Stenotrophomonas maltophilia is a multi-drug resistant gram-negative bacillus that is an opportunistic pathogen [1-4], particularly among hospitalized patients. Stenotrophomonas infections have been associated with high morbidity and mortality in severely immunocompromised and debilitated individuals.
Stenotrophomonas (Xanthomonas) maltophilia is a ubiquitous, aerobic, non-fermentative, gram-negative bacillus that is closely related to the Pseudomonas species . The name signifies “a unit feeding on few substrates,” based on the Greek roots stenos (narrow), trophos (one who feeds), and monas (a unit). Maltophilia means “affinity for malt,” based on the Greek roots maltum (malt) and philia (affinity).
S. maltophilia was first isolated in 1943 and, at the time, was named Bacterium bookeri. It was later classified within the genus Pseudomonas, then Xanthomonas, and then finally Stenotrophomonas in 1993 [4,6,7]. S. maltophilia is the only species of Stenotrophomonas known to infect humans , whereas its closest genetic relatives are plant pathogens [7,8]. It is frequently isolated from soil, water, animals, plant matter, and hospital equipment [4,9-21].
S. maltophilia has inherent ability to adhere to foreign materials and form a biofilm, rendering protection from host defenses as well as antimicrobial agents [18,19,22-26]. Factors contributing to this behavior include its positively charged surface and fimbrial adhesions [7,22-24,26-28]. In addition, Stenotrophomonas has intrinsic or acquired resistance mechanisms to a number of antibiotic classes, including beta-lactams, aminoglycosides, carbapenems, and fluoroquinolones. Resistance to beta-lactams is conferred by two inducible beta-lactamases, a zinc-containing penicillinase (L1) and a cephalosporinase (L2) [21,29-32]. An aminoglycoside acetyl-transferase confers resistance to aminoglycoside antibiotics [33-39]. Temperature-dependent changes in the outer membrane lipopolysaccharide (LPS) structure have been associated with added resistance to aminoglycoside antibiotics [18,40-43]. In addition, many strains of S. maltophilia possess efflux pumps, which confer further resistance to multiple antibacterial classes [33,44-47].
Stenotrophomonas infections have been associated with high morbidity and mortality in severely immunocompromised and debilitated individuals. Risk factors associated with Stenotrophomonas infection include admission to an intensive care unit, HIV infection, malignancy, cystic fibrosis, neutropenia, mechanical ventilation, central venous catheters, recent surgery, trauma, and previous therapy with broad-spectrum antibiotics [1,2,4,20,21,48-51].