Correlation Between Genetic Resistance Factors and the Antibiotic Resistance Phenotypes in MRSA Isolates of Animals and Humans

Abstract Background: Methicillin resistant Staphylococcus aureus (MRSA) as an infectious organism of public health significance has evolved to a genetically distinct community-acquired MRSA with extended resistance to other than β-lactams. Methods: A cross-sectional study was conducted among 149 participants handling 446 animals (240 horses & 206 companion animals). The isolates were characterized as S . aureus and MRSA with based on PCR detection of nuc , mecA or mecC , with further DNA sequencing of mepR , mepA , mepB , and sapep genes for correlation between these genes and the MRSA antimicrobial resistance phenotypes. Results: Transcriptional profiling revealed that both animal and human MRSA isolates exhibited a gene cluster mepRAB (multidrug export protein gene), encoding a MarR-like transcriptional regulator ( mepR ), a M20/M25/M40 metallo-hydrolase protein gene ( sapep ) encoding resistance to biocides and carbapenems, and a hypothetical protein gene of unknown function ( mepB ). Conclusion: Extensive multidrug resistance for MRSA has been demonstrated in this study with similarity between the isolates in the pattern of resistance and multiple antibiotic resistance indices. This thus demonstrates possible resistance genes transfer and conferment of non- mec resistance mechanisms to MRSA in addition to the mec gene mechanism that allow the isolates repress beta-lactamases and use the efflux pumps against other antibiotics.