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Survival of Staphylococcus aureus on sampling swabs stored at different temperatures
D Panisello Yagüe1, J Mihaljevic2, M Mbegbu1
1Pathogen & Microbiome Institute, Northern Arizona University, Flagstaff, AZ, USA.
Aims:
To understand the impact of storage temperature on recovery of Staphylococcus aureus on sampling swabs. Staphylococcus aureus is a common cause of skin and soft tissue infections, but also causes a variety of life-threatening diseases. With a large pool of asymptomatic carriers and transmission that can occur even through indirect contact, mitigation efforts have had limited success. Swab sampling, followed by culturing, is a cornerstone of epidemiological studies, however, S. aureus viability on swabs stored at different temperatures has not been characterized.
Methods And Results:
We determined survival rates on swabs stored at five different temperatures. Samples stored at -70°C had no decay over time while samples stored at higher temperatures showed an exponential decay in viability. Mortality rates were greatest for swabs stored at 37°C. Survival at intermediate temperatures (-20 to 20·5°C) did not differ significantly, however, we observed more variation at higher temperatures.
Conclusions:
To maximize recovery of S. aureus cells, samples should be stored at -70°C or processed for culturing without delay.
Significance And Impact Of The Study:
Epidemiological studies of bacterial diseases are typically limited to determination of pathogen presence/absence, yet quantitative assessments of pathogen load and genetic diversity can provide insights into disease progression and severity, likelihood of transmission and adaptive evolutionary potential. For studies of S. aureus where time or access to a microbiology laboratory may delay culturing, deep freezing or timely culturing will maximize the degree to which sampling results reflect source status.
Insights
To maximize Staphylococcus aureus recovery, store sampled swabs at -70°C or culture them immediately. Cold storage preserves bacterial viability, crucial for accurate epidemiological studies.
Area of Science:
- Microbiology
- Epidemiology
- Infectious Diseases
Background:
- Staphylococcus aureus causes significant skin and systemic infections.
- Transmission occurs readily due to asymptomatic carriers and indirect contact.
- Effective mitigation strategies for S. aureus are limited.
- Swab sampling and culturing are vital for epidemiological research.
- Bacterial viability on stored swabs is not well-characterized.
Purpose of the Study:
- To evaluate the impact of storage temperature on Staphylococcus aureus recovery from sampling swabs.
- To determine optimal storage conditions for maintaining S. aureus viability on swabs for epidemiological studies.
Main Methods:
- Determined S. aureus survival rates on swabs stored at five different temperatures (-70°C, -20°C, 4°C, 20.5°C, and 37°C).
- Monitored bacterial viability over time at each temperature.
- Analyzed decay rates and mortality at different storage conditions.
Main Results:
- No viability decay of S. aureus was observed on swabs stored at -70°C.
- Samples stored at higher temperatures exhibited exponential decay in viability.
- Highest mortality rates for S. aureus were recorded at 37°C.
- Survival rates at intermediate temperatures (-20°C to 20.5°C) showed no significant differences but higher variation at elevated temperatures.
Conclusions:
- Deep freezing at -70°C or immediate culturing are essential to maximize S. aureus recovery.
- Proper sample handling is critical for accurate quantitative assessments in epidemiological studies.
- Timely processing or deep freezing ensures that sampling results accurately reflect the source bacterial status.
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