Discussion Of Evaluation Methods For Cleaning Effect Of Tube-type Instruments

Objectives:Two simulated laboratory methods,which were Enterococcus faealis Test and Bacillus Test, were introduced for evaluating the cleaning effect of tube-type instruments,comparing the repeatability and stability of these test;establishment of a biofilm model in vitro;then the bacterial biofilm was introduced for cleaning effect laboratory evaluation.Methods:1.Detergent or water cleaning effect was evaluated by Enterococcus faealis Test and Bacillus Test respectively.By comparing Log₁₀ reduction of factors(RF),coefficient of variation(CV) and 95%confidence interval(95%CI),the repeatability and stability of these two methods were analysied.2.Test Bacterial was chosen,in accordance with the naked eye observation of 4 kinds of standard strains generating membrane-like substance in cell plate after 24h cultured;optical microscope(OM),colony-counting method was used to determine the culture time of the mature biofilm.Based on the results,the biofilm model was established:the broth contain Pseudomonas aeruginosa was flowed inside the test tube(Teflon,PVC) in a continuous, with 10mL/min flow rate,flowing 4h every day.After 6 days,the mature bioflim was formatted in the test tubes.3.The two cleaning methods(detergent,water) and two cleaning and disinfection methods (detergent+OPA,water+OPA) were used to deal with the test tube attached the mature bioflim.Using ordinary optical microscope(OM),scanning electron microscopy(SEM) and colony-counting method,qualitative and quantitative evaluation of the effects of the 4 means dealing with biofilm.4.Using carrier quantitative bactericidal test and broth culture,comparative analysis of the different between planktonic bacteria and biofilm bacteria which were deal with by 0.55% OPA.Results:1.Evaluation of the cleaning effect of detergent,Entercoccus feacalis Test RF was 4.07, Bacillus Test RF was 4.83,the difference was statistically significant(p＜0.05);evaluation of water cleaning effect,Entercoccus feacalis Test and Bacillus Test RF was 2.57,2.22 respectively,the difference was not statistically significant(p＞0.05).Evaluation of the cleaning effect of detergent,Entercoccus feacalis Test CV was 0.247,95%CI(3.69,4.99), Bacillus Test CV was 0.117,95%CI(4.58,5.97);evaluation of water cleaning effect, Entercoccus feacalis Test CV was 0.334,95%CI(2.24,2.91),and Bacillus Test CV was 0.229,95%CI(1.94,2.47).2.The adhesion of Pseudomonas aeruginosa biofilm was stable after 6 days,and the bacterial concentration was 10⁷cfu/cm².After crystal violet staining,thickness biofilm can be seen by OM,and can not be washed easily by water.3.Evaluation of cleaning effect,"detergent" and "water" handle the biofilm attached on the Teflon test tube,colony residual average values were 6.16 and 6.32 respectively,the difference was not statistically significant(p＞0.05);Evaluation of cleaning and disinfection effect,"detergent+OPA" and "water+OPA" handle the biofilm attached on the Teflon test tube,colony residual average values were 0.77 and 0.59,the difference was not statistically significant(p＞0.05);residual bacterial extracelluar matrix of the "detergent" group were less than "water" group;"water+OPA" group residual biofilm bacteria more than "detergent+OPA" group.SEM observation results and colony-counting results were inconsistent.PVC tube results were similar with Teflon tube.4.0.55%OPA deal with the test tube attached by planktonic Pseudomonas aeruginosa,after 1min immersion,the kill rate was 100%;0.55%OPA deal with the test tube attached by biofilm Pseudomonas aeruginosa,after 5min immersion,there were still 53.8%(14/26) of recoverable viable test tube,the average residual values was.Negative viable test tubes were placed in the nutrition broth,37℃culture 24h,25%(3/12) tubes were nepheloid.Conclusions:1.Enterococcus faecalis and Bacillus Test to evaluate the cleaning effect results are not entirely consistent.The stability of Bacillus Test was better than Enterococcus faecalis's,and owning the same representative.However,the concentration of bacteria need to increase,and the length of the test tube need to increase also.2.6-day Pseudomonas aeruginosa biofilm can not be washed from the test tube easily,can be used for evaluation cleaning effect.3.The extracellular matrix removed by the test detergent more than water's;After cleaning and disinfection treatment,the residual biofilm bacterial were inactive;compared with water washing,washing by detergent was more conductive to further removal and kill the biofilm bacterial in disinfection procedure followed.4.The tolerance of 0.55%OPA,Pseudomonas aeruginosa biofilm was better than planktonic one.