DISINFECTION OF AIR-CONDITIONERS WITH ANOLYTE SOLUTION

Yu. G. Suchkov, I. I. Strelnykov, V. G. SIizkova, B. I. Leonov, V. P. Ippolitov, V. M. Bakhir

Moscow City Disinfection Center’s Testing Laboratory Center,

All-Russian Scientific-Research and Testing Institute of Medical Facilities (VNIIIMT MZ RF)

The disinfection effect of anolyte was investigated by means of irrigating the internal surfaces of air- conditioners. The disinfectant was found to be highly efficient in its action on microorganisms including spore-forming bacteria. The conclusion about expediency of anolyte application to disinfect household air-conditioners without coal filters was made.

In the last decades of the 20-th century, about 30 previously unknown microorganisms that are pathogenic for humans were discovered. Especially dangerous are air-borne infections. Within the current year great human efforts were taken to prevent the mass spread of a new virus – the originator of so-called SARS. It is not out of place here to recall an outbreak in 1976 of an unknown disease in Philadelphia (the USA), when 182 American Legion veterans got sick, and 29 of them died [1]. It was found later that all the patients had lived in a comfortable hotel – the venue of an annual meeting of the organization’s veterans. 5 months later, during another outbreak of a similar disease, a pathogen Legionella pneumophila was isolated. The disease was called “legionellosis”. The major vehicle of the pathogen transmission is aerosol, and particles of contaminated dust or soil. Afterwards, it was determined that the commonest cause of legionellosis spread were centralized aqueous air-conditioning systems, as well as household air-conditioners, easily contaminated with bacteria commonly occurring everywhere and freely inhabiting water basins and soil. Legionellosis has been categorized as a “civilization disease”.

The objective of the conducted research investigation was to work out and test a simple and safe way to disinfect household air-conditioners.

The research was conducted at the bacteriologic laboratory of the Moscow City Disinfection Center’s testing laboratory center. Tests were performed at the All-Russian Scientific-Research and Testing Institute of Medical Facilities using two split-system household air-conditioners (АU-126Е model , Sharp), which before the tests had been operated under similar conditions for one and a half year 1,5 years.

One of the air-conditioners was a control one not being exposed to anolyte treatment and the other was a test specimen. ANK anolyte is a solution of multi-purpose use, therefore it is applied not only for disinfection, pre-sterilization cleansing and sterilization, but also for general indoor cleaning, disinfection of equipment in medical and prevention facilities, clothes, surgeon’s hands, etc.

Active ingredients of ANK anolyte are mixed peroxide compounds (НО· — hydroxyl radical; НО2- — peroxide anion; 1О2 — singlet molecular oxygen; О2- — superoxid-anion; О3 — ozone; О· — atomic oxygen) and chlorine-oxygen compounds (НСlO — hypochlorous acid; СlO- — hypochlorite-ion; СlO· — hypochlorite-radical; СlО2 — chlorine dioxide). The low total content of active oxygen and active chlorine compounds guarantees absolute safety for humans and the environment even in the course of long-term application [2].

The tests were carried out in conformity with the same method [3] in two stages:

I stage (02.04.03) — on naturally contaminated air-conditioners;

II stage (04.04.03) — on the same air-conditioners artificially contaminated with bacterial spores of Bacillus stearothermophilus.

I stage

1. Samples were collected by washing away 10 segments of inner surfaces (evaporators and filter) with wads of cotton wool moistened in 0.85% NaCl solution, which were placed into test tubes containing 4 ml of the same solution.

Table1

Results of studying natural bacterial dissemination in air-conditioners and efficiency of their treatment (02.04.03)

Study object

Amount of bacteria in 1 ml of sample

Prior to treatment

After treatment

1. Control air-conditioner

Evaporator

75

0

Filter

60

0

Discharged liquid

-

2600

2.Test air-conditioner

Evaporator

105

0

Filter

50

0

Discharged liquid

-

0

Table 2

Results of studying bacterial dissemination in the air-conditioner artificially contaminated with spores of Bacillus stearothermophilus

1st air-conditioner (irrigation by anolyte)

Study object

Amount of bacteria in 1 ml of sample

Before disinfectant treatment

After treatment

spores

vegetative cells клетки

spores

vegetative cells клетки

Evaporator

1890

113

0

0

Filter

1760

30

0

0

Discharged liquid жидкость

-

-

0

0

Table 3

Results of studying bacterial dissemination in the air-conditioner artificially contaminated with spores of Bacillus stearothermophilus

2nd air-conditioner (irrigation by water)

Study object

Amount of bacteria in 1 ml of sample

Prior to treatment

After treatment

spores

vegetative cells клетки

spores

vegetative cells

Evaporator

0

0

0

0

Filter

0

0

0

0

Discharged liquid жидкость

-

-

310

0

2. The control air-conditioner was irrigated with 0.5 l of sterile distilled water using a hand pulverizer. 2 ml of discharged liquid was taken for analysis.

The test specimen was irrigated with the same amount of anolyte, using the same pulverizer as in the control study. After 15 minutes samples were taken in the way described above (paragraph 1).

3. Test-tubes containing samples were brought to the TLC’s laboratory for bacteriologic investigation.

For this purpose, volume-averaged samples were made up based on the washes-out taken separately from the evaporators and the filters. By titration and subsequent culturing of 0.1 ml batches on agar nutrient media, after the cultures’ incubation for 24 and 48 hours at 37 °С, the number of grown colonies — CFU (colony forming units) was determined per 1 ml. As neutralizer, a 1% sodium thiosulphate solution was applied. The results are given in Table 1.

The data in Table 1 indicates that after treatment of the control air-conditioner with sterile water no bacteria were detected in cultures from washes-out (taken with tampons) incubated at 37 and 55 °С. This may be due to a comparatively small quantity of colony forming units (CFU) before the air-conditioner was treated with water. However, there were 2600 viable bacteria washed away by water in 1 ml of discharged liquid.

In the test air-conditioner, before anolyte treatment, there was approximately the same quantity of bacteria on evaporator and filter surfaces as in the control one. After treatment with anolyte, no bacteria were found in the wash-out content of the tampons. Nor were any viable bacteria detected in the discharged liquid. Incubation was performed at 37 and 55°С.

Consequently, the tested agent – anolyte – proved to be effective in disinfection of air-conditioners.

II stage

This stage of experiment was different from the one described above only in that the air-conditioners tested before were artificially contaminated with spores of Bacillus stearothermophilus (strain ВКМ В-718) — a non-pathogenic obligate thermophilic microorganism with optimal growth temperature 50—60°С, not growing at 37 °С. The initial suspension contained 107 CFU/ml.

In this study, the test specimen was the air-conditioner that had been used as control one in the study of 02.04.03, i.e., it had not been treated with anolyte, and, therefore, did not contain the disinfectant residue.

The findings in the study of 04.04.03 are presented in Table 2. In that study, the culture media containing agar plates were placed into a thermostat at different temperatures: 37 and 55 °С. During these procedures, bacteria — natural air-conditioner contaminants (vegetative cells) — did not proliferate at 55°С, and thermophile spores — did not grow at 37°С.

Simultaneously, the other air-conditioner, which had been used as a test specimen during the 1st stage and had been treated with a disinfectant, was studied using the same method (Table 3). This air-conditioner was irrigated with anolyte in the previous study (02.04.03). In the study of 04.04.03, the evaporator and the filter were contaminated in the same way and with the same amount of spores as in the case with the first air-conditioner. Washes-out and cultures were taken in the same way. The results of that study are presented in Table 3.

In the air-conditioner that had earlier been subjected to disinfectant treatment (on 02.04.03), the washes-out contained in tampons revealed no spores or vegetative cells. The discharged liquid (rinse water) contained 310 CFU. The outcomes indicate that the disinfectant ability of the agent used was preserved for the entire study period (48 hours).

Conclusion. The tested method of treating household air-conditioners (except for those with carbon filters) by irrigating them with the anolyte as a disinfectant produces a reliable decontaminating effect.

REFERENCES

  1. Medical microbiology / Chief editor V.I. Pokrovsky, О.К. Pozdeyev. Moscow: GEOTAR, Medicine, 1999. - Pp. 336-343.
  2. Bakhir V.M., Vtorenko V.I., Leonov B.I. et al. Effectiveness and Safety of Chemicals Used in Disinfection, Pre-sterilization Cleansing and Sterilization // Dezinfektsionnoye delo, 2003. — Issue 1. — Pp. 29-36.
  3. Methods of Testing Disinfectant Agents to Estimate Their Safety and Efficiency. Moscow, 1998.

Published in Dezinfektsionnoye Delo Journal, Issue 3, 2004.