The resistance mechanisms of b-lactam antimicrobials in clinical isolates of Acinetobacter baumannii.
- Author:
Na Young KWON
1
;
Jae Deok KIM
;
Hyun Joo PAI
Author Information
1. Department of Internal Medicine, College of Medicine, Dankook University, Chonan, Korea.
- Publication Type:Original Article
- Keywords:
Acinetobacter baumannii;
beta-lactam;
carbapenem;
beta-lactamase;
OMP
- MeSH:
Acinetobacter/*drug effects/isolation & purification/metabolism;
Acinetobacter Infections/drug therapy/microbiology;
Antibiotics, Lactam/*pharmacology;
Bacterial Outer Membrane Proteins/biosynthesis;
Carbapenems/pharmacology;
Cross Infection/drug therapy/microbiology;
Drug Resistance, Bacterial;
Human;
beta-Lactamases/biosynthesis
- From:The Korean Journal of Internal Medicine
2002;17(2):94-99
- CountryRepublic of Korea
- Language:English
-
Abstract:
BACKGROUND: Despite increasing importance of Acinetobacter baumannii in nosocomial infections and rapid development of multi-antimicrobial resistance in this strain, the resistance mechanisms of beta-lactam antimicrobials in A. baumannii were not clearly defined. In order to observe the resistance mechanisms against beta-lactams and carbapenem, we characterized the production of beta-lactamases and outermembrane protein (OMP) profiles for the 44 clinical isolates of A. baumannii. METHODS: The MICs of antimicrobials were determined by agar dilution test. The secondary beta-lactamases were characterized by isoelectric focusing, polymerase chain reactions and nucleotide sequencing, and the production of chromosomal beta-lactamases was quantitated by spectrophotometric method. For two strains with an elevated MIC of carbapenem, outermembrane protein (OMP) profile was analyzed by ultracentrifugation of the sonicated bacteral cells and SDS-PAGE. RESULTS AND CONCLUSION: Twenty two or 4 of 44 strains produced TEM-1-like beta-lactamase or PER-1 extended-spectrum beta-lactamase, respectively. However, when we analyzed the MICs of several beta-lactams with the beta-lactamase production, the resistance level of beta-lactam was mainly determined by the production of chromosomal beta-lactamase, not by the secondary beta-lactamases in the clinical isolates of A. baumannii. In two strains with an elevated MIC of imipenem, a decrease or loss of about 35 kDa and 22 kDa proteins in OMP was observed, which suggested that the change of OMP played a role in carbapenem resistance.
