Carbapenem resistance in Pseudomonas aeruginosa from cystic fibrosis patients

• Published in: Journal of antimicrobial chemotherapy 1996-07, Vol.38 (1), p.39-45
• Main Authors: Ballestero, S., Fern´ndez-Rodriguez, A., Villaverde, R., Escobar, H., Pérez-Diaz, J. C., Baquero, F.
• Format: Article
• Language: English
• Subjects: Adolescent; Adult; Antibacterial agents; Antibiotics. Antiinfectious agents. Antiparasitic agents; beta-Lactamases - biosynthesis; Biological and medical sciences; Carbapenems - pharmacology; Child; Child, Preschool; Cystic Fibrosis - drug therapy; Cystic Fibrosis - enzymology; Cystic Fibrosis - microbiology; Drug Resistance, Microbial - genetics; Evaluation Studies as Topic; Humans; Imipenem - pharmacology; Infant; Infant, Newborn; Medical sciences; Microbial Sensitivity Tests; Pharmacology. Drug treatments; Phenotype; Pseudomonas aeruginosa; Pseudomonas aeruginosa - drug effects; Pseudomonas aeruginosa - genetics; Species Specificity; Thienamycins - pharmacology
• ISSN: 0305-7453; 1460-2091
• DOI: 10.1093/jac/38.1.39

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 percent of the imipenem resistant isolates were also meropenem resistant and showed low susceptibility to the other β-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 β-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 β-lactamase derepression phenotype.