mycology & viro_04

7/25/2019 Mycology & Viro_04

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FUNGAL CULTURE

Fungal culture is frequently performed for isolation and correctidentication of fungi. Following types of culture media are used:

- Sabourauds dextrose agar (SDA): Most commonly usedmedia in diagnostic mycology. It contains peptone (1%),detrose (!%) and "as a p# of $.. It may not support somepat"ogenic fungi.

- Neutral SDA (Emmons mod!"atons): It di&ers fromoriginal ' in "a*ing neopeptone (1%) and detrose (+%)and p# of .+.

- Corn meal agar and r"e star"# agar: -"ey are t"e

nutritionally decient media used for stimulation ofc"lamydospore production.

- $ran #eart n%uson agar and blood agar: -"ey areenric"ed media, used for growing fastidious fungi lieCryptococcusand Histoplasma.

- Nger seed agar and brd seed agar: /sed for selecti*e


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CULTURE C'NDT'NS

*+ Tem,erature: Most of t"e fungi grow well at +$0234 eceptt"e dimorp"ic fungi t"at grow 5ot" at +$34 and 34.

-+ $'D n"ubators: it is a special incu5ator used in diagnosticmycology, w"ic" is capa5le of maintaining low temperature.

.+ n"ubaton tme: 4ulture plates s"ould 5e incu5ated for +0wees.

/+ Antbot"s:suc" as cyclo"eimide (actidione),c"loramp"enicol and gentamicin can 5e added to t"e culturemedia to in"i5it 5acterial growt".


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Sabouraud Dextrose Agar (SDA):

- It is a selecti*e medium primarily used for t"e isolation ofdermatop"ytes, ot"er fungi and yeasts 5ut can also growlamentous 5acteria suc" as Nocardia. -"e acidic p# of t"ismedium (p# a5out $.) in"i5its t"e growt" of 5acteria 5utpermits t"e growt" of yeasts and most lamentous fungi.

Antba"teral agents can also 5e added to augment t"eanti5acterial e&ect.

- -"is medium is also employed to determine mycologicale*aluation of food, contamination in cosmetics and clinically toaid in t"e diagnosis of yeast and fungal infections.

- nti5iotics lie c"loramp"enicol, gentamicin, and tetracyclinecan 5e added as selecti*e agents to in"i5it 5acterial o*ergrowt"of competing microorganisms w"ile permitting t"e successfulisolation of fungi and yeasts. 7arious ot"er modications arealso reported 5y using cyclo"eimide, penicillin, streptomycin,neomycin depending upon t"e intended use.


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1rn",le :

-"e ' media is comprised of en23mat" dgest o% "asenandanimal tissues w"ic" pro*ide a nutritious source of amino acids andnitrogenous compounds for t"e growt" of fungi and yeasts.

Dextroseis t"e fermenta5le car5o"ydrate incorporated in "ig"concentration as a car5on and energy source. Agaris t"e solidifyingagent. ddition of antbot"slie 4"loramp"enicol and8or tetracycline acts as 5road spectrumantimicro5ials to in"i5it t"e growt" of a wide range of gram0positi*eand gram0negati*e 5acteria. 9entamicin is added to furt"er in"i5itt"e growt" of gram0negati*e 5acteria.


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ngredents n gm4L

etrose (9lucose) !2 gm

eptone 12 gm

gar 1$ gm

istilled ;ater 1222 ml

Com,oston o% SDA:

Final pH 5.6 +/- 0.2 at 25C.


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1re,araton o% SDA-

4om5ine all ingredients in ed water.- d?ust to p# $. wit" "ydroc"loric acid and ad?ust nal *olumeto 1 liter.

- #eat to 5oiling to dissol*e t"e medium completely.- utocla*e at 1+134 for 1$ minutes.

4ool to


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Lmtatons o% SDA- 'ome strains may 5e encountered t"at grow poorly or fail togrow on t"is medium.

- ntimicro5ial agents added into a medium to in"i5it 5acteriamay also in"i5it certain pat"ogenic fungi.

- *oid o*er"eating a medium wit" an acidic p#, t"is may result

in a soft medium.- For identication, organisms must 5e in pure culture.- Morp"ological, 5ioc"emical, and8or serological tests s"ould 5e

performed for nal identication.- It does not promote conidiation of lamentous fungi.


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1otato Dextrose Agar (1DA)

otato etrose gar () is a general purpose medium foryeasts and molds t"at can 5e supplemented wit" acid oranti5iotics to in"i5it 5acterial growt". It is recommended for platecount met"ods for foods, dairy products and testingcosmetics. can 5e used for growing clinically signicant yeastand molds. -"e nutritionally ric" 5ase (potato infusion)

encourages mold sporulation and pigment production insome dermatop"ytes.

otato etrose gar is composed of de"ydrated otato Infusionand etrose t"at encourage luuriant fungal growt". gar isadded as t"e solidifying agent. Many standard procedures use aspecied amount of sterile tartaric acid (12%) to lower t"e p# oft"is medium to .$ A80 2.1, in"i5iting 5acterialgrowt". 4"loramp"enicol acts as a selecti*e agent to in"i5it5acterial o*ergrowt" of competing microorganisms from miedspecimens, w"ile permitting t"e selecti*e isolation of fungi.


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otato infusion +22 gm

etrose +2 gm

gar +2 gm

istilled water 1 liter

4ommercial owder (+2gm detrose, 1$ gm agar,and ! gm potato starc")

= gm

istilled water 1 liter

Com,oston o% 1otato Dextrose Agar (1DA)

5 1re,arng 'ursel%

5 1re,arng %rom Commer"al edum 1o6der

Note: 200 gm of potato infusion is equivalentto 4.0 gm of potato extract.


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1re,arng 'ursel%:- -o prepare potato infusion, 5oil +22 g sliced, unpeeled

potatoes in 1 liter distilled water for 2 min.

- Filter t"roug" c"eeseclot", sa*ing eBuent, w"ic" is potatoinfusion (or use commercial de"ydrated form).

- Mi wit" etrose, gar and ;ater and 5oil to dissol*e.

-

utocla*e 1$ min at [email protected] ispense +20+$ ml portions into sterile 1$ C 122 mm petri

dis"es.

- Final p#, $. D 2.+.

1re,arng %rom Commer"al edum 1o6der:

- dd = gm of 4ommercial owder to 1 Eitre of istilledwater.

-

oil w"ile miing to dissol*e.


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Uses o% 1otato Dextrose Agar (1DA)

otato etrose gar is used for t"e detection of yeasts andmolds in dairy products and prepared foods.

It may also 5e used for t"e culti*ation of yeasts and molds fromclinical specimens.

otato etrose gar wit" - (-artaric cid) is recommended fort"e micro5ial eamination of food and dairy products.

otato etrose gar wit" 4"lortetracycline is recommended fort"e micro5ial enumeration of yeast and mold from cosmetics.

otato etrose gar wit" 4"loramp"enicol is recommended fort"e selecti*e culti*ation of fungi from mied samples.


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