1. Who is at risk of developing slow-growing Non-tuberculous mycobacteria? 2. What are the different types of slow growing NTM and where are they found?

1. Immunocompetent and immunocompromised (at risk of disseminated infection) 2. Mycobacterium avium intracellulare/ M.avium complex M.marinum - swimming pool granuloma M.ulcerans - Skin lesions e.g. Bairnsdale ulcer, Buruli ulcer - causing a chronic progressive painless ulcer

1. What are the different 'rapid-growing' NTM? 2. What do they cause?

1. M.abscessus M.chelonae M.fortuitum 2. Skin and soft tissue infections In hospital settings, isolated BCs - vascular catheters and other devices

1. Describe post-primary TB 2. What are the risk factors for reactivation of TB?

1. Post-primary TB: reactivation or exogenous re-infection \> 5 years after primary infection 5-10% risk per lifetime 2. Risk factors for reactivation Immunosuppression Chronic alcohol excess Malnutrition Ageing Clinical presentation - pulmonary or extra-pulmonary

Mycobacterial disease Flashcards by Harriet Powell

Describe where non-tuberculous mycobacteria can be found, and how it spreads

Non-tuberculous mycobacteria is environmental and atypical - found in lakes/water and soil
Ubiquitous in nature
Varying spectrum of pathogenicity
No person-to-person transmission
Commonly resistant to classical anti-TB prescriptions
May be founf colonizing

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Who is at risk of developing slow-growing Non-tuberculous mycobacteria?
What are the different types of slow growing NTM and where are they found?

Immunocompetent and immunocompromised (at risk of disseminated infection)

Mycobacterium avium intracellulare/ M.avium complex
M.marinum - swimming pool granuloma
M.ulcerans - Skin lesions e.g. Bairnsdale ulcer, Buruli ulcer - causing a chronic progressive painless ulcer

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What are the different ‘rapid-growing’ NTM?
What do they cause?

M.abscessus
M.chelonae
M.fortuitum

Skin and soft tissue infections
In hospital settings, isolated BCs - vascular catheters and other devices

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Describe the diagnosis of Non-tuberculous mycobacteria from the 2007 American thoracic society guidelines

Clinical - pulmonary symptoms, nodular/cavitary opacities, multifocal bronchiectasis with multiple small nodules
Exclusion of other diagnoses
Microbiologic:
- Positive culture >1 sputum samples
- OR +ve BAL
- OR +ve biopsy with granulomata

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What is the treatment of Non-tuberculous mycobacteria?

Susceptibility testing results may not reflect clinical usefulness
MAI:
- Clarithryomycin/azithromycin
- Rifampicin
- Ethamnutol
- +/- Amikacin/streptomycin
Rapid-growing NTM
- Based on susceptibility testing, usually macrolide-based

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What are the two types of mycobacterium leprae?

Paucibacillary tuberculoid
Multibacillary lepromatous

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Describe the epidemiology of mycobacterium tuberculosis

Multi-system disease
Common worldwide
- 2nd most common cause of death by infectious agent
- 2 million deaths each year
Increasing prevalence since 1980s
- Most common opportunistic infection in HIV
- Immigration
9000 cases reported per annum in UK

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What is the transmission of TB?

Droplet nuclei/airborne
- <10um particles
- Suspended in air
- Reach lower airway macrophages
Infectious dose 1-10 bacilli
3000 infectious nuclei
- cough
- talking for 5 minutes
Air remains infectious for 30 minutes

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How can TB be prevented?

Detection of cases
Treatment of TB in a timely manner
Prevention of transmission
- PPE
- Negative pressure isolation
Optimisation of susceptible contacts
- Address risk factors
- Vaccination
  - Bacille Calmette-Guerin (BCG): Live attenuated M.bovis strain
  - Given to babies in high prevalence communities (only since 2005)
  - 70-80% effectiveness in preventing severe childhood TB
  - Protection wanes
  - Little evidence in adults

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What is the natural history of pulmonaryTB?

Primary TB
- Usually asymptomatic
- Ghon focus/complex
- Limited by CMI
- Rare allergic reactions include EN
- Occassionally disseminated/miliary
Latent TB
Reactivation

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Describe post-primary TB
What are the risk factors for reactivation of TB?

Post-primary TB:

reactivation or exogenous re-infection
> 5 years after primary infection
5-10% risk per lifetime

Risk factors for reactivation

Immunosuppression
Chronic alcohol excess
Malnutrition
Ageing

Clinical presentation - pulmonary or extra-pulmonary

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Describe the radilogical features of pulmonary TB

Caseating granulomata
- Lung parenchyma
- Mediastinal Lymph nodes
Commonly upper lobe

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Describe what can develop in people with Extra-pulmonary TB

Lymphadenitis
- AKA scrofula
- Cervical lymph nodes most commonly
- Abscesses and sinuses
Gastrointestinal
- Swallowing of tubercules
Peritoneal
- Ascitic or adhesive
Genitiurinary
- Slow progression to renal disease
- Subsequent spreading to lower urinary tract
Bone and joint
- Haematogenous spread
- Spinal TB most common
- Pott’s disease
Miliary TB:
- Millet seeds on CXR
- Progressive disseminated haematogenous TB
- Increasing due to HIV
Tuberculous meningitis

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What does this image show?

Millet seeds, a signs of Miliary TB

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What is spinal TB known as?

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Pott’s disease

Describe the demographics and risk factors for TB

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Non-UK born/recent migrants
- south asia 54.8%
- sub-saharan africa 29.5%
HIV or other immunocompromise
Homeless
Drug users, prison
Close contacts
Young adults

What is the presentation of TB?

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Fever
Weight loss 74%
Night sweats 55%
Pulmonary symptoms
- cough 80%
- haemoptysis 6-37%
Malaise 68%
Anorexia

What are important questions to ask for someone who you suspect has TB?

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Ethnicity
Recent arrival or travel
Contacts with TB
BCG vaccination
Non-specific examination findings

What investigations should be performed in suscpected TB?

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CXR and other radiology
Spuum x3 - induced sputum
Bronchoscopy
Biopsies
EMU

stain for AAFBs ‘smear’

culture

NAAT

Histology

Tuberculin skin test

IGRAs

What does the image show?

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Mediastinal lymph node

Describe a smear for TB

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Uses sputum
- 60% sensitivity
- Increases with more samples
Gastric aspirates in kids
Other specimens centrifuged
Rapid
Operator dependent

Summarise different bacteriological examinations for TB

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Describe the use of cultures for diagnosing TB

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Culture is gold standard
Solid and liquid culture systems
Takes up to 6 weeks - less with modern automated systems

What do tuberculin skin tests show?

* Tuberculin skin test shows previous exposure to mycobacteria * 2 units tuberculin * Delayed type hypersensitivity reaction (type 4) * Cross-reacts with BCG * Poor sensitivity * HIV, age, immunosuppressants * Overwhelming TB

Describe the use of interferon gamma release assays (IGRAs)

* Detection of antigen-specific IFN-gamma production * ELISpot * Quantiferon * No cross reaction with BCG * Cannot distinguish latent and active TB * Similar issues with sensitivity and specificity

What are the first line medications for TB?

* Rifampicin * Isoniazid * Pyrazinamide * Ethambutol RIPE

What are the second line medications for TB?

* Quinolones (moxifloxacin) * Injectables - capreomycin, kanamycin, amikacin * Ethionamide/prothioamide * Cycloserine * PAS * Linezolid * Clofazamine

The treatment for TB is RIPE, a multi-drug therapy. Describe the side effects of each of the antibiotics

* Rifampicin * Raised transaminases and induces cytochrome P450 * Orange secretions * Isoniazid * Peripheral neuropathy * Hepatotoxicity * Pyrazinamide * Hepatotoxicity * Ethambutol * Visual disturbance

Describe the duration of treatment for TB

* 3 or 4 drugs of RIPE for 2/12 * Then Rifampicin and Isonazid 4/12 * 10/12 if CNS TB * Cure rate 90%

Describe Multidrug resistance TB * What is it against? * What has caused it?

* Multidrug resistance TB - resistant to rifampicin and isonazid * Extremely drug resistant TB * Also resistant to fluoroquinolones and at least 1 injectable * Spontaneous mutation + inadequate treatment * Liklihood increased * Previous TB prescription * HIV positive * Known contact of multi-drug resistant TB * Failure to respond to conventional Rx * \> 4 months smear +\>5 months culture +ve * 4/5 drug regimen, longer duration * Quinolones, aminoglycosides, PAS, cycloserine and ethionamide

Describe the following challenges with having TB and HIV when it comes to diagnosis of TB: 1. Clinical history 2. Chest X ray 3. Smear microscopy and culture 4. Tuberculin skin test 5. Sensitivity of interferon gamma release assays for active tuberculosis

1. Clinical history * Less likely to be classical * Symptoms and signs are often absent in population with low CD4 count 2. Chest X-ray * More likely extrapulmonary * X-ray changes variable 3. Smear microscopy and culture * Less sensitive 4. Tuberculin skin test * More likely to be negative 5. Sensitivity of IGRAs for active TB * Quantiferon - reduced * T SPOT - reduced

What are the challenges in TB and HIV when it comes to treatment?

* Timing of treatment initiation * Drug interactions * Overlapping toxicity * Duration of treatment - adherence * Health care resources

Name two novel diagnostic tests

* IGRAs - interferon gamma release assays * NAATs - Nucleic acid amplification tests

Mycobacterial disease Flashcards

(34 cards)