Wellcogen Latex Agglutination Test for Bacterial Antigen (PHADEBACT)

Principle:
To detect qualitative strep group “B” antigen from CSF and urine samples, H. influenzae Type b, Streptococcus pneumoniae, Neisseria meningitis groups A,B,C,Y or W135, E. coli K1 present in the CSF

Note: CSF or urine (at least 1ml) should be tested as soon after collection as possible. If the fluid can not be tested immediately it may be stored overnight at 2 to 8 0Celsius or if for longer period, store frozen at -15 to -25 deg Celsius.

Specimen Preparation:

• Body fluid samples must be heated before testing by the Wellcogen procedure to minimize non-specific reactions. The following procedures are recommended: 

1. For CSF and urine, heat the sample for 5 minutes in a boiling water bath. Cool the sample to room temperature (18-30 0Celsius) and clarify by centrifugation or membrane filtration. ( 0.45 µm) prior to testing. 
2. For serum, add 3 volumes 0.1 M disodium ethylenediaminetetraacetate (EDTA) ph 7.4 per 1 volume serum, heat the sample for 5 minutes in a boiling water bath, cool to room temperature and clarify as above. 

• Blood cultures. Centrifuge 1-2 ml sample pellet to the red blood cells, for example at 1000g for 5-10 minutes. 
• Perform the latex test on the supernatant. 
• Plate cultures ( N. meningitidis B/E.coli only). Test directly from the plate culture. 

Procedure (Body Fluids)

• Process sample as described under Preparation of Clinical Specimens. 
• Shake the Latex Reagents. 
• Place 1 drop of each Test Latex or Control Latex into a separate circle on a Reaction 
• Ensure that the dropper bottles are held vertically to dispense an accurate drop. 
• Using a disposable dropper, dispense 1 drop (approximately 40 µl) to test sample nest to each drop of latex. 
• Mix the contents of each circle with a Mixing Stick and spread to cover the complete area of the circle. Use a separate stick for each circle. 
• Rock the card slowly and observe for agglutination for 3 minutes. 
• Discard used reaction cards for safe disposal. 

Procedure (Plate Culture N. meningitidis B/E. coli K1 only)

• Shake the latex reagents. 
• For each culture to be tested place 1 drop of Test Latex in one circle on Reaction Card and 1 drop of Control Latex in a separate circle. 
• Take a mixing stick and use the flat end to pick up 1 large colony. 
• Emulsify the sample of culture in the drop of test Latex . Discard the stick. 
• Using a separate stick, emulsify a similar sample of culture in the Control Latex. 
• Rock the card slowly and observe agglutination for 20 seconds. 
• Discard the used reaction cards. 

Interpretation:

• A positive reaction is indicated by agglutination or visible clumping after 3 minutes for body fluids and 20 seconds for colony testing. 
• Negative result has no agglutination or clumping.