Evaluation of a Stenotrophomonas maltophilia bacteremia cluster in hematopoietic stem cell transplantation recipients using whole genome sequencing

Stefanie Kampmeier,Evgeny A Idelevich,Aleksandra Pettke,Mike H Pillukat,Annelene Kossow,Alexander Mellmann

doi:10.1186/s13756-017-0276-y

Abstract

BackgroundStenotrophomonas maltophilia ubiquitously occurs in the hospital environment. This opportunistic pathogen can cause severe infections in immunocompromised hosts such as hematopoietic stem cell transplantation (HSCT) recipients. Between February and July 2016, a cluster of four patients on the HSCT unit suffered from S. maltophilia bloodstream infections (BSI).MethodsFor epidemiological investigation we retrospectively identified the colonization status of patients admitted to the ward during this time period and performed environmental monitoring of shower heads, shower outlets, washbasins and toilets in patient rooms. We tested antibiotic susceptibility of detected S. maltophilia isolates. Environmental and blood culture samples were subjected to whole genome sequence (WGS)-based typing.ResultsOf four patients with S. maltophlilia BSI, three were found to be colonized previously. In addition, retrospective investigations revealed two patients being colonized in anal swab samples but not infected. Environmental monitoring revealed one shower outlet contaminated with S. maltophilia. Antibiotic susceptibility testing of seven S. maltophlia strains resulted in two trimethoprim/sulfamethoxazole resistant and five susceptible isolates, however, not excluding an outbreak scenario. WGS-based typing did not result in any close genotypic relationship among the patients’ isolates. In contrast, one environmental isolate from a shower outlet was closely related to a single patient’s isolate.ConclusionWGS-based typing successfully refuted an outbreak of S. maltophilia on a HSCT ward but uncoverd that sanitary installations can be an actual source of S. maltophilia transmissions.

Highlights

Stenotrophomonas maltophilia ubiquitously occurs in the hospital environment
Whole genome sequence-based typing (WGS) approaches are increasingly seen as gold standard method for highly discriminatory typing [12] and the superiority of whole genome sequence-based typing (WGS) in comparison to other typing methods was already demonstrated for several bacterial pathogens [13,14,15,16,17]
We could recently demonstrate the high reproducibility of WGS, which is another prerequisite for the applicability in clinical routine [18]

Summary

Introduction

Stenotrophomonas maltophilia ubiquitously occurs in the hospital environment. This opportunistic pathogen can cause severe infections in immunocompromised hosts such as hematopoietic stem cell transplantation (HSCT) recipients. Stenotrophomonas maltophilia, an intrinsically multidrug resistant gram negative pathogen, is widely distributed in aqueous habitats such as, sink drains, endoscopes and hemodialysis water within clinical settings [1, 2] This pathogen is not highly virulent in immunocompetent individuals but can cause severe infections including. Kampmeier et al Antimicrobial Resistance and Infection Control (2017) 6:115 investigations, different typing methods, e.g. pulse field gel electrophoresis (PFGE) and multi locus sequence typing (MLST) are used to identify the genetical relationship among different S. maltophilia isolates [8,9,10,11] These techniques are useful in excluding outbreak scenarios, if MLST sequence types (ST) or PFGE patterns of isolated pathogens differ. We could recently demonstrate the high reproducibility of WGS, which is another prerequisite for the applicability in clinical routine [18]

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Results

Discussion

Conclusion