Reduced Production of OprM May Promote oprD Mutations and Lead to Imipenem Resistance in Pseudomonas aeruginosa Carrying an oprD-Group 1A Allele

Jwu Ching Shu, Lin Hui Su, Cheng Hsun Chiu, An Jing Kuo, Tsui Ping Liu, Ming Hsun Lee, I. Ning Su, Tsu Lan Wu*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

5 Scopus citations

Abstract

Resistance mechanisms in a group of carbapenemase-negative Pseudomonas aeruginosa that were susceptible to all antibiotics except carbapenems (carbapenem resistance-only P. aeruginosa [CROPA]) were studied. Ten genetically nonrelated CROPA isolates and their carbapenem-susceptible counterparts were further investigated. OprD production was demonstrated by protein electrophoresis in only 1 of the 10 carbapenem-susceptible isolates, while the other 9 isolates showed hyperproduction of OprM. DNA sequencing of oprD revealed a shortened loop 7 domain (group 1A allele) in eight carbapenem-susceptible isolates. Various oprD mutations, leading to early terminations, were found in 9 of the 10 CROPA isolates. RNA analysis demonstrated hyperexpression of oprM with normal expression of mexA in eight of the carbapenem-susceptible isolates, while in seven of their CROPA counterparts, the oprM expression was significantly reduced. Deletion of oprM was performed in two pairs of representative isolates. Selection of imipenem resistant variants by a disc assay indicated that the lost-of-function mutations in oprD occurred relatively faster in the ΔoprM mutants compared with their corresponding parent strains. Under selection pressure, reduced production of OprM may promote the selection of spontaneous changes in oprD, resulting in the carbapenem resistance in a group of pan-susceptible P. aeruginosa isolates characterized by harboring an oprD-group 1A allele.

Original languageEnglish
Pages (from-to)149-157
Number of pages9
JournalMicrobial Drug Resistance
Volume21
Issue number2
DOIs
StatePublished - 01 04 2015

Bibliographical note

Publisher Copyright:
© 2015, Mary Ann Liebert, Inc.

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