Small plasmids carrying vga(A) or vga(C) genes mediate resistance to lincosamides, pleuromutilins and streptogramin A antibiotics in methicillin-resistant Staphylococcus aureus ST398 from swine — J Antimicrob Chemother.
Methicillin-resistant Staphylococcus aureus (MRSA) isolates of the sequence type ST398 have been identified recently from cases of exudative epidermitis in swine, but also as colonizers of apparently healthy swine in Portugal.1,2 A considerable number of these isolates displayed an unusual resistance phenotype, namely resistance to the lincosamide clindamycin, but susceptibility to the macrolide erythromycin.1,2 Since the genetic basis of this resistance phenotype is unknown, we selected five representative isolates to identify the respective resistance genes, to determine whether they are transferable and to investigate their genetic environment. Of the five MRSA ST398 isolates, three (E32, E33 and E49) were obtained from dust samples in three different holdings of breeding pigs during the European Community baseline study, one (E8) was from the nasal swab of an apparently healthy sow and the remaining one (E18) was from a skin lesion of a piglet suffering from exudative epidermitis. PCR screening for the presence of the lincosamide resistance gene lnu(A)3 yielded negative results in repeated experiments using plasmid DNA or chromosomal DNA as targets.
