title: Carbapenem resistance in Pseudomonas aeruginosa from cystic fibrosis patients.
abstract: The evolution of imipenem resistance was evaluated in Pseudomonas aeruginosa sequentially isolated from 42 patients with cystic fibrosis. Susceptibility was determined using a commercial microdilution system and imipenem resistance was confirmed by the agar dilution technique. Resistance to imipenem increased during the years from 1988 to 1992. A total of 12 patients (28.5%) carried resistant strains (11.6% of the total P. aeruginosa isolates) but only two of them were treated with the carbapenem. The other patient under imipenem treatment did not harbour resistant isolates. Sixty-four per cent of the imipenem resistant isolates were also meropenem resistant and showed low susceptibility to the other beta-lactams and tobramycin and amikacin. Twenty-one strains were selected for biochemical study. Imipenem susceptible strains showed normal OprD in two strains and diminished OprD in two more. Five strains with MIC of imipenem of 4-8 mg/L lacked OprD while another two had a band with decreased density. All strains with MIC higher than 8 completely lacked this band in western-blot analysis. Imipenem MICs of 0.5-2 mg/L only slightly increased to 1-4 mg/L when a pattern of beta-lactamase derepression was observed. While those with imipenem MICs between 8-16 mg/L increased the imipenem MIC to 16-64 mg/L in the population with a beta-lactamase derepression phenotype.
authors.affiliation: Servicios de Microbiologia y Pediatría, Hospital Ramón y Cajal, Madrid, Spain.
authors.forename: S
authors.initials: S
authors.lastname: Ballestero
authors.forename: A
authors.initials: A
authors.lastname: Fernández-Rodríguez
authors.forename: R
authors.initials: R
authors.lastname: Villaverde
authors.forename: H
authors.initials: H
authors.lastname: Escobar
authors.forename: J C
authors.initials: JC
authors.lastname: Pérez-Díaz
authors.forename: F
authors.initials: F
authors.lastname: Baquero
mesh_terms: D000293:Adolescent; D000328:Adult; D015780:Carbapenems / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D003550:Cystic Fibrosis / Q000188:drug therapy* / Q000201:enzymology / Q000382:microbiology; D004352:Drug Resistance, Microbial / Q000235:genetics; D005069:Evaluation Studies as Topic; D006801:Humans; D015378:Imipenem / Q000494:pharmacology*; D007223:Infant; D007231:Infant, Newborn; D008826:Microbial Sensitivity Tests; D010641:Phenotype; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000235:genetics; D013045:Species Specificity; D013845:Thienamycins / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D015780:Carbapenems; D013845:Thienamycins; D015378:Imipenem; D001618:beta-Lactamases