title: Detection of an IS21 insertion sequence in the mexR gene of Pseudomonas aeruginosa increasing beta-lactam resistance.
abstract: To understand the regulation of the MexAB OprM efflux system in a clinical strain of Pseudomonas aeruginosa presenting a decreased susceptibility to ticarcillin and aztreonam, the mexR repressor gene was amplified by polymerase chain reaction (PCR) and was shown to be disrupted by an insertion sequence of more than 2 kb, with characteristic direct and inverted repeat sequences. Sequencing revealed a 2131-bp IS21 insertion sequence. A reverse transcription PCR method was used to quantify mexA transcripts and showed an increased transcription rate of mexA in this strain, compared with a PAO1 control strain. The nalB phenotype in P. aeruginosa may be due to point mutations, but also to the presence of an insertion sequence in the mexR regulator gene.
authors.affiliation: Laboratoire de Bactériologie-Virologie-Hygiène Hospitalière, CHU de Nantes, France.
authors.forename: David
authors.initials: D
authors.lastname: Boutoille
authors.forename: Stéphane
authors.initials: S
authors.lastname: Corvec
authors.forename: Nathalie
authors.initials: N
authors.lastname: Caroff
authors.forename: Cécile
authors.initials: C
authors.lastname: Giraudeau
authors.forename: Eric
authors.initials: E
authors.lastname: Espaze
authors.forename: Jocelyne
authors.initials: J
authors.lastname: Caillon
authors.forename: Patrick
authors.initials: P
authors.lastname: Plésiat
authors.forename: Alain
authors.initials: A
authors.lastname: Reynaud
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D004251:DNA Transposable Elements / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D006801:Humans; D007223:Infant; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008826:Microbial Sensitivity Tests; D009876:Operon; D016133:Polymerase Chain Reaction / Q000379:methods; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D014158:Transcription, Genetic; D018440:beta-Lactam Resistance / Q000235:genetics*; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D004251:DNA Transposable Elements; D026901:Membrane Transport Proteins; C118598:MexA protein, Pseudomonas aeruginosa; C118597:MexB protein, Pseudomonas aeruginosa; C423620:MexR protein, Pseudomonas aeruginosa; C402263:OprM protein, Pseudomonas aeruginosa; D012097:Repressor Proteins; D047090:beta-Lactams