DETECTION OF TN917-LIKE SEQUENCES WITHIN A TN916-LIKE CONJUGATIVE TRANSPOSON (TN3872) IN ERYTHROMYCIN-RESISTANT ISOLATES OF STREPTOCOCCUS-PNEUMONIAE

A series of macrolide-lincosamide-streptogramin B (MLS)-resistant pneu mococcal isolates of a variety of serotypes was examined and was found to contain Tn917-like elements by DNA-DNA hybridization. Like Tn1545, Tn917 also encodes an ermAM gene but does not mediate resistance to o ther antimicrobial agents. Furthermore, nucleotide sequence analyses o f the DNAs flanking three of the Tn917-like elements revealed that the y were inserted into orf9 of a Tn916-like element in a composite trans poson-like structure (Tn3872). Other MLS-resistant strains appeared to contain Tn1545-like elements that had suffered a deletion of sequence s including the aphA-3 sequences responsible for kanamycin resistance. Thus, the MLS resistance phenotype in pneumococci appears to be media ted by the ermAM present on a much wider variety of genetic elements t han was previously appreciated.