Lecture 10: Mycobacterium tuberculosis Flashcards
TB is caused by?
mycobacterium tuberculosis complex
How did TB first present
affected everyone, slow progression, thought to be hereditery, chronic disease, respectable symptoms
How was it discovered that TB was infectious
Robert Koch - infected peice of lung from human in rabbit - identified mycobateria reponsible
Describe the morphological features of M. tuberculosis
- complex lipid-rich cell wall
- acid fast bacilli (AFB)
- grows very slowly
- resistant to common ABs
- lives inside **macrophages **
How is Tb transmitted?
Airborne, bacilli released in droplets that survive in the air for house, indectious dose is <5 bacilli, droplets settle in alveolus - engulfed by alveolar macrophages
how do granulomas grow in TB?
infected macrophages recriuit additional macrophages and other immune cells to form organised structures - critical for restricting bacterial expansion
In TB most infections are ____ and ____ lead to active disease. The quartet of symptoms include ____ , ____ ,____, ____. Untreated TB progresses to ____ ____ and a ____ cough. Active disease is when bacteria are ____ . If untreated death rate is ____.
asymptomatic, 10%, weight loss, night sweats, fever, malaise, chest pains, bloody cough, infectious, 50%
Who gets the disease?
1/3 worlds population is infected
15-34 year old highest incidence
How are HIV and TB related
HIV impacts immune system
HIV patients are up to ____ x more likely to develop TB. ____% of TB cases are HIV+. In. 2021 TB accounted for ____ deaths of HIV/Aids patients. Most cases are in Africa with many in South Africa. Major benefits of Anti Retroviral Therapy (ART) in terms of TB risk and mortality
20, 10%, ~200,000
what sex is most likely to get TB
males, 6.8 rate
compared to females - 6.1
What age group is hospitalized most?
15-39
risk factors of TB
- born outside of NZ
- resident with person outside NZ
TB treatment
M. bocis Bacille Calmette Guerin (BCG)
derived from virulent isolate of bovine tuberculosis
BCG vaccination given >____ people but efficacy varies, ____% in trials. This is thougth to be due to ____ ____ to ____ ____. It is also only effective druing ____ . Risk of disseminated infection in ____
3 billion, 0-80%, prior exposure, environmental mycobacteria, childhood, HIV-infected infants
it is _ to diagnose TB as most people are _.
difficult, asymptomatic
How can TB be diagnosed?
chest x ray, Ziehl Neelsen stain from sputum, Interferon testing, Quantiferon gold test of blood, Mantoux skin test.
in a Ziehl Neelsen stain ____ is ____ into bacilli with ____. Background decolorized with ____ and coutnterstained with ____ ____. TB does not decolerise with acid/alcohol. = acid fast baciullus (AFB)
arbol fuschin (red) in phenol, driven, heat, acid/alcohol. methylene, blue
interferon testing dects the release of interferson by ____ in respone to mycobacterial antigens. a positive result indicates presence of previously ____ lymphoctes. But it cant distinguish between ____ infection and ____
lymphocytes, sensitised, latent, disease
What will a quantiferon gold test indicate?
Fill TB test tube with venous blood, after 3 day incubation, lymphocytes previously exposed to Mtb will release IFNgamma
Mantoux test - 0.1ml of ____ is injected into the ____. This is a purified protein derivative, ____ extract of Mtb. Lymphocytes in a person previously exposed to similar mycobacterial antigens will migrate to the injection site. Lymphoctes release ____ and other cytokines which result in ____
tuberculin, dermis, cell wall, interferon, swelling,
BCG vaccine contains
live attenuated M. bovis
BCG vaccinated people will have a ____ Mantoux test
+
What is the current treatment for TB
Multidrug regimens taken for 6 months
Why do many people not complete TB treatment
side effects many drugs have
MDR
multi-drug resitant
treatment for MDR-TB
Group A medicine (prioritzed), Group B medicine (next), Group C medicine (when A and B dont work)
XDR
extensively drug resistant
Pre-XDR-TB drugs
resistant to rifampicin and any fluoroquinolone
XDR-TB drugs
resistant to rifampicin, any fluoroquinolone, and at least one of bedaquiline or linezolid
all group A
