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Experimental Endocarditis Model of Methicillin Resistant Staphylococcus aureus (MRSA) in Rat
Published on: June 4, 2012
An investigation of an outbreak: Methicillin resistant Staphylococcus aureus colonization in an intensive care
Inemesit Umoren1, Raul Nakamatsu, Carmen Sciortino
1University of Louisville, Department of Medicine, Division of Infectious Diseases, Louisville, Kentucky, USA.
Background:
Colonization in the nares with Methicillin Resistant Staphylococcus aureus (MRSA) has been described as a risk factor for eventual MRSA infection. The objective of this report is to describe the outbreak investigation, to identify the risk factors involved, and to evaluate and recommend control measures.
Methods:
This study was a retrospective observational outbreak study carried out in the Intensive Care and Cardiac Unit. Percentages of patients with positive conversions were graphically plotted out and were used to determine expected percentage of conversions versus observed. The case definition was determined to be a patient with a positive culture for MRSA from a nasal swab upon discharge or transfer from the ICCU whose initial swab on admission was negative.
Results:
The expected number of conversions was 2% per month and the newly observed number of conversions was 6%, which was >3 standard deviations from the mean. Repetitive sequence-based PCR (rep-PCR) was performed for the microbial DNA typing, which discovered genetically identical strains.
Discussion:
The main finding in this outbreak investigation was that the common room which housed four of these patients was contaminated with MRSA. A limitation was that some patients who would have been included in the study did not get screened at discharge and their conversion status could not be ascertained and environment cultures were not performed. Active surveillance allowed for the detection of an outbreak of MRSA colonization which led to early intervention that prevented more patients from becoming colonized. Prevention of colonization should be one of the primary goal in the prevention of MRSA.
Insights
An outbreak of Methicillin-Resistant Staphylococcus aureus (MRSA) colonization occurred in an ICU, with a 6% conversion rate. A contaminated common room was identified as the source, highlighting the need for active surveillance and environmental control to prevent MRSA spread.
Area of Science:
- Infectious Diseases
- Epidemiology
- Critical Care Medicine
Background:
- Nasal colonization with Methicillin-Resistant Staphylococcus aureus (MRSA) is a known risk factor for MRSA infections.
- Outbreaks of healthcare-associated infections necessitate thorough investigation to identify sources and implement control measures.
Purpose of the Study:
- To investigate an MRSA colonization outbreak in an Intensive Care and Cardiac Unit (ICCU).
- To identify risk factors contributing to the outbreak.
- To evaluate and recommend control strategies for MRSA colonization.
Main Methods:
- Retrospective observational outbreak study design.
- Graphical plotting of patient MRSA conversion rates (positive nasal swab on discharge/transfer, negative on admission).
- Repetitive sequence-based PCR (rep-PCR) for microbial DNA typing to identify strain relatedness.
Main Results:
- Observed MRSA conversion rate was 6% per month, significantly higher than the expected 2% (>3 standard deviations).
- Genetically identical MRSA strains were identified using rep-PCR.
- A common room housing four affected patients was found to be contaminated with MRSA.
Conclusions:
- The common room environment was identified as the primary source of MRSA contamination during the outbreak.
- Active surveillance is crucial for early detection of MRSA colonization outbreaks.
- Prompt intervention, including environmental decontamination and isolation, can prevent further MRSA spread and colonization.
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