The most pathogenic Brucella spp for man is
Answer: A
Correct answer: B melitensis
B. melitensis, whose natural hosts are goats and sheep, causes the most severe and most protracted human disease of the four and accounts for most clinical cases worldwide. B. suis from pigs is next, B. abortus from cattle produces milder illness, and B. canis is an uncommon cause of human infection.
Please log in or register to report this question.
Brucella are
Answer: D
Correct answer: Very short rods
Brucella are Gram-negative organisms so short that they appear almost oval - small enough to be mistaken for cocci at first glance, which is why they are so often described as coccobacilli. They are non-motile, non-sporing and non-capsulated, and being intracellular they are typically seen within phagocytes rather than free.
Please log in or register to report this question.
Agglutination test for Brucella mainly identifies which class of antibodies?
Answer: B
Correct answer: IgM
The plain agglutination test detects chiefly IgM, which is the earliest antibody produced and, being pentameric, by far the most efficient agglutinator - a single molecule can bridge several bacteria. That is precisely why the mercaptoethanol variant exists: removing the IgM contribution leaves the IgG titre, which carries the different information described above.
Please log in or register to report this question.
Human transmission of Brucellae occurs by
Answer: D
Correct answer: all of these
All three are established routes. Ingestion of unpasteurised milk and its products is the commonest source in the general population; contaminated meat carries the organism as well; and direct contact with infected tissues, placentas and abortion material makes brucellosis an occupational disease of farmers, abattoir workers, veterinarians and laboratory staff. Person-to-person spread, by contrast, is very rare.
Please log in or register to report this question.
Which of the following can be identified by milk ring test?
Answer: A
Correct answer: Brucellosis
The milk ring test detects antibody to Brucella in bulk milk: stained antigen is added and, if antibody is present, the agglutinated complexes rise with the cream to form a coloured ring at the top. It is cheap, rapid and applied to whole herds at once, which makes it the standard screening test for bovine brucellosis - and it works only for that organism.
Please log in or register to report this question.
For brucellosis, 2 ME agglutination test is used to identify
Answer: A
Correct answer: IgG
Mercaptoethanol breaks the disulphide bonds holding the IgM pentamer together, destroying its agglutinating activity while leaving IgG unaffected. Agglutination that survives treatment is therefore due to IgG. That matters clinically: IgM appears early and may persist after cure, whereas continuing IgG indicates chronic or active infection rather than a past exposure.
Please log in or register to report this question.
