Mutations in Chromosomal oprD Gene of Endotracheal Aspirate’s Isolates of Carbapenem-Resistant Pseudomonas Aeruginosa

The objective of the study was to evaluate the association between mutations in oprD gene and carbapenem resistance. Eight carbapenem resistant Pseudomonas aeruginosa, evaluated in this study, were isolated from pediatric ventilated patients. Drug pattern of imipenem and meropenem was determined according to the Clinical and Laboratory Standards Institute (CLSI) criteria. The oprD gene was amplified by PCR using specific primers, and sequencing was performed. The amino acid alterations in the oprD gene of carbapenem-resistant isolates were compared with the corresponding sequence of P. aeruginosa PAO1. OprD gene of all eight carbapenem-resistant isolates of P. aeruginosa was found having defective chromosomal mutations. Different classes of mutations were found. In this study, distinct base substitution was the commonest aberration in oprD gene, causing premature termination. Other frequent mechanisms of oprD inactivation resulted from 1-bp insertions or deletions or point mutation, leading to premature stop codon. In these isolates, amino acid variations among oprD groups were observed mainly at the external loops. Different classes of mutations of P. aeruginosa oprD gene were associated with carbapenem-resistant isolates from endotracheal aspirates of pediatric ventilated patients.