[Bacteremia caused by Stenotrophomonas maltophilia: a clinical-epidemiological study and resistance profile]

Abstract

Over a 7-year period (1990-1996), the causal disease, predisposing factors, focus infection, clinical manifestations, complications and evolution of patients presenting bacteremia from Stenotrophomonas maltophilia were analyzed retrospectively in a university hospital. A microbiological study was carried out to determine the percentage of positive blood cultures per episode and the characteristics of bacteremia and to evaluate the antibiotic susceptibility of the isolated strains. Twenty-seven episodes of bacteremia from S. maltophilia were identified in 26 patients, half of whom were women, and the median age was 40 years. A total of 48% of the patients had blood malignancy (12 cases), with acute myeloid leukemia (5 cases) being the most frequent. Seven patients (27%) needed to be admitted to an intensive care unit for some type of vital support and/or intensive treatment. The previous administration of large spectrum antimicrobials (21/26) and the presence of a catheter or central catheter (19/26) were the most frequently found predisposing factors (81% and 73%, respectively). One-quarter of the patients had received treatment with carbapenems. Immunodepression caused by chemotherapy or corticosteroids occurred in 65% of the cases. Half of the patients had undergone a major surgical procedure or had been intubated and submitted to mechanical ventilation. One-third presented granulocytopenia on the detection of bacteremia and 6 of the 12 patients with blood malignancy showed severe neutropenia (<500 neutrophils/mm3). The bacteremia was acquired in hospital in 78% of the cases (21/27). In 26% of these cases, S. maltophilia was diagnosed as the probable cause of bacteremia; in 34% this was just a possibility. The origin of the bacteremia was unknown in 11 cases (40%). Infection from the vascular catheter was the most frequent focus infection (7 cases). An average of 3.6 blood cultures were performed per patient, out of a total of 92, and 54% showed positive. The average time of growth for S. maltophilia in the blood culture bottles was 30 hours. One-third of the bacteremia episodes from S. maltophilia were polymicrobial (9/27). Clinical evolution was favorable in 18 patients, while 8 died (31%), 5 cases (20%) from causes directly related to the bacteremia (4 from septic shock). The mortality associated with the polymicrobial bacteremia was not significantly different from that for single microbial bacteremia from S. maltophilia. Ninety percent of the isolated strains showed susceptibility to co-trimoxazole, 77% to ticarcillin-clavulanic acid, 60% to ciprofloxacin, 62% to ceftazidime, 20% to amikacin and just 18% to imipenem.