Molecular investigation of carbapenem resistance among multidrug-resistant Pseudomonas aeruginosa isolated clinically in Thailand.

Carbapenem resistant Pseudomonas aeruginosa were isolated among multidrug-resistant (CR-MDR) organisms from tertiary hospitals in Thailand. Decreased expression of oprD mRNA (93.65%) was predominant followed by increased expression of mexAB-oprM mRNA (92.06%) and mexXY mRNA (63.49%). Interestingly, 23 of 126 (18.25%) isolates were susceptible to imipenem with down-regulated oprD expression and non-up-regulated mexCD-oprJ mRNA expression. Metallo-β-lactamases production was clearly positive in 24 isolates (18.46%) and weakly positive in 12 isolates (9.23%). Among both of these sets of isolates, imp-1, imp-14 and vim-2 were identified. Hyperproduction of AmpC β-lactamase had the lowest prevalence rate (3.97%). It was concluded that CR-MDR P. aeruginosa clinical isolates in Thailand possess multifactorial resistance mechanisms.