Abstract
Stenotrophomonas maltophilia is a ubiquitous environmental bacterium that has recently emerged as a multidrug-resistant opportunistic pathogen causing bloodstream, respiratory, and urinary tract infections. The connection between the commensal environmental S. maltophilia and the opportunistic pathogen strains is still under investigation. Bacterial toxin–antitoxin (TA) systems have been previously associated with pathogenic traits, such as biofilm formation and resistance to antibiotics, which are important in clinical settings. The same species of the bacterium can possess various sets of TAs, possibly influencing their overall stress response. While the TA systems of other important opportunistic pathogens have been researched, nothing is known about the TA systems of S. maltophilia. Here, we report the identification and characterization of S. maltophilia type II TA systems and their prevalence in the isolates of clinical and environmental origins. We found 49 putative TA systems by bioinformatic analysis in S. maltophilia genomes. Despite their even spread in sequenced S. maltophilia genomes, we observed that relBE, hicAB, and previously undescribed COG3832-ArsR operons were present solely in clinical S. maltophilia isolates collected in Lithuania, while hipBA was more frequent in the environmental ones. The kill-rescue experiments in Escherichia coli proved higBA, hicAB, and relBE systems to be functional TA modules. Together with different TA profiles, the clinical S. maltophilia isolates exhibited stronger biofilm formation, increased antibiotic, and serum resistance compared to environmental isolates. Such tendencies suggest that certain TA systems could be used as indicators of virulence traits.
Highlights
Stenotrophomonas maltophilia is a bacterium of class Gammaproteobacteria, ubiquitously found in the natural environment [1]
S. maltophilia isolates exhibited stronger biofilm formation, increased antibiotic, and serum resistance compared to environmental isolates
We showed that clinical and environmental S. maltophilia isolates differed in biofilm formation abilities, which was in line with previous studies [9,69]
Summary
Stenotrophomonas maltophilia is a bacterium of class Gammaproteobacteria, ubiquitously found in the natural environment (soil, plants, animals, foods, or aqueous habitats) [1]. S. maltophilia came into attention as a globally emerging multidrug-resistant opportunistic pathogen causing nosocomial and community-acquired infections to immunocompromised patients [2]. S. maltophilia as one of the leading multidrug-resistant pathogens [4]. S. maltophilia is known as a highly diverse species, since numerous studies have revealed genotypic diversity between clinical S. maltophilia isolates [7,8,9], even when analyzing samples from the same hospital [10,11]. No significant genotypic or phenotypic differences between clinical and environment S. maltophilia isolates could be identified [12]. There is still an open question whether all the members of this species can become virulent and is there a specific marker to distinguish clinical and environmental S. maltophilia isolates
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