Cinnamaldehyde (CNA), the main component of cinnamon essential oil, is one of the most active pla... more Cinnamaldehyde (CNA), the main component of cinnamon essential oil, is one of the most active plant compounds against nosocomial pathogen Pseudomonas aeruginosa. Exposure of wild-type strain PA14 (MIC 700 µg/mL) for 5 to 10 days to fixed (900 µg/mL) or increasing (from 900 to 1400 µg/mL) concentrations of this natural antibacterial resulted in emergence of resistant mutants CNA-A1 to A3, and CNA-B1 to B7, respectively. Genome sequencing experiments showed that each of CNA-A1 to A3 mutants differed from PA14 by one SNP, and a slight increase in CNA resistance level (from 700 to 900 µg/mL). By comparison, mutants B1 to B7 were more resistant (up to 1100 µg/mL); each of them harbored multiple SNPs (from 24 to 39) likely as a consequence of alteration of DNA mismatch repair gene mutS. Of the ten mutants selected, eight contained mutations in gene nalC, which indirectly downregulates expression of the operon that codes for multidrug efflux system MexAB-OprM, and showed increased resistan...
Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis patients. The multidrug res... more Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis patients. The multidrug resistance of these bacteria remains poorly understood. We have characterized in a clinical strain the first resistance-nodulation-cell division (RND)-type multidrug efflux pump in this species: AxyABM. The inactivation of the transporter component axyB gene led to decreased MICs of cephalosporins (except cefepime), aztreonam, nalidixic acid, fluoroquinolones, and chloramphenicol. Achromobacter xylosoxidans is a nonfermentative Gram-neg-ative bacillus considered to be an opportunistic agent (1, 25). It is an emerging pathogen in cystic fibrosis (CF) (6, 20). Cur-rently, 120 patients are followed at our CF center, of whom 24 (20%) have been colonized at least once by A. xylosoxidans. It has recently been suggested that A. xylosoxidans might be re-sponsible for a high inflammatory response and therefore might be involved in the decline in lung function (9). This microorganism exhibits innate ...
Objectives: To investigate the resistance mechanisms of b-lactam-resistant Pseudomonas aeruginosa... more Objectives: To investigate the resistance mechanisms of b-lactam-resistant Pseudomonas aeruginosa isolated from cystic fibrosis (CF) patients in France. Methods: Two-hundred-and-four P. aeruginosa CF isolates were collected in 10 French university hospitals in 2007. Their susceptibility to 14 antibiotics and their resistance mechanisms to b-lactams were investigated. Their b-lactamase contents were characterized by isoelectric focusing, PCR and enzymatic assays. Expression levels of efflux pumps and the intrinsic b-lactamase AmpC were quantified by reverse transcription real-time quantitative PCR. Genotyping was performed using multiple-locus variable number of tandem repeats analysis (MLVA). The oprD genes were sequenced and compared with those of reference P. aeruginosa strains. To assess deficient OprD production, western blotting experiments were carried out on outer membrane preparations. Results: MLVA typing discriminated 131 genotypes and 47 clusters. One-hundred-and-twenty-f...
Cinnamaldehyde (CNA), the main component of cinnamon essential oil, is one of the most active pla... more Cinnamaldehyde (CNA), the main component of cinnamon essential oil, is one of the most active plant compounds against nosocomial pathogen Pseudomonas aeruginosa. Exposure of wild-type strain PA14 (MIC 700 µg/mL) for 5 to 10 days to fixed (900 µg/mL) or increasing (from 900 to 1400 µg/mL) concentrations of this natural antibacterial resulted in emergence of resistant mutants CNA-A1 to A3, and CNA-B1 to B7, respectively. Genome sequencing experiments showed that each of CNA-A1 to A3 mutants differed from PA14 by one SNP, and a slight increase in CNA resistance level (from 700 to 900 µg/mL). By comparison, mutants B1 to B7 were more resistant (up to 1100 µg/mL); each of them harbored multiple SNPs (from 24 to 39) likely as a consequence of alteration of DNA mismatch repair gene mutS. Of the ten mutants selected, eight contained mutations in gene nalC, which indirectly downregulates expression of the operon that codes for multidrug efflux system MexAB-OprM, and showed increased resistan...
Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis patients. The multidrug res... more Achromobacter xylosoxidans is an emerging pathogen in cystic fibrosis patients. The multidrug resistance of these bacteria remains poorly understood. We have characterized in a clinical strain the first resistance-nodulation-cell division (RND)-type multidrug efflux pump in this species: AxyABM. The inactivation of the transporter component axyB gene led to decreased MICs of cephalosporins (except cefepime), aztreonam, nalidixic acid, fluoroquinolones, and chloramphenicol. Achromobacter xylosoxidans is a nonfermentative Gram-neg-ative bacillus considered to be an opportunistic agent (1, 25). It is an emerging pathogen in cystic fibrosis (CF) (6, 20). Cur-rently, 120 patients are followed at our CF center, of whom 24 (20%) have been colonized at least once by A. xylosoxidans. It has recently been suggested that A. xylosoxidans might be re-sponsible for a high inflammatory response and therefore might be involved in the decline in lung function (9). This microorganism exhibits innate ...
Objectives: To investigate the resistance mechanisms of b-lactam-resistant Pseudomonas aeruginosa... more Objectives: To investigate the resistance mechanisms of b-lactam-resistant Pseudomonas aeruginosa isolated from cystic fibrosis (CF) patients in France. Methods: Two-hundred-and-four P. aeruginosa CF isolates were collected in 10 French university hospitals in 2007. Their susceptibility to 14 antibiotics and their resistance mechanisms to b-lactams were investigated. Their b-lactamase contents were characterized by isoelectric focusing, PCR and enzymatic assays. Expression levels of efflux pumps and the intrinsic b-lactamase AmpC were quantified by reverse transcription real-time quantitative PCR. Genotyping was performed using multiple-locus variable number of tandem repeats analysis (MLVA). The oprD genes were sequenced and compared with those of reference P. aeruginosa strains. To assess deficient OprD production, western blotting experiments were carried out on outer membrane preparations. Results: MLVA typing discriminated 131 genotypes and 47 clusters. One-hundred-and-twenty-f...
Uploads