Bacteriological study on staphylococcal bovine clinical mastitis with reference to methicillin-resistant Staph. aureus (MRSA)

Abstract

This descriptive study was done on 101 milk samples obtained from clinically mastitic dairy cows in Assiut Governorate, Egypt. Staphylococcus aureus (S. aureus) was the main causative agent of clinical mastitis (34.65%) followed by S. saprophyticus (10.89%), S. intermedius and S. epidermidis (8.91%, for each). The other causative agents (non Staph. Spp.) were identified. Sensitivity test of S. aureus isolates was performed against 11 antimicrobial agents, where found that 21 S. aureus strains (60%) were methicillin resistant S. aureus (MRSA). Ten MRSA strains were subjected for: I- slime-producing factor on Congo Red Agar (CRA) plates phenotypically, as 6 isolates (60%) were positive for slime production. II- PCR which was optimized targeting mecA, icaA and icaD genes, where 5 isolates (50%) were positive for mecA gene. Six isolates (60%) and 8 isolates (80%) were positive for icaA and icaD genes, respectively. Five strains (50%) were positive for both icaA and icaD genes. Also 3 strains (30%) were positive for all mecA, icaA and icaD genes. Conclusion, it was concluded that bovine staphylococcal mastitis was the most predominant issue where S. aureus was the main cause. Detection of mecA gene in S. aureus isolates indicating that several cases suffering from S. aureus mastitis have an MRSA problem. Genotypic determination of mecA gene proved the most reliable method for detection of methicillin-resistant S. aureus. The present work paid an attention to the 3 MRSA strains (30%) were positive to all tested genes rather than slime production as the worst isolated strains all over this study (multidrug resistant, slime producing as well as carrying mecA, icaA and icaD genes). In vitro Enrofloxacin, Gentamicin and Doxycycline the most effective drugs for Staph. spp. clinical mastitis and should be recommended for treatment of such cases of bovine mastitis.