The Influence of Livestock on Human Infections with LA-MRSA

Infections caused by the methicillin resistant Staphylococcus aureus (MRSA) are traditionally nosocomial, but recent reports have indicated an increased frequency of community acquired infections. Livestock associated MRSA (LA-MRSA) is usually present in livestock, especially in pigs. Although LA-MRSA strains usually don't cause the disease in animals, they might function potential source for human infections. In Slovenia, the number of people colonized with LA-MRSA is increasing. Both human and animal samples additionally to environmental samples were collected from 16 farms in Slovenia, where a minimum of one case of LA-MRSA was previously confirmed per family. All the obtained isolates were tested for his or her antimicrobial susceptibility with the microdilution method for the minimal inhibitory concentration (MIC). In addition, they were confirmed by the multiplex PCR for 16S rRNA, nuc, mecA, mecC and PVL genes. Spa arrange was also performed, using the Ridom StaphType software. All the humanc of LA-MRSA were immune to Cefoxitin, Tetracycline and Penicillin, a number of them also to Ciprofloxacin and Clindamycin. In animals, similar susceptibility patterns were found, but none of the animal isolates were immune to Ciprofloxacin. The human confine mostly belonged to spa types t011 and t034, but t1451, t10765 and t1344 were also present. The evidence of LA-MRSA in animals was confirmed for five farms and every one of these isolates belonged to the spa type t011. It are often assumed that pigs are a possible source of human infection, but it also can be concluded that LA-MRSA strains are already spreading within the human population. Namely, LA-MRSA was isolated from humans at farms, where both the animal samples and dust samples collected from the stables were negative.