Tn5253Family Integrative and Conjugative Elements Carryingmef(I) andcatQDeterminants in Streptococcus pneumoniae and Streptococcus pyogenes

Abstract

ABSTRACTThe linkage between the macrolide efflux genemef(I) and the chloramphenicol inactivation genecatQwas first described inStreptococcus pneumoniae(strain Spn529), where the two genes are located in a module designated IQ element. Subsequently, two different defective IQ elements were detected inStreptococcus pyogenes(strains Spy029 and Spy005). The genetic elements carrying the three IQ elements were characterized, and all were found to be Tn5253family integrative and conjugative elements (ICEs). The ICE fromS. pneumoniae(ICESpn529IQ) was sequenced, whereas the ICEs fromS. pyogenes(ICESpy029IQ and ICESpy005IQ, the first Tn5253-like ICEs reported in this species) were characterized by PCR mapping, partial sequencing, and restriction analysis. ICESpn529IQ and ICESpy029IQ were found to share theintSp23FST81integrase gene and an identical Tn916fragment, whereas ICESpy005IQ hasint5252and lacks Tn916. All three ICEs were found to lack the linearized pC194 plasmid that is usually associated with Tn5253-like ICEs, and all displayed a single copy of a toxin-antitoxin operon that is typically contained in the direct repeats flanking the excisable pC194 region when this region is present. Two different insertion sites of the IQ elements were detected, one in ICESpn529IQ and ICESpy029IQ, and another in ICESpy005IQ. The chromosomal integration of the three ICEs was site specific, depending on the integrase (intSp23FST81orint5252). Only ICESpy005IQ was excised in circular form and transferred by conjugation. By transformation,mef(I) andcatQwere cotransferred at a high frequency fromS. pyogenesSpy005 and at very low frequencies fromS. pneumoniaeSpn529 andS. pyogenesSpy029.