A microagglutination test for human Brucella canis antibodies

Area of Science:

• Veterinary Medicine
• Immunology
• Infectious Diseases

Background:

• Brucella canis infection in humans is often underdiagnosed.
• Limited serologic testing facilities contribute to underdiagnosis.
• Misconceptions regarding Brucella canis prevalence impact diagnostic efforts.

Purpose of the Study:

• To describe a novel microagglutination test for detecting Brucella canis antibodies in human serum.
• To evaluate the test's performance, including its specificity and ability to detect blocking antibodies.
• To assess the test's utility in identifying Brucella canis infections in patients with undiagnosed febrile illnesses.

Main Methods:

• Development of a microagglutination test using safranin-dyed Brucella canis organisms as antigen.
• Testing of 1,147 human sera to identify antibodies against Brucella canis.
• Employing a high salt concentration (0.6 M NaCl) diluent to differentiate true positives and detect blocking antibodies.

Main Results:

• The microagglutination test demonstrated easily interpretable patterns and reproducible endpoints.
• A presumed false-positive rate of 1.6% was observed (18 out of 1,147 sera with titers ≥ 1:160).
• High salt concentration reduced titers in eight sera, indicating false positives, and revealed blocking antibodies in two previously negative sera.
• Serologic evidence of Brucella canis infection was found in four patients with undiagnosed febrile illness.

Conclusions:

• The described microagglutination test is a reliable method for detecting Brucella canis antibodies in human serum.
• The test's ability to identify blocking antibodies and differentiate true positives enhances diagnostic accuracy.
• Improved serologic testing for Brucella canis is crucial for accurate diagnosis and understanding the disease's true prevalence.