Stenotrophomonas maltophilia isolated from patients exposed to invasive devices in a university hospital in Argentina: molecular typing, susceptibility and detection of potential virulence factors

Abstract

<b>Purpose.</b> The aim of this work was to investigate the presence of selected potential virulence factors, susceptibility and clonal relatedness among 63 <i>Stenotrophomonas maltophilia</i> isolates recovered from patients exposed to invasive devices in a university hospital in Argentina between January 2004 and August 2012.<b>Methodology.</b> Genetic relatedness was assessed by enterobacterial repetitive intergenic consensus PCR (ERIC-PCR) and pulsed-field gel electrophoresis (PFGE). Isolates were characterized by antimicrobial resistance, the presence and/or expression of potential virulence determinants, and virulence in the <i>Galleria mellonella</i> model.<b>Results/Key findings.</b> ERIC-PCR generated 52 fingerprints, and PFGE added another pattern. Resistance to trimethoprim-sulfamethoxazole (6.35 %), levofloxacin (9.52 %) and ciprofloxacin (23.80 %) was detected. All isolates were susceptible to minocycline. All isolates were lipase, protease and siderophore producers, while all but Sm61 formed biofilms. However, 11/63 isolates did not amplify the major extracellular protease-coding gene (<i>stmPr1</i>). Sm61 is an <i>stmPr1-</i>negative isolate, and showed (as did Sm13 and the reference strain K279a) strong proteolysis and siderophore production, and high resistance to hydrogen peroxide. The three isolates were virulent in the <i>G</i>. <i>mellonella</i> model, while Sm10, a low-resistance hydrogen peroxide <i>stmPr1-</i>negative isolate, and weak proteolysis and siderophore producer, was not virulent.<b>Conclusion.</b> This is the first epidemiological study of the clonal relatedness of <i>S. maltophilia</i> clinical isolates in Argentina. Great genomic diversity was observed, and only two small clusters of related <i>S. maltophilia</i> types were found. Minocycline and trimethoprim-sulfamethoxazole were the most active agents. <i>S. maltophilia</i> virulence in the <i>G. mellonella</i> model is multifactorial, and further studies are needed to elucidate the role of each potential virulence factor.