Mycobacterial infection - RTD Jan 2018

Question 1

What is a feature of the cell wall of mycobacteria?

Answer 1

Lipoarabinomannan (LAM) - similar to LPS of Gram negative bacteria

Question 2

Name acid-fast stain

Answer 2

Ziehl Neelsen, Fite-Faraco

Question 3

What stain is better for leproid mycobacteria?

Answer 3

Fite-Faraco

Question 4

What is added into mycobacteria (tuberculosis) culture to prevent overgrowth of contaminants?

Answer 4

Malachite green

Question 5

What is an important virulence factor of tuberculous mycobacterium?

Answer 5

Cord factor, a glycolipid molecule found in the cell wall

Question 6

Name the 3 main Mycobacterium tuberculosis Complex (MTBC) species

Answer 6

M tuberculosis, M bovis, M microti

Question 7

Name the main reservoir host of M tuberculosis

Answer 7

Humans

Question 8

Name the reservoir host of M. microti

Answer 8

Rodents (voles and shrews)

Question 9

Name the reservoir host of M. bovis

Answer 9

Cattle and various wildlife species

Question 10

How does M tuberculosis survive inside phagocytic cells?

Answer 10

Resistant waxy cell wall (protects against lysosomal enzymes)
Antioxidants (catalase)
Cytotoxic factors
Interfere with maturation of phagosome, lysosome Escape phagocytosis and live freely in cytoplasm

Question 11

What test is used to differentiate M bovis and M avium in cattle? Why is this important?

Answer 11

Comparative cervical test or IFN-gamma

M bovis cattle are culled

Question 12

True/False

Humans can infect domestic animals with M tuberculosis, but domestic animals cannot infect humans

Answer 12

True

Question 13

Features of Mycobacterium avium complex (MAC)

Answer 13

Slow growing, do not produce true tubercles

Question 14

What cat breeds are predisposed to disseminated MAC disease?

Answer 14

Abyssinian and Somali cats

Question 15

What are the 4 subspecies of Mycobacterium avium complex?

Answer 15

M. avium spp. hominissuis, avium, paratuberculosis, and silvaticum

Question 16

What animals are most susceptible to MAC?

Answer 16

Poultry and Swine

Question 17

What are the 2 main species of Mycobacterium avium complex (MAC)? (closely related)

Answer 17

M. avium and M. intracellulare

Question 18

What are the 3 forms of feline leprosy?

Answer 18

1) Syndrome in young adult cats caused by Mycobacterium lepraemurium (Cause of leprosy in rodents)
2) Syndrome in older cats associated with M. visible (United States) and an unnamed novel mycobacterial species (in Australia and NZ) – (M. sp. “cat”)
3) New fastidious species (Mycobacterium sp. strain tarwinense) identified in rural Victoria, Australia – has features of both of the above syndromes

Question 19

What can be used to grow M lepraemurium on culture?

Answer 19

Ogawa’s egg yolk

Question 20

What are the 2 types of reactions on histopathology in feline leprosy?

Answer 20

1. Tuberculoid response- caseous necrosis, few organisms (paucibacillary), AFB often only in the necrotic areas
2. Lepromatous response -granuloma composed of solid sheets of large foamy macrophages containing large numbers of AFB (multibacillary)

Question 21

What is the dog breed predisposed to Canine leproid granuloma?

Answer 21

Boxers and crosses

Question 22

Name the rapidly growing mycobacteria (RGM) groups

Answer 22

M fortuitum, M chelonae/abscessus, M smegmatis

Question 23

What stain is preferred for rapid growing mycobacteria (RGM)?

Answer 23

Fite Faraco

RGM is not as acid fast as the other mycobacterial species

Question 24

Rapidly growing mycobacteria culture

Answer 24

Lowenstein-Jensen or 5% sheep blood

Question 25

What is the specific lipid component of the mycobacterial cell envelope?

Answer 25

Mycolic acids