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Disinfecting properties of performic acid against bacteriophage phi X 174 as a model of small envelope--free viruses
Abstract:
Performic acid HCOOH (PFA) is a wide-spectrum disinfectant. It inactivates viruses, bacteria and bacterial spores, mycobacteria as well as microscopic fungi. Its main drawback is its instability, which makes it a logical necessity that it is to be prepared prior to use from its components HCOOH and H2O2. The mixing of 8 ml HCOOH of the concentration 850 ml/l and 17 ml H2O2 of the concentration 300 ml/l in a 100 ml-volume reagent bottle with a ground-in glass stopper gives, after an 1-hour rest at room temperature and after another 1 hour in a refrigerator, a stock solution that contains about 50 ml/l of PFA the actual concentration of which is determined iodometrically. Bacteriophage phi X 174 (host E. coli C) is characterized by cubic ikosahedral-type symmetry of particles free of envelope, has 27 mm in diameter and contains single-strand cyclic DNA; formerly was classed among Parvoviridae. The possibility of plaque assay-based quantitative determination of the number of infectious particles makes if it a feasible model for assessing disinfectant action on small hydrophilic viruses under conditions close to those of practical disinfection procedures. PFA stock solution diluted to 1 X 10(-3) (0.05 ml/l of effective component) inactivates the model virus of a concentration 10(8) pfu/ml aqueous suspension within 5 min so that no virus is detectable; the drop in the number of pfu amounts to 7 log orders of magnitude. In the presence of 400 ml/l of serum, the identical effect is achieved within 5 min by PFA stock solution diluted to 5 X 10(-3). The lowest PFA concentration that reliably inactivates bacteriophage phi X 174 in aqueous suspension is identical with the lowest concentration inactivating Coxsackie B 1 virus in tissue cultures. On textile, glass, plastic, rubber and metal carriers contaminated by swabbing or by a dried drop of bacteriophage suspension containing about 1 X 10(9) pfu/ml, the lowest reliably effective concentrations of PFA range within 0.25-0.025 ml/l, i.e. PFA stock solutions diluted to 5 X 10(-3)-5 X 10(-4), depending on the type of carrier and the type of contamination.
Insights
Performic acid (PFA) is a potent disinfectant effective against a broad spectrum of microbes. This study demonstrates PFA
Area of Science:
- Microbiology
- Disinfection Science
- Virology
Background:
- Performic acid (PFA) is a broad-spectrum disinfectant with instability issues, necessitating preparation before use from formic acid (HCOOH) and hydrogen peroxide (H2O2).
- Bacteriophage phi X 174 serves as a model for assessing disinfectant efficacy on small hydrophilic viruses due to its quantifiable plaque assay.
- Disinfectant efficacy is often challenged by organic matter and surface types.
Purpose of the Study:
- To evaluate the efficacy of freshly prepared Performic acid (PFA) against viruses, bacteria, and fungi.
- To determine the optimal preparation method and concentration of PFA for disinfection.
- To assess PFA's effectiveness on various surfaces and in the presence of organic load.
Main Methods:
- PFA was prepared by mixing HCOOH and H2O2, followed by resting periods at room and refrigerator temperatures.
- Bacteriophage phi X 174 was used as a model virus for quantitative assessment via plaque assays.
- Disinfection efficacy was tested on viral suspensions, in serum-containing media, and on contaminated carriers (textile, glass, plastic, rubber, metal).
Main Results:
- PFA stock solution (50 ml/l) inactivated a viral suspension (10^8 pfu/ml) within 5 minutes at a 1:1000 dilution (0.05 ml/l effective component).
- In the presence of 400 ml/l serum, a 1:200 dilution of PFA stock solution achieved inactivation within 5 minutes.
- Effective PFA concentrations on various carriers ranged from 0.25-0.025 ml/l (stock dilutions of 5 x 10^-3 to 5 x 10^-4).
Conclusions:
- Performic acid is a highly effective disinfectant against a wide range of microorganisms, including viruses, bacteria, and fungi.
- The preparation method yields a stable stock solution suitable for practical disinfection.
- PFA demonstrates potent virucidal activity even in the presence of organic matter and on diverse surfaces.