Novel mechanisms of resistance to lincosamides in Staphylococcus and Arthrobacter spp

Clinical isolates of Staphylococcus and Arthrobacter spp. were screened for lincosamide resistance. Six different patterns of resistance were found. Strains designated SF27 and SF28 showed low-level resistance to lincosamides: one was susceptible to erythromycin (SF27) and the other was resistant (SF28). Analysis of ribosomes from the resistant strains in an in vitro poly(U)-dependent protein-synthesizing system showed that ribosomes of both strains were sensitive to lincomycin and clindamycin. Four patterns of high-level resistance to lincosamides were observed (strains SF4, SF19, SF30, and SF31). All of these except SF30 had ribosomes which were highly resistant in vitro to the antibiotics and showed a close correlation with results of the in vivo experiments. In vivo protein synthesis by strain SF30 was resistant to lincomycin and sensitive to clindamycin, whereas the ribosomes were sensitive when assayed in vitro. Lincosamide-inactivating enzymes were not detected in cell extracts of the six resistant strains. Strains SF19 and SF31 demonstrated two ribosome-mediated lincosamides resistance mechanisms that were not previously reported. Both strains were highly resistant to lincosamides and susceptible to erythromycin, but SF19 was also highly resistant to oleandomycin and partially resistant to various macrolides.