Filamentous and Mycobacteria - SRS Flashcards Preview

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Flashcards in Filamentous and Mycobacteria - SRS Deck (28)
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1
Q

What are the members of the CMN group?

A

Corynebacteria

mycobacteria

nocardia

2
Q

What is the gram stain character of the members of the CMN group?

A

Nocardia and actinomyces are gram positive

corynebacteria are gram positive and often pleomorphic

mycobacteria are gram ? (+ d/t cell wall structure but - d/t DNA)

3
Q

Mycobacteria have a polymer complex that is comprised of…

  1. peptidoglycan
  2. arabinogalactan
  3. ?
A

Mycolic acid

4
Q

Since mycobacteria and nocardia are “acid fast”, what stain is used for identification?

A

Ziehl-Neelsen stain

5
Q

Mycobacteria have something called cord factors, what are these and what do they do?

A

Dimycolates of trehalose that…

  1. give rise to growth in serpentine rods
  2. inactivate mitochondrial membranes of phagocytes, allowing organism to survive and multiply in phagocytes
6
Q

How is M. tuberculosis spread?

A

Airborne droplets

7
Q

How does M. bovis spread?

A

oropharyngeal and intestine via unpasteurized cow milk

8
Q

What are the two types of disease processes we see arise from M. leprae?

A

Tuberculoid leprosy

Lepromatous leprosy

9
Q

Tuberculosis has primary and secondary infection stages. Describe the primary infection stage.

A
  1. Ghon complex
  2. Granulomatous response, typically asymptomatic and self-limiting but clinically sympomatic in 5%
10
Q

What is the Ghon complex?

A

Parenchymal lesion and an involved lymph node

11
Q

Secondary Tb infection occurs when old walled off lesions are reactivated, usually in apical lung regions d/t high ppO2. What is the course of the disease from this point?

A

Variabe, but often cavitary caseous necrosis with subsequent scarring or progressive disease

12
Q

What is shown in the attached picture? In what type of disease do we see this?

A

Scrofula - non-pulmonary TB may present with cervical lymphadenitis

13
Q

When does miliary TB occur?

A

When a tubercle erodes a blood vessel

14
Q

In the immunosuppressed patient, what can we see as far as tuberculosis presentation?

A

Dissemination in 10-15% of those who are mildly immune suppressed.

Dissemination in more than 50% of severely immunocompromised

15
Q

What immune cells are needed to form a granuloma?

A

TH1

16
Q

Describe the two paths that can lead to miliary TB

A

I.

  1. Primary infection –> Primary complex (localized caseation) –> progressive primary TB –> massive hematogenous dissemination –> miliary TB
  2. Primary infection –> Primary complex (localized caseation) –> Latent Lesions –> Secondary TB (either by reinfection or reactivation) –> Progressive secondary TB –> massive hematogenous dissemination –> miliary TB
17
Q

What organism causes Hansen disease?

A

M. leprae

18
Q

What are the two directions an M. leprae infection can take? What determines the progression?

A

Depending on the patients cellular defensive capacity…

If intact - will progress to the tuberculoid (paucibacillary) form

If compromised - will progress to Lepromatous form

19
Q

Persons with a vigorous cellular immune response may develop the Tuberculoid form of M. leprae.

Describe the following:

  1. Level of pain
  2. Impact on skin
  3. Nerve involvement pattern

For our purposes, what is the distinguishing aspect of this version of the disease we should use?

A
  1. Painless
  2. Skin lesions are limited, and they tend to be dry and hypoesthetic
  3. Nerve involvement is usually asymmetric

** 5 or fewer skin lesions with absence of organisms on smears ** (to distinguish from lepromatous)

20
Q

Persons with a compromised cellular immune response may develop the lepromatous form of M. leprae.

Describe the impact of this disease on the skin.

A

•Extensive skin involvement in the cooler areas of the body, with sparing of the groin, axilla, and scalp

21
Q

How are the nerves affected in the lepromatous M. leprae progression?

What is the key aspect of this we are to use to distinguish this from the tuberculoid presentation on exam questions?

A

Nerve involvement tends to be symmetric

•6 or more lesions with possible visualization of bacilli on smear

22
Q

What is the arrow pointing to in this image?

A

A macrophage loaded with tons of M. leprae

23
Q

In which version of an M. leprae infection are skin tests with antigen from killed organisms pisitive?

A

Only in the tuberculoid form do you see a positive lepromin (Injected M. leprae antigen) result

24
Q

The Mycobacterium avium complex does not typically cause problems, but can lead to issues in immunocompromised patients. In these patients what can infection with these agents lead to?

A

Can cause pulmonary disease resembling tuberculosis, lymphadenitis, skin disease, soft tissue disease or disseminated disease

25
Q

What organism is described here?

  • Gram positive filamentous bacteria
  • Aerobic
  • Found in soil and gingiva
  • Opportunistic intracellular pathogens (replicate within cells)
  • Acute, subacute, or chronic infectious disease that occurs in cutaneous, pulmonary, and disseminated forms
A

Nocardia

26
Q

What does N. asteroides cause?

A

•Pleurocutaneous nocardiosis (opportunistic respiratory infections resembling tuberculosis and CNS infections)

27
Q

What does N. brasilienses cause?

A

•Primary cutaneous nocardiosis (cellulitis, lymphocutaneous disease and actinomycetoma)

28
Q

Actinomycosis is similar to nocardosis but is anaerobic. What does it typically cause?

What are the characteristic granules associated with this bacteria called and filled with?

A
  • Cause painful abscesses in the mouth, lungs, or gastrointestinal tract
  • sulfur granules: filled with progeny bacteria