Advanced Diagnostic Laboratories

Bactericidal Assay

Test Code

BACT

Description

The innate and adaptive immune responses work in concert to protect the body against infection or foreign invasion. The innate response is the first line of defense against microbial infection and involves a complex system of chemical messages produced by the microorganism and the injured tissues or by components of the Complement system. Neutrophils, a type of white blood cell (WBC) are attracted to the area of invasion or infection by these messages (a process called chemotaxis) where they engulf and destroy the organism.

Genetic conditions involving neutrophil dysfunction are rare but life threatening, with affected patients presenting with recurrent bacterial or fungal infections. These deficiencies include Chronic Granulomatous Disease (CGD), Wiskott Aldrich Syndrome (WAS), Severe Congenital Neutropenia 4 (SCN4) and Neutrophil Immunodeficiency Syndrome (Rac2).

The bactericidal assay measures neutrophil killing function by incubating opsonized bacteria with neutrophils at 1:1 ratio and determining the number of viable bacteria remaining over time after phagocytosis (engulfment) has taken place. The response is compared to that of neutrophils obtained from a normal donor.
A patient with CGD or a similar neutrophil defect will show a diminished or absent killing activity.

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