Academic Center

1 Materials and methods

1.1 Reagents and Carriers 1.1.1 Reagents: ① Disinfection Solution: 0.5 Phthalaldehyde Disinfection Solution (pH 7.40);② Test bacteria: Bacillus subtilis var. niger (ATCC9372, Disinfection and Detection Center, Academy of Military Medical Sciences);③ Organic interfering substance: tryptone soybean broth medium (TSB, Beijing Luqiao). 1.1.2 Carrier: stainless steel sheet, hemostatic forceps teeth.

The 1.2 method was based on the "Disinfection Technical Specification (2002 Edition)" (hereinafter referred to as the "Specification"), and the disinfection effect was evaluated by carrier quantitative sterilization test and simulated field test. 1.2.1 Preparation of bacterial suspension and infected carrier: Take Bacillus subtilis var. niger for purification, separation and enrichment culture; Select a single typical colony, inoculate nutrient broth for enrichment culture, inoculate the culture on the surface of nutrient agar medium in Roche bottle, and wash it to make spore suspension; Take 1O L of bacterial spore suspension with test concentration and dye it on sterilized stainless steel sheet and teeth of hemostatic forceps for natural drying and standby. 1.2.2 Neutralizer Carrier Quantitative Identification Test: The Bacillus subtilis black variant Bacillus species as the test bacteria, set up 6 groups of tests, according to the carrier quantitative sterilization test procedures. The results showed that group 1 had no test bacteria or only a small amount of test bacteria grew. The amount of test bacteria in group 2 was significantly more than that in group 1, but significantly less than that in groups 3, 4 and 5. The error rate of colony number between groups 3, 4 and 5 should be ≤ 15; Group 6 (negative control) had no test bacteria, indicating that the selected neutralizer and its concentration were appropriate, and the test was repeated 3 times. 1.2.3 Carrier quantitative sterilization test: soak the infected stainless steel sheet with phthalaldehyde according to 5 mL/piece, and after acting for the specified time, move the stainless steel sheet into a test tube containing 5mL of neutralizer solution for neutralization for 10min. The spores on the bacterial sheet were eluted by full shaking, the viable bacteria were counted, the killing value (the number of colonies) was calculated, and the tryptone physiological saline solution was used as a positive control, and each group of tests was repeated 3 times. According to the Code, the sterilization of Bacillus subtilis var. niger spores contaminated on stainless steel sheets was determined to be qualified in the laboratory. The killing logarithm value was> 3.00. 1.2.4 Disinfection simulation field test of medical devices: soak the teeth of bacteria-infected hemostatic forceps with phthalaldehyde according to 10mI/piece, act for the specified time, move the carrier into a test tube containing 10mI neutralizer solution, and neutralize for 10min. Count the viable bacteria after full shaking elution, and calculate the killing value. Take 3O samples for testing, with sterile distilled water as the positive control. According to the Code, the sterilization simulation test of medical devices is qualified if the killing logarithm values of 3O samples are all> 3.O0.

2 Results

2.1 Neutralizer Identification Test Results The experimental results show that tryptone soybean broth (TSB) containing 10g/L lecithin and 10g/L Tween-8O as neutralizer can effectively neutralize the residual effect of phthalaldehyde disinfectant on test bacteria. The neutralizer and its neutralization products have no obvious effect on Bacillus subtilis var. niger spores and culture medium, as shown in Table L. 2.2 Carrier Quantitative Germicidal Test Results The results of the test showed that the killing of Bacillus subtilis var. niger spores contaminated on the carrier stainless steel sheet for 6h with o-phthalaldehyde disinfectant was> 3.00.

2.3 medical device disinfection simulation field test results with hemostatic forceps teeth as the carrier, o-phthalaldehyde disinfection solution for 5h, on the carrier contamination of Bacillus subtilis black variant spores on the average kill value of 2.44; 6h, the average kill value of 2.94; 7h, the kill value is more than 3.00.

3 Discussion o-phthalaldehyde disinfectant is a broad-spectrum disinfectant, with low corrosion, non-irritating, can extend the advantages of action time, can kill Bacillus subtilis black variant spores, disinfection effect is good, its sterilization effect can achieve the same effect of glutaraldehyde disinfectant, the effect of mycobacteria is better than glutaraldehyde disinfectant, currently used in medical equipment immersion disinfection and automatic endoscope cleaning machine. Its dosage form is diverse, there are single, compound, sterilization effect difference is big, widely used in the disinfection of medical devices still need to be further explored. This test showed that the killing logarithm value of Bacillus subtilis var. noir spores stained on stainless steel sheet was> 3.00 when ortho-phthalaldehyde disinfectant (0.5) was used for 6h. When used for 7h, the killing logarithm value of Bacillus subtilis var. noir spores stained on the teeth of hemostatic forceps was> 3.00. Compared with Yuan Guogang and other reports Ⅲ 2], the effect is poor, which may be related to the concentration of disinfectant, pH and other factors. In addition, the disinfection effect of single-factor chemical disinfectants is usually poor, and compound disinfectants can improve the disinfection effect, which has become a new direction of disinfectant research in recent years and needs further research.

References [1] Yang Yongyan, Zhou Yonglin. Analysis of disinfection quality monitoring results of medical institutions in Lhasa FJ]. Jiangsu Preventive Medicine, 2014,25(4):68. [2] Yuan Guogang, Wang Changde, Chen Jinlong, et al. COMPARISON OF EFFICACY OF FIVE OPHTHALDEHYDE DISINFECTANT PRODUCTS IN KILLING Spores OF Bacillus subtilis var. niger [J]. Chinese Journal of Disinfection, 2014, 3l(9):918.