Molecular Characterization of Class 1, 2 and 3 Integrons in Serratia spp. Clinical Isolates in Poland - Isolation of a New Plasmid and Identification of a Gene for a Novel Fusion Protein.

Abstract

PurposeGram-negative rods of the genus Serratia play an increasing role as etiological agents of healthcare-associated infections (HAI) in humans. These bacteria are characterized by natural and acquired resistance to several groups of antibacterial agents. The aim of the study was to characterize class 1, 2 and 3 integrons in the clinical isolates of Serratia spp. in Poland.MethodsThe study comprised 112 clinical strains of Serratia, isolated from patients hospitalized in Poland in 2010–2012. Identification of strains was confirmed using MALDI-TOF MS (matrix-assisted laser desorption/ionization time-of-flight mass spectrometry) system. Detection of class 1, 2 and 3 integrase DNA sequence was performed by multiplex-PCR. Amplicons obtained in the PCR reactions were purified and then sequenced bidirectionally.ResultsAmong the analyzed strains, Serratia marcescens was a predominant species (103/112, 92.0%). All three classes of integrase DNA sequence were detected in the analyzed strains of Serratia spp. DNA sequence of class 3 integron, besides integrase gene, revealed three gene cassettes (dfrB3, blaGES-7,blaOXA/aac(6ʹ)-Ib-cr). BLAST analysis of DNA sequence revealed that class 3 integron was carried on 9448 bp plasmid which was named pPCMI3 – whole sequence of its DNA was submitted to GenBank NCBI (National Center for Biotechnology Information) – NCBI MH569711.ConclusionIn this study, we identified a new plasmid pPCMI3 harboring class 3 integron. This is the first report of a gene oxa/aac(6ʹ)-Ib-cr coding for a novel fusion protein, which consists of OXA β-lactamase and acetyltransferase aac(6ʹ)-Ib-cr. In the analyzed strains, class 1 and 2 integrons were also detected. Among the strains with class 1 integron, nine contained cassette array 5ʹCS-aadA2-ORF-dfrA12-3ʹCS, and two – cassette array 5ʹCS-aacC1-ORF-ORF-aadA1-3ʹCS, which were not previously reported in Serratia spp.