Analysis of the Pseudomonas aeruginosa oprD gene from clinical and environmental isolates

Abstract

Genomes are constantly evolving. Our report highlights the wide mutational diversity of clinical as well as environmental isolates, compared with the laboratory strain(s), through the systematic genetic analysis of a chromosomal porin gene (oprD) in relation to a specific antibiotic resistance. Mutational inactivation of the oprD gene is associated with carbapenem resistance in Pseudomonas aeruginosa. The sequence of the oprD gene of 55 Pseudomonas aeruginosa natural isolates obtained from across the world--from sources as diverse as patients and rhizospheres--was analysed. A microscale mosaic structure for this gene--resulting from multiple intra- and possibly interspecies recombinational events--is reported. An array of independent and seemingly fast-occurring defective oprD mutations were found, none of which had been described before. A burn wound isolate demonstrated unusually high overall sequence variability typical of mutator strains. We also present evidence for the existence of OprD homologues in other fluorescent pseudomonads.

Molecular characterization of resistance mechanisms in Pseudomonas aeruginosa isolates resistant to carbapenems

“…Overexpression of efflux pump MexAB-OprM was established when the expression of mexB was 2-3 folds its expression level in the wild isolate PAO1 [19][20]. The expression level of oprD was also calibrated relative to PAO1 [21].…”

Antibiotic Resistance in the Environment, with Particular Reference to MRSA

“…Some bacteria stop the antibiotic entering the cell or by efflux, pumping the compound out of the cell. Carbapenemlactam antibiotics enter Gram negative bacteria via a membrane protein known as a porin, resistant bacteria can lack the specific D2 porin responsible for transport and are therefore resistant (Pirnay et al, 2002). Efflux via a membrane pump is a common mechanism and is found in Gram negative and Gram positive bacteria where five different superfamilies of efflux pumps conferring antibiotic resistance have been reported (Mahamoud et al, 2007) .…”

Horizontal Gene Transfer and Assortative Recombination within the Acinetobacter baumannii Clinical Population Provide Genetic Diversity at the Single carO Gene, Encoding a Major Outer Membrane Protein Channel

“…Thus, the comparative sequence analysis of genes encoding surface-exposed proteins among members of a given bacterial population can reveal significant clues into both their roles in the adaptability to particular environments and the mechanisms of variant generation. Pertinent examples in the context of this work are the sequence variations of surfaceexposed antigenic proteins, which allow evasion of the host immune system (16), and OprD, the OM channel for basic amino acids in Pseudomonas aeruginosa, which also allows imipenem entrance and whose sequence variability has been associated with significantly altered drug influx efficiency (33,37,43).…”