Mechanism of imipenem resistance acquired by threePseudomonas aeruginosa strains during imipenem therapy

Abstract

Imipenem sensitive pretherapy isolates (MICs 1-2 mg/l) and the corresponding resistant posttherapy isolates (MICs 16 mg/l) of Pseudomonas aeruginosa from three patients undergoing imipenem treatment were analyzed to establish the resistance mechanism. The identity of pyocin types, serotypes, DNA restriction endonuclease profiles and plasmid profiles strongly suggested isogenicity of pre- and posttherapy isolates. The imipenem resistant posttherapy isolates showed cross-resistance only to another carbapenem, meropenem. There were neither qualitative nor quantitative differences between pre- and posttherapy isolates in beta-lactamase production. Affinity of the penicillin-binding proteins 1A, 1B, 2, 3, 4,4' and 5 for [14C]imipenem was the same in pre- and posttherapy isolates. One-dimensional and two-dimensional gel electrophoresis of outer membrane protein preparations showed diminished expression of an outer membrane protein of about 46.5 and 47.5 kilodaltons, respectively, in the posttherapy isolates. This protein had an apparent isoelectric point of about pH 5.2 in two-dimensional gel electrophoresis. Growth in proteose peptone no. 2 broth did not reduce expression of this outer membrane protein, which spoke against its identity with the outer membrane protein D1. The permeability of the outer membrane for imipenem was reduced in the posttherapy isolates, since addition of 0.5 or 0.25 of the MIC of the permeabilizing agent ethylene-diaminetetraacetate reduced the MICs of imipenem for all isolates from each patient to the same (susceptible) level. The diminished expression of one of the outer membrane proteins might be the reason for this reduced permeability.

Activity of carbapenem BMS-181139 against Pseudomonas aeruginosa is not dependent on porin protein D2

“…Selective resistance to imipenem, but not to other ␤-lactam antibiotics, has emerged in P. aeruginosa during imipenem therapy (21,38). These imipenem-resistant mutants lack or produce diminished levels of a 45-or 48-kDa outer membrane protein, designated D2.…”

“…Data from this study indicated that BMS-181139 was also active against imipenemresistant, clinical isolates of P. aeruginosa. Unlike the carbapenem meropenem, which has diminished activity against imipenem-resistant strains of P. aeruginosa (39), the activity of BMS-181139 against these strains was unaffected.Essentially all imipenem-resistant P. aeruginosa isolates produce low or undetectable levels of the porin protein D2 (2,8,21,33,35,38), suggesting its role in the permeation of imipenem across the outer membrane. The D2 channel was shown to facilitate the specific permeation of basic amino acids and, because of their structural similarities to basic amino acids, also imipenem and meropenem (36).…”

Aspects actuels des infections nosocomiales au Centre Hospitalier Libanais de Beyrouth

“…Cette résistance peut être expliquée par la perte de la porine D2 qui entraîne une diminution spécifique de la perméabilité pour l'imipénème. La résistance ne s'exprime à haut niveau que si la perte de D2 est accompagnée d'une hyperproduction de la céphalosporinase chromosomique [24]. Les souches de P. aeruginosa peuvent avoir encore une tendance à acquérir des plasmides qui leur confèrent un haut degré de résistance par exemple à la gentamycine et à la tobramycine [25].…”

Prevalence and charaterization of carbapenem-resistant Pseudomonas aeruginosa carrying metallo-β-lactamases at different wards

“…Reference strains were included as internal standards in all tests: Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aeruginosa ATCC 27853. The O serotype of the isolates was determined by slide agglutination using commercially available antisera (BIO-RAD, Marnes la Coquette, France) as previously described [7].…”