SIP

Subject: MMIC
Topic: Reading of urine cultures

Some of the properties that can be used to identify the organisms
· Colony appearance (colour and shape)
· Ability to ferment lactose
· Ability to haemolyse red blood cells
· Ability to produce cytochrome oxidase

Lactose Fermentor (LF) Vs Non-Lactose Fermentor (NLF)

LF	NLF
Able to utilize lactose on CLED	Unable to utilize lactose on CLED
Forms white to grey colonies on BAP but forms yellow colonies on CLED	Forms white to grey colonies on BAP and CLED
Produces acid causing CLED to turn yellow	May produce alkaline causing CLED to turn blue

Haemolysis

Some organisms are able to cause the lysis of the sheep red blood cells found on BAP. Haemolysis can be detected through holding up the back of plate against a source of light.

Haemolysis on BAP can be classified into two categories:
• α-haemolytic
o greenish-looking colonies
• β-haemolytic
o forms a clearance around the colonies

Oxidase Test
The oxidase test checks for the production of cytochrome oxidase (an enzyme). The oxidase reagent contains a compound that changes color when it becomes oxidized (i.e. chromogenic reducing agent).

Procedure:
A drop of oxidase reagent is dropped onto the test strip. The test strip is then used to lightly touch the colonies.
Positive: Blue (cytochrome oxidase present)
Negative: No colour change

Identification of Microorganism

Microorganism	Colony Appearance	Ferment Lactose	Other Properties
Escherichia Coli	• Flat, grey colonies on BAP • Form yellow colonies on CLED	Yes	-
Klebsiella spp.	• Mucoid, convex colonies • Form white colonies on BAP • Form yellow colonies on CLED	Yes	-
Streptococcus spp. (GPC)	• Small, white colonies on BAP • Form yellow colonies on CLED	Yes	• Catalase negative Haemolysis: • α-haemolytic: eg. Streptococcus pneumoniae • β-haemolytic: Streptococcus group A, B etc • Non-haemolytic: E.g. Enterococcus spp. (Greyer appearance)
Staphylococcus spp. (GPC)	• Small, white, flat colonies on BAP • Form yellow colonies on CLED	Yes	• Catalase positive • Can be hemolytic positive or negative
Pseudomonas spp.	• Swarms on BAP • Spready colonies on CLED	No	• Pungent smell • Oxidase positive • Swarming ability
Proteus spp.	• Swarms on BAP • Glossy	No	• Pungent smell • Swarming ability
Candida spp.	• Small, flat, white colonies on BAP and CLED • Slightly spready • Not glossy	No	-

E. Coli














Klebsiella spp.














Pseudomonas and Klebsiella spp.














Proteus spp.














Candida spp.
















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