This document provides precautions and procedures for urine/stool culture and sensitivity testing. Key precautions include properly labelling specimens with patient information and collection date to avoid confusion and misleading results. Mid-stream urine specimens should be collected in sterile containers and tested promptly. Tests like catalase and coagulase activity help identify organisms, with catalase distinguishing staphylococci from streptococci based on hydrogen peroxide breakdown, and coagulase detecting pathogenic Staph. aureus by plasma clotting. Sensitivity testing using disc methods and organism identification tests ensure accurate culture results.

1. URINE/STOOL CULTURE AND
SENSITIVITY

2. PRECAUTIONS:
• The specimen should be properly labelled with the patient's name,
hospital number, ward and date of collection. This is essential in order
to prevent confusion of specimens from patients of similar name.
• The date of collection is required so that delays in reaching the
laboratory are apparent, and misleading results avoided; for example,
pathogens in urines may be overgrown by contaminants if there is a
long delay in transit from ward to laboratory.
• The correct container should be used. Most specimens for
bacteriological examination should be received in a sterile container.
• With all specimens extreme care must be taken with all manipulations
and they should be carried out under the protection of an exhaust
inoculating cabinet.

3. URINE
• Mid-stream specimens of urine should be sent to the laboratory in
suitable sterile containers, with the minimum of delay.
• Appearance: Colour Pale Amber, Deep amber, Cloudy etc
• Microscopy: Centrifuge 10ml of urine in test tube at 2500 rpm for 5
minutes. Examine the deposit for presence of Pus cell, Parasites, Cast,
crystals, RBCs etc.
• Inoculation Technique
• Using a standard sterile loop, insert vertically into the urine and
inoculate CLED and blood agar plates. Incubate at 37 °C identify any
organisms present.

4. Inoculation Technique

6. Sensitivity (Disc Method)

7. SOME TESTS USED FOR THE IDENTIFICATION OF ORGANISMS
Catalase activity:
• The use of this test is to differentiate staphylococci (catalase+ ) from streptococci (catalase — ).
• Principle: The enzyme catalase mediates the breakdown of hydrogen peroxide into oxygen and water.
• The presence of the enzyme in a bacterial isolate is evident when a small inoculum is introduced into
hydrogen peroxide, and rapid elaboration of oxygen bubbles occurs.
METHOD
1.Emulsify a colony of staphylococci in one drop of sterile distilled water on a clean glass slide. The opacity
should be such the hands of a watch can be seen through the suspension.
2. Add 2 drops of hydrogen peroxide and mix.
• Examine immediately, and after a few minutes, for bubbles of gas which indicates catalase production.

8. Coagulase activity
• Principle: Coagulase is an enzyme-like protein that causes plasma to clot by converting
fibrinogen to fibrin.
• A pathogenic staphylococcus. Staph, aureus, has the power of clotting or coagulating blood
plasma. This is due to the production by the pathogenic staphylococci of the enzyme coagulase.
Coagulase may be bound to the organism, in which case it is demonstrated by the slide test.
METHOD 1 : SLIDE TEST
1. Emulsify a colony of staphylococci in one drop of distilled water on a clean glass slide. The
opacity should be such the hands of a watch can be seen through the suspension.
2. Add a small loopful of rabbit plasma and mix.
3. A positive coagulase test will show immediate clumping— a negative test will show no
clumping.
A known positive staphylococcus should be tested at the same time, to check that the plasma is
working properly.