HOW TO READ A CULTURE PLATEOR

INTERPRETATION OF A CULTURE PLATE

Dr.I.Wani,Centre for Interdisciplinary Biomedical Research

Adesh Institute of Medical Sciences & Research,Bathinda

Obectives: why to interpret?To have a clear idea about pathogen isolatedTo identify it using suitable presumptive &

diagnostic modules used in that particular infection it causes

To study its sensitivity profileTo arrive at most suited treatment

recommended to treat that infection.

IDENTIFICATION METHODSCultural characteristicsStaining reactionSize: in microns(μ )or micro meters(μm)Shape: circular,irregular or rhizoidSurface: smooth,wavy,rough,granular,glistening etc.Elevation: elevated,effuse,convex,concave,umbonate or

umblicateEdge : entire,undulate,crenated,curledColor: colorless,pink,black,red,bluish-greenStructure: opaque,translucent or transparentConsistancy: friable,viscid,butyrous or membranous

CULTURAL CHARACTERISTICS

Examples : Colony characteristics

COLONY CHARACTERISTICS OF SOME COMMON PATHOGENS

1.Staphylococcus(Staph.aureus/Staph.pyogenes)On Nutrient agar: large,pin-head size(2-4

mm),circular,convex,smooth,shiny,entire edge ,opaque & emulsify easily

Most strains produce golden yellow to white,orange pigments

On Blood Agar : β-Haemolysis

On MacConkey agar: Pink colonies

HAEMOLYSIS1.Alpha (α)hemolysis: Partial hemolysis/Greenish

discoloration

2.Beta(β) hemolysis : Complete hemolysis/Colorless

3.Gamma(γ) hemolysis : No hemolysis/no change

2.Streptococcus(Streptococcus pyogenes)

On Blood agar: Colonies are small, pin-point(0.5-1.0 mm),circular,semi-transparent

with an area of clear hemolysis(β-haemolysis) around them

Virulent strains on fresh isolation produce ‘matt’(finely granular)colonies

3.Escherichia coli(E.coli)

On Nutrient agar: Circular(1-3 mm),smooth,greyish-white,moist ,having entire edge

with butyrous consistency. Colonies emulsify easily

On Blood agar: Some strains show zone of β- hemolysis

On MacConkey agar: Pink colonies

4.Salmonella(S.typhii)

Blood agar: Large colonies(2-3 mm), circular, low convex,translucent,smooth

& non-hemolytic

MacCankoy agar: Colorless

Deoxycholate citrate agar: Colonies show black heads

Wilson & Blair bismuth sulphite agar: Jet black colonies with metallic sheen

5. Pseudomonas aeruginosa

On Blood agar: β-hemolysis

On MacConkey agar: Non-lactose fermenting

On Nutrient agar: Large,opaque,irregular colonies with butyrous consistency & fruity odor or earthy smell

Produces water soluble pigments which diffuse into the medium

i. Pyocyanin- bluish green ii. Fluorescein- yellowish green

iii. Pyorubin- red iv. Pyomelanin- black

THANK YOU

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