What are the sources of Serratia marcescens bacteremia in patients, particularly those with compromised immune systems, such as cancer, diabetes, or chronic kidney disease?

Sources of Serratia marcescens Bacteremia

Serratia marcescens bacteremia primarily originates from healthcare-associated sources, with the most common portals being contaminated intravenous fluids and devices, urinary tract infections, and respiratory tract infections, particularly in patients with severe underlying diseases such as diabetes mellitus, malignancy, and chronic kidney disease. 1, 2

Healthcare-Associated Sources

Intravenous Access and Contaminated Fluids

• Contaminated intravenous fluids represent a critical source of S. marcescens bacteremia, with documented outbreaks traced to in-use IV fluids and transmission via medical personnel handling 3
• Central venous catheters are present in the majority of cases (82% in one series), though catheter-related infection criteria are met in only a minority of patients 1
• Primary bacteremia without identifiable source accounts for 64-68% of cases, suggesting occult contamination of IV access or fluids 1, 2

Urinary Tract Sources

• Urinary tract infections represent 9-22% of S. marcescens bacteremia cases, particularly in patients with indwelling urinary catheters 1, 2
• Nosocomial outbreaks have been traced to contaminated urine collection jugs and improper handling practices in intensive care units 4
• Prolonged urinary catheterization in neurosurgical ICU patients significantly increases risk 4

Respiratory Tract Sources

• Pneumonia accounts for 13-14% of S. marcescens bacteremia cases 1, 2
• Hospital-acquired pneumonia with S. marcescens occurs more commonly in late-onset infections and patients with multiple risk factors 5

Patient-Specific Risk Factors

Underlying Conditions

• Diabetes mellitus is the most common underlying disease associated with S. marcescens bacteremia 1
• Chronic kidney disease and end-stage renal disease increase susceptibility 5
• Malignancy and immunocompromised states elevate risk 1
• Cardiovascular disease represents an additional risk factor 4

Healthcare Exposures

• Nosocomial acquisition accounts for 74-82% of all S. marcescens bacteremia cases 1, 2
• Prolonged intensive care unit stays significantly increase risk 4
• Mechanical ventilation exposure 4
• Receipt of total parenteral nutrition 4
• Prior antimicrobial therapy, particularly with beta-lactams and aminoglycosides 4

Other Identified Sources

Surgical and Procedural Sources

• Biliary tract infections (9% of cases) 2
• Intra-abdominal infections (4% of cases) 2
• Surgical wound infections (5% of cases) 1
• Suppurative thrombophlebitis (5% of cases) 1
• Neurosurgical procedures, particularly brain or spine surgery 4

Skin and Soft Tissue

• Skin and soft tissue infections account for approximately 4% of bacteremia cases 2
• S. marcescens is isolated in 2% of complicated skin and soft tissue infections overall 5

Critical Clinical Considerations

The portal of entry remains unknown in 48-64% of cases, emphasizing the importance of heightened surveillance for occult sources 1, 2. Polymicrobial bacteremia occurs concurrently in 23% of patients, complicating source identification 1.

Community-acquired S. marcescens bacteremia is rare (26% of cases) but can occur in previously healthy individuals without identifiable risk factors, occasionally presenting with severe manifestations such as respiratory distress syndrome 2, 6.

The mortality rate ranges from 39-50%, with 23-32% of deaths directly attributable to S. marcescens bacteremia, underscoring the importance of rapid source identification and appropriate antimicrobial therapy 1, 2.