Distribution of resistance genes tet(M), aph3′-III, catpC194 and the integrase gene of Tn1545 in clinical Streptococcus pneumoniae harbouring erm(B) and mef(A) genes in Spain

The most prevalent macrolide resistance phenotype and genotype among pneumococcal isolates was the cMLS(B) phenotype [erm(B) or erm(B)/mef(A)] (91.3%). We studied the distribution of other resistance genes, tetM), cat(pC194), aph3 ' -III, in these strains, seeing evolution at work in that some strains carried different combinations of resistance determinants. The most prevalent patterns associated with resistance to erythromycin [erm(B)] were resistance to tetracycline [tet(M)] and chloramphenicol (cat(pC194)) (48.2%) or resistance to tetracycline tet(M)] alone (42.2%). In our isolates of Streptococcus pneumoniae there was a strong association of the erm(B) and tet(M) genes with Tn 1545-related elements.