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Prof. Dr. Marlina, MS., Apt.
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Phenol coefficient
is a measure of the bactericidal activityof a chemical compound in relation tophenol.
When listed numerically, the gureexpressing the disinfecting poer of a
substance by relating it to thedisinfecting poer of phenol may be afunction of the standardi!ed test performed.
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Phenol coefficient test is best knownscreening test in which potency of a
disinfectant is compared with that ofphenol.
A series of a dilutions of phenol and thedisinfectant being tested are prepared.
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A standard amount of Salmonella tyhpiiand Staphylococcus aureus are addedto each dilution"
the dilutions are then placed in a #$ to
%&o' ater bath. At ()minute intervals, samples are
ithdran from each dilution and used
to inoculate a groth medium, hich isincubated for to or more days andthen examined the groth.
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*f there is no groth in the grothmedium, the dilution at that particulartime of sampling +illed the bacteria.
he highest dilution that +ills thebacteria after -o min. exposure, but notat (min.
is used to calculate the phenol
coecient. his is done by dividing thereciprocal of the appropriate phenoldilution.
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/or example,
the 0ideal)Wal+er method gives a
0ideal)Wal+er coecient and the 1.S. Department of
Agriculture method gives a 1.S.Department of Agriculturecoecient.
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o calculate phenol coecient "
the concentration of phenol at hich thecompound +ills the test organism in -$
minutes, but not in ( minutes, is divided by the concentration of the test
compound that +ills the organism under thesame conditions
2or, probably more common, dividing thedilution factor at hich the tested substanceshos activity by the dilution factor at hichphenol shos comparable activity3.
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he phenol coecient may bedetermined in the presence of astandard amount of added organicmatter or in its absence.
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A related ay to express thebactericidal activity of an agent 2at agiven concentration3 is by employingthe formula 4
+ 5 67'8 here 6 is the number of surving cells,
' is the concentration of agent applied and is the time for hich the agent is applied,
so + is inversely proportional to dose
2'8 is collectively called dose3.
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Phenol coecient test is best +nonscreening test in hich potency of adisinfectant is compared ith that ofphenol.
A series of a dilutions of phenol and thedisinfectant being tested are prepared.
A standard amount of Salmonella tyhpiiand Staphylococcus aureus are added toeach dilution" the dilutions are thenplaced in a #$ to %&o' ater bath.
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At ()minute intervas, samples areithdran from each dilution andused to inoculate a groth medium,
hich is incubated for to or moredays and then examined the groth.
*f there is no groth in the grothmedium, the dilution at that particulartime of sampling +illed the bacteria.
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he highest dilution that +ills the bacteriaafter -o min exposure, but not at (min.
is used to calculate the phenol coecient.
his is done by dividing the resiprocal ofthe appropriate phenol dilution.
0ead more4http477i+i.ansers.com797Phenol:coecient:test:in:microbiology;ix!!-t<+i=>?@
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