Phenotypic and genotypic characterization of Stenotrophomonas maltophiliaisolates from patients with cystic fibrosis: Genome diversity, biofilm formation, and virulence

Abstract

BackgroundStenotrophomonas maltophilia is emerging as one of the most frequently found bacteria in cystic fibrosis (CF) patients. In the present study, phenotypic and genotypic traits of a set of 98 isolates of S. maltophilia obtained from clinical (CF and non-CF patients) and environmental sources were comparatively evaluated.ResultsS. maltophilia exhibited a high level of genomic diversity in both CF and non-CF group, thus possibly allowing this bacterium to expand its pathogenic potentials. Strains sharing the same pulsotype infected different patients, thus likely indicating the occurrence of clonal spread or acquisition by a common source. CF isolates differed greatly in some phenotypic traits among each other and also when compared with non-CF isolates, demonstrating increased mean generation time and susceptibility to oxidative stress, but reduced ability in forming biofilm. Furthermore, in CF isolates flagella- and type IV pili-based motilities were critical for biofilm development, although not required for its initiation. Sequential isogenic strains isolated from the same CF patient displayed heterogeneity in biofilm and other phenotypic traits during the course of chronic infection. CF and non-CF isolates showed comparable virulence in a mouse model of lung infection.ConclusionsOverall, the phenotypic differences observed between CF and non-CF isolates may imply different selective conditions and persistence (adaptation) mechanisms in a hostile and heterogeneous environment such as CF lung. Molecular elucidation of these mechanisms will be essential to better understand the selective adaptation in CF airways in order to design improved strategies useful to counteract and eradicate S. maltophilia infection.

Biofilm Production by Multi Drug Resistant Bacterial Pathogens Isolated From Patients in Intensive Care Units in Egyptian Hospitals

“…Our results revealed that rmlA, spgM, rpfF genes in S. maltophilia which are responsible for biofilm formation showed 100% occurrence in all isolates which are moderately adherent and strongly adherent, these results shows little difference than that presented by Pompilio et al which showed an overall prevalence of 65.2, 88.8 and 61.8%, respectively [14]. This difference may come from the genetic diversity of MDR S. maltophilia isolates between Egyptian and overseas hospitals worldwide.…”

“…Detection of rmlA, spgM, rpfF genes in S. maltophilia which are responsible for biofilm formation [14]: Fifty isolates were tested for the presence of rmlA, spgM, rpfF genes that are responsible for their abilities to produce biofilm using PCR. 49, 50 and 50 Isolates showed positive results to the three genes respectively by showing a band on 82 bp, 80 bp and 151 bp, respectively as illustrated in Figures 6-8.…”

“…Mutants for the glucose-1-phosphate thymidyltransferase rmlA gene and for the cis-11-methyl-2-dodecenoic acid rpfF gene were reported to decreases biofilm formation [12,13]. Further, the spgM gene, encoding a bifunctional enzyme with both phosphoglucomutase (PGM) and phosphomannomutase activities, is involved in biofilm-forming ability in S. maltophilia [14].…”

The effect of interspecies signaling on Stenotrophomonas maltophilia growth.

“…Biofilms are a community of microbial organisms (either one or multiple species of bacteria) that inhabit a favorable growing environment such as an extracellular mucus (in the case of biofilms for cystic fibrosis patients) but also including nonorganic environments such as rocks (3) . The exact mechanism that facilitates biofilm creation and adhesion is not well understood for most species (5) . However, it is understood that the physical structure of the biofilm (which often exists as an extracellular matrix or slime layer secreted by the organisms) creates an environment that is both ideal for bacterial growth and adaptation while simultaneously severely hindering the effectiveness of antibiotic treatment (3) .…”

“…Although the specific nature of the effectors resulting in synergism between bacteria that makes the multi-species biofilms so robust are not fully understood, intercellular signaling is expected to be involved (5,7) . Quorum sensing could play a role, as it is known to play an important role in the virulence of P. aeruginosa (14) P. aeruginosa uses three different types of signaling systems (for quorum sensing) to communicate with itself as well as other species.…”