Study On Sanitation Conservancy And Legionella Pneumophila Contamination Of Centralized Air-conditioning Cooling System

BACKGROUND:Legionnaires' disease is an atypical pneumonic illness caused by the Legionella bacteria.These bacteria cause respiratory disease in humans when a susceptible host inhales aerosolized water containing the bacteria or aspirates water containing the bacteria.Since Legionaires' disease was initially found in United States in 1976,there are many outbreaks and sporadic cases of legionaires' disease were reported in many countries and areas in world.Along with the process in Legionaires' disease studying,centralized air-conditioning cooling system as an origin of infection has been recongnized.Recent research results of Legionella contamination in centralized air-conditioning system(CACS) cooling water in some big cities showed the situation was quite serious.Many hygiene items have been released to control Legionella contamination as far as possible and reduce the resulting harm.Acquainting the implement status of the measures in practical application and the effect on controlling the Legionella pneumophila contamination in CACS may be helpful to improve and enhance our management on controlling Legionella contamination and draw up the management measures to control CACS Legionella pneumophila contamination.AIM:To acquaint with the present management status in public place CACS,and to assess Legionella contamination in CACS cooling water;To put forward the reasonable proposal on formulating administrative regulations for controlling CACS Legionella pneumophila contamination;And to search for a fast screening method available to detect Legionella pneumophila contamination.METHODS:Three kinds of methods were utilized in this investigation:â‘ Questionnaire survey;â‘¡Consulting CACS daily running records;andâ‘¢Laboratory detection:plate cultivation method and an antigen detection assay were used to detect Legionella pneumophila contamination.RESEARCH CONTENT:â‘ To survey sanitation management status of CACS;â‘¡The current situation of the design,installation,operation and maintenance of CACS cooling tower,and the influence of these factors on Legionella pneumophila contamination;â‘¢The utility assessment on the antigen detection assay RESULTS:â‘ Results showed that 48.7%of the public places investigated had no complete sanitation conservancy;about 75.0%did not perform sanitation monitor on the CACS in the past 3 years;84.3%were found no dehydrator installed;34.7%did not carry on disinfection to the CACS cooling water;39.9%did not treated the cooling water with antiseptic;and about half of the public places without regular Legionella exalnination;â‘¡Legionella detection rate was 74.3%in CACS cooling water.And the Lp1 strain found as high as 86.4%;â‘¢Lp1 Legionella positive rate utilizing the plate cultivation way and the antigen box method were 64.2%and 58.1%separately.The sensitivity and specificity of antigen detection assay drawen regarded the plate cultivation way as the golden standard were 64%and 47%respectively.CONCLUSION:This investigation demonstrated that the sanitation conservancy situation on the CACS in the researched cities is not optimistic.The implementation of sanitation management measures was not effective and inefficient in controlling Legionella contamination;the results of the research indicated that some treatments on the cooling water such as disinfection,antiseptic,along with the regular examination to the cooling water could reduce Legionella pnemophila contamination;The low sensitivity of the antigen detection assay in detecting Legionella pnemophila makes it unsuitable for daily monitoring plan,while it seemed suitable for rapidly screening large sample numbers for heavy contamination with legionella pneumophila.