Evaluation of the efficacy of disinfectants used in hospital aseptic dispensing against Bacillus spores

Abstract number: 1733_612

Mehmi M., Smith J., Lambert P.

Objectives: To evaluate disinfectants currently used for transfer sanitisation in hospital aseptic dispensing processes. These disinfectants were assessed for efficacy against spores of Bacillus subtilis ATCC 6633 in suspension and carrier tests. Techniques of disinfectant application such as spraying, wiping or both were investigated.

Methods:Suspension testing: An aqueous spore suspension of B. subtilis ATCC 6633 was added to the disinfectant solution for a 2 minute contact time. The mixture was then neutralised, exposed to germinant solution and viable numbers determined by plating.

Hard-surface testing: Stainless steel carriers were aseptically inoculated with B. subtilis ATCC 6633 spores. After drying the carriers were sprayed, wiped, or sprayed and then wiped with disinfectant. After 2 minutes any surviving spores were recovered by agitation following neutralisation. Recovered spores were exposed to germinant solution and a dilution series was carried out.

Time-kill testing: As the suspension test, but samples were removed and enumerated over 24 hours. All dilutions were plated out onto tryptone soya agar and incubated overnight at 37°C. Any resulting colony forming units observed were counted. A control was used in each of the experiments.

Results: Of the 6 disinfectants tested a quaternary ammonium compound/chlorine dioxide formulation and 6% hydrogen peroxide were the more consistently effective biocides (approximate log 2 reduction after 24 hours). The disinfection method found to be the most effective in killing of the Bacillus spores was spraying followed by wiping, with the least effective being spraying alone. Overall, wiping as a method of disinfection was found to be very effective, with all disinfectants achieving similar reductions in spore levels. Disinfectants generally performed better in the carrier tests than the suspension tests. For carrier tests, spraying alone with a disinfectant was not as effective as wiping alone, or both spraying and wiping.

Conclusion: Disinfectant efficacy increased on an increase in contact time. However, longer contact times are not feasible and therefore a compromise may be required. The results obtained re-enforce research that indicates the insufficiency of current aseptic transfer disinfection protocols. Spores are very hard to kill with the use of chemical disinfectants currently available and therefore other methods of disinfection such as rapid gassing techniques need to be considered.

Session Details

Date: 31/03/2007
Time: 00:00-00:00
Session name: European Society of Clinical Microbiology and Infectious Diseases
Location: ICC, Munich, Germany
Presentation type:
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