Insertion sequence ISRP10 inactivation of the oprD gene in imipenem-resistant Pseudomonas aeruginosa clinical isolates

• ISRP10 disrupted the oprD gene in 31 of 32 imipenem-resistant Pseudomonas aeruginosa isolates.
• MLST and RAPD were used to discriminate the isolates.
• MLST analysis showed that 68.3% of the tested strains belonged to clone ST253.
• The isolates displayed a relatively high degree of genetic variability.

Carbapenem resistance mechanisms were investigated in 32 imipenem-resistant Pseudomonas aeruginosa clinical isolates recovered from hospitalised children. Sequence analysis revealed that 31 of the isolates had an insertion sequence element ISRP10 disrupting the porin gene oprD, demonstrating that ISRP10 inactivation of oprD conferred imipenem resistance in the majority of the isolates. Multilocus sequence typing (MLST) was used to discriminate the isolates. In total, 11 sequence types (STs) were identified including 3 novel STs, and 68.3% (28/41) of the tested strains were characterised as clone ST253. In combination with random amplified polymorphic DNA (RAPD) analysis, the imipenem-resistant isolates displayed a relatively high degree of genetic variability and were unlikely associated with nosocomial infections.