Mastitis in dairy animals poses both economic and public health challenges in Nepal, particularly where antimicrobial-resistant pathogens are emerging. This study aimed to determine the prevalence of Staphylococcus aureus in bovine milk and to characterize the antibiotic resistance patterns of isolates recovered from lactating cows and buffaloes in Bardaghat Municipality, Nepal.
A cross-sectional survey design was used. The study screened a total of 196 milk samples collected from lactating cows and buffaloes. The California Mastitis Test (CMT) was employed as the screening tool for mastitis prior to bacteriological analysis. Isolates identified as Staphylococcus aureus were subjected to antimicrobial susceptibility testing, and resistance patterns were summarized. The antimicrobial susceptibility profile of the 78 S. aureus isolates is presented in the article as a figure (Figure 1).
Among the 196 samples screened, 39.79% yielded Staphylococcus aureus, corresponding to 78 isolates. This overall prevalence indicates that S. aureus was commonly recovered from CMT-positive bovine milk samples in the study area.
All recovered S. aureus isolates (100.00%) exhibited resistance to oxacillin, consistent with the identification of methicillin-resistant Staphylococcus aureus (MRSA) among the bovine mastitis isolates.
Beyond oxacillin resistance, the study reported that 25.64% of isolates were multidrug-resistant (MDR), defined as resistance to three or more classes of antibiotics. Additionally, 18% of isolates had a multiple antibiotic resistance (MAR) index > 0.2, a marker often used to indicate isolates originating from environments with high antibiotic exposure or misuse.
The full antimicrobial susceptibility profile for the 78 isolates is included in the published figure (Figure 1). Specific per-antibiotic susceptibility percentages other than oxacillin resistance are not detailed in the abstract.
The investigators assessed associations between the prevalence of S. aureus and selected risk factors in the sampled population. No statistically significant associations were identified between S. aureus prevalence and the evaluated risk factors according to the abstract. The exact risk factors examined and statistical measures used were not reported in the abstract.
The findings highlight a substantial presence of MRSA and a notable proportion of MDR S. aureus among bovine mastitis isolates in Bardaghat Municipality. These results underscore the need for improved mastitis control practices on dairy farms, including routine bacteriological screening of clinical and subclinical mastitis cases.
Judicious use of antimicrobials in veterinary practice and strengthened stewardship measures are emphasized to help limit further selection and spread of resistant S. aureus strains. The authors also call for public health measures to mitigate the potential transmission of resistant S. aureus from cows and buffaloes to humans.
The abstract provides core prevalence and resistance metrics but does not report several details that may be of interest to clinical readers: the specific antibiotics tested and their individual susceptibility percentages (beyond oxacillin), the exact list of risk factors evaluated, sampling dates and farm-level characteristics, or the laboratory methods and interpretive criteria used for antimicrobial susceptibility testing. These details would need to be consulted in the full text for comprehensive appraisal.
This cross-sectional study of bovine milk in Bardaghat Municipality found that S. aureus was isolated from 39.79% of samples and that all isolates were oxacillin-resistant, consistent with MRSA. A quarter of isolates were multidrug-resistant and a subset had elevated MAR indices. No evaluated risk factors were significantly associated with S. aureus prevalence in the abstracted results. The authors recommend routine bacterial screening, conservative and appropriate antibiotic use, and public health interventions to reduce the risk of transmission of resistant S. aureus from animals to humans.
Figure note: The article includes an antimicrobial susceptibility profile for the 78 S. aureus isolates (Figure 1) showing the distribution of susceptibilities; specific numeric results for each antibiotic were not reported in the abstract.