Monday, March 27, 2006
Epidemiology, clinical features and prognosis of infections due to Stenotrophomonas maltophilia
Seccion de Enfermedades Infecciosas, Servicio de Medicina Interna, Hospital Universitario Virgen Macarena, Sevilla, Spain.
Stenotrophomonas maltophilia is a multiresistant pathogen that is being isolated with increasing frequency from patients with predisposing factors. Few studies have assessed the epidemiology and clinical relevance of this pathogen in various types of patients from general hospitals.
This is a prospective study performed in the cohort of patients with infection due to S. maltophilia in Hospital Univeritario Virgen Macarena (Seville, Spain) between January 1998 and January 2001. The following data were collected: demographics, underlying diseases, APACHE II score at admission, invasive procedures, previous antimicrobial treatment, systemic response, therapy and outcome.
S. maltophilia was isolated from a clinical sample in 87 patients and was considered to be the cause of infection in 45 (52%) of them, who were included in the study. Among the total, 40% were in the ICU and 13% were outpatients. The infection was considered health care-associated in 91%; 82% had received antimicrobial treatment. The most frequent type of infection was pneumonia, followed by other infections of the respiratory tract, urinary tract infections, and skin and soft tissue infections. Criteria for severe sepsis or septic shock were present in 12%. The most common antimicrobials used were the combination trimethoprim-sulfamethoxazole (60%). Crude mortality was 44% and the only associated variable was the APACHE II score. Infection-related mortality was 13%; all deaths occurred in patients with pneumonia.
S. maltophilia caused a wide range of health care-associated infections in debilitated patients, even though half the patients from whom the organism was isolated were considered only colonized. Crude mortality was associated with the severity of the baseline situation. Pneumonia was associated with high mortality.
What is it?
Stenotrophomonas maltophilia is an aerobic gram-negative bacillus. It has previously been known as Xanthomonas maltophilia and Pseudomonas maltophilia.
S. maltophilia has recently emerged as an important hospital-associated pathogen as a result of the increasing number of susceptible hosts (due to immunocompromise) and to the use of antimicrobial agents such as Imipenem. It is not associated with infection in healthy individuals.
How is it spread?
S. maltophilia is present in the environment, in soil, water, animals and vegetation. In the hospital it may be associated with water (faucets, sinks), respirometers, suction catheters and ventilation equipment, and can become endemic in critical care units. It is not part of the normal skin or gastrointestinal flora.
Person-to-person transmission of S. maltophilia occurs via the hands of healthcare workers to patient devices such as catheters, needles and respiratory equipment. S. maltophilia is transferred via hands, but does not actually colonize the hands and may be removed with proper handwashing. Shared equipment, such as respirometers, facilitates the spread of this organism.
Signs and Symptoms of S. maltophilia infection
S. maltophilia has been isolated from a variety of sites, including wounds, the respiratory tract and blood. It often is associated with life-threatening systemic infections in a debilitated host.
Infection with S. maltophilia should be suspected in patients who develop superinfection while receiving Imipenem or multiple antibiotics.
Prevention of Transmission
Prevention is based on good personal hygiene, particularly handwashing to remove transient organisms. Minimize environmental contamination by prompt disposal of contaminated gloves, catheters or other patient care articles. Equipment should not be shared. If sharing of equipment is necessary, it must be adequately disinfected between patients.
If respiratory secretions are growing S. maltophilia, the patient requires a private room. In Intensive Care Units, doors between patients must be kept closed. In the event of multiple cases on a unit, cohorting and the use of antiseptic soap may be necessary.