Pseudomonas aeruginosa is an aerobic, gram-negative bacillus with a diversified ecologic niche. Pseudomonas aeruginosa is highly pathogenic among immunocompromised patients and is responsible for substantial morbidity and mortality. Pseudomonas aeruginosa is principally a health care–associated pathogen, although community-onset infection has been described among immunocompetent and immunocompromised patients (ie, neutropenia, human immunodeficiency virus [HIV], acquired immunodeficiency syndrome [AIDS]). Such patients may be encountered by primary care and subspecialty physicians alike, and diagnosis requires a high index of suspicion. Infections commonly associated with P. aeruginosa include pneumonias, bloodstream infections (BSI), urinary tract infections, and surgical site infections (Table 146.1). Two related species, Stenotrophomonas maltophilia and Burkholderia cepacia, are briefly discussed.

EPIDEMIOLOGY

The epidemiology of P. aeruginosa infections reflects its predilection for moist environments. In hospitals, P. aeruginosa has been isolated from respiratory devices, disinfectants, distilled and tap water, and sinks. Pseudomonas aeruginosa can readily colonize the upper respiratory tract of mechanically ventilated patients, the gastrointestinal tract of patients receiving chemotherapy or broad-spectrum antibiotics, and the wounds of burn patients. Colonization usually precedes invasive infection.

Among health care–associated infections occurring in intensive care units, P. aeruginosa is the most commonly identified gram-negative pathogen, and the second most commonly identified organism overall. Emergence and spread of antimicrobial resistance, especially multidrug resistance (MDR), among P. aeruginosa is frequent.