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Why Should We Care
About TB?
Two billion
people have latent TB -- about 1/3 of the
world’s population!
It kills around two
million people annually! In fact, 25% of
avoidable death in the working age group is
caused by tuberculosis
But… It is
completely curable and relatively
inexpensive to treat
Ancient History
Picture:
Hippocrates
Source
 4000
BC – Skeletal remains show evidence of TB
3000 BC – Egyptian
mummies revealed signs of tubercular decay
2000 BC – Presence in
the Americas
460 BC – Hippocrates
identified as “phthisis;” it was the most
widespread disease of the time
Modern History
1820s – TB identified
as a disease
1839 – “Tuberculosis”
named by J. L. Schonlein
1838-1845 – Dr. John
Croghan attempts treatment in Mammoth Cave
because he thought the constant temperature
and purity of the cave would help treat or
even cure the disease
1859 – First TB
sanatorium opened in Poland
1882 – Mycobacterium
tuberculosis identified by Robert Koch
1885 – First TB
sanatorium in the US opened
1890 – Koch proposes an
ineffective remedy to TB involving glycerine
extract of the tubercle bacilli
1906 – Calmette and
Guerin developed BCG (bacillus of Calmette
and Guerin) vaccine
Recent Developments
1921 – BCG vaccine
first used on humans
Late 1940s – BCG gained
more global acceptance
Picture:
Girls
preparing to be vaccinated
Source
1946 – Streptomycin
developed and changed the TB focus from
prevention to treatment
1980s – Drug-resistant
strains on the rise
1993 – WHO declares a
global health emergency
Mycobacterium
tuberculosis
That slow-growing,
aerobic bacterium is the cause of
tuberculosis. It divides every 16-20 hours
as opposed to most others which can divide
every 20 minutes. Mycobacterium
tuberculosis can survive in a dry state
of weeks. Additionally, it is an “acid-fast
bacillus.” This particular bacterium can be
identified by its staining characteristics.
When using the Ziehl-Neelson stain, they
stain bright red.
Picture:
Mycobacterium tuberculosis
Source
Transmission
TB is transmitted via
aerosol droplets expelled from people (when
coughing, sneezing, spitting, speaking) with
active tuberculosis Picture
Source
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There is an increased risk
of infection for…
Immunocompromised patients
(HIV/AIDS)
Children of high-risk adults
People who inject drugs
Healthcare workers
Certain racial/ethnic
minorities
Diagnosis
-Tuberculin skin test
Picture:
Reading of Mantoux skin
test
Source
---Mantoux Skin Test
---Heaf (used in the UK until
2005)
-X-ray (never conclusive, only
suggestive)
Picture:
Chest X-ray of person
with TB
Source
-Surgical biopsy
-Microbiologic smears or
cultures of sputum
Progression
*90% infected have asymptomatic
latent TB infection (LTBI)
*10% chance of progression to
TB disease
*If untreated, active TB has a
death rate of over 50%
--Interestingly, some
rheumatoid arthritis drugs can cause an increased
risk of progression. Those block tumor necrosis
factor-alpha, which is an inflammation causing
cytokine. However, cytokines are important in the
defense of the immune system against TB.
Treatment
Treated TB has a death rate of
< 5%, but one of the main problems faced is that
people do not take their medications for the
specified length of time. This is suspected to have
played a large role in the current increase of
individuals with drug-resistant strains.
Standard treatment for
active TB:
Isoniazid (1952)
Rifampicin (1963)
Pyrazinamide (1954)
Ethambutol (1962)
Picture:
Daily dose of TB drugs
Source
-Take all four for two months,
then just Isoniazid and Rifampicin for four more
months
Standard treatment for
latent TB:
Isoniazid – alone for six to
nine months
Multidrug-resistant TB (MDR-TB):
Resistant to isoniazid and
rifampicin
Extensively drug-resistant
TB (XDR-TB):
Resistant to 3+ of the 6
classes of second-line drugs
*The largest reported outbreak
of XDR-TB was in KwaZulu-Natal, South Africa where
52/53 people died from the disease.
Epidemiology
Picture Source
High ~400
cases per 100,000 people
Low ~40
cases per 100,000 people
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