Question

1. Which of the following is false concerning Mycobacterium tuberculosis

		It has a very low infectious dose
		A large percentage of the world population is infected
		Produces granulomas in affected tissues
		A positive tuberculin test indicates past infection, current infection, or BCG                                   immunization.
		All of the above are true.

2. Which of the following is false concerning infection with Chlamydia trachomatis

		Certain serovars cause lymphogranuloma venerum, a rare but serious STD.
		It is an obligate intracellular pathogen transmitted by contact.
		It is the most common cause of bacterial STD & preventable blindness (trachoma
		It has a complex life cycle with external elementary bodies and intracellular          replicating reticulate bodies
		All of the above are true.

3.

Results of antigen-antibody binding include all of the following except

		Opsonization.
		Neutralization
		Lysis (MAC) through activation of complement by antibody via all three (Classical, Alternate, and Mannan Lectin Binding) pathways of complement activation.
		Agglutination
		Antibody dependent cell-mediated cytotoxicity (ADCC )

Answer 1

1. The answer is - It has a very low infectious dose.

Explanation :

Mycobacterium tuberculosis is a pathogenic bacteria causing tuberculosis disease. It needs high amounts of oxygen and usually infects lungs of the mammals. It has very high pathogenic dose and spreads easily through droplets in air. Therefore, the sentence saying, it has low infectious dose is false.

While all the other options are correct.

Tuberculosis has affected most of the world particularly underdeveloped and developing countries. The granulomas are formed in the affected tissues. There is also lympadenopathy which can be palpable . A positive tuberculin test shows , current or past infection or BCG immunization.

2. The answer is - All of the above are True.

Certain serovars causes Lymphogranuloma venereum which is rare but causes serious effects without treatment. Since 10 years, it is seen in North America, Europe, Australia in a population of men who have sex with men.

Chlamydia trachomatis is an intracellular pathogen which is usually transmitted by contact. It is most common bacterial STD and cause of preventable non congenital blindness having a complex lifecycle with infectious external elementary bodies and non infectious intracellular reticulate bodies.

Therefore , all the statements are correct.

3. The answer is- Neutralisation.

Antigen antibody binding includes all the options except neutralisation. Neutralisation is a process wherein reactions are used to inactivate virus . When there is entry of virus to the host , the host antibody form virus- antibody complex which blocks viral infection . This complex prevents viral infections. Thus there is no binding of antigen here and hence Neutralisation dose not involve antibody antigen binding.

Thank you.