Mycobacteria & Nocardia Flashcards by Walker Short

What makes mycobacterium resistant to gram staining?

-glycolipids in cell wall

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What do glycolipids in the cell wall of mycobacterium do?

-protects bacteria from effects of phagolysosomal components -enhance antibody responses to protein Ags

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What organism causes leprosy?

Mycobacterium leprae

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In what populations and areas do most cases of leprosy occur in the U.S.?

-Majority of cases in Asian & Hispanic immigrants; -Most cases occur in New York, Texas, Louisiana & California.

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How is Mycobacterium leprae cultivated?

-cannot be cultivated in vitro -must inject into mouse foot

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What might be the reservoir of M. leprae?

Armadillos

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Distinguish the severity and characteristics of Lepromatous Leprosy and Tuberculoid Leprosy.

Lepromatous Leprosy: -most severe -multiple skin lesions, intact sensation -Few T cells, no granulomas -Lots of bacteria in skin Tuberculoid Leprosy: -Least severe -Few, raised skin lesions -Abundant T cells, well formed granulomas -Almost no bacteria in lesions

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How does M. leprae result in nerve damage?

-direct bonding of organisms to schwann cells -immunologic damage to infected nerve cells

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How is leprosy related to diabetes?

-both involve loss of sensation in extremities in a glove and stocking distribution -inability to feel leads to repetitive trauma and 2’ infections, leading to resorption

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What stain is used on the skin to detect leprosy?

Fite stain (acid fast)

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What is the treatment of leprosy?

-prolonged therapy with dapsone & rifampin

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What is a reversal reaction in leprosy?

-Immunologic reaction that complicates diease -result from development of a more appropriate Th1 cellular immune response; -Increased erythema of skin plaques & swelling of peripheral nerves.

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What is erythema nodosum leprosum

-Immunologic reaction that complicates diease -Panniculitis, arthralgias/arthritis, mouth ulcers, fever, proteinuria

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What syndromes are caused by Mycobacterium avium-intracellulare(Mycobacterium avium complex)?

Chronic pulmonary disease: -Fibrocavitary -Fibronodular -Disseminated disease in people with AIDS; -Miscellaneous, mostly localized soft tissue infections.

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Who is usually infected with Mycobacterium avium-intracellulare, causing Fibrocavitary disease?

-elderly men who are smokers and have COPD

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Why is fibrocavitary disease caused by Mycobacterium avium-intracellulare very refractory?

anatomic abnormalities & development of drug resistance.

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Who is usually infected with Mycobacterium avium-intracellulare, causing Fibronodular bronchiectasis?

-non-smoking women without predisposing lung disease -Characteristic asthenic (thin) body habitus with scoliosis, pectus excavatum, mitral valve prolapse

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Which responds better to therapy, fibronodular bronchiectasis or fibrocvavitary disease? What organism causes it?

-Fibronodular bronchiectasis -Mycobacterium avium-intracellulare

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What are the 6 major clinical syndromes caused by nontuberculous mycobacteria?

-Chronic pulmonary disease -Lymphadenitis -Localized cutaneous & soft tissue infections -Infection of tendon sheaths, bones, bursae & joints with all species -Disseminated disease -Catheter-related infections in patients with long-term indwelling intravascular catheters

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What is lymphadenitis? What organisms cause it?

-Tends to be painless, anterior cervical adenopathy; -80% in children is MAC; remainder is M. scrofulaceum -TB as well

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“swimming pool” or “fish tank” granuloma

Mycobacterium marinum

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What is the presentation of Mycobacterium marinum infection?

Violet papules on hands & arms that progress to ulcerations.

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_____________ was implicated in an outbreak of soft tissue abscesses associated with nail salons

Mycobacterium chelonae

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“Rice Bodies” in tendon sheaths, bones, bursa, and joints

-All species of non-TB mycobacteria -frequently M. avium-intracellulare

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Where is Nocardia normally found?

-soil

What does Nocardia brasiliensis cause?

-lymphocutaneous infection, abscess or cellulitis & mycetomas \*results from traumatic inoculation

When you see a pulmonary-CNS syndrome in an immunocompromised patient, what organism should you be thinking?

Nocardia

Growth of Nocordia is \_\_\_\_\_\_\_than most conventional bacteria, & other organisms can overgrow colonies of Nocardia unless plates are carefully inspected

slower

A patient with HIV infection (CD4 = 23 cells/ L) presented to the Thomas Street Clinic with weight loss, low grade fevers, Hgb=7.2 mg/dL, enlarged liver & alkaline phosphatase = 584 IU/dL. Chest radiograph is clear. He most likely has: a. Disseminated Mycobacterium marinum b. Disseminated Brucella melitensis c. Disseminated Nocardia brasiliensis d. Disseminated Mycobacterium avium-intracellulare

d. Disseminated Mycobacterium avium-intracellulare

You were consulted by a hand surgeon who biopsied one of the lesions depicted below. The patient had been treated with clindamycin without response. The culture from the biopsy is now growing Mycobacterium marinum. You should ask the patient about: A. An injury related to a salt water aquarium. B. If his occupation is a custodian. C. Exposure to hot springs. D. Both a & c.

D. Both a & c.

A kidney transplant patient is admitted to St. Luke’s with the radiographs showing a brain lesion and right lower lobe infiltrate. This is probably caused by infection by: A. Nocardia brasiliensis B. Mycobacterium tuberculosis C. Nocardia asteroides D. Streptococcus intermedius E. Pseudomonas aeruginosa

C. Nocardia asteroides

Which of the following is not a characteristic of the “Lady Windermere Syndrome”? A. Causative agent is within the Mycobacterium avium-intracellulare complex. B. Occurs in older women who smoked cigarettes & have underlying chronic obstructive lung disease. C. Radiographic appearance is nodular bronchiectasis. D. Recurrences are common with antimicrobial susceptible organisms.

B. Occurs in older women who smoked cigarettes & have underlying chronic obstructive lung disease.

You have been providing health care to an indigenous population of natives in Brazil. A patient comes in, shows you his hands and asks you what the problem is. He cannot smoke cigarettes without burning his hands, but does not feel it. He likely has: A. Diabetic peripheral neuropathy. B. Infection with Mycobacterium leprae. B. Actinomycetoma. D. Infection with Nocardia brasiliensis.

B. Infection with Mycobacterium leprae.

A patient with facies had a sural nerve biopsy which was stained with a Fite stain and revealed a bunch of acid-fast bacteria with no inflammatory cells. What does this patient have? A. Nocardia brasiliensis B. Mycobacterium marinum C. Tuberculoid leprosy D. Lepromatous leprosy

D. Lepromatous leprosy

This patient is an agricultural worker from Guatemala who fell and injured his left elbow several months ago. He now has this chronic, draining lesion. The gram stain chains of Gm (+) bacteria. The likely agent is? A. Mycobacterium marinum B. Mycobacterium fortuitum C. Nocardia asteroides D. Nocardia brasiliensis

D. Nocardia brasiliensis

A 56-year-old man developed swelling of his wrist flexor sheath. At surgery, material was removed that was described as “rice bodies”. The likely organism was: a. Mycobacterium leprae b. N. asteroides c. M. fortuitum d. S. pneumoniae

c. M. fortuitum

Which of the following is not true regarding the diagnosis of pulmonary infections due to the non-tuberculous mycobacteria, such as M. avium-intracellulare? A. Isolation of any number of colonies is always significant, as the NTM should not be in pulmonary secretions. B. There should be histological evidence of pulmonary infection. C. There should be repeated isolation of an organism from pulmonary specimens. D. There should be radiographic evidence of disease.

A. Isolation of any number of colonies is always significant, as the NTM should not be in pulmonary secretions.

"serpentine cording on culture"

M. Tuberculosis

How is M. tuberculosis differentiated from other mycobacteria?

-M. tuberculosis lacks pigment production; -Niacin (+); -Species-specific DNA probes are now used to differentiate the various species (GenProbe®).

2 essential features for its rapid spread of TB are:

-Crowded living conditions (favoring airborne transmission); -A population with little native resistance

What is the chance of reactivation of tuberculosis from its dormant form after primary TB has healed in a normal human?

-5% chance of progression within the first 2 years -5% chance of progression after 2 years -thus, 10% total chance of progression

TB infection results from inhalation of \_\_\_\_\_\_\_.

droplet nuclei

Describe the primary infection of TB.

1) M. Tuberculosis transimitted via droplet nuclei 2) droplets land in alveoli, and are phagocytosed by inactive macrophages 3) spread to lynphatics 4) activate T cells and increase TNF-a production 5) cell mediated immunity develops, macrophages activated to kill mycobacteria, granulomas are formed

What is a Ghon complex?

-A calcified mid-lung nodule + calcified hilar lymph node. -after 1' TB

When do you show a positive PPD?

6-8 weeks after infection by M. tuberculosis

"Simon focus in apex of the lung"

In children with TB, there is prominence of the \_\_\_\_\_\_\_\_\_, which may cause middle lobe collapse.

hilar nodes

What usually results in TB pleuritis?

Most commonly results from rupture of a subpleural caseous focus (Ghon complex), usually several months after a 1' infection:

What is Miliary TB?

-Miliary TB is disseminated disease that can occur during 1' infection or after late reactivation; -Seen in AIDS and other immunocompromised patients -Multiple organs are involved.

What is frequently the initial presentation of TB in children?

Meningeal/CNS tuberculosis

"infection of vertebral body"

TB = Pott's Disease

When can you get a false positive PPD?

mycobacteria other than TB & previous BCG vaccination.

When can you get a false negative PPD?

immunosuppressed individuals, patients on steroids, viral infections, overwhelming TB & malnutrition

What is the BCG vaccine?

-Live, attenuated vaccine derived from an M. bovis strain -May prevent disseminated disease, not pulmonary disease

How do we diagnose TB?

-Sputum smear (3 early morning sputums) -first morning voided midstream urine -Bactec culture

What are the chest X-ray residuals for a 1' TB infection?

-apical fibronodular scarring due to inflammation -dense calcified hilar lymph nodes -Ghon complex

What is a Simon's focus?

-seen in latent TB -apical fibronodular scarring due to inflammation after bacillemia

What is primary progressive TB?

-Results from failure of timely development of a sufficient immune response to limit bacillary growth Occurs in very young, elderly & immunodeficient

What is the reason behind the progressive nature of primary progressive TB?

-Tendency of apical caseous foci to liquefy; -Enormous # of bacilli in cavities; -Spread of this bacilli-rich material through the bronchial tree.

What is TB lymphadenitis (Scrofula)?

-most common extrapulmonary manifestation of 2' TB -results from hematogenous seeding of lymph nodes during 1' infection -Cervical lymph nodes usually involved

What are the organ systems that can be involved in 2' TB?

-Pulmonary TB (most common) -Pleural and pericardial infection -Lymph node infection (2nd most common) -Kidney -Skeletal (Pott's Disease) -Joints -CNS (granulomas in brain) -Miliary TB

When can Miliary TB occur?

-during 1' infection or after late reactivation

Meningeal TB is usually caused by rupture of a meningeal or subependymal tubercle into the \_\_\_\_\_\_\_\_\_\_\_\_space

subarachnoid

Meningeal involvement is usually most prominent at the \_\_\_\_\_\_\_\_\_of the brain

base

What is Pott's disease?

infection of the vertebral bodies, usually more than 1, by TB

What is the most common organ affected by Antituberculous drugs?

Liver

What is the usual 4 drug cocktail used to treat TB?

-Rifampin -Isoniazid -Pyrazinamide -Ethambutol

A Ghon complex consists of: A. An apical calcified granuloma. B. A subependymal granuloma. C. A calcified mid-lung nodule + calcified hilar lymph node. D. Apical fibronodular scarring + paratracheal calcified lymph node.

C. A calcified mid-lung nodule + calcified hilar lymph node.

A (+) PPD skin test indicates: A. Exposure to Mycobacterium tuberculosis. B. Infection due to Mycobacterium tuberculosis. C. Disease due to Mycobacterium tuberculosis. D. Development of an adequate humoral immune response to Mycobacterium tuberculosis.

B. Infection due to Mycobacterium tuberculosis.

A 65-year-old alcoholic man presented to the Emergency Room at Ben Taub General Hospital with an apical, cavitary pulmonary lesion. This likely represents: A. Reactivation tuberculosis. B. 1' tuberculous infection. C. Acute tuberculous infection. D. Primary progressive disease.

A. Reactivation tuberculosis.

Meningeal tuberculosis: A. Is frequently the initial clinical presentation of TB in young children. B. Is most prominent in the base of the brain. C. Is usually caused by rupture of a subependymal tubercle into the subarachnoid space. D. All of the above.

D. All of the above.

The Hunchback of Notre Dame likely suffered from: A. Pott’s disease. B. Poncet’s disease. C. Miliary tuberculosis. D. Meningeal tuberculosis.

A. Pott’s disease.

A 45-year-old RN, originally from India, has a PPD of 11 mm induration. She received BCG vaccination when she was 3-years-old. Your interpretation of her PPD is: A. It is a false (+) due to the BCG vaccination. B. It is likely a true positive and she deserves INH/pyridoxine preventive therapy for 9 months. C. It is not significant as she needs a 15 mm PPD to be positive. D. It can be ignored because her risk of TB disease is negligible due to the BCG vaccination.

B. It is likely a true positive and she deserves INH/pyridoxine preventive therapy for 9 months.

The optimal time to collect a urine specimen for microscopy & TB culture from this patient is: A. Immediately after placement of a Foley catheter. B. After the patient spikes a fever. C. In the early am during the first morning void. D. In the evening just before going to bed.

C. In the early am during the first morning void.

On physical examination, this recent immigrant from Vietnam has dullness to percussion & absent breath sounds in the left lung base. Xray shows pleural infiltrate. Based on your suspicions of the etiology, the highest yield diagnostic test would be: A. Expectorated sputum B. Pleural biopsy C. Pleural fluid D. Quantiferon gold test

B. Pleural biopsy

This giant cervical Lymph node likely resulted due to: A. Spread from laryngeal TB. B. Contiguous spread from an apical pulmonary cavity. C. A result of hematogenous seeding during 1o TB infection. D. A manifestation of miliary TB

C. A result of hematogenous seeding during 1o TB infection.

You are working in the TB lab at the VA hospital. You have done a Kinyoun stain of a sputum culture from a patient and see serpentine cording. You call the physicians caring for the patient and tell them their patient likely has: A. Nocardia asteroides B. M. avium-intracellulare C. M. marinum D. M. tuberculosis

D. M. tuberculosis

14. The patient with the radiographs showing military TB most likely: A. Is very young or very old. B. Has poor nutritional status. C. Is immunocompromised. D. May have all of the above.

D. May have all of the above.

"leonine facies"

Leprosy -Lepromatous

What type of patient is more at risk for infection due to Nocardia?

immunocompromised patients

What will be seen in a smear containing Nocardia?

-G. (+) beaded, branching filaments

Mycobacteria & Nocardia Flashcards

(81 cards)