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IMD > PBL 11: George Salang -Bacterial infection > Flashcards

PBL 11: George Salang -Bacterial infection Flashcards

1
Q

List the Common Causes of Fever

A
  1. TB and abscesses are among the most common
  2. Infection (Viral, Parasitic, Bacterial)
  3. Malignancies
  4. Drugs
  5. Foreign Bodies
  6. Allergies (circulating antigen antibody complexes)
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2
Q

What are the characteristics of mycobacterium?

A
  1. Faculative aerobic
  2. Faculative intracellular
  3. Rod Shaped
  4. Weakly gram +ve
  5. Contain a waxy cell wall composed of mycolic acid
  6. Mycolic acid linked to peptidoglycan -very selectively permeable
  7. acid fast
  8. Lipoarabinomanan (LAM) in cell wall and contributes to host-pathogen interaction/evasion of immune response
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3
Q

Give an outlike of the basic clinical course and progression of TB

A
  1. Primary Infection
  2. Primary complex (localized caseation) >>
  3. Latent Lesions or Progressive Primary TB > Massive Hematogenous DIssemination > Miliary TB
  4. Latent > Secondary Tuberculosis (reactivation or reinfection) > Progressive secondary TB > Massive Hematogenous dissemination > Miliary TB
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4
Q

What is the clinical course of TB?

A

Someone sneezes → Aerosolized droplets → Colonize middle/lower respiratory zone → start to replicate → initia lesion increases in size (Fever, Cough, Night Sweats, Weight Loss, Productive Cough) → More replication (Pleural effusion) → Enlarged lymph nodes → Disseminated TB

Hepatic TB

Kidney TB

Done Barrow TB

Spleen TB

Potts Disease

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5
Q

What mechanisms do Mycobacteria use to avoid host defences?

A
  1. Slow generation time
  2. Catalase Peroxidase + Lipoarabinomanan (LAM) on MBT lowers phagolysozyme formation
  3. LAM + Catalase Peroxidase increases resistance to ROS
  4. Cord factor + sulphatides are cytotoxic
  5. Mycolic acid promotes granuloma formation
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6
Q

What is the rationale for different investigations when a patient presents in the clinic with fever and trouble breathing?

A
  1. Lung percussion and auscultation -crepitation, depressed breath sounds, pleural rubbing, decreased resonance on percussion, deepening, hoarse, harsh void
  2. Chest x-ray -granulomas, consolidation, cavity, midline shift, pleural thickening
  3. Sputum Sample -gram stain, ziehl neelsen stain, culture, MCR, PCR
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7
Q

What is a Mantoux Test used for?

A

Tests the cell mediated hypersensitivity response after the intra-dermal injection of 0.1ml of tuberculin. Test is examined 48 to 72 hours later, with positivity determined on size of reaction

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8
Q

What are some limitations of the Mantoux Test?

A

Low Specificity and Sensitivity

False negatives: HIV, Individuals with overwhelming TB

False Positives: presence of other mycobacterium, BCG vaccine, cannot differentiate between active and latent TB

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9
Q

What are direct methods of infection spread?

A
  1. Coughing, getting coughes on, sneezing, saliva, semen, direct blood contact, aerosols
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10
Q

What are indirect methods of infection spread?

A

Touching infected surface, nosocomial infections

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11
Q

What are the 4 antibiotics used in short course therapy for MTB?

A

Isoniazid

Rifampin

Ethambutol

Pyrazinamide

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12
Q

Which 2 antibiotics are continued after 2 months (long-term)

A

Isoniazid and Rifampin

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13
Q

Isoniazid

A

Inhibits/degrades mycolic acid synthesis required for cell wall production

Bacteriostatic and bacteriocidal

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14
Q

Rifampin

A

Inhibits DNA dependant RNA polymerase

Bacteriostatic

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15
Q

Ethambutol

A

Inhibits Cell Wall Production

Bacteriostatic

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16
Q

Pyrazinamide

A

Improves macrophage phagolysosome function -mechanism unknown

Bacteriocidal

17
Q

Why is pyroxidine also given during MTB therapy?

A

Pyroxidine is a vitamin B6 supplement which is required because Isioiazid competed with Vitamin B6 in synaptic NT synthesis. This may lead to neuropathy.

18
Q

What is the definition of Multi-Druig Resistant TB?

A
  1. Resistant to isoniazid and rifampicin
  2. Intense treatment with a range of antibiotics for 8 months > 20 months

IMD (5 decks)

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