M103 T4 L12 Flashcards
How is TB spread?
by airborne droplets
when it is inhaled, it is deposited in terminal airspaces
How does a patient develop an active primary TB infection?
when the TB bacteria transported to the regional lymph node start to multiply inside the macrophage endosome
How does a patient develop an latent TB infection?
when the TB bacteria transported to the regional lymph node lie dormant inside the macrophage endosome
If a patient with a latent TB infection is immunocompetent, what is the chance of the bacteria reactivating?
15%
If a patient with a latent TB infection is immunocompetent, what is the chance of the bacteria reactivating within the first five years of the primary infection?
half of the people that are going to reactivate it will activated within the first five years.
Is TB bacteria aerobic or not?
aerobic
How often do TB bacteria divide?
16 - 20 hours
slowly
Does TB bacteria have a cell wall and a cell membrane?
has a cell wall
doesn’t have a PPLPD cell membrane
Does TB bacteria respond to Gram stains and why?
no bc it doesn’t have a PPLPD cell membrane
How is TB bacteria stained?
with acid - it is an acid fast bacilli
it retains stains after treatment with acids
What type of necrosis is affiliated with TB?
caseation
Where are acid fast bacilli found in TB bacteria when looking down a microscope?
in granulomas
Where are acid fast bacilli found in TB bacteria when looking down a microscope?
in granulomas
Who are particularly at risk of transmitting TB to others?
people who are the close contacts of infectious cases (smear +)
people who have contact with high risk groups
people who are immunedeficient
people who have high risk lifestyle factors
What are two types of high risk groups for TB?
High incidence country
Frequent travel to high incidence areas
What conditions would compromise the immunocompetency of pneumonia patients?
HIV Steroids Chemotherapy and biologics Nutritional deficiency (lack of vit D) Diabetes End stage renal failure
people who have high risk lifestyle factors
Drug/alcohol misuse
Homelessness/hostels/overcrowding
Prison inmates
Genetic susceptibility (twin studies of gene polymorphisms)
Which vitamin is tested for in pneumonia?
vitamin D
How is active TB diagnosed?
the infected area is identified
the organism is isolated
info regarding susceptibility to antibacterials is obtained
How is latent TB diagnosed?
the immune response to TB proteins or TB-specific antigens is identified
What was the most common type of latent screening test?
The tuberculin skin test (Mantoux)
What are disadvs of the tuberculin skin test?
requires a nurse to see the patient on two occasions, one
ideally requires blood tests
the tuberculin can cross react with other mycobacteria antigens
if the patient is really ill or is immunosuppressed, the patient won’t mount a response
What is one limitation of the Interferon Gamma Release Assays?
cannot tell us is whether there’s active disease
What is the most common type of latent screening test?
Interferon Gamma Release Assays
What does pulmonary TB disease cause?
consolidation
cavities (commonly at the top of the lungs)
lung abscesses
How does an Interferon Gamma Release Assay work?
interferon-gamma is released into the blood following stimulation by specific TB antigen
What are two advs of Interferon Gamma Release Assays?
More specific than Mantoux
Correlates better with degree of exposure than Mantoux
What is a disadv of an Interferon Gamma Release Assay?
does not differentiate between latent infection and disease
What are the symptoms of pulmonary TB disease?
Cough Weight loss Haemoptysis Fever Chest pain Night sweats
What sites in the body does Extrapulmonary disease occur in?
Lymph nodes CNS Bone (Pott’s disease of the spine) Genitourinary system GI tract Disseminated/miliary
Which ethnic group is Extrapulmonary disease more common in?
non-UK born Asian origin
How does TB Lymphadenitis react to treatment?
often gets worse on treatment
paradoxical reaction
What are the physiological effects of TB Lymphadenitis?
Can form sinus tracts with chronic discharge
Cold abscess formation
What are the symptoms of TB Lymphadenitis?
fevers sweats weight loss malaise very common Respiratory symptoms in majority GI or CNS symptoms in 20%
What are the GI or CNS symptoms in TB Lymphadenitis?
Abdominal pain, diarrhoea
Hepatomegaly in 50%
Headache or confusion in 20%
How can CNS TB affect the patient?
TB meningitis
TB arachnoiditis
Tuberculomas in the brain
Spinal cord compression from extension of discitis
What is patient mortality for CNS TB?
15-40% (can be high) despite effective treatment
How is TB controlled?
Government global policy
Early diagnosis AND treatment (even if negative cultures/smear)
Optimal treatment and adherence (DOT/VOT/Section)
Contact tracing
How is TB prevented?
BCG (Vaccination)
Latent treatment programs - prevent TB becoming active
How was TB treated historically?
patients sent away to sanatoriums
surgeries to collapse the lung so that the aerobic conditions weren’t as beneficial to the bacteria
How long does standard treatment for TB last?
a minimum of 6 months
What drugs does the initial phase of TB treatment involve?
Isoniazid
Rifampicin
Pyrazinamide
Ethambutol
How long does the initial phase of TB treatment last?
2 months
How long does the continuation phase of TB treatment last?
4 months
What drugs does the continuation phase of TB treatment involve?
Isoniazid
Rifampicin
How should the patient take TB treatment?
they should be taken all together on an empty stomach one hour before breakfast; compliance is essential for cure.
Latent treatment : 3 months Rifampicin/Isoniazid 6 M isoniazid
How long does treatment for CNS TB last?
12 months
How long does the continuation phase of CNS TB treatment last?
10 months
What are the side effects of Pyrazinamide?
Hepatoxicity joint pain N&V nausea skin rashes
What are the side effects of Rifampicin?
Hepatoxicity
reddish colour to the urine
nausea
skin rashes
What are the side effects of Isoniazid?
Hepatoxicity fever peripheral neuropathy optic neuritis nausea skin rashes
What are the side effects of Ethambutol?
peripheral neuropathy optic neuropathy gout nausea skin rashes
