Genetic resistance factors and antimicrobial resistance phenotypes in methicillin-resistant Staphylococcus aureus isolates of animals and humans

Abstract

Objective: To investigate the prevalence, genetic resistance factors, and antimicrobial resistance phenotypes of methicillin-resistant Staphylococcus (S.) aureus (MRSA) from clinically healthy animals (horses, dogs, and cats) and their human handlers, providing a baseline for broader genes sequencing based on One Health studies to the emergence of resistance as well as guides regarding specific therapies, hospital antibiotic usage/stewardship, and target-specific infection control measures.
Methods: This cross-sectional study involved both human and animals. S. aureus isolates derived were characterised for their antimicrobial phenotypes through antimicrobial susceptibility testing with PCR detection of mecA, mecC, and DNA sequencing of mepR, mepA, mepB, and sapep genes for correlation with their antimicrobial resistance phenotypes.
Results: Seventy S. aureus isolates from 149 human handlers, 240 horses, and 206 companion animals, including dogs and cats were studied. The prevalence of resistance was highest for penicillins (100.0%) and amoxicillin (94.3%), followed by erythromycin (87.7%), trimethoprim (78.6%), azithromycin (77.1%), imipenem (61.4%), and tetracycline (40.0%). Lower resistance prevalences were observed for ciprofloxacin (27.1%), chloramphenicol (20.0%), trimethoprim-sulfamethoxazole (12.9%), and gentamicin (2.9%). Twenty-six isolates had their DNA sequenced for mepR, mepA, mepB, and sapep genes for correlation with their antimicrobial phenotypes. 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).
Conclusions: This study demonstrated extensive multidrug resistance in MRSA, revealing similarities in the resistance patterns and multiple antibiotic resistance indices among the isolates. These findings suggest the potential presence of non- mec resistance mechanisms in MRSA, in addition to the mec gene mechanism.

Keywords

MRSA / Community-acquired / Resistance / One Health

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