Bacteremia caused by Achromobacter and Alcaligenes species in 46 patients with cancer (1989-2003).

BACKGROUND:

Achromobacter and Alcaligenes are emerging infectious gram-negative bacterial species that can affect immunosuppressed patients. The authors sought to determine the incidence and characteristics of bloodstream infections caused by these organisms in patients with underlying malignancies.

METHODS:

All consecutive episodes of hematogenous Achromobacter and Alcaligenes infections recorded from December 26, 1989, to July 27, 2003, were studied retrospectively.

RESULTS:

Fifty-two episodes occurred in 46 patients; 31 patients (67%) had hematologic malignancies, and 24 (52%) experienced neutropenia (< 500 cells/microL). Diabetes mellitus was present in 12 patients (26%), and high-dose corticosteroids were administered to 12 patients (26%). Seventeen of the 52 infectious episodes (33%) were nosocomial in origin, and 10 patients (22%) had sepsis syndrome. Achromobacter xylosoxidans was the most common cause of infection (47 of 52 episodes [94%]), followed by Ach. denitrificans (2 of 52 episodes [4%]) and Alcaligenes faecalis (1 of 52 episodes [2%]). Twenty-seven episodes (52%) were polymicrobial, and 3 patients (7%) had concurrent fungemia. Infected intravascular catheters were present in 13 of 52 cases (25%), pneumonia was encountered in 6 of 52 cases (12%), and urinary tract infections were present in 5 of 52 cases (10%). Most isolates exhibited in vitro susceptibility to carbapenems, antipseudomonal penicillins, and trimethoprim-sulfamethoxazole. Resistance to ciprofloxacin, levofloxacin, aminoglycosides, and monobactam was common. Seven deaths (15%) were attributable to Achromobacter species. Incidence rates for sepsis syndrome, multiorgan dysfunction (Acute Physiology and Chronic Health Evaluation [APACHE] II score > 16), and use of mechanical ventilation and pressor support were significantly higher in patients who died (P < 0.001). Logistic regression analysis revealed that sepsis syndrome and high APACHE II scores were predictors of increased 30-day mortality.

CONCLUSIONS:

Most infections caused by this group of nonfermentative gram-negative bacteria were attributable to Ach. xylosoxidans, and only one-third were acquired during hospitalization. The presence of sepsis syndrome has evolved as an independent predictor of poor outcome in patients with high-risk malignancies accompanied by Achromobacter bloodstream infections.