Decreased permeability to imipenem is the most frequent mechanism of imipenem resistance in Pseudomonas aeruginosa. We have determined the presence of OprD porin protein, an imipenem influx channel, in 70 carbapenem-resistant P. aeruginosa clinical isolates by Western blot analysis using rabbit anti-OprD polyclonal antibody. Ninety-eight percent (54 of 55 isolates) of imipenem-and meropenem-res...

conclusions although the data support the idea that the basic mechanism of imipenem resistance could be via the loss of oprd, they do not fully explain the role of oprd and indicate that other mechanisms may play an important role. additionally, the significant decrease in the oprd levels in mdr strains suggests that oprd also plays a role in the emergence of both carbapenem and non-carbapenem ...

We investigated the unusual susceptibility to meropenem observed for seven imipenem-resistant clinical isolates of Pseudomonas aeruginosa. These strains were genetically closely related, expressed OprD, as determined by Western blot analyses, and were resistant to imipenem (>5 microg/ml) but susceptible to meropenem (<1 microg/ml). The oprD genes from two isolates were entirely sequenced, and t...

The increasing number of carbapenem-resistant Acinetobacter baumannii isolates is a major cause for concern which restricts therapeutic options to treat severe infections caused by this emerging pathogen. To identify the molecular mechanisms involved in carbapenem resistance, we studied the contribution of an outer membrane protein homologue of the Pseudomonas aeruginosa OprD porin. Suspected t...

Pseudomonas aeruginosa OprD is a specific porin which facilitates the uptake of basic amino acids and imipenem, a carbapenem antibiotic. Resistance to imipenem due to the loss of OprD is an important mechanism for the loss of clinical effectiveness. To investigate the negative regulatory mechanisms influencing oprD expression, a gene upstream of the coregulated mexEF-oprN efflux operon, designa...

BACKGROUND The Pseudomonas aeruginosa porin OprD is a substrate-specific porin that facilitates the diffusion of basic amino acids, small peptides, and carbapenems into the cell. OprD-mediated resistance occurs as a result of decreased transcriptional expression of oprD and/or loss of function mutations that disrupt protein activity. OBJECTIVES In this study, we examined the level of oprD exp...

Earlier studies proved that Pseudomonas aeruginosa OprD is a specific porin for basic amino acids and imipenem. It was also considered to function as a nonspecific porin that allowed the size-dependent uptake of monosaccharides and facilitation of the uptake of quinolone and other antibiotics. In the present study, we utilized P. aeruginosa strains with genetically defined levels of OprD to cha...

Mutant proteins with eight amino acid deletions in putative surface loops 2 and 3 of the imipenem-specific porin OprD of Pseudomonas aeruginosa failed to reconstitute imipenem susceptibility in an oprD-deficient background. The loop 3 deletion prevented the ability of imipenem to inhibit KCl conductance through the OprD channel, as previously shown for a loop 2 deletion. This suggests that both...

To circumvent the permeability barrier of its outer membrane, Pseudomonas aeruginosa has evolved a series of specific porins. These channels have binding sites for related classes of molecules that facilitate uptake under nutrient-limited conditions. Here, we report on the identification of a 19-member family of porins similar to the basic-amino-acid-specific porin OprD. The members of this fam...

A Tn501 mutant of Pseudomonas aeruginosa resistant to imipenem and lacking the imipenem-specific outer membrane porin protein OprD was isolated. The mutation could be complemented to imipenem susceptibility and OprD-sufficiency by a cloned 6-kb EcoRI-PstI fragment of DNA from the region of chromosome of the wild-type strain surrounding the site of Tn501 insertion. However, this fragment did not...