Stenotrophomonas maltophilia

However clinically-significant infections usually only occur in those with significantly impaired immune defences, such as severely immuno-compromised patients.  Infections in previously normal patients are unusual.Risk factors pre-disposing a hospitalised patient towards infection include prior exposure to antimicrobials (especially broad-spectrum antibiotics), mechanical ventilation, and prolonged hospitalisation. S. maltophilia may also affect the lungs of patients with cystic fibrosis.  Stenotrophomonas maltophilia does not readily spread between patients and is not a common cause of healthcare-associated infection. While hospital outbreaks for many pathogens (e.g. Acinetobacter baumannii) are usually caused by a single strain, apparent outbreaks attributed to S. maltophilia are frequently caused by multiple strains, implying acquisition from environmental sources as opposed to inter-patient spread. 

S. maltophilia is inherently resistant to many antibiotic classes (e.g. cephalosporins, carbapenems, and aminoglycosides) meaning that treatment options are relatively limited.   However, most strains remain susceptible to co-trimoxazole which is regarded as the drug of choice for treating infections.