Molecular epidemiology and genetic linkage of macrolide and aminoglycosideresistance in Staphylococcus intermedius of canine origin

A collection of 77 Staphylococcus intermedius isolates from dogs and cats i n Switzerland was examined for resistance to erythromycin. Resistance profi les for 14 additional antibiotics were compared between erythromycin-resist ant and susceptible isolates. A resistance prevalence of 27% for erythromyc in was observed in the population under study. Complete correlation between resistance to erythromycin, and to spiramycin, streptomycin, and neomycin was observed. The erythromycin-resistant isolates all had a reduced suscept ibility to clindamycin when compared to the erythromycin-susceptible isolat es. Both constitutive and inducible resistance phenotypes were observed for clindamycin. Ribotyping showed that macrolide-aminoglycoside resistance wa s randomly distributed among unrelated strains. This suggests that this par ticular resistance profile is not related to a single bacterial clone but t o the horizontal transfer of resistance gene clusters in S. intermedius pop ulations. The erythromycin-resistant isolates were all carrying erm(B), but not erm(A). erm(C), or msr(A). The erm(B) gene was physically linked to Tn 5405-like elements known as resistance determinants for streptomycin, strep tothricin, neomycin and kanamycin. Analysis of the region Ranking erm(B) sh owed the presence of two different groups of erm(B)-Tn5405-like elements in the S. intermedius population examined and of elements found in Gram-posit ive species other than staphylococci. This strongly suggests that erm(B) or the whole em(B)-Tn5405-like elements in S. intermedius originate from othe r bacterial species, possibly from enterococci. (C) 2001 Elsevier Science B .V. All rights reserved.