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

PURPOSE: The aim of this work was to investigate the presence of selected potential virulence factors, susceptibility and clonal relatedness among 63 Stenotrophomonas maltophilia isolates recovered from patients exposed to invasive devices in a university hospital in Argentina between January 2004 and August 2012.

METHODOLOGY: 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 Galleria mellonella model.Results/Key findings. 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 (stmPr1). Sm61 is an stmPr1-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 G. mellonella model, while Sm10, a low-resistance hydrogen peroxide stmPr1-negative isolate, and weak proteolysis and siderophore producer, was not virulent.

CONCLUSION: This is the first epidemiological study of the clonal relatedness of S. maltophilia clinical isolates in Argentina. Great genomic diversity was observed, and only two small clusters of related S. maltophilia types were found. Minocycline and trimethoprim-sulfamethoxazole were the most active agents. S. maltophilia virulence in the G. mellonella model is multifactorial, and further studies are needed to elucidate the role of each potential virulence factor.