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Insertion of a novel DNA sequence, IS 1186 , upstream of the silent carbapenemase gene cfiA , promotes expression of carbapenem resistance in clinical isolates of Bacteroides fragilis
Author(s) -
Podglajen Isabelle,
Breuil Jacques,
Collatz Ekkehard
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb00999.x
Subject(s) - biology , bacteroides fragilis , gene , carbapenem , microbiology and biotechnology , dna , insertion sequence , genetics , computational biology , bacteria , genome , antibiotics , transposable element
Summary A small number of isolates of Bacteroides fragilis , an anaerobic pathogen of the human intestinal flora, carries a copy (or copies) of the carbapenem‐resistance gene, cfiA , which may be silent or expressed. We have studied the mechanism of activation of the frequently silent gene in in vitro ‐selected mutants and in clinical isolates. In both types of strains, activation was observed as the consequence of the insertion, at several possible sites, of a novel 1.3 kb insertion sequence, IS 1186 , immediately upstream of the carbapenemase gene. IS 1186 has two open reading frames, on opposite strands, with coding capacities for a 41.2kDa (ORF1) and a 22.5 kDa (ORF2) protein. The 41.2kDa protein has homology with some proteins predicted from open reading frames of IS elements or DNA direct repeats of aerobic, but not anaerobic, Gram‐negative bacteria. Upon insertion, transcription of cfiA was found to be driven from a promoter identified on the right end of IS 1186. In one instance, insertion occurred into the putative ribosome‐binding site of cfiA , leaving intact the tetranucleotide AGAA which is concluded to be a fully functional ribosome‐binding site. Between 3 and 14 copies of IS 1186 were detected per genome and the element was found, within the species B. fragilis , almost exclusively in the subgroup carrying the cfiA gene.