BlaIMP-45 and armA co-carrying multidrug resistance Pseudomonas isolates and characterization of their genetic environment

Abstract

Objective The primary goal of this work is to discuss the molecular mechanism of multi-drug resistant Pseudomonas spp. resistance to carbapenam and aminoglycoside antibiotics. Methods From June 2012 to March 2013, six strains of P. aeruginosa and P. putida producing carbapenemasefrom 4 different district were collected. Species identification was performed using VITEK-2 compact system and by sequencing of 16S rDNA amplicons. Minimum inhibitory concentrations were determined by E-test method. Production of carbapenemase were detected by Carba NP method. Carbapenemase genes and aminoglycoside 16s rRNAmethylase genes were screened by PCR, and their subtypes combined with their immediate genetic context were worked out by assemble the sequence of overlapped PCR amplicons. SpeI-PFGE (Pulse field gel electrophoresis after SpeI enzyme digestion) were conducted to evaluate their clonal relatedness. S1-PFGE (Pulse field gel electrophoresis after S1 enzyme digestion) were conducted to conform the relatedness of plasmids they carried. Results Three multidrug resistant P. aeruginosa and three P. putida, were all positive for Carba NP test and conformed producing class B carbapenemase. PCR screening followed by sequencing confirmed carriage of blaIMP-45 and armA, which confer resistance to β-lactams (except aztreonam) and aminoglycosides. These two genes co-located in a Tn1548-associatedregion. SpeI-PFGE disclosed that these isolates were not clonal closely related to each other, except two P. aeruginosa isolates were clonal related. S1-PFGE results showed that these isolates all carried plasmids of large size (300-600 kb). Conclusions This study showed that Pseudomonas spp. isolates co-carried blaIMP-45 and armA were disseminated in clinical settings. Spread of these genes may attribute to horizontal gene transfer of related entities. Key words: Pseudomonas; Drug resistance, multiple, bacterial; Methyltransferases; Escherichia coli proteins; beta-Lactams