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An outbreak of multiply resistant Serratia marcescens: the importance of persistent carriage
1Department of Clinical Microbiology, St James's Hospital, Dublin, Ireland.
Abstract:
An outbreak of multi-resistant Serratia marcescens involving 24 patients occurred in a bone marrow transplant and oncology unit, from September 1998 to June 1999, of whom 14 developed serious infection. This is the first such outbreak described in a BMT unit. All isolates demonstrated the same antimicrobial susceptibility pattern and were the same unusual serotype O21:K14. The antimicrobial susceptibility profile showed reduced susceptibility to ciprofloxacin, gentamicin and piperacillin-tazobactam. As the latter two antimicrobials are part of our empiric therapy for febrile neutropenia, they were substituted with meropenem and amikacin during the outbreak. Investigation revealed breaches in infection control practices. Subsequently, the outbreak was contained following implementation of strict infection control measures. A prominent feature of the outbreak was prolonged carriage in some patients. These patients may have acted as reservoirs for cross-infection. This report also indicates that patients who become colonised with Serratia marcescens may subsequently develop invasive infection during neutropenic periods.
Insights
A multi-resistant Serratia marcescens outbreak in a bone marrow transplant unit highlights infection control challenges. Strict measures contained the spread, emphasizing patient carriage as a reservoir for infection.
Area of Science:
- Infectious Diseases
- Hospital Epidemiology
- Microbiology
Background:
- Bone marrow transplant (BMT) and oncology units are vulnerable to multidrug-resistant organism (MDRO) outbreaks.
- Serratia marcescens is an opportunistic pathogen that can cause severe infections in immunocompromised patients.
- Limited data exist on Serratia marcescens outbreaks specifically within BMT settings.
Purpose of the Study:
- To describe the epidemiology and characteristics of a multi-resistant Serratia marcescens outbreak in a BMT and oncology unit.
- To identify risk factors and transmission dynamics.
- To evaluate the effectiveness of infection control interventions.
Main Methods:
- Retrospective case-finding and cohort analysis.
- Microbiological investigation including serotyping and antimicrobial susceptibility testing.
- Review of infection control practices and environmental assessments.
Main Results:
- An outbreak involving 24 patients (14 with serious infections) occurred between September 1998 and June 1999.
- All isolates were identified as serotype O21:K14 with a consistent multi-resistant profile, including reduced susceptibility to ciprofloxacin, gentamicin, and piperacillin-tazobactam.
- Breaches in infection control were identified, and prolonged patient carriage was noted as a potential reservoir for transmission.
Conclusions:
- This is the first described outbreak of multi-resistant Serratia marcescens in a BMT unit.
- Strict infection control measures were crucial for outbreak containment.
- Colonization with Serratia marcescens may precede invasive infection, particularly during neutropenic periods in immunocompromised patients.