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Better environmental survival of outbreak vs. sporadic MRSA isolates
J H Wagenvoort1, W Sluijsmans, R J Penders
1Department of Medical Microbiology, Atrium Medical Centre, Regional Public Health Laboratory, Heerlen, The Netherlands. J.Wagenvoort@gozl.nl
Abstract:
Environmental sources have been associated with prolonged epidemics of methicillin-resistant Staphylococcus aureus (MRSA). Our objective was to evaluate whether outbreak MRSA strains differ in their environmental survival from sporadic MRSA strains. The strains were detected in five adult patients unknowingly colonized by MRSA. The MRSA strains from patients No. 1 (phage pattern; III-29) and No. 2 (III-215) caused extensive outbreaks in our hospital. Contact tracing after detection of the different MRSA strains in the three other patients did not reveal further spread. Suspensions of MRSA with and without added hospital dust were made in sterile PBS. Surviving counts of MRSA were made by culture at two-weekly or longer intervals up to approximately one year. For each MRSA strain the ultimate day of viability was ascertained. The environmental survival patterns of the five MRSA strains showed qualitative and quantitative differences between the two outbreak and three sporadic strains. A gradual decline was noted for all strains. All survived longer than 6 months, but the two outbreak strains survived significantly better (P<0.01), i.e. in higher quantities (circa 1000-fold) and for a 1-3 months longer period. The survival patterns of the MRSA strains with and without added dust were similar.
Insights
Outbreak strains of methicillin-resistant Staphylococcus aureus (MRSA) survive longer in the environment than sporadic strains. This finding highlights the importance of environmental cleaning in controlling MRSA hospital outbreaks.
Area of Science:
- Microbiology
- Infectious Diseases
- Environmental Health
Background:
- Environmental contamination is linked to prolonged methicillin-resistant Staphylococcus aureus (MRSA) epidemics.
- Understanding MRSA strain survival in the environment is crucial for infection control.
Purpose of the Study:
- To compare the environmental survival of MRSA strains causing hospital outbreaks versus sporadic strains.
- To determine if MRSA strain characteristics influence environmental persistence.
Main Methods:
- Five MRSA strains from colonized patients were isolated.
- Environmental survival was assessed by culturing MRSA suspensions over approximately one year.
- MRSA survival was evaluated with and without added hospital dust.
Main Results:
- All MRSA strains survived longer than six months in the environment.
- Outbreak MRSA strains demonstrated significantly better survival (P<0.01) than sporadic strains.
- Outbreak strains persisted in higher quantities and for 1-3 months longer, irrespective of added dust.
Conclusions:
- MRSA strains responsible for hospital outbreaks exhibit enhanced environmental survival.
- Environmental persistence of MRSA strains may contribute to prolonged epidemic potential.
- Effective environmental decontamination strategies are vital for managing MRSA outbreaks.