The fluorescent antibody blocking antibody (FABA) test has been discribed and compared with the conventional antistreptolysin 0 antibody (ASOA) test in the detection of Streptococcus pyogenes group A antibodies in sera samples.

A slide inhibition test was used to detect the presence of FABA in the following manner; (a) fix group A streptococcal cells to a slide, (b) incubate these cells with the patient's serum for thirty minutes, (c) wash off serum with buffered saline and dry, (d) incubate these same cells with group A streptococcal fluorescent tagged antibody for thirty minutes, (e) wash and dry as before, and (f) mount and examine slide with a fluorescent microscope. The presence of streptococcal antibodies in the patients serum will block the staining of the cells with the fluorescent tagged antibody. The FABA titer can be determined by diluting the serum until there is no more blocking effect.

Sera from one hundred hospital patients were tested for the presence of FABA and ASOA titers. The probability of a patient having FABA increased in those with elevated ASOA titers, although there was poor correlation of the titers of the two tests.

The above experiment was followed by a more controlled experiment using rabbits immunized with different group A streptococcal The antigens were given as follows; (a) two rabbits received Todd-Hewitt broth (THE) as a control, (b) two rabbits received washed antigens. group A streptococcal cells, (c) two rabbits received streptolysin 0 reagent, (d) one rabbit received a THB cell free filtrate of a group A streptococcal culture, (e) two rabbits received live cultures of group A streptococci in THB, and (f) one rabbit received heat killed streptococcal cells in the THB followed by antigen (e).

There was no FABA or ASOA response from the rabbit which received antigen (a) and (b). Only the ASOA titer rose with the rabbits receiving antigen (c). Both FABA and ASOA titers rose in rabbits receiving antigen (c). Both FABA and ASOA titers rose in rabbits receiving antigens (d), (e) and (f). The FABA titer rose earlier, went higher and returned to pre-immunizing level before the AOSA titer did. The highest FABA and ASOA titers were reached with using antigen (d).

It is evident from the results of this experiment that both the FABA and ASOA are elevated in streptococcal infections but are not the same. The FABA has the characteristics of an antibody. This antibody titer rises earlier and goes higher than the ASOA titer and therefore might be a better diagnostic test for the early detection of streptococcal antibodies in sera of patients. The antigen stimulating the production of FABA has proven to be some portion of the group A streptococcal exudate other than the streptolysins.

LLU Discipline





Graduate School

First Advisor

Charles E. Winter

Second Advisor

Raymond E. Ryckman

Third Advisor

U. D. Register

Degree Name

Master of Science (MS)

Degree Level


Year Degree Awarded


Date (Title Page)




Library of Congress/MESH Subject Headings

Streptococcus; Streptolysins



Page Count

ix; 66

Digital Format


Digital Publisher

Loma Linda University Libraries

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This title appears here courtesy of the author, who has granted Loma Linda University a limited, non-exclusive right to make this publication available to the public. The author retains all other copyrights.


Loma Linda University Electronic Theses and Dissertations

Collection Website



Loma Linda University. Del E. Webb Memorial Library. University Archives

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Microbiology Commons