Serratia marcescens carries a chromosomally encoded pentapeptide repeat protein, conferring reduced susceptibility to quinolones in E.coli

Abstract number: P1476

Velasco C., Rodríguez-Martínez J.M., Briales A., Díaz de Alba P., Alvaro P.

Objectives: Since the discovery of qnrA1 in 1998, related plasmid-mediated genes and chromosomal homologues have been described. The presence of peptapeptide repeat proteins (PRPs) with activity against quinolones have been described in the chromosome of several Gram-positive and Gram-negative species. A new pentapeptide repeat protein from clinically relevant specie, Serratia marcescens, which confers reduced susceptibility to quinolones when expressed in E. coli, is herein reported.

Methods: A protein BLAST analysis revealed the presence of a gene encoding for PRP in S. marcescens strain Db11with 80% of amino acid identity with QnrB1. By using the information deposited in the databases, primers suitable for PCR amplification were designed. Fragments carrying the coding region and upstream non coding sequences from several clinical isolates were cloned in pCR-Blunt TOPO. MIC values of quinolones were determined in E. coli DH10B and E. coli ATCC 25922 using the E test strips. Southern hybridisation was used to explore the presence of this gene within the genus Serratia.

Results: Recombinant plasmids coding for PRPs reduced the susceptibility to ciprofloxacin between 8–16 folds in E. coli ATCC 25922 and between 3–11 folds in E. coli in DH10B, depending on the allele. MIC against nalidixic acid also increases 3–4 folds in the later strain. The sequence upstream from theses genes contains a LexA box involved in SOS response. Results of Southern hybridisation analysis suggest the presence of similar genes in several species within the genus Serratia.

Conclusion: The PRP analysed conferred a reduced susceptibility phenotype against fluoroquinolones in E. coli. These data provide evidence of its possible role in quinolone resistance in S. marcescens. This Gram-negative specie may constitute a reservoir for Qnr-like quinolone resistance protein

Session Details

Date: 16/05/2009
Time: 00:00-00:00
Session name: 19th European Congress of Clinical Microbiology and Infectious Diseases
Location: Helsinki, Finland, 16 - 19 May 2009
Presentation type:
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