High Incidence of Oxacillin-Susceptible mecA-Positive Staphylococcus aureus (OS-MRSA) Associated with Bovine Mastitis in China

Abstract

Staphylococcus aureus is a main cause of bovine mastitis and a major pathogen affecting human health. The emergence and spread of methicillin-resistant Staphylococcus aureus (MRSA) has become a significant concern for both animal health and public health. This study investigated the incidence of MRSA in milk samples collected from dairy cows with clinical mastitis and characterized the MRSA isolates using antimicrobial susceptibility tests and genetic typing methods. In total, 103 S. aureus isolates were obtained from dairy farms in 4 different provinces in China, including Gansu, Shanghai, Sichuan, and Guizhou. Antimicrobial susceptibility testing of these isolates revealed that the resistance rates to penicillin and sulfamethoxazole were high, while the resistance rates to ciprofloxacin and vancomycin were low. Among the 103 isolates, 49 (47.6%) were found to be mecA-positive, indicating the high incidence of MRSA. However, 37 of the 49 mecA-positive isolates were susceptible to oxacillin as determined by antimicrobial susceptibility assays and were thus classified as oxacillin-susceptible mecA-positive S. aureus (OS-MRSA). These isolates could be misclassified as methicillin susceptible Staphylococcus aureus (MSSA) if genetic detection of mecA was not performed. Molecular characterization of selected mecA-positive isolates showed that they were all negative with Panton-Valentine leukocidin (PVL), but belonged to different spa types and SCCmec types. These results indicate that OS-MRSA is common in bovine mastitis in China and underscore the need for genetic methods (in addition to phenotypic tests) to accurately identify MRSA.

Prevalence and Characterization of Oxacillin Susceptible mecA-Positive Clinical Isolates of Staphylococcus aureus Causing Bovine Mastitis in India

“…Therefore, the findings of the strains with MLST and spa type known in human infection in the current study may point towards transmission between human to animals. We also found pvl positive isolates, which are rarely reported in animal origin strains [8]-[10]. The pvl gene is also a virulence factor that is mainly associated with community acquired-MRSA (CA-MRSA) infections that causes serious pathology including skin infections and necrotizing pneumonia in humans [46–48].…”

Methicillin-resistant coagulase-negative staphylococci in healthy dogs

“…Recent studies suggested that amino acid mutations in the Fem proteins (involved in cell wall synthesis) might lead to the oxacillin-sensitive methicillin-resistant staphylococcus phenotype, but the association of mutations with the phenotype has not been formally proven (Giannouli et al 2010;Pu et al 2014). Furthermore, Fem genes that encode proteins which considerably affect the level of methicillin resistance were suggested to be specific only for Stahylococcus aureus (Kobayashi et al 1994).…”

Mastite bovina causada por Staphylococcus spp. resistentes à meticilina: revisão de literatura

“…que se caracteriza pela forma subclínica da infecção, com elevação na quantidade de células somáticas (>200.000 céls/mL). Entretanto há relatos da manifestação clínica da doença, ocasionada por MRS, nesses casos os animais apresentam um quadro agudo da infecção, onde são observadas alterações macroscópicas no leite, no tecido mamário e sistêmicas no animal (Chandrasekaran et al 2014a, Pu et al 2014, Lim et al 2013, Vanderhaeghen et al 2010.…”