RNA-seq-based transcriptome analysis of a cefquinome-treated, highly resistant, and virulent MRSA strain

The emergence and dissemination of methicillin-resistant Staphylococcus aureus (MRSA) strains of animal origin that are resistant to several antibiotics is of great concern. Cefquinome is a fourth-generation cephalosporin developed specifically for veterinary use. The mechanism of MRSA resistance to cefquinome is still not established. Therefore, we designed this study to evaluate the effect of cefquinome on the transcriptome of MRSA1679a, a strain that was isolated from a chicken. The transcriptome analysis indicated that multiple efflux pumps (QacA, NorB, Bcr, and ABCb) were upregulated in MRSA1679a as a resistance mechanism to expel cefquinome. Additionally, penicillin-binding protein 1A was overexpressed, which conferred resistance to cefquinome, a β-lactam antibiotic. Adhesion and the biofilm-forming capacity of the MRSA strain was also enhanced in addition to overexpression of many stress-related genes. Genes related to carbohydrate metabolism, secretion systems, and transport activity were also significantly upregulated in MRSA1679a. In conclusion, global transcription was triggered to overcome the stress induced by cefquinome, and the MRSA1679a showed a great genetic potential to survive in this challenging environment. This study provides a profound understanding of MRSA1679a as a potentially important pathogen and identifies key resistance characteristics of MRSA against cefquinome. Studies should be aimed to demonstrate multidrug resistance mechanisms of virulent strains by exposing to different antibiotic combinations.