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Mycobactericidal testing of disinfectants: an update
S A Sattar1, M Best, V S Springthorpe
1Faculty of Medicine, University of Ottawa, Ontario, Canada.
The Journal of Hospital Infection
|June 1, 1995
Summary
Disinfectant testing for tuberculosis (TB) and other mycobacteria is unreliable due to flawed protocols. Improved methods are needed to ensure disinfectant efficacy against drug-resistant TB strains and prevent nosocomial spread.
Area of Science:
- Microbiology
- Infectious Diseases
- Public Health
Background:
- Tuberculosis (TB) incidence is increasing globally, exacerbated by HIV/AIDS, immunosuppression, and multidrug-resistant Mycobacterium tuberculosis (MDR-TB).
- Mycobacteria pose a significant risk for nosocomial and iatrogenic transmission, necessitating a review of infection control practices and disinfectant efficacy.
- Current data on disinfectant mycobactericidal activity is unreliable due to numerous flaws in existing testing protocols.
Purpose of the Study:
- To highlight the deficiencies in current protocols for assessing mycobactericidal activity of disinfectants.
- To propose improvements for more precise and reliable testing of disinfectants against mycobacteria.
- To emphasize the urgent need for standardized protocols, especially for disinfectants used under conditions of reuse.
Main Methods:
- Critique of existing methodologies for evaluating disinfectant efficacy against mycobacteria.
- Identification of specific flaws including lack of quantitation, unrealistic conditions, absence of organic load, ineffective neutralizers, unsuitable surrogates, and improper recovery media.
- Presentation of recent findings suggesting improved testing parameters.
Main Results:
- Current protocols are inadequate, leading to unreliable data on disinfectant efficacy, particularly against MDR-TB.
- A specific disinfectant failed to maintain mycobactericidal activity after one week of reuse in an endoscopy unit, contrary to its intended 14-day reuse.
- Proposed improvements include using Mycobacterium terrae as a surrogate, better recovery media, flat surfaces, eliminating neutralizers, and requiring a > or = 4 log10 reduction in colony-forming units.
Conclusions:
- Existing methods for testing disinfectant mycobactericidal activity are flawed and yield unreliable results.
- Revised testing protocols incorporating specific improvements can enhance precision and reliability.
- Standardized, reliable testing is crucial for effective infection control and selection of disinfectants, especially given the threat of MDR-TB and reuse conditions.