Test 59  (microbiology)

1. The following are true about Clostridium tetani:

a. it is a Gram positive bacilli with terminal spore

b. tetanus can occur weeks after the initial infection

c. the symptoms of tetanus is produced by an endotoxin

d. tetanus antitoxin is ineffective when the toxin enters 
    the nervous tissue

e. gas gangrene can result from Clostridium tetani 
    infection

Answera.T   b.T   c.F   d.T   e.F
Tetanus is produced by an exotoxin.
Gas gangrene is caused by Clostridium perfringens.

2. With regard to Treponema pallidum:

a. the bacteria can be found in lesions of primary syphilis

b. the bacteria can be found in lesions of secondary 
    syphilis

c. the bacteria can be found in the cerebrospinal fluid of 
    tertiary syphilis

d. VDRL is specific for Treponema pallidum infection

e. it is resistant to penicillin

Answera.T   b.T   c.F   d.F   e.F
Bacteria can be recovered from lesions of primary and secondary syphilis but not the CSF in tertiary syphilis.
VDRL may be positive in malaria, leprosy and collagen diseases. It is used as a screening test; FTA-ABS is used as a confirmatory test.
It is sensitive to penicillin.
 

3. The following are true about hepatitis B:

a. it is a RNA virus

b. immunity can be acquired by vaccination with a live 
    attenuated virus

c. persistent presence of HBsAg increases the risk of 
    chronic liver disease

d. the average incubation period is 30 days

e. the presence of antibody to hepatitis B surface 
    antigen is a reliable indicator of non-infectivity

Answera.F   b.F   c.T   d.F   e.T
Hepatitis B is a DNA virus. 
Vaccination uses hepatitis B surface antigen.
The average incubation period is between 60 to 90 days.

4. Onchocerciasis:

a. is transmitted by mosquito bite

b. is only found in West Africa

c. causes nodular lesions in the eyes and skin

d. causes corneal scarring

e. causes optic neuritis

Answera.F   b.F   c.T   d.T   e.T
Onchocerciasis is caused by the parasite Onchocerca volvulus infection transmitted by  simulian fly.
It is found in West Africa and part of South America.
 

5. The following are true about leprosy:

a. it is caused by an acid fast bacteria

b. it causes facial nerve palsy

c. tuberculoid leprosy occurs in patients with poor 
    cellular immunity

d. more bacilli are found in the skin of patients with 
    lepromatous leprosy than tuberculoid leprosy.

e. granuloma is a feature of tuberculoid leprosy

Answera.T   b.T   c.F   d.T   e.T
Tuberculoid leprosy occurs in patients with good T cell response to the bacillus. The number of bacilli is therefore less than in lepromatous leprosy. Because of the good T cell response, granuloma is a feature of tuberculoid leprosy.