Outbreak of Mastitis Caused by Strains of Methicillin-Resistant Staphylococcus aureus(MRSA)in a Closed Dairy Herd

摘要

Mastitis caused by Staphylococcus aureus (S.aureus)is one of the main diseases in dairy herds.This is an important pathogen due to a combination of toxin-mediated virulence,invasiveness,and antibiotic resistance.Cows are probably the main source of contamination of raw milk with S.aureus.In particular,cows with subclinical mastitis can shed large numhers of S.aureu.s in their milk.The epidemiology of S.aureu.s has changed radically in particular.methicillin-resistant S.aureus (MRSA),originally restricted to hospital,has emerged as a significant pathogen in the community,and true community-acquired MRSA (CA-MRSA).Considering the potential risk to the public health as well as to animal health,the aim of this study was to verify an outbreak of mastitis caused by S.aureus m one dairy farm and were analyzed the presence of the mecA gene.Milk samples were obtained from all mammary glands of all lactating cows.The isolates were identified by conventional methods.To confirm the identification of S.aureu.s we used the primers Staur 4 e Staur 6 previously descrihed.Polimerase Chain Reaction was used to determine the presence of mecA gene using primers previously descrihed.A total of 103 cows was analyzed,of the 407 mammary glands screened with CMT.115 were positive and from those,Staphylococcu^s spp.were isolated from 61 (59％ ).Of these isolates,60 (98.4％ )were S.aureus and 1 (1.6％ )were S.epidermidis.It was detected the presence of gene mecA in 48.3％ S.aureus strains.The detection of this large number of MRSA was a great concern in the animal health,considering that beta-lactams are still the most important antimicrobials in the treatment of mastitis.Besides that Staphylococcu.s aureu.s isolates from hovine mastitis represent a potential hazard to public health.