TOPIC :EVALUATION OF ANTIMICROBIAL
EFFECTIVENESS & FUNCTION OF LAF
SUBMITTED BY :GAURAV KUMAR PAL
M.Sc.Applied Microbiology
Content :• INTRODUCTION
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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 1881.
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 20-37 *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 :•
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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
 http://WWW.ncbi.nlm.nih.gov/pmc/articles
 http://www.antimicrobialtestlaboratories.com
 http://www.microrao.com/micronotes/pg/testing_for_disinfectants.pdf
THANKS