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3rd Year MBBS Microbiology Slides & Tests

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Blood Agar

 Chocolate Agar

Nutrient Agar

RBCs in Urine


Slide of Stool

Gram positive Cocci

Mycobacerium Tuberculsis (Ziehl-Neilsen stain)
Ziehl Neelson Staining:
1. Cover with tissue paper
2. Flood slide with carbolfuchsin, the primary stain, for 2 minutes while heating with steam.
3. Remove paper cover, decolorize slide with a mixture of hydrochloric acid and ethanol.
4. Counter stain with methylene blue.

Urease Test:
Indicator --- Phenol Red
Urease producing org. will convert urea in test tube to ammonia, pH becomes alkaline, the indicator becomes red.
Urease +ve --- Red --- H.pylori, Proteus, Klebsiella, Yersinia, Enterocolitica
Urease -ve --- Yellow --- Salmonella, Shigella.

Triple Sugar Iron:
contains Ferous Sulfate, 3 sugars(glucose, lactose, sucrose) (glucose in 1 tenth the conc. Of other sugars)
Butt – poorly oxygenated area
Slant – inclined well oxygenated area
In the presence of (A)cid the indicator will turn --- yellow (sugar fermented acid produced)
in the prescense ofAl(K)aline the indicator will remain --- pink
if lactose is not fermented but the glucose is... butt will be yellow(no O2) but on slant the acid will be oxidised so it will be red.
H2S production--- black
(slant/deep/gas/H2S) (organisms)
A A + - Klebsiella, Enterobacter, E.Coli
K A - - Shigella, Serratia
K A + + Salmonella, Proteus
K K - - Pseudomonas
A A - - Vibrio
A A + + Citrobacter
K A - + S. typhi

Oxidase Test:
It is used to differentiate aerobic n facultative aerobes from anaerobes based on the formers oxygen utilization ability n the presence of oxidase enzyme.
Phenylene diamine dihydrochloride(subd. 4 oxidase) acts as an electron receptor and gets oxidized to produce purple or black colour.
Oxidase +ve --- Purple --- P.aeru, vibrio, nisseria, brucella n pasturella
Oxidase -ve --- E.coli, salmonella, shigella
Specimen/Slide --- filter paper showing purple colour.

Motility Test:
semisolid agar --- 0.4% conc. Of agar is used
medium is made in an upright position
a straight wire is used to innoculate at centre of medium
motile org. produce haze --- E.coli n Salmonella, Proteus
non motile org. produce discrete line --- Klebsiella, Shigella

DNAse test:
is used to identify S.Aureus that produces deoxyribonuclease enzymes
+ve is seen as a clearing around the colonies

Citrate Test:
differentiates family of enterobacter based on their utilization of citrate as a source of carbon.
Contents :
Sodium Citrate --- Source of carbon
Ammonium Phosphate --- source of nitrogen
org. that extract carbon also extract nitrogen, turn medium alkaline
Indicator --- Bromothymol Blue (blue at alkaline pH, green at acidic)
Simmons Citrate agar is used 4 culture, slope of medium streaked, incubated at 37 deg 4 24 hrs.
Citrate Test +ve --- Blue --- Citrobacter, Klebseilla, Salmonella
Citrate Test -ve --- Green --- E.Coli


Anonymous said...

Anonymous said...

thanx a lot

Anonymous said...


Anonymous said...

thankz a load...............

Anonymous said...


Anonymous said...

gud work doc...........

Anonymous said...

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Anonymous said...


Anonymous said...

it is very goos

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Anonymous said...

keep up the good work.thumbs up for your effort


DNAase is produced by streptococcus not staphylococcus

ali said...

amy ye o add kiye hn 3 internal k pass yehe hn...??

ukm medical student said...

very good....
but from what i learn in TSI test serratia do produce gas... =)

Captopril said...

Thank you soo much!

Anonymous said...

thanks a lot

Anonymous said...


Anonymous said...

Stay blessed!!!

Anonymous said...

its really helpful! thanx alot