Prevalence of Bovine Subclinical Mastitis and Antibiogram Pattern of Isolated Organisms from Mastitic Milk in Chattagram, Bangladesh

Objective: This research investigated the prevalence and risk factors of subclinical mastitis (SCM) in dairy cows within the Chattogram, Bangladesh, focusing on its effects on milk production and quality, as well as the antibiotic resistance profiles of Staphylococcus spp. and Escherichia coli        (E. coli). Materials and Methods: Fifty lactating cows from five dairy farms were studied over eight months (January to August 2018). Milk samples were collected aseptically and screened using the California Mastitis Test (CMT) to identify SCM. Bacterial cultures were conducted to isolate Staphylococcus spp. and E. coli, and their antibiotic susceptibility was assessed using the Bauer-Kirby disk diffusion method. Farm management data were collected via structured questionnaires. Results: The SCM prevalence was 50%, with Staphylococcus spp. and E. coli each found in 32% of cases. Staphylococcus spp. showed 100% resistance to amoxicillin, enrofloxacin, and azithromycin, while E. coli demonstrated similar resistance patterns. Gentamycin was more effective, with only 25% resistance against Staphylococcus spp. Key factors influencing infection included farm size, housing system, lactation stage, and udder cleanliness. Farms with poor hygiene practices, such as infrequent floor cleaning without disinfectant, had higher infection rates. Conclusion: The findings highlight the necessity for routine SCM screening and improved farm hygiene practices. Combating antibiotic resistance demands careful antibiotic use guided by sensitivity testing. Effective management requires regular monitoring, hygiene enhancements, and strategic treatments to protect dairy production.