The role of the polysaccharide capsule as a novel virulence-associated trait of Stenotrophomonas maltophilia complex bacteria
5 affiliations
- 1Department of Biochemistry and Molecular Biology, Institute of Biosciences, Life Sciences Center, Vilnius University, Vilnius, Lithuania
- 2Department of Molecular Biology, Faculty of Sciences, Université Libre de Bruxelles, Gosselies, Belgium
- 3WEL Research Institute, Wavre, Belgium
- 4Center of Laboratory Medicine, Vilnius University Hospital Santaros Clinics, Vilnius, Lithuania
- 5Department of Physiology, Biochemistry, Microbiology and Laboratory Medicine, Faculty of Medicine, Institute of Biomedical Sciences, Vilnius University, Vilnius, Lithuania
Abstract
The polysaccharide capsule is recognized as a major virulence factor of many bacterial pathogens, playing a significant role in evading host immunity. However, it has not yet been characterized for the bacteria within the emerging multidrug-resistant opportunistic pathogens of the Stenotrophomonas maltophilia complex. In this study, we aimed to evaluate whether bacteria of the S. maltophilia complex form a bona fide polysaccharide capsule and determine its virulence-related functions. We demonstrated that a part of clinical and environmental isolates of the S. maltophilia complex forms a polysaccharide capsule and identified a distinct group IV-like, Wzx/Wzy-dependent capsule-associated locus architecture in these bacteria, with capsule-associated genes organized within one or two loci. Comparison of capsulated clinical isolates and their capsule-deficient mutants showed that the polysaccharide capsule protects bacteria of the S. maltophilia complex from blood plasma-mediated killing, phagocytosis, and desiccation. However, formation of the polysaccharide capsule can also limit biofilm formation and adhesion to epithelial cells in some isolates, suggesting a potential trade-off for the bacteria. Altogether, our results pinpoint the polysaccharide capsule as one of the previously undescribed virulence-associated factors of the S. maltophilia complex, enhancing its ability to escape host innate immunity mechanisms and contributing to pathogenicity.
IMPORTANCE: The emerging pathogens employ a variety of diverse virulence strategies, which must be thoroughly investigated to uncover effective ways of preventing and combating their infections. In this work, emerging multidrug-resistant bacterial pathogens belonging to the Stenotrophomonas maltophilia complex were analyzed, with the goal of identifying their mechanisms responsible for evasion of the host immune system. A polysaccharide capsule, a previously uncharacterized virulence-associated trait of S. maltophilia complex bacteria, was identified and characterized in this work, revealing both the genetic factors required for its synthesis and its biological importance to the bacteria. This work expands our understanding of the survival strategies of emerging multidrug-resistant bacteria.
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BibTeX
@article{klimkaitė2026role,
title = {{The role of the polysaccharide capsule as a novel virulence-associated trait of Stenotrophomonas maltophilia complex bacteria}},
author = {Laurita Klimkaitė and Aleksandras Konovalovas and Jūratė Skerniškytė and Dukas Jurėnas and Asta Mačionienė and Silvija Kiverytė and Julija Armalytė},
journal = {mBio},
year = {2026},
month = sep,
doi = {10.1128/mbio.01635-26},
url = {https://doi.org/10.1128/mbio.01635-26},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - The role of the polysaccharide capsule as a novel virulence-associated trait of Stenotrophomonas maltophilia complex bacteria
AU - Laurita Klimkaitė
AU - Aleksandras Konovalovas
AU - Jūratė Skerniškytė
AU - Dukas Jurėnas
AU - Asta Mačionienė
AU - Silvija Kiverytė
AU - Julija Armalytė
PY - 2026
DA - 2026/09/11
JO - mBio
DO - 10.1128/mbio.01635-26
UR - https://doi.org/10.1128/mbio.01635-26
AB - The polysaccharide capsule is recognized as a major virulence factor of many bacterial pathogens, playing a significant role in evading host immunity. However, it has not yet been characterized for the bacteria within the emerging multidrug-resistant opportunistic pathogens of the Stenotrophomonas maltophilia complex. In this study, we aimed to evaluate whether bacteria of the S. maltophilia complex form a bona fide polysaccharide capsule and determine its virulence-related functions. We demonstrated that a part of clinical and environmental isolates of the S. maltophilia complex forms a polysaccharide capsule and identified a distinct group IV-like, Wzx/Wzy-dependent capsule-associated locus architecture in these bacteria, with capsule-associated genes organized within one or two loci. Comparison of capsulated clinical isolates and their capsule-deficient mutants showed that the polysaccharide capsule protects bacteria of the S. maltophilia complex from blood plasma-mediated killing, phagocytosis, and desiccation. However, formation of the polysaccharide capsule can also limit biofilm formation and adhesion to epithelial cells in some isolates, suggesting a potential trade-off for the bacteria. Altogether, our results pinpoint the polysaccharide capsule as one of the previously undescribed virulence-associated factors of the S. maltophilia complex, enhancing its ability to escape host innate immunity mechanisms and contributing to pathogenicity. IMPORTANCE: The emerging pathogens employ a variety of diverse virulence strategies, which must be thoroughly investigated to uncover effective ways of preventing and combating their infections. In this work, emerging multidrug-resistant bacterial pathogens belonging to the Stenotrophomonas maltophilia complex were analyzed, with the goal of identifying their mechanisms responsible for evasion of the host immune system. A polysaccharide capsule, a previously uncharacterized virulence-associated trait of S. maltophilia complex bacteria, was identified and characterized in this work, revealing both the genetic factors required for its synthesis and its biological importance to the bacteria. This work expands our understanding of the survival strategies of emerging multidrug-resistant bacteria.
SN - 2150-7511
ER -