How is Stenotrophomonas maltophilia transmitted to patients, particularly in healthcare settings?

Stenotrophomonas maltophilia Transmission in Healthcare Settings

Stenotrophomonas maltophilia is primarily transmitted through environmental water sources and contaminated hospital equipment, with sink drains, faucets, and water-contact surfaces serving as the main reservoirs, rather than through direct patient-to-patient spread. 1

Primary Transmission Routes

Environmental Water Sources

• The organism is ubiquitously found in hospital water systems, sink drains, and faucets, making these the most common sites of contamination in healthcare facilities. 1, 2
• Water-contact surfaces including mattresses, bedside tables, chairs, washbasins, and window sills serve as important environmental reservoirs when they have contacted colonized or infected patients. 1, 3
• The organism is widespread in both hospital and home environments, with studies showing 32% of hospital ward sites and 36-42% of home environment sites testing positive for S. maltophilia. 2

Medical Equipment and Devices

• Respiratory equipment and ventilators are critical transmission vehicles, with documented outbreak investigations linking contaminated ventilators to patient infections. 1, 4
• Endoscopes, urinary catheters, and in-line suction catheters serve as colonization sites and transmission sources. 5, 4
• The organism's ability to form biofilms on medical device surfaces facilitates persistent contamination and subsequent patient acquisition. 5

Patient-to-Patient Transmission

• Direct patient-to-patient transmission is uncommon—molecular epidemiology studies using pulsed-field gel electrophoresis have found that most patients are colonized with unique strains, with only rare instances of shared strains between patients. 2
• When patient-to-patient transmission does occur, it is typically mediated through contaminated equipment or healthcare worker hands rather than direct contact. 4
• Cross-contamination from shared equipment between patients represents a more significant risk than direct transmission. 6, 4

Healthcare Worker Role in Transmission

• Healthcare workers can serve as vectors for transmission when proper hand hygiene and contact precautions are not followed. 3, 6
• The organism can be transferred on healthcare worker hands after contact with contaminated environmental surfaces or colonized patients. 6
• Gloves and gowns must be worn for all patient encounters and removed promptly after care, followed by immediate hand hygiene, to prevent healthcare worker-mediated transmission. 6, 3

High-Risk Patient Populations

• Immunocompromised patients, particularly hematopoietic stem cell transplant recipients with neutropenia, mucositis, or graft-versus-host disease, are at highest risk for acquisition and infection. 7
• Patients with cystic fibrosis show high colonization rates (25% in one study), likely due to repeated environmental exposures and compromised respiratory defenses. 2
• Patients with indwelling central venous catheters or receiving broad-spectrum antibiotics face increased acquisition risk. 7

Important Caveats

• Genetic drift of environmental strains complicates source tracking—the same environmental site may harbor genetically distinct strains over time, making it difficult to definitively link specific environmental sources to patient isolates. 2
• The majority of patient strains likely represent multiple independent acquisitions from various environmental sites both within and outside the hospital, rather than a single common source. 2
• Standard disinfection protocols may be inadequate, as the organism exhibits environmental persistence and can survive on surfaces despite routine cleaning. 1, 8