First report of clinical linezolid-resistant Staphylococcus cohnii mediated by the cfr gene

cfr (chloramphenicol-florfenicol resistance) gene, initially associated with chloramphenicol resistance, represents an additionally natural linezolid resistance mechanism, which could be transmitted between species. Coagulase-negative staphylococci may be a reservoir of cfr gene and cfr -carrying isolates may become a serious threat to several potent Gram-positive-active agents. We isolated two linezolidresistant Staphylococcus cohnii from clinical patients in China for the first time. Both isolates were carrying cfr gene and no G2576T mutation. They are resistant to quinolones, tetracycline, erythromycin, clindamycin, trimethoprim/sulfamethoxazole and chloramphenicol, and susceptible to vacomycin, teicoplanin, rifampicin, gentamicin, tigecycline, quinupristin/dalfopristin. The minimum inhibitory concentrations (MICs) of linezolid to each S. cohnii were more than 256 mg/L; the MICs of vancomycin were 2 mg/L. Our results raise concerns about the future clinical efficacy of several antimicrobial classes; effective measures, such as hygiene, separate and prospective resistance surveillance, should be taken to prevent cfr gene transmission.