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Epidemiological analysis defining concurrent outbreaks of Serratia marcescens and methicillin-resistant
J R Campbell1, E Zaccaria, E O Mason
1Department of Pediatrics, Baylor College of Medicine, Houston, TX 77030, USA.
Objective:
To describe the epidemiology, interventions, and molecular typing methods used during the investigation and control of concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus (MRSA) infections in a neonatal intensive-care unit (NICU).
Setting:
A 206-bed women's and infants' hospital with a 48-bed NICU.
Design:
A 22-week, prospective, descriptive study of all NICU infants with S marcescens or MRSA infection or colonization. Repetitive polymerase chain reaction (rep PCR) and pulsed-field gel electrophoresis (PFGE), respectively, were applied to the typing of S marcescens and MRSA isolates.
Interventions:
Infants with S marcescens or MRSA infection or colonization were placed in isolation; all other infants were cohorted. A multidisciplinary task force implemented education for all hospital and medical staff regarding policies essential for outbreak control. Changes in physical setting and patient contact procedure were required to promote adherence to existing policies.
Results:
Two premature infants had S marcescens infection, and five were colonized; rep PCR verified that both invasive and three of five colonizing isolates were related genotypically. Five bacteremic and 10 MRSA-colonized infants were identified; PFGE confirmed that 12 of the isolates had similar electrophoretic patterns. S marcescens infection was eliminated from the NICU 3 weeks after interventions were initiated. MRSA infections also were eliminated, and MRSA colonization fell to below pre-outbreak rates within 8 weeks. Despite a 100% increase in NICU patient days per month during the subsequent 2 years, no further clusters of S marcescens or MRSA infection have occurred.
Conclusions:
Concurrent outbreaks of S marcescens and MRSA in an NICU were confirmed by genotyping of strains. Control was achieved by isolation and cohorting of patients and strict adherence to NICU policies and procedures.
Insights
Concurrent outbreaks of Serratia marcescens and MRSA in a neonatal intensive-care unit (NICU) were successfully controlled. Strict adherence to isolation, cohorting, and NICU policies eliminated both infections and colonization.
Area of Science:
- Neonatal intensive care
- Infectious disease epidemiology
- Molecular microbiology
Background:
- Neonatal intensive-care units (NICUs) are vulnerable to healthcare-associated infections.
- Concurrent outbreaks of Serratia marcescens and methicillin-resistant Staphylococcus aureus (MRSA) pose significant risks to vulnerable infants.
- Effective control strategies are crucial for managing these outbreaks in NICUs.
Purpose of the Study:
- To investigate the epidemiology of concurrent Serratia marcescens and MRSA outbreaks in a NICU.
- To describe the interventions implemented for outbreak control.
- To detail the molecular typing methods used to confirm strain relatedness.
Main Methods:
- A prospective, descriptive study was conducted over 22 weeks in a 48-bed NICU.
- Repetitive polymerase chain reaction (rep PCR) and pulsed-field gel electrophoresis (PFGE) were used for molecular typing of S. marcescens and MRSA isolates, respectively.
- Interventions included patient isolation, cohorting, staff education, and modifications to physical setting and patient contact procedures.
Main Results:
- Genotyping confirmed relatedness among S. marcescens and MRSA isolates from infected and colonized infants.
- S. marcescens infection was eliminated within 3 weeks of intervention.
- MRSA infections and colonization were eliminated within 8 weeks, with colonization rates falling below pre-outbreak levels.
Conclusions:
- Concurrent S. marcescens and MRSA outbreaks in an NICU can be effectively controlled.
- Molecular genotyping confirmed the outbreaks and guided control efforts.
- A combination of patient isolation, cohorting, and strict adherence to NICU policies was key to successful outbreak management.