Phenotypic and Molecular Characteristics of the MDR Efflux Pump Gene-Carrying Stenotrophomonas maltophilia Strains Isolated in Warsaw, Poland

Abstract

An increase of nosocomial infections caused by Stenotrophomonas maltophilia strains has recently been observed all over the world. The isolation of these bacteria from the blood is of particular concern. In this study we performed the phenotypic and genotypic characterization of 94 S. maltophilia isolates, including isolates from patients hospitalized in a tertiary Warsaw hospital (n = 79) and from outpatients (n = 15). All isolates were found to be susceptible to trimethoprim-sulfamethoxazole and minocycline, while 44/94 isolates demonstrated a reduction in susceptibility to levofloxacin. A large genetic variation was observed among the isolates tested by pulsed-field gel electrophoresis. A clonal relationship with 100% similarity was observed between isolates within two sub-pulsotypes: the first included nine bloodstream isolates and the second involved six. Multilocus sequence typing showed two new sequence types (ST498 and ST499) deposited in public databases for molecular typing. Moreover, the presence of genes encoding ten different efflux pumps from the resistance-nodulation-division family and the ATP-binding cassette family was shown in the majority of the 94 isolates. The obtained knowledge about the prevalence of efflux pump genes in clinical S. maltophilia strains makes it possible to predict the scale of the risk of resistance emergence in strains as a result of gene overexpression.

The Contribution of Efflux Systems to Levofloxacin Resistance in Stenotrophomonas maltophilia Clinical Strains Isolated in Warsaw, Poland

“…Isolates were derived from January 2010 to October 2013 from a variety of clinical materials obtained during routine diagnostic testing of adult patients in microbiology laboratories. All clinical materials from which the tested isolates were derived are listed in our previous publication [ 14 ]. Most of the isolates ( n = 27) were obtained from blood samples.…”

“…In our previous article, all of these isolates were characterized by determination of the susceptibility profiles for three anti- S. maltophilia agents (including levofloxacin) and tested for the presence of genes encoding efflux pumps from the RND and ABC families. Moreover, the genetic relationship between clinical isolates and their similarity to the strains isolated in other countries was investigated [ 14 ]. All isolates were stored in Luria Bertani broth (BioMaxima SA, Lublin, Poland) with 20% glycerol at −80 °C until analysis.…”

“…Generally, resistance rates to levofloxacin of S. maltophilia strains are relatively similar or higher than that of trimethoprim/sulfamethoxazole and range between 3% and 30% [ 9 , 12 , 13 ]. In our previous publication, all 94 investigated S. maltophilia clinical isolates were susceptible to trimethoprim/sulfamethoxazole and minocycline, but 7 of them were resistant and 37 were intermediately susceptible to levofloxacin [ 14 ].…”

“…These systems were classified into three families of MDR efflux pumps: RND, ABC, and MFS (major facilitator superfamily). The following efflux systems, SmeDEF [ 15 ], SmeMN [ 14 ], SmeABC [ 16 ], SmeYZ [ 17 ], SmeIJK [ 17 ], SmeVWX [ 18 ], SmeOP [ 19 ], and SmeGH [ 20 ], are described from the RND family. The other four efflux pumps, SmrA [ 21 ], MacABCsm [ 22 ], SmaCDEF, and SmaAB [ 23 ], belong to the ABC family.…”

“…In the previous article, we performed phenotypic and molecular characterization of the collection of 94 S. maltophilia clinical isolates, including the prevalence of efflux systems. The investigation revealed the presence of smeD and smeH genes in all isolates, smeW in 93 out of 94 isolates, smeI or smeK in 86, and smeA or smeB in 72 isolates [ 14 ]. Among them, 7 isolates were resistant, and 37 isolates demonstrated an intermediate level of susceptibility to levofloxacin.…”