title: Composite structure of Streptococcus pneumoniae containing the erythromycin efflux resistance gene mefI and the chloramphenicol resistance gene catQ.
abstract: In recent years mef genes, encoding efflux pumps responsible for M-type macrolide resistance, have been investigated extensively for streptococci. mef(I) is a recently described mef variant detected in particular isolates of Streptococcus pneumoniae instead of the more common mef(E) and mef(A). This study shows that mef(I) is located in a new composite genetic element, whose sequence was completely analyzed and the left and right junctions determined, demonstrating a unique genetic organization. The new composite structure (30,505 bp), designated the 5216IQ complex, consists of two halves: a left one (15,316 bp) formed by parts of the known transposons Tn5252 and Tn916, and a right one (15,115 bp) formed by a new fragment, designated the IQ element. While the defective Tn916 contained a silent tet(M) gene, the IQ element, ending with identical transposase genes on both sides and containing the mef(I) gene with an adjacent new msr(D) gene variant and a catQ chloramphenicol acetyltransferase gene, was completely different from the genetic elements carrying other mef genes in pneumococci. This is the first report demonstrating catQ in S. pneumoniae and showing its linkage with a mef gene. Analysis of the chromosomal region beyond the left junction revealed an organization more similar to that of S. pneumoniae strain TIGR4 than to that of strain R6. The 5216IQ complex was apparently nonmobile, with no detectable transfer of erythromycin resistance being obtained in repeated transformation and conjugation assays.
authors: Institute of Microbiology and Biomedical Sciences, Polytechnic University of Marche Medical School, Via Tronto 10/A, 60020 Ancona, Italy.
authors: Marina
authors: M
authors: Mingoia
authors: Manuela
authors: M
authors: Vecchi
authors: Ileana
authors: I
authors: Cochetti
authors: Emily
authors: E
authors: Tili
authors: Luca A
authors: LA
authors: Vitali
authors: Aldo
authors: A
authors: Manzin
authors: Pietro E
authors: PE
authors: Varaldo
authors: Maria Pia
authors: MP
authors: Montanari
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology; D002702:Chloramphenicol Resistance / Q000235:genetics*; D004251:DNA Transposable Elements / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics; D004917:Erythromycin / Q000378:metabolism / Q000493:pharmacokinetics / Q000494:pharmacology*; D023061:Gene Order; D005798:Genes, Bacterial / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D016366:Open Reading Frames / Q000235:genetics; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics*
chemical_list: D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D004917:Erythromycin
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