Antibiotics trigger initiation of SCCmec transfer by inducing SOS responses.
The rise of antimicrobial resistance limits therapeutic options for infections by methicillin-resistant staphylococci. The staphylococcal cassette chromosome mec (SCCmec) is a mobile genetic element as the only carrier of the methicillin-resistance determinants, the mecA or mecC gene. The use of antibiotics increases the spread of antibiotic resistance, but the mechanism by which antibiotics promote horizontal dissemination of SCCmec is largely unknown. In this study, we demonstrate that many antibiotics, including β-lactams, can induce the expression of ccrC1 and SCCmec excision from the bacterial chromosome. In particular, three widely used antibiotics targeting DNA replication and repair (sulfamethoxazole, ciprofloxacin and trimethoprim) induced higher levels of ccrC1 expression and higher rates of SCCmec excision even at low concentrations (1/8 × minimum inhibitory concentration). LexA was identified as a repressor of ccrC1 and ccrAB by binding to the promoter regions of ccrC1 and ccrAB. The activation of RecA after antibiotic induction alleviated the repression by LexA and increased the expression of ccrC1 or ccrAB, consequently increasing the excision frequency of the SCCmec for SCCmec transfer. These findings lead us to propose a mechanism by which antimicrobial agents can promote horizontal gene transfer of the mecA gene and facilitate the spread of methicillin resistance.
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
Pilong
P
Liu
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
Zhaowei
Z
Wu
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.
Huping
H
Xue
College of Animal Science and Technology, Northwest A&F University, Yangling, Shaanxi 712100, China.|Department of Animal Science, McGill University, Ste Anne de Bellevue, Quebec H9X3V9, Canada.
Xin
X
Zhao
D000900:Anti-Bacterial Agents / Q000633:toxicity; D001426:Bacterial Proteins / Q000378:metabolism; D001665:Binding Sites; D004249:DNA Damage; D004251:DNA Transposable Elements; D015964:Gene Expression Regulation, Bacterial; D022761:Gene Transfer, Horizontal; D016106:Methicillin Resistance / Q000235:genetics*; D011401:Promoter Regions, Genetic; D011938:Rec A Recombinases / Q000378:metabolism; D045522:Recombinases / Q000096:biosynthesis / Q000235:genetics*; D013014:SOS Response, Genetics; D012697:Serine Endopeptidases / Q000378:metabolism; D013210:Staphylococcus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D000099160:LexA Repressor Protein
D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D011938:Rec A Recombinases; D045522:Recombinases; D012697:Serine Endopeptidases; D000099160:LexA Repressor Protein