Identification of Coagulase Negative Staphylococci causing subclinical mastitis and their antimicrobial resistance patterns
2000
Kittisak Ajariyakhajorn(Chulalongkorn Univ., Bangkok (Thailand). Faculty of Veterinary Sciences. Dept. of Veterinary Medicine) | Chaidate Inchaisri(Chulalongkorn Univ., Bangkok (Thailand). Faculty of Veterinary Sciences. Dept. of Veterinary Medicine) | Thanasak Boonserm(Chulalongkorn Univ., Bangkok (Thailand). Faculty of Veterinary Sciences. Dept. of Veterinary Medicine) | Sukuma Samngamnim(Chulalongkorn Univ., Bangkok (Thailand). Faculty of Veterinary Sciences. Dept. of Veterinary Medicine)
Coagulase Negative Staphylococci (CNS) are an important group of bacteria that cause subclinical mastitis in dairy cattle. Isolation and identification of CNS gives useful information about the epidemilology of subclinical mastitis and therapeutic treatment strategies. We attempted to isolate, identify and characterize the antimicrobial resistance patterns of CNS causing subclinical mastitis in small dairy herds based in Nakornpathom province, Thailand. Ten herds with a total form 6 to 27 cows per farm (median=13 cows). The prevalence of subclinical mastitis caused by CNS ranged from 6 to 66.7 percent (median=25.5 percent). Forty four isolates of CNS were identified to the species level using a commercial biochemical test (API STAPH). Our results indicated that the 44 isolates were Staphylococcus chromogenes (17/44), Staphylococcus epidermidis (7/44), Staphylococcus hyicus (2/44), Staphylococcus carprae (1/44) Staphylococcus warneri (1/44), Micrococcus spp. (2/44), Staphylococcus spp. (14/44). The fourteen isolates in the last group could not be positively identified. Antimicrobial susceptibility tests on CNS isolates indicated that 42.9 percent were susceptible to all antimicrobial agents. However, the number having multiple drug resistance was higher than expected (45.6 percent). Seventeen percent (6/35) of the tested isolates were resistant to oxacillin, which may suggest that methicillin resistant staphylococci are also present in dairy cattle. The Variety of species, the variation of prevalence of CNS causing subclinical mastitis and their antimicrobal resistance patterns should be further investigated and monitored so that appropriate control and prevention strategies can be formulated.
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