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Hard surface carrier test as a quantitative test of disinfection: a collaborative study
M A Hamilton1, T A DeVries, J R Rubino
1Montana State University, Bozeman 59717, USA.
Journal of AOAC International
|July 1, 1995
Summary
The hard surface carrier test (HSCT) can quantify disinfectant efficacy by measuring bacterial log reduction. This quantitative approach, focusing on log reduction (LR) and lower confidence limits (LLR), offers a more robust standard than qualitative carrier counts.
Area of Science:
- Microbiology
- Disinfectant Efficacy Testing
- Quantitative Analysis
Background:
- The hard surface carrier test (HSCT) was initially proposed as a qualitative method for assessing disinfectant effectiveness.
- A collaborative study suggested a qualitative performance standard based on the number of positive carriers (≤2 or 3 out of 60).
Purpose of the Study:
- To reanalyze HSCT data from a quantitative perspective, focusing on log10 reduction of bacteria.
- To establish a quantitative performance standard for disinfectant efficacy based on log reduction estimates.
Main Methods:
- Reanalyzed data from a collaborative HSCT study.
- Calculated log reduction (LR) and 99% lower confidence limit (LLR) for bacterial inactivation.
- Assessed interlaboratory and intralaboratory variance components for LR estimates.
Main Results:
- Quantitative analysis revealed LR values ranging from 7.0 to 9.0 for tested disinfectants.
- LLR values exceeded 6.0 for all disinfectants, except the negative control.
- Variances in LR estimates were quantified for Pseudomonas aeruginosa, Staphylococcus aureus, and Salmonella choleraesuis.
Conclusions:
- The HSCT can be effectively utilized as a quantitative test for disinfectant efficacy.
- A performance standard based on the lower limit of log reduction (LLR) provides a more precise and informative measure.
- Quantitative HSCT allows for calculation of false-effective and false-ineffective decision probabilities, enhancing risk assessment.