Stenotrophomonas maltophilia: an emerging global opportunistic pathogen

Abstract

Stenotrophomonas maltophilia is an emerging multidrug-resistant global opportunistic pathogen. The increasing incidence of nosocomial and community-acquired S. maltophilia infections is of particular concern for immunocompromised individuals, as this bacterial pathogen is associated with a significant fatality/case ratio. S. maltophilia is an environmental bacterium found in aqueous habitats, including plant rhizospheres, animals, foods, and water sources. Infections of S. maltophilia can occur in a range of organs and tissues; the organism is commonly found in respiratory tract infections. This review summarizes the current literature and presents S. maltophilia as an organism with various molecular mechanisms used for colonization and infection. S. maltophilia can be recovered from polymicrobial infections, most notably from the respiratory tract of cystic fibrosis patients, as a cocolonizer with Pseudomonas aeruginosa. Recent evidence of cell-cell communication between these pathogens has implications for the development of novel pharmacological therapies. Animal models of S. maltophilia infection have provided useful information about the type of host immune response induced by this opportunistic pathogen. Current and emerging treatments for patients infected with S. maltophilia are discussed.

Fig 1

(A to E) Scanning electron micrographs of S. maltophilia SM33 biofilms formed on polystyrene surfaces at 2, 4, 8, 16, and 24 h, respectively. Magnifications, ×1,000 (A to D) and ×2,000 (E). (F) Transmission electron micrograph of a 24-h biofilm produced by S. maltophilia SM33. Arrows indicate glycocalyx surrounding bacteria. The asterisk indicates the biofilm limit line in contact with the polystyrene surface. Bar, 0.5 μm. (Reprinted from reference with permission.)

Fig 2

Scanning electron micrographs of Stenotrophomonas maltophilia adhering to plastic. (A) SMDP92 cells adhere tightly to the plastic surface. (B) Structures resembling flagella appear to protrude from the cell surface and interconnect bacteria (arrowheads) or connect bacteria to the plastic (arrows). (C) In addition to the flagellum-like filaments (arrowheads), high-power magnification shows the presence of thin fibrillar structures (arrows) connecting the bacterial cells to the abiotic surface. Bars, 10 μm (A), 1 μm (B), and 2 μm (C). (Reprinted from reference .)

Fig 3

High-resolution scanning electron microscopy. (A) Adherence of SMDP92 cells to HEp-2 cells. In addition to the association of bacteria with eukaryotic cells, many bacteria adhere to the glass substratum. Bar, 10 μm. (B) High-magnification image of adhering SMDP92 cells with lateral fimbriae protruding from the bacteria (arrows). Bar, 1 μm. (C) SMDP92 cells adhering to the glass surface (biofilm formation) without epithelial cells. Bar, 10 μm. (D) High-resolution image of biofilm-forming bacteria showing peritrichous fibers attaching to bacteria. Long and thick filaments, probably flagella, are also shown. Bar, 2 μm. (Reprinted from reference with permission of John Wiley & Sons.)

Fig 4

Scanning electron micrographs of antibiotic activity against S. maltophilia SM33 biofilm. Shown are the effects of rufloxacin at 100 μg/ml (A) and 500 μg/ml (B) against preformed S. maltophilia biofilm. Magnifications, ×2,500 (A) and ×2,000 (B). (Reprinted from reference with permission.)

Fig 5

Transmission electron micrographs of epithelial respiratory cells exposed to S. maltophilia CF 1 (A) and NCF 13 (B) for 3 h. Note the presence of intracellular bacteria in membrane-bound endocytic vacuoles. Magnifications, ×30,000 (A) and ×35,000 (B). (Panel A courtesy of M.-C. Plotkowski; panel B reprinted from reference with permission of Wiley-Blackwell.)

Fig 6

The biofilm architecture of P. aeruginosa is influenced by S. maltophilia and DSF. Images are of 4-day-old biofilms in flow cells in FABL medium. (A) P. aeruginosa PAO1; (B) S. maltophilia K279a; (C) coculture of P. aeruginosa PAO1 and S. maltophilia K279a; (D) coculture of P. aeruginosa PAO1 and S. maltophilia K279arpfF; (E) P. aeruginosa PAO1 with 50 μM exogenous DSF; (F) coculture of P. aeruginosa PAO1 and the complemented S. maltophilia K279arpfF mutant. P. aeruginosa was tagged with mini-Tn7gfp, and S. maltophilia was visualized with Syto62. Scale bars, 20 μm. The confocal scanning laser microscopy images shown are representative of 12 images from three independent experiments. (Reprinted from reference with permission of John Wiley & Sons.)