Detection of an IS21 insertion sequence in the mexR gene of Pseudomonas aeruginosa increasing beta-lactam resistance.

David Boutoille (1) , Stéphane Corvec , Nathalie Caroff , Cécile Giraudeau , Eric Espaze , Jocelyne Caillon , Patrick Plesiat (2, 3, 4) , Alain Reynaud

1 Service de bactériologie et hygiène hospitalière [Nantes]
2 Service de bactériologie [Besançon]
3 CHRU Besançon - Centre Hospitalier Régional Universitaire de Besançon
4 API - Agents pathogènes et inflammation - UFC (EA 4266)

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.

Domaines: Bactériologie

David Boutoille, Stéphane Corvec, Nathalie Caroff, Cécile Giraudeau, Eric Espaze, et al.. Detection of an IS21 insertion sequence in the mexR gene of Pseudomonas aeruginosa increasing beta-lactam resistance.. FEMS Microbiology Letters, 2004, pp.143-6. ⟨hal-01696314⟩