated with presence of mastitis. The current study has shown a relatively high prevalence of subclinical mastitis with CNS as predominant bacteria. Therefore, control measures are urgently warranted. Management factors such as milking mastitic cows last, using a clean towel for udder drying for each cow, and culling mastitic cows should be considered and included in the Kenyan mastitis control programs.

Increasing numbers of potentially zoonotic multidrug-resistant (MDR) staphylococci strains, associated with mastitis in dairy cows, are being reported globally and threaten disease management in both animal and human health. However, the prevalence and antimicrobial resistance profiles of these strains, including methicillin-resistant staphylococci (MRS), in Kenya is not well known. This study investigated the drug resistance profiles and genes carried by 183 staphylococci isolates from 142 dairy cows representing 93 farms recovered from mastitis milk of dairy cows in two selected counties in Kenya. Staphylococci isolates were characterized by phenotypic characteristics, polymerase chain reaction (PCR) amplification, partial sequencing and susceptibility testing for 10 antimicrobial drugs. Detection of seven resistance genes to the various antimicrobial drugs was conducted using PCR. Overall, phenotypic resistance among the staphylococci ranged between 66.1% for ampicillin and 3.5% for fluoroquinolones. Twenty-five percent (25%) of S. aureus and 10.8% of the coagulase-negative staphylococci (CoNS) isolates, were methicillin-resistant staphylococci phenotypically (defined as resistance to cefoxitin disk diffusion). The most common genes found in S. aureus and CoNS were blaZ and strB at 44.3% and 26%, and 78% and 50%, respectively. MDR was observed in 29.67% and 16.3% of S. aureus and CoNS, respectively. These findings pose a threat to bovine mastitis treatment and management as well as human health.

Campylobacter is a zoonotic foodborne pathogen that is often linked with gastroenteritis and other extraintestinal infections in humans. This study is aimed at determining the genetic determinants of virulence‐encoding genes responsible for flagellin motility protein A (flaA), Campylobacter adhesion to fibronectin F (cadF), Campylobacter invasion antigen B (ciaB) and cytolethal distending toxin (cdt) A (cdtA) in Campylobacter species. A total of 29 Campylobacter coli isolates (16 from cattle, 9 from chicken, and 4 from water samples) and 74 Campylobacter jejuni isolates (38 from cattle, 30 from chicken, and 6 from water samples) described in an earlier study in Kajiado County, Kenya, were examined for the occurrence of virulence‐associated genes using polymerase chain reaction (PCR) and amplicon sequencing. The correlations among virulence genes were analyzed using Pearson’s correlation coefficient (R) method. Among the 103 Campylobacter strains screened, 89 were found to harbour a single or multiple virulence gene(s), giving an overall prevalence of 86.4%. C. jejuni strains had the highest prevalence of multivirulence at 64.9% (48/74), compared to C. coli (58.6%, 17/29). The ciaB and flaA genes were the most common virulence genes detected in C. jejuni (81.1% [60/74] and 62.2% [46/74], respectively) and in C. coli (each at 62.1%; 18/29). Campylobacter isolates from chicken harboured the most virulence‐encoding genes. C. jejuni strains from chicken and cattle harboured the highest proportions of the cdtA and ciaB genes, respectively. All the C. coli strains from water samples harboured the cadF and flaA genes. The results obtained further revealed a significant positive correlation between cadF and flaA (R = 0.733). C. jejuni and C. coli strains from cattle, chicken, and water harbour virulence markers responsible for motility/colonization, invasion, adherence, and toxin production, evoking their important role in campylobacteriosis development among humans and livestock. The identification of cattle, chicken, and water samples as reservoirs of virulent Campylobacter spp. highlights the possible risk to human health. These data on some virulence genes of Campylobacter will assist food safety and public health officials in formulating policy statements.

Globally, Escherichia coli (E. coli) and Campylobacter spp. are key foodborne pathogens and important indicators for antimicrobial resistance (AMR) surveil

Background and Aim: Antimicrobial resistance (AMR) has emerged as a major One Health threat driven by inappropriate antimicrobial use (AMU) in humans, animals, and the environment. Poultry production is recognized as a key reservoir of antimicrobial-resistant bacteria, yet few studies in Kenya examine AMU and AMR across interconnected human–animal–environment domains. This study assessed AMU patterns among poultry farmers in Kiambu County and characterized phenotypic resistance in Escherichia coli and Enterococcus spp. isolated from humans, chickens, and chicken environments. Materials and Methods: A cross-sectional study was conducted from May to September 2024, involving 102 poultry farms. Farm demographics and AMU data were collected using a semi-structured questionnaire. Archived E. coli (n = 92) and Enterococcus spp. (n = 101) isolates from chicken handlers’ hands, chickens, and environmental samples were subjected to antimicrobial susceptibility testing using the Kirby–Bauer method per Clinical and Laboratory Standards Institute (CLSI) 2024 guidelines. Descriptive and inferential statistics, including logistic regression with false discovery rate correction, were used to assess associations between AMU and phenotypic resistance. Results: Macrolides (69%), tetracyclines (48%), and sulfonamides (21%) were the most commonly used antimicrobials; 7% of farms reported colistin use. Among E. coli isolates, resistance was highest to ampicillin (77%), tetracycline (72%), and trimethoprim–sulfamethoxazole (49%), with 35% exhibiting multidrug resistance (MDR). No carbapenem resistance was detected. Enterococcus isolates showed high erythromycin resistance (61%) and moderate ciprofloxacin resistance (26%), with 6.9% exhibiting MDR; no vancomycin-resistant enterococci (VRE) were observed. Penicillin use strongly predicted ampicillin resistance in both organisms, whereas sulfonamide use was associated with reduced trimethoprim–sulfamethoxazole resistance. Macrolide use did not correlate with erythromycin resistance. Conclusion: High AMU in poultry farming, particularly of macrolides, tetracyclines, and sulfonamides, has created significant selection pressure, contributing to MDR emergence across One Health interfaces. Detection of resistance in humans, poultry, and shared environments underscores the bidirectional risk of AMR transmission. Strengthened antimicrobial stewardship, regulation of critically important antimicrobials, and enhanced farm hygiene are essential to mitigate AMR. These findings directly support Kenya’s Vision 2030 and SDGs targeting health, responsible production, and environmental protection. Keywords: Antimicrobial use, antimicrobial resistance, poultry farming, Escherichia coli, Enterococcus, One Health, Kenya.