Microscopic agglutination test Flashcards
what do agglutination reactions produce
visible aggregates of antibody-antigen complexes
what do we use MAT for
serological diagnosis of leptospirosis
classification of leptospira
what does MAT detect
antibodies to specific serovars using live bacteria (antigens)
describe genus leptospira
immunologically and genetically heterogeneous spiral shaped bacteria
taxonomy fo leptospira
22 recognised genomospecies (pathogenic, intermediate and non pathogenic)
300+ serovars divided in to 29 serogroups
primary reservoir of leptospira
rodents
pathology of leptospira
leptospires enter the body by penetrating mucous membranes or skin abrasions and disseminate through blood
antibody formation and clearance of organisms from the blood stream
colonisation of proximal renal tubules in carrier animals leads to intermittent urinary shedding
why do we use a panel of antigens when using MAT
due to serological diversity of leptospira genus
what is the panel of antigens made of
composed of strains of reference serovars, whose presence in the area has been confirmed by previous epidemiological and epizootiological investigations
panel must represent the locally circulating strains that cause disease
selection of panel important because
there is no cross reactivity between serogroups of leptospira included in the conduct of microscopic agglutination
is MAT qualitative or quantitative
both
quantitative - established whether antibodies to a specific leptospira serovar exist in the basic dilution (1:20, 1:50 or 1:100)
qualitative - can be positive or negative
if positive - a quantitative MAT is performed to know the quantity of antibodies in titre
quantitative part of test
a double series of serum dilutions is made and kept in contact with equal volume of well grown suspension of serovars (which produced a positive result in the qualitative part of the reaction)
end point titre (positive reaction)
final dilution of serum at which 50% of the leptospires are agglutinated
ie 50% of leptospires remain free - in relation to the negative control
titre threshold (cut off titre) is…
when the antibody titre is deemed positive - it is defined depending on the legislation, the epizootiological/epidemiological situation in the specific area and the species of animal we are testing
what happens in initial phase of illness
antibodies often found in serum and react with several serovars = cross reaction
