Prevalence and Distribution of Bovine Mastitis Pathogens and their Antimicrobial Resistance in Primiparous Dairy Heifers in Northern Jordan

The objectives of this study were to determine the most common bacterial etiology of mastitis, their sensitivity patterns to commonly used antimicrobial agents, the prevalence of clinical and sub clinical mastitis in holstein friesian primiparous dairy heifers in northern jordan. eighty five heifers that were in their third trimester of pregnancy, located in twenty farms were used in this study. a total of 634 quarters samples of pre-calving secretion (156) and post-calving (180 colostrums; 298 milk) were aseptically collected and grossly examined for abnormalities. normally appearing milk samples were further tested for sub clinical mastitis using california mastitis test. all collected samples were cultured and antibacterial sensitivity patterns were determined. seventy-one percent (449 of 634) of the examined samples were apparently normal. clinical mastitis was diagnosed in 29% (185 of 634) of the examined quarter. the prevalence rate of clinical mastitis in pre-calving secretions, colostrum and milk were 57% (89 of 156), 22% (40 of 180) and 19% (56 of 298), respectively. the prevalence rate of sub clinical mastitis was 94% (239 of 254 milk samples). different bacterial isolates were identified in 48.6% (308 of 634 quarter samples). bacteria were isolated from 58% (52 of 89) of pre-calving secretions, 75% (30 of 40) of colostrum and 54% (30 of 56) of milk samples. staphylococcus aureus was the most frequent pathogen (38%) followed by corynebacterium bovis (24%), coagulase negative staphylococci (cons) (15%), streptococci spp. (10%), escherichia coli (5.5%), actinomyces pyogenes (4.9%) and klebsiella pneumoniae (1%). these pathogens were isolated from 61% of clinical mastitis and 42% of sub clinical mastitis samples. after statistical analysis the isolated pathogens were found significantly (p < 0.05) resistant to ciprofloxacin, gentamicin, lincomycin, streptomycin and penicillin and susceptible to amoxicillin, cephalexin, neomycin, oxytetracycline and sulphamethexazole - trimethoprim