Bacterial and Parasitic Checkpoint

Question 1

1. Where do the most cases of leprosy occur globally? Does leprosy occur in the U.S.?

Answer 1

a. India, China, Myanmar, Indonesia, Brazil, Nigeria, Madagascar, and Nepal
b. US 4000 have it and 100-200 cases every year

Question 2

2. How is M. leprae commonly transmitted from person-to-person?

Answer 2

Coughing or exposure to nasal secretions

Question 3

3. Which animal is a known carrier of M. leprae

Answer 3

armadillos

Question 4

4. Which systems are typically involved in cases of lepromatous leprosy? Tuberculoid leprosy?

Answer 4

Skin, PNS, URT, eyes, testes

Question 5

5. Once transmitted, does it take a short time (days) or long time (months-years) for the clinical manifestations of M. leprae to occur?

Answer 5

Months-40 years, average is 5-7 years

Question 6

6. Describe the taxonomy of M. leprae. Leprosy patient’s extremities are commonly affected instead of the trunk. Why?

Answer 6

a. Rod-shaped, acid-fast, obligate intracellular bacteria

b. Grows better at temps less than core body temp

Question 7

7. What are the major differences between lepromatous leprosy and tuberculoid leprosy based on patient presentation?

Answer 7

a. LL
i. Symmetrical skin nodules, leonine facies, loss of eyebrows, eyelashes, thickening of the ears, nasal cartilage destroyed. High numbers bacterial in peripheral nerves.
b. TL
i. Hypopigmented elevated macules or plaques. One lesion usually seen

Question 8

8. How does the balance of Th1 (cytotoxic) and Th2 (antibody-mediated) adaptive immune responses strongly determine the severity of a M. leprae infection? Which T cell polarization, Th1 or Th2, leads to efficient clearance of the pathogen?

Answer 8

a. Th2 leads to poor clearance and worse outcome, strong Th1 leads to clearance and self-limiting infection

Question 9

9. How is M. marinum commonly transmitted?

Answer 9

a. Small lesions infected by bacteria in pools, aquariums, rivers

Question 10

10. Why does M. marinum typically only impact the extremities?

Answer 10

a. Core temp not facilitate growth

Question 11

11. Describe the commonly clinical manifestations of a M. marinum infection

Answer 11

ulcerations and adenopathy

Question 12

12. Is the clinical manifestation of M. marinum unique? If not, then which other pathogens should be considered in a DDX?

Answer 12

a. Nontuberculous mycobacterial infection, Nocardia, leishmanial, tularemia, plague, cutaneous anthrax, fungal infetions

Question 13

13. Which states in the U.S. have the highest rates of Rocky Mountain Spotted Fever (RMSF)?

Answer 13

a. Oklahoma, Arkansas, Missouri, Tennessee, North Carolina

Question 14

14. How is RMSF transmitted?

Answer 14

a. Tick bite attached 6-10 hours

Question 15

15. Can R. rickettsi be cultured on agar

Answer 15

no

Question 16

16. Which cell type does R. rickettsi commonly infect?

Answer 16

endothelial cells

Question 17

17. What are the common symptoms that present in patients with RMSF? Is the rash commonly associated with early symptoms?

Answer 17

a. Fever, headache, disseminating maculopaular rash, malaise, n/v, anorexia
b. Rash typically after initial symptoms

Question 18

18. Are antibody titers useful when a patient initially presents with RMSF symptoms?

Answer 18

a. No, it takes weeks

Question 19

19. The gold standard for confirming a case of RMSF is to measure the antibody titers (IgG, IgM) against R. rickettsi antigens. Two patient samples are taken: one as early as possible and the other 2-4 weeks later. Why are two samples taken?

Answer 19

a. To measure elevation of titers

Question 20

20. Starting in the sandfly, how does the life cycle of Leishmania progress when transmitted into humans?

Answer 20

a. Promastigotes injected into human after being bitten by a sandfly, then phagocytized and turn into amastigote stage

Question 21

21. What are the three broad disease categories of leshmaniasis infections? What are the common clinical manifestations of each? Geographically, where are these diseases common?

Answer 21

a. Cutaneous
i. Both eastern and western continents
ii. Most common form, bite site presents with a papule or nodule but may advance into an ulcer, lesions typically heal themselves (2-15 months)
iii. L. tropica is common in urban and suburban areas in eastern countries
iv. Western, L. Mexicana most common
b. Visceral
i. Second most common cause of death globally by parasitic infection, infects phagocytes in spleen, bone marrow, liver, and lymph nodes
ii. Severe fever on and off for weeks, splenomegaly
iii. If untreated near 100% fatality
iv. India and Africa, some complications after being cured, hypopigmented skin lesions
c. Mucocutaneous
i. Can occur during cutaneous or years after resolution
ii. Typically as nose bleeds that progress to destruction of nasal cartilage, pharynx and larynx can be affected

Question 22

22. Which two species of Leishmania cause visceral leshmaniasis? Which species is most commonly associated with mucocutaneous leshmaniasis?

Answer 22

a. L. donovani and L. infantum (L. Chagas)

b. L. braxiliensis most common etiologic agent for mucocutaneous

Question 23

23. In patient samples, in which cell types are Leshmania spp. commonly found and how do they appear upon staining?

Answer 23

a. Skin biopsies and spleen samples, bone marrow works well too. Cell with multiple amastigotes