Comparative Study On Germicidal Efficacy Of Several Chemical Disinfectants For Bacteria From Hospital

Background:Nosocomial infection emerged, following with the establishment of hospitals, Common bacteria of hospital infection are Escherichia coli, Pseudomonas aeruginosa(PA), Staphylococcus aureus (SA), and Candida albicans, etc. With the far-ranging use of antibiotics, the resistance of pathogens to drugs become multiple. The analysis on nosocomial infection showed that beta-lactamase producing Escherichia coli account for 74% of Escherichia coli, methicillin-resistant staphylococcus aureus account for 76% of Staphylococcus aureus, beta-lactamase producing Pseudomonas aeruginosa(PA) is a common drug-resistant strain, and the incidence of fungal infection appears in rising trend yeaanalysis by year with candida albicans as the representative.The analysis on nosocomial infection showed that 74% of Escherichia coli can produce beta-lactamase,76% of Staphylococcus aureus are methicillin-resistant staphylococcus aureus, the Pseudomonas aeruginosa(PA) which can produce beta-lactamase is a frequent drug-resistant strain, and the detection rate of fungal infection appears in rising trend year by year with candida albicans as the representative.Disinfectant and antibiotics both have special inhibition and kill effects to microbial, with the same or similar mechanism. The above strains can induce resistance to disinfectant. They are important pathogenic bacteria in nosocomial infection. Therefore, it is important subject that each hospital is facing to effectively killing hospital infection bacteria and controling hospital infection.In this paper, we systematically studied the killing effect of five common disinfectants on hospital infection bacteria and disinfection control bacteria and the bactericidal effect underservice conditions.In this paper, we systematically studied the killing and bactericidal effect of this five common disinfectants on hospital infection bacteria and disinfection control bacteria, the bactericidal effect in serviceable range, and furthermore, whether hospital infection bacteria have resistance to these five disinfectants in working concentration.It is guidance for hospitals to kill hospital infection bacteria with reasonable and appropriate disinfectants, reduce nosocomial infection and decrease environmental pollution by disinfectants. Little has been reported about the systematic research at home and abroad.Objective:Compare the germicidal efficacy, the field test results, and influencing factors of this five common disinfectants on hospital infection bacteria, for instance, beta-lactamase producing Pseudomonas aeruginosa, beta-lactamase producing Escherichia coli, methicillin-resistant staphylococcus aureus, and on disinfection control bacteria,suchasStaphylococcusaureus(ATCC6538),Pseudomonasaeruginosa(ATCC 1544 2), escherichia coli(8099) and candida albicans(ATCC 10231). Study the germicidal efficacy and the germicidal dose of these five disinfectants. Investigate the resistance of hospital infection bacteria to disinfectants.Methods:1.Strains:1.1 Clinical isolates of hospital infection bacteria:Hospital infection bacteria isolated from Clinic:methicillin-resistant staphylococcus aureus(MRSA), Pseudomonas aeruginosa producing beta-lactamase and Escherichia coli producing beta-lactamase.1.2 Disinfection control bacteria:Staphylococcus aureus(ATCC6538), seudomonas aeruginosa(ATCC 15442), escherichia coli(8099) and candida albicans(ATCC 10231). 2.Disinfectants and the using dosage:2%glutaraldehyde(neuter consolidated), 200mg/L trichlorosocynuric,0.2% anerdian,75% ethyl alcohol, and 0.1% benzalkonium bromide.3.Neutralizer selection experiment:Staphylococcus aureus(ATCC6538) was chosen as the experimental bacteria. Every kind of the five disinfectants was divided into 6 groups, to select the neutralizer to accord with the requirements underservice conditions according to the test procedures specified in《Disinfection Technical Guidelines》published in 2002.4.Suspended liquid quantitative sterilization test:Dilute the different disinfectants into a series of the test concentration with standard hard water. Mix disinfectant with bacterial suspension to interact with different time. Then take disinfectant/bacteria mixture into nutrient broth with relevant neutralizer. Carry out laboratory observations of culture results and negative/positive control.5. The field disinfection test5.1 The simulated field disinfection test of object surfaceCarry out the simulated field disinfection test of object surface with 200mg/L trichlorosocynuric acid and 75% ethyl alcohol, according to the test procedures specified in《Disinfection Technical Guidelines》published in 2002. Calculate the killing rate.5.2 The simulated field disinfection test of medical device using 2% glutaraldehydeTake the superior part of medical haemostat as experimental object. Determine the disinfection effect by carrier immersion quantitative germicidal test. Calculate the killing rate for ten minutes.5.3 The field disinfection test of skin with AnerdianSwab positive control sampling at the middle inner side under the left arm of the 5cm X 5cm area,on trial volunteers with sterilized cotton stick. Smear Anerdian on the skin, and detain for one minute. Then take neutralizer as disinfectant for live bacteria counting culture and calculate the killing rate.5.4 The simulated field disinfection test of skin with 0.2% Anerdian18 persons have healthy skin and body were selected as donors. The experiment was conducted according to the test procedures specified in《Disinfection Technical Guidelines》published in 2002 and the killing rate was calculated.5.5 The simulated field disinfection test of hands with 0.1% benzalkonium bromide14 volunteers were randomly divided into two groups. One group used reference samples. The other used test samples. The test was conducted and the decrease in bacterial count of the two groups were calculated separately, by reference to《Disinfection Technical Guidelines》in 2002.6. Test of influence of organic matter:Add calf serum as organic matter to experimental bacteria suspension. Follow the procedures of suspended liquid quantitative sterilization test and investigate the organic matter influence to germicidal efficacy of disinfection solution.Experimental Result:1.Result of neutralizer appraisal test1.1 The experiments selected Staphylococcus aureusto represent vegetative forms of bacteria. At temperature of 20±1℃, the results of neutralizer appraisal tests were as follows:Neutralizes of 2% glutaraldehyde:0.2% glycine,2% tween80,0.07% lecithin Neutralizes of 200mg/L trichlorosocynuric:0.5% sodium thiosulfate,2% tween80, 0.07% lecithinNeutralizes of 0.2% Anerdian:0.5% sodium thiosulfate,,2% tween80,0.07% lecithin Neutralizers of 0.1% benzalkonium bromide:0.3% lecithin,2% tween80 phosphate buffer 75% ethyl alcohol, diluted by 10 times, was eliminated germicidal action.1.2 Result of neutralizer appraisal test for fungi:At temperature of 20±1℃, represented by candida albicans, result of the five disinfectants neutralizers for fungi were consistent with vegetative forms of bacteria.2 Result of suspended liquid quantitative sterilization test:The hospital infection bacteria from yuhuangding hospital and disinfection control bacteria were exposed to five disinfectants in using dosage for 1min,3min, and 5min. And all the killing rates were 100%, which could display that the hospital infection bacteria had no resistance to the five disinfectants in using dosage.3 Result of the field disinfection test3.1 Result of the simulated field disinfection test of object surface:We wiped the mesas polluted by 7 strains with 200mg/L trichlorosocynuric acid and 75%ethyl alcohol, and collected samplings after 5 minutes. There was no bacterial growth. The result satisfied the disinfection requirement.3.2 The simulated field disinfection test of medical device using 2%glutaraldehyde:The medical haemostat was polluted with 7 strains respectively and marinated in 2% glutaraldehyde for 10min. There was no bacterial growth after cultivation. The hospital infection bacteria and standard bacteria marinated in 2%glutaraldehyde for 10min could fulfil the disinfection requirement.3.3 The field disinfection test of skin with Anerdian:Skin of forearm was disinfected with Anerdian in application concentration for 2min. Rate of bacterial removal was 100%. The average value of natural bacteria on skin before disinfection was 102cfu/cm2. There was no bacterial growth after disinfection.3.4 The simulated field disinfection test of skin with 0.2% Anerdian:The skin was polluted with 7 strains respectively and disinfected for lmin. The disinfection effects could meet the requirements.3.5 The simulated field disinfection test of hands with 0.1% benzalkonium bromide: The test hands were polluted with 7 strains respectively and disinfected for 5min. Effects of disinfection could meet the requirements.4 Test of influence of organic matter:25% and 50% calf serum had no effect on 2% glutaraldehyde,200mg/L trichlorosocynuric acid and 0.2% Anerdian, but had significant influence on 75% ethyl alcohol and 0.1% benzalkonium bromide.Conclusion:According to the using dosage and application scope of instruction, exposing the hospital infection bacteria to the five disinfectants the five disinfectants could reach good effect of disinfectation. The three hospital infection bacteria had no resistance to the disinfectants commonly used in hospitals.