Prevalence and Antibiogram of Escherichia Coli and Staphylococcus Species in Subclinical Mastitis among Dairy Cows in Western Chitwan, Nepal

Mastitis is a major economically important disease manifested in clinical and subclinical forms among dairy animals. This study aimed to isolate the mastitiscausing bacteria, their prevalence, and associated risk factors of subclinical mastitis (SCM) with their antibiogram. This study was conducted from July 2017 to May 2019 in Western Chitwan, Nepal. Approximately 10 ml milk samples were collected from each quarter in a sterilized bottle from 340 cows. The California Mastitis test (CMT) was performed for screening of mastitis, which was followed by immediate bacteriological culture in both Nutrient Agar (NA) and Selective
media [Mannitol Salt Agar (MSA), Eosin Methylene Blue (EMB) Agar, Mac Conkey Agar], Grams’ staining, and confirmatory biochemical test for respective organisms. The results from CMT revealed that the prevalence of SCM was 41.47% (141/340). The biochemical cultural characteristics found that the most common Staphylococcus (39.01%) followed by E. coli (23.40%), Streptococcus (17.73%), and others unidentified (19.85%). The statistical analysis shows a non-significant association between breed, stage of lactation, milk yield, farming system, and prevalence of SCM among dairy cattle. Antibiogram profile indicated that tetracycline (80.3%) was the most effective drug followed by ceftriaxone (70.5%), Gentamicin (59.0%), and Enrofloxacin (44.3%). In conclusion, there was a high prevalence of subclinical mastitis in western Chitwan. Mastitis pathogens develop resistance against ampicillin. Further studies are required to develop alternative control strategies for mastitis in Nepal