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Year 3: Medicine Block CARDIORESPIRATORY year 5 > Tuberculosis > Flashcards

Tuberculosis Flashcards

1
Q

Which countries have more prevalence of tuberculosis?

A
  • Majority of cases are seen in Africa and Asia.
  • Co-infection with HIV is a problem, not only because of the economic health burden but also growing incidence of multi and extremely drug resistant strains and high mortality of coexistent disease
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2
Q

What are risk factors for Tuberculosis?

A
  • Contact with high risk groups from high incidence countries -Immune deficiency
  • Lifestyle factors
  • Genetic susceptibility
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3
Q

What causes Tuberculosis?

A
  • Caused by mycobacterial species.
  • They are obligate aerobes and facultative intracellular pathogen usually infecting mononuclear phagocytes.
  • Slow-growing with generation time of 12-18 hours.
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4
Q

How are Mycobacterial species stained?

A
  • Due to high lipid content in cell wall, relatively impermeable and stain only weakly with gram stain.
  • When stained with dye combined with pnenol and washed with acidic organic solvents, they resit decolorization so termed acid-fast bacilli
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5
Q

What are examples of mycobacterial species?

A
  • Mycobacterium Tuberculosis
  • Mycobacterium Bovis
  • Mycobacterium Africanum
  • Mycobacterium Microti
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6
Q

How is TB spread?

A
  • TB is an airborne infection spread through respiratory droplets.
    • Not all who inhale the infection develop active disease.
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7
Q

How does primary TB develop?

A
  • 1st infection with Mycobacterium Tuberculosis.
  • Alveolar macrophages ingest bacteria which proliferate in macrophages
  • Release of neutrophil chemoattractants and cytokines resulting in inflammatory cel infiltrate aching lung and draining hilarity lymph nodes
  • Macrophages present antigens to T lymphocytes to develop cellular immune response
  • Delayed hypersensitivity type reaction resulting in tissue necrosis and formation of granulomas
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8
Q

What is contained in TB granulomas?

A
  • Granulomas consists of central necrotic material called caseation, surround by epithelioid cells and Langhans giants cells with multiple nuclei. Both cells driven by macrophages.
  • Lymphocytes are present and varying degree of fibrosis
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9
Q

What happens to caseated areas in TB?

A
  • Caseated areas heal completely and many become calcified.
  • Calcified nodules contain bacteria which are contained by immune system and are capable of lying dormant for years.
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10
Q

What is the name of the initial focus in the patogenesis of TB?

A

-The initial focus is termed Ghon’s Focus.

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11
Q

How does the focus present on X-Ray?

A

Chest X-ray

  • Ghon focus is evident as small, calcified nodule often within upper part of lower lobes or lower parts of upper lobes.
  • Focus can also develop within trigonal draining lymph node (Primary complex of Ranke)
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12
Q

What is latent TB?

A

Immune system contains infection for most people who are infected with Mycobacterium species so patient develops cell-mediated immune memory to bacteria termed latent TB.

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13
Q

When does reactivation TB occur?

A
  • Reactivation of latent infection gives rise to majority of TB cases.
  • In patient with HIV infection, new cured TB infection also common
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14
Q

What can lead to reactivation of TB?

A

Factors implicated are:

  • Diabetes mellitus
  • End-Stage CKD
  • HIV co-infection
  • Immunosuppressant therapy
  • Ageing
  • Malnutrition
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15
Q

What are the symptoms of pulmonary TB?

A
  • Productive cough
  • Haemoptysis
  • Weight loss
  • Fevers
  • Sweats (commonly end of day and through night)
  • Hoarse voice and Severe cough found if laryngeal involvement
  • Pleuritic chest if the disease involves pleura
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16
Q

What are the symptoms of lymph nodes TB?

A

Usually present as

  • Firm
  • Non-tender enlargemet of Cervical or Suproclavicular node

Extrathoracic nodes more commonly involved than intrathoracic or mediastinal

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17
Q

What are the symptoms of Miliary TB?

A
  • Systemic upset is the rule with respiratory system in majority
  • Liver and Splenic micro abscess with deranged liver enzyme or cholestasis and gastrointestinal symptoms
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18
Q

What are the symptoms of TB of the heart?

A

Pericarditis

  • Chronic low grade fever particularly in evening
  • Dyspnoea
  • Malaise
  • Night sweats
  • Weight loss
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19
Q

What are the symptoms of Bone TB?

A
  • Local Pain
  • Swelling
  • Systemic symptoms of:
    • Malaise
    • Fever
    • Night sweats
20
Q

What are the symptoms of Gastrointestinal TB?

A
  • Abdominal pain
  • Weight loss
  • Anaemia
  • Fever with night sweats
  • Obstruction
  • Right Iliac Fossa Pain, Palpable mass.
  • Ileocecal area most commonly affected
  • Third of patients present acutely with intestinal obstruction or generalized peritonitis
21
Q

How does Miliary TB spread?

A

-Spread primarily through the Pulmonary Venous System

22
Q

What is the name given to TB that involves the spine?

A
  • Spinal involvement is called Pott’s Disease with veterbral collapse and acute angulation of spine.
  • Later an abscess form and tracks along tissue planes and discharge at a point far from affected vertebrae.
23
Q

How long is the drug regimen extended in TB of the Bone?

A

Drug regimen extended to 9 months as a result of this

24
Q

How is TB investigated microbiologically?

A
  • Stains
  • Culture
  • Nucleic Acid Amplification
25
Q

What are the different types of stains?

A
  • Auramine-Rhodamine more sensitive
  • Ziehl-Neelsen
26
Q

What are investigations undertaken for Pulmonary TB?

A
  • Smear and culture of 3 samples of the selection of sputum
  • Induced sputum
  • Bronchoalveolar lavage
  • Aspiration of pleural fluid and pleural biopsy
  • Gastric Aspirate
  • Nasoendoscopic or bornchoscopic examination.
  • Radiology
    • Consolidation with or without cavitation
    • Pleural effusion or thickening or widening of mediastinum
  • If non-productive cough; pulmonary TB suspected consider bronchoscopy
  • Consider CT chest if pulmonary TB suspected but clinical features/ CXR not typical
27
Q

What are investigations for Miliary TB?

A
  • Blood cultures
  • Bronchoalveolar lavage fluid (usually smear-negative but culture positive)
  • Lumbar puncture should be performed in all cases unless contraindication. It is to assess for CNS involvement
  • Sampling of other involved organs often necessary
28
Q

What are investigations for Miliary TB?

A

MRI before LP if miliary TB suspected.

Lumbar puncture if no contraindication. Shows:

  • High CSF protein
  • Lower than half the blood glucose
  • CSF lymphocytosis
29
Q

What are investigations for Lymph Node TB?

A
  • Samples should be sent for histopathological examination as well as culture and smear
  • Fine needle aspiration or biopsy of involved lymph node usually under radiological guidance
  • Mediastinal nodal sampling
30
Q

How is TB acutely managed?

A
  • ABCDE approach & aim to culture whenever possible
  • Admit to a side room& start infection control measures
  • If productive cough: x3 sputum samples for Alcohol Acid Fast Bacilli & TB culture
  • Routine bloods
  • If diagnosis between pneumonia and TB not clear: start antibiotics for pneumonia whilst investigating possibility of TB.
  • If patient critically unwell and high likelihood of TB then start anti-TB therapy AFTER sputum samples sent.
  • Notify case to TB nurse specialists
  • TB culture can take 6-8 weeks. So, treatment is often started before a culture confirmed diagnosis can be made. In some cases, positive culture is not obtained and treatment depends on a strong clinical suspicion
31
Q

What is Anti-TB therapy?

A

-6 months of treatment for patients who are fully sensitive to TB medications -2 months of Rifamipicin, Ethambutol, Pyrazinamide, Isoniazid with 4 further months of Rifampicin and Isoniazid

32
Q

How is CNS TB treated?

A

CNS TB

  • 2 months of Rifamipicin, Isoniazid, Pyrazinamide, Ethambutol,
  • 10 further months of Rifampicin and Isoniazid plus
  • Prednisolone weaning over 2-4 weeks
33
Q

How is Latent TB treated prophylactically?

A
  • 3 months of Rifampicin and Isoniazid or
  • 3 months of Isoniazid
34
Q

What are considerations before commencing TB therapeutics?

A
  • Check baseline LFTs and monitor closely
  • Check visual acuity before giving Ethambutol
  • Compliance crucial and Directly observed therapy sometimes use
  • Provide leaflets on treatment
  • Pyridoxine given as prophylaxis against peripheral neuropathy
35
Q

What is Directly Observed Therapy?

A
  • Defined as treatment supervised by healthcare professional or family member where the person is observed swallowing their medication
  • Employed to achieve treatment completion rates
  • Criteria for DOT
    • History of mental illness
    • History of non-adherence to TB therapy in past or during current treatment course
    • Street or shelter dwelling homelessness
    • Multi drug resistant TB
36
Q

What are side effects of Rifampicin?

A
  • Liver enzymes elevated in many patient and if it is 3 times elevated than the normal level then the drug should be stopped due to risk of Hepatitis
  • Rashes
  • Febrile reaction
  • Thrombocytopenia reported
  • Stains body secretion pink
  • Alternative birth control methods should be used as interaction with OCP
  • Warfarin drug interaction
37
Q

What are side effects of Isoniazid?

A
  • Polyneuropathy due to B6 deficiency due to interaction with pyridoxal phosphate. Extremely rare side effect
    • Pyridoxine 10mg daily to prevent this
  • Allergic reaction such as skin rash and fever
  • Hepatitis is less than 1% cases and may be fatal
  • Rashes and psychosis possible
38
Q

What are side effects of Pyrazinamide?

A
  • Hepatic toxicity
  • Hyperuricaemic Gout
    • Reduced renal excretion of urate and may precipitate
  • Arthralgia
  • Rashes and vomiting
39
Q

What are side effects of Ethambutol?

A
  • Dose-related optic retrobulbar neuritis presenting with colour blindness for green, reduction in visual acuity and central scotoma.
    • Reversed provided drug is stopped when symptoms develop.
    • Patients should be seen by ophthalmologist prior to treatment and doses of 15mg/kg used.
40
Q

What are side effects of Streptomycin?

A
  • Irreversible damage to vestibular nerve and more likely to occur in elderly and those in renal impairment
  • Allergic reactions to Streptomycin more common than those in other drugs
  • Only used in patient that are very ill, multidrug resistant TB and not responding adequately to therapy
41
Q

How does CKD affect a patient as a risk factor for TB?

A
  • Risk factor for reactivation of latent TB infection due to relative immune paresis
  • Patients due to undergo renal transplantation screened for latent TB infection and given chemoprophylaxis if necessary
42
Q

How is Latent TB identified?

A
  • Tuberculin Skin Test – positive result indicated
  • Interferon-gamma release assays – does not differentiate between active and latent infection.
43
Q

Who should be treated for Latent TB?

A
  • People aged ≤35 years with positive TST or IGRA
  • Healthcare workers with positive TST or IGRA
  • Patients commencing anti-TNF therapy with positive IGRA
  • HIV-positive people with positive IGRA
  • People with evidence of previous TB on Chest X-ray and inadequate treatment
44
Q

How are TB cases found?

A
  • Contact Tracing: carried out after new case of TB and involves identifying close contacts
  • Screening of healthcare workers and new entrants
  • Street-homeless or Hostel dwellers
  • Immunocompromised People
45
Q

What is the Vaccine for TB?

A

BCG Vaccination

  • Live attenuated M.Bovis but reduced efficacy and not cost effective.
  • Shown to reduce disseminated and CNS TB in babes and children
46
Q

Describe differences between latent TB and Active TB?

A

Latent infection

  • Bacilli present in Ghon focus
  • Sputum smear- and culture-negative
  • Tuberculin skin test usually positive
  • Chest X-ray normal (small calcified Ghon focus frequently visible)
  • Asymptomatic and not infectious to others

Active disease

  • Bacilli present in tissues or secretions
  • Sputum commonly smear- and culture-positive in pulmonary disease
  • MTb can usually be cultured from infected tissue -
  • Tuberculin skin test usually positive (and can ulcerate)
  • Chest X-ray shows signs of consolidation/cavitation/effusion in pulmonary disease
  • Symptomatic – night sweats, fevers, weight loss and cough common
  • Infectious to others if bacilli detectable in sputum

Year 3: Medicine Block CARDIORESPIRATORY year 5 (28 decks)

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