Robbins 9th ed - Chapter 8 - Infectious Disease - Rickettsia, Chlamydia, Mycobacteria (1)

Question 1

Name three species of clinically-significant Mycobateria.

Answer 1

M. tuberculosis
M. avium complex (MAC in AIDS patients)
M. leprae (leprosy)

Question 2

After infection with M.tuberculosis, how long will it be before the Mantoux test is positive?

Answer 2

2-4 weeks.

Question 3

In a positive Mantoux test, how long does it take until the palpable skin induration is maximal?

Answer 3

48-72 hours.

Question 4

In the initial stages of tuberculosis infection, which cell does the mycobacterium infect? How does it get into this cell?

Answer 4

Macrophages. Entry via macrophage surface receptors such as CR3 and mannose-binding lectin.

Question 5

What is the Ghon focus? What is the Ghon complex?

Answer 5

In initial tuberculosis infection of the lung, an area of grey-white inflammation occurs in the lung parenchyma: this is the Ghon focus. It usually drains to a regional lymph node or nodes. The combination of the Ghon focus and the nodal involvement is called the Ghon complex.

Question 6

Where is the initial Ghon focus usually found within the lung?

Answer 6

Either the lower part of the upper lobe, or the upper part of the lower lobe.

Question 7

What are the key distinguishing features of all Rickettsia?

Answer 7

All rickettsia are gram-negative bacilli, obligate intracellular bacteria, transmited by arthropod vectors. They primarily infect endothelial cells.

Question 8

Give a few examples of Rickettsial infections, and which vector is used for transmission.

Answer 8

Epidemic typhus - transmitted by body lice.

Rocky Mountain spotted fever - transmitted by dog ticks.

Question 9

What are the key distinguishing features of Chlamydia?

Answer 9

Chlamydia species are small, gram-negative, obligate intracellular bacteria, that usually invade epithelial cells.

Question 10

Name three body systems that are common sites of infection for Chlamydia.

Answer 10

Urogenital. Ocular. Respiratory.