Prevalence and Antimicrobial Resistance Profiles of Bacterial Isolates Associated with Intramammary Infections in Malaysian Dairy Herds

Abstract Intramammary infections are costly endemic disease in dairy cows and it highly affects both the quality and quantity of milk production in addition to the animal well-being. It a major cause of considerable economic losses to the dairy farmers. This study was aimed to determine the prevalence of mastitis pathogens and antimicrobial resistance pattern of selected most prevalent pathogens. A total of 1945 quarter samples from 517 cows across 33 dairy herds were used. Isolation and identification of mastitis pathogens was carried out based on standard bacteriological procedures. Antimicrobial resistance profile was conducted by disk diffusion technique. The overall culture prevalence was 67.6% (n=503/744, CI= 64.1-70.9). The respective states’ culture prevalence were 66.4% (n=71/107, CI= 56.5-75.0), 60.3% (184/305, CI= 54.6-65.8), 58% (n=94/162, CI= 50-65.6), 100% (n=75/75, CI= 93.9-100), and 83.3% (n=79/95, CI= 73.8-89.8) for Pahang, Perak, Selangor, Negeri Sembilan and Johor respectively. The most prevalent isolates identified were non-aureus staphylococci (NAS) 39.5%, S. aureus 13.1%, K. pneumoniae 6.5%, S. agalactiae 4.8%, and S. uberis 4.3%. Resistance profile of K. pneumoniae isolates against ampicillin and Penicillin G were 70.4% and 88.9% respectively while that of Actinobacter spp against chloramphenicol and streptomycin were 71.4% and 35.7% respectively. For S. uberis isolates, 66.7% and 73.3% have shown resistance to tetracycline and streptomycin respectively. This study provides knowledge of the epidemiology of bacterial isolates associated with subclinical mastitis in Malaysia and their resistance profile. The high prevalence of these pathogens in milk and multidrug resistance observed should not be over looked.