TUBERCULOSIS Flashcards
what is tuberculosis, TB?
a bacterial infection affecting the lungs.
how is TB spread?
spread from person to person through inhaling tiny droplets of coughs and sneezes of a infected person.
what are the 4 types of mycobacterium that cause TB collectively known as?
collectively known as Mycobacterium Tuberculosis Complex (Mtb).
What are the 4 types of mycobacterium that cause TB?
1) mycobacterium tuberculosis
2) mycobacterium bovis
3) mycobacterium africanum
4) mycobacterium microti
what are the 3 different types of tuberculosis?
1) primary TB
2) latent TB
3) re-activation TB
4) Pulmonary TB
5) extra-pulmonary TB
6) Miliary TB
7) Bovine TB
8) lymph node TB
9) GI TB
10) TB of bone and spine
what is primary TB?
describes the FIRST INFECTION with Mtb
what is latent TB?
= dormant M. tuberculosis infection that can reactivate decades after initial infection.
What role does the immune system have in TB?
- people who are first infected with M. tuberculosis
- the immune system contains the infection and the patient develops a cell mediated immune memory to the bacteria.
what is reactivation TB?
the majority of TB cases are due to reactivation of latent infections.
- the initial contact occurred many years or decades earlier.
what is pulmonary TB?
= active tuberculosis affecting the lungs
what are the symptoms of pulmonary TB?
- productive cough
- occasionally haemoptysis
Systemic symptoms;
- weight loss
- fever
- sweats
If there is laryngeal involvement;
- hoarse voice
- severe cough
If disease involves pleura;
- pleuritic chest pain
what is extra pulmonary TB?
= active tuberculosis affecting other organs
what is miliary TB?
= active tuberculosis spread by the blood throughout the body
What is bovine TB?
How is M. Bovis acquired?
What do people with M. Bovis presents with?
How is M. Bovis treated?
= tuberculosis caused by M. Bovis
Acquired form;
- ingesting infected cows’ milk
- farmers working with infected cows for over 3 years
- abattoir workers (manage slaughtered animals)
They present with;
- similar symptoms to ordinary TB in the chest
- but extra pulmonary sites of infection are common
- immunosuppression is a risk factor
Treatment;
- isoniazid, rifampicin, ethambutol
- resistance to pyrazinamide is common
what is lymph node TB?
= tuberculosis that affects the lymph nodes
what does lymph node TB do to the lymph nodes?
- causes SWELLING of lymph nodes
- lymph nodes are firm, non-tender enlargement of cervical or supraclavicular node.
what is GI TB?
= tuberculosis or infection that affects the peritoneum, hollow or solid abdominal organs and abdominal lymphatics
what are the risk factors for getting TB?
1) recent immigration
2) malnutrition
3) overcrowding or homelessness
4) immune defects
5) smoking & alcohol
what are the symptoms of TB?
- coughing that lasts a prolonged period of time
- haemoptysis
- chest pain, or pain when breathing or coughing
- unintentional weight loss
- fatigue
- fever
- night sweats
- chills
describe some different in features between latent and active tuberculosis infections.
LATENT;
- bacilli present in Ghon focus
- sputum smear & culture negative
- Chest X-ray normal
- asymptomatic
- not infectious to others
ACTIVE;
- bacilli present in tissues or secretions
- sputum commonly smears & culture positive
- Chest X-ray shows signs of consolidation
- symptomatic;
= night sweats
= fevers
= weight loss
= cough common
- infectious to others if bacilli detectable in sputum.
what are 3 things that allow you to diagnose TB?
1) stains
2) cultures
3) nucleic acid amplification
what 2 stains could be used to diagnose TB?
1) Auramine-rhodamine staining
2) Ziehl Neelson (ZN)
Out of these two stains;
- Auramine rhodamine and
- Ziehl Neelson
Which one is most used and why?
Auramine rhodamine is most commonly used.
Because;
- it is more sensitive than ziehl Nelson (ZN)
- but it is less specific
how do you treat TB?
- 6 months of treatment
= Two months of 4 drugs
= Four months of 2 drugs
What are the 4 drugs involved in the two months of treatment?
What 4 letter word helps you remember them?
1) rifampicin
2) isoniazid
3) Pyrazinamide
4) Ethambutol
= RIPE
What are the 2 drugs involved in the four months of treatment?
1) Rifampicin
2) isoniazid
when treating tuberculosis that affects the CNS, what is the recommended duration for treatment?
recommended duration is AT LEAST 12months
In what sort of TB’s should corticosteroids be used and why?
should be used in CNS & pericardial diseases
- it reduces long term complications.
what effect does Rifampicin have on the liver?
- induces liver enzymes, which may be elevated in the serum of patients.
- induction of liver enzymes means that naturally accompanying drug treatments may be less effective.
what effect does rifampicin have on the colour of body secretions and body fluids?
- it stains the body secretions pink
- there is a change in colour of their urine, tears and sweat
is oral contraception still effective when taking rifampicin?
- NO.
- so alternative birth control methods should be used.
what side effects of isoniazid have?
- it has very few side effects.
But examples are;
- can cause allergic reactions e.g. skin rashes & fevers
- at high doses it may produce a polyneuropathy
= this is rare when the normal dose is given
- it can also give rise to hepatitis in 1% of cases
as polyneuropathy is an unwanted side effect of isoniazid, what is a polyneuropathy and how is it caused?
Its is a degeneration of peripheral nerves the spread towards the centre of the body.
Caused due to;
= a B6 deficiency, as isoniazid interacts with pyridoxal phosphate
what are the unwanted side effects of pyrazinamide?
1) hepatic toxicity
2) reduces renal excretion of rate
3) may precipitate hyperuricaemic gout
what side effect does ethambutol produce?
- can cause a dose related optic retrobulbar neuritis
Presents as;
- colour blindness for green
- reduction in visual acuity
- central scotoma
= usually reverses provided the drug is stopped
how does drug resistance arise?
1) incomplete drug treatment
2) incorrect drug treatment
how can drug resistance be spread?
- it can be spread from person to person
what are the 3 types of drug resistance that can occur?
1) mono-resistance
2) multi-drug resistance
3) extensive drug resistance
what does mono-resistance mean?
and what drug is it most commonly resistant to?
= means it is resistant to a SINGLE drug
- most commonly resistance to isoniazid
what drugs are multi-drug resistant dugs resistant to?
1) rifampicin
2) isoniazid
what drugs are extensive drugs resistance drugs resistant to?
1) rifampicin
2) isoniazid
3) quinolone
4) at least one INJECTABLE AGENT, such as - amikacin, capreomycin or kanamycin
what is the link between TB and HIV?
- there has been an increase in TB seen over the years in association with incidence of HIV infection
what specific areas have the incidence of TB increased in correlation with HIV?
- africa
- india
- parts of Eastern Europe & Russia
why is there issues with treating TB & HIV?
- incidence of drug interactions & intolerability
- increased risk of treatment toxicity
- higher incidence of drug resistance
what is chronic kidney disease (CKD) a risk factor of?
chronic kidney disease is a risk factor for reactivation of latent TB infections due to relative immune paresis.
how are latent TB infections (LTBI) diagnosed?
- diagnosed by demonstrating immune memory to mycobacterial proteins
what 2 tests ensure the diagnosis of LTBI?
1) tuberculin skin test
2) interferon gamma release assay
how is a positive tuberculin skin test result indicated?
- indicated by a delayed hypersensitivity reaction event 48-72hours after the intra-dermal injection of purified protein derivative (PPD).
what type of patients are false negative tuberculin skin tests common in?
patients with immunosuppression due to HIV infection.
how do false positive results occur?
due to cross-reactivity with non-tuberculosis mycobacteria & BCG vaccination.
what do interferon gamma release assays detect?
they detect T cells secretion of IFN-gamma following exposure to M. tuberculosis specific antigens
what vaccine can be given to help TB?
BCG vaccine
what sort of vaccine is the BCG vaccine?
a live attenuated vaccine derived from M. Bovis that has lost its virulence
