Abstract
Background: Carbapenem-resistant Pseudomonas aeruginosa (CRPA) is the one of the main Gram-negative bacterium cause of infections in hospital settings and the spread of them is significant challenge to public health.
Methods: In this study, a total of 30 non-duplicate isolates of CRPA were collected. Antibacterial susceptibility of bacteria to antibiotic agents and AmpC overproducer isolates were determined. Minimal biofilm inhibitory concentration (MBIC) of isolates to cefepime (FEP), imipenem (IPM), ceftazidime (CAZ), and meropenem (MEM) were evaluated with/without cloxacillin (CLX). The carbapenemase and 16S rRNA methylase genes were identified by PCR and the transcription levels of oprD, ampC, and mexA genes were determined by quantitative real-time PCR. ERIC-PCR was used to detect genetic relationships among the isolates.
Results: All isolates were resistance to IPM, MEM, CAZ, FEP, CIP, GEN, TOB and strong biofilm producer. The resistance genes including blaNDM, blaIMP, blaVIM, blaSIM, blaGES, and armA were detected in 21 (70%), 6(20%), 3 (10%), 2 (6.6%), 1 (3.3%), and 56.6% of the isolates, respectively. CLX at 250 and 500 µg/mL significantly reduced the level of MIC to MEM, IPM, CAZ, and FEP and at 2000 µg/mL significantly reduced the level of MBIC to MEM, IPM, CAZ, and FEP. In all of isolates the transcription levels of oprD were significantly downregulated as well as were showed significantly increasing for ampC and mexA. ERIC-PCR typing results divided 30 isolates into four clusters.
Conclusion: In this study we reported the spread of different clone of CRPA harboring co-existence various carbapenemase genes with armA 16S rRNA methylase for the first time in Kerman, Iran. Also, our isolates had a combination of resistance mechanisms to carbapenems as well as biofilm formation along with resistance to aminoglycosides, the further spread of which could cause serious challenge in hospital settings. Therefore, serious monitoring is necessary to reduce their prevalence in our hospital.