TOPIC :- EVALUATION OF ANTIMICROBIAL EFFECTIVENESS & FUNCTION OF LAF SUBMITTED BY :- GAURAV KUMAR PAL M.Sc.Applied Microbiology

Content :- I NTRODUCTION HISTORY METHOD FOR TESTING DISINFECTANTS SUSPENSION TEST PHENOL COEFFICIENT TEST METHOD FOR DETERMINATION OF PHENOL COEFFICIENT TEST CARRIER TEST IN USE TEST PRACTICAL TEST LAMINAR AIR FLOW FUNCTION OF LAF

INTRODUCTION:-  Testing of disinfectant is a complex process.  are used to test the efficacy of disinfectant.  Requlated by two different federal agencies-  U.S.environment protection assay-regulate to disinfectants.  Food &drug administration –regulated to disinfectants used on human & animals.  Disinfectants used mainly in hospital & labs, so periodally effectiveness of disinfectant is checked.

HISTORY :-  Robert Koch described a disinfectant test in  Used a liquid culture of Bacillus anthracis for testing of disinfectant.  A silk thread contaminated in liquid culture & drying  Immersed in several disinfectants & cultured in nutrient broth &incubated. 1. Growth occur – less effective disinfectants. 2. No Growth occur – more effective disinfectants.

METHOD FOR TESTING DISINFECTANTS :- 1.Suspension tests 2.Carrier tests 3.In –use test 4.Practical test

SUSPENSION TEST :- A sample of bacterial culture is suspended into the disinfectant solution. After exposure, it is verified by subculture of bacterial culture. After subculture :- 1.Growth occur – less effective disinfectants. 2. No Growth occur – more effective disinfectants.

PHENOL COEFFICIENT TEST :- This method is used to evaluating the effectiveness of disinfectants. Best known disinfectant test. Staphylococcus aureus or Salmonella typhi are used for testing. Dilution of phenol &experimental disinfectant are inoculated with Staphylococcus aureus &incubated at *c for 2-3 days. Samples are removed at 5 min intervals and inoculated into fresh broth. Highest dilution that kills the bacteria after the 10 mintues, but not after 5 mintues,is used to calculate the phenol coefficient test.

PHENOL COEFFICIENT TEST (CONT.) Phenol coefficient is calculated by dividing the reciprocal dilution of test disinfectants by the reciprocal dilution of phenol. For example :- The reciprocal of max. effective dilution of phenol =100 & the reciprocal of max. effective dilution for disinfectant=600, then phenol coefficient =600/100= 6 If the value of phenol coefficient is more then 1 then test disinfectant is more effective then phenol.

Method for determination of phenol coefficient:- 1.Rideal walker method :- In this method different dilution of phenol & disinfectant is used. Phenol coefficient is calculated by this method Phenol coefficient =the dilution of disinfectant (which disinfects the suspension in a given time )/dilution of phenol in same time. Disadvantage :- No organic matter is included. Time allowed for disinfectant is short.

CHICK MARTIN METHOD :- In this method water is used with yeast suspension to stimulate the organic matter. Time of subculture is fixed at 30 mintues. Phenol coefficient is calculated as fellows- Phenol coefficient = mean conc. of phenol /mean conc. of test disinfectant.

CARRIER TEST :- USE DILUTION TEST :- These test are the oldest test. AOAC used dilution test is a carrier based test. S.aureus bacteria culture is used. Metal cylinder dipped into broth culture. Cylinder washed & placed into tube of medium for 48 hours. Used disinfectant for 10 mintues. 1. Growth occur – less effective disinfectants. 2. No Growth occur – more effective disinfectants

In use test Use disinfectant to injured cell. Swab taken before and after use of disinfectant. Inoculated in growth medium. Incubated for 48 hours. Growth occurred-less effective No growth- more effective.

Practical test Filter paper method:- Disc of filter paper are used. Filter paper are soaked with a chemical disinfectant. They are placed in agar plate and incubated. If the chemical is effective then clear zone appears near the disc.

FILTER PAPER METHOD :-

Laminar air flow Laminar air flow is an equipment which can produce air flow continuously with uniform velocity. Containing special HEPA filter which can remove microorganism and particles as small as 0.3 micrometer. They are containing U.V. light to kill the microbes. These are two types….

Horizontal Laminar Air Flow Hood

Vertical Laminar Flow Hood

Function of L.A.F It provide the sterile environment for the culturing. Transfer any media for culturing the fungi and bacteria. Use to prevent from contamination during the process of pouring in plates. Observation of microbes.

Reference  Prescott & harley,Klein (2002),Microbiology second edition, wm.C.brown publishers.  Tortora J.G., Funk R.b.,Christine l. case, (1997),microbiology an introduction sixth edition,Addison Wesley Longman  ALCAMO I. EDWARD(2001), Fundamentals of microbiology fifth edition,Jones and Bartlett publishers  Wistreich A.G.,MAX. D.lechtman(1988) Microbiology fifth edition, Collier macmillan publishers LANDON   

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