Molecular basis of resistance to macrolides and lincosamides among staphylococci and streptococci from various animal sources collected in the resistance monitoring program BfT-GermVet

In this study, erythromycin- and/or clindamycin-resistant isolates among 248 coagulase-positive and coagulase-variable staphylococci and 500 streptococci, collected all over Germany during 2004-2006 in the resistance monitoring program BfT-GermVet, were investigated for their genetic basis of macrolide and/or lincosamide resistance. Staphylococci were sampled from various disease conditions of dogs/cats or pigs, whereas streptococci were from dogs/cats, pigs or horses. Resistant staphylococci were further identified biochemically to species and subspecies level and tested for the resistance genes erm(A), erm(B), erm(C), erm(TR), msr(A), msr(D), mef(A), mph(C), lnu(A), lnu(B) and lnu(C). The methylase genes erm(A), erm(B) and erm(C) were detected in staphylococci, alone or in different combinations. The erm(B) gene was the predominant gene in Staphylococcus intermedius and streptococci. The efflux gene msr(A) and the genes mph(C) and lnu(A) coding for inactivating enzymes were detected in single staphylococcal isolates. The efflux genes mef(A) and msr(D) were detected in three streptococci, in one of them together with the erm(B) gene. The lnu(B) gene was detected in seven porcine streptococcal isolates with reduced susceptibility to clindamycin. These data confirm that high-level resistance to erythromycin and clindamycin in staphylococci and streptococci was mainly due to rRNA methylases. The Inu(B) gene was detected for the first time in streptococci of animal origin.