TB Flashcards
how did we double the human life expectancy
conquering infectious disease
what are the 3 big components of conquering infectious disease
1) knowledge of the true method of transmission of disease = Germ Theory (for some disease we can take action - cholera - clean water supplies)
2) development of antibiotics (treat bacterial disease)
3) development of an effective vaccine (prevent disease from spreading
what did John Snow do
1850-1900 transmission of Miasma Theory - Germ Theory
name the bacteria that cause Tb
Mycobacterium tuberculosis
before antibiotics for Tb
millions of people died, no treatment or cure for tb
after antibiotics
the disease could be cured
last few years what has happened to Tb
increase in the prevalence of drug-resistant Tb = hard to treat >inurable Tb
how many people infected with Tb in the world
1/4 of the population infected 1.8 billion people
incidence
new cases of Tb = active cases
what countries are most likely to have TB
India and China = vast populations
mode of transmission for Tb
DIRECT CONTACT = person with active case of Tb: coughs, spits, sneezes, expels droplets with bacteria
what was an attempt to stop the spread of Tb in the past
stop people from spitting/coughing in public
if exposed to someone with Tb will you get Tb
probably not 1/5 chance
why will you be unlikely to get infected by someone who has Tb
of those infected 90% = do not develop active case of tb - still, have Tb bacteria, not multiplying, low number, dormant, not infectious, not symptomatic
what happens to 10% of the population infected
immediately develop an active case of Tb = no of bacteria increase and cause problems
what happens to 90% Asymptomatic/latent Tb cases
immune system fought bacteria but some still survive = if something changes > later develop Tb
a difference between cholera and Tb
Tb = slow disease
changes that cause latent Tb to become active
- age (older immune system changes)
- general welfare (nutrition)
- other diseases (AIDS/Cancers)
- immunosuppression for cancer therapy
- immunosuppression for transplants
- stress
if untreated active cases of Tb have a death rate of
50% within 2 years
how does Tb affect you
inhaling droplets > respiratory system > lung function lost
if you’re vaccinated against Tb what will be the result of a skin test
postive skin test - detects if the immune system has mounted response
what are 3 reasons why you can get a positive result for a standard Tb test
- active case
- latent case
- had vaccine
1815 how many people died of Tb in England
1/4
who did Tb affect
rich and poor equally
what kind of disease is Tb, contrast to cholera
endemic (cholera = epidemic)
where is Tb more likely and what age group were mostly affected
crowded urban cities - prime age of life
can Tb be caused by other species
yes in cattle = can affect humans and vice versa
what causes Tb in cattle
Mycobacterium Bovis (slow-growing)
what causes Tb in humans
Mycobacterium tuberculosis (slow-growing)
a way in which Tb can be transmitted
via milk
how do you kill microbes - Louis Pasteur
boil them
what happens if you boil milk
changes chemistry
what did Louis Pasteur realize
raise temp - reach point where you kill microbes before boiling = repeat several times = kill most of microbes (low level = decreases chances of infection)
what years did Louis Pasteur carry out relevant work
The 1860s, 1870s, 1880s
vaccine
a preparation of killed microorganisms, living attenuated organisms or living fully virulent organisms administered to produce or artificially increase immunity to a particular disease
vaccination
administering weakened or dead pathogens to a healthy person or animal, with the intent of conferring immunity against a targeted form of a related disease agent
BCG
is a vaccine against Tb that is prepared from a strain of the attenuated (weakened) live Mycobacterium Bovis
attenuated
reducing the virulence of an organism, usually a virus whilst keeping it viable (can infect a person but the immune system can fight it)
what countries use BCG
countries with Tb
The US and Western European countries do not use BCG, how do they then detect Tb
simple test: Tb Skin Test
use a purified protein from Tb (not infectious/bacteria) - recognized by immune system
measure size of the raised area
never seen before = small reaction
why do the US and Western European countries do not use BCG
because of the low risk of infection
how did we develop 2 strains of Tb
early human history: single disease only affected cattle, then evolved to affect humans, humans became more abundant - evolutionary event = two different strains
asymptomatic
individuals affected by the disease but do not show any of the typical symptoms
Tb
a chronic infectious disease usually caused by mycobacterium tuberculosis in humans
how did strain specialized in humans spread
human density increased, as people moved to cities
where was a common site of breeding for Tb in Victorian England
in Debtor’s prison
how was Tb exported to different countries
people moved from England to colonies > returned back brought Tb with them
why did people not think Tb was infectious
slow disease - thought it ran in the family
when did Robert Koch find a causative agent for Tb
1982
when did we find out Tb was infectious
The 1860s
when were antibiotics discovered and by who and what was the first antibiotic
1928, Alexander Flemming, penicillin
what did we do to treat Tb without antibiotics and why, did it help
place people in sanitoriums, get fresh air
50% of people died within 5 years
how did Alexander Flemming discover antibiotics
knew that bacteria grown in different conditions = show different results
Staphylococcus aureus -grow well in the human body and not room temperature
Fungi - optimum at room temperature
Halo around fungus - fungus producing something killing bacteria - isolated fungi and identified it, substance it produced = penicillin
how was penicillin obtained
solely from fungal growth
how was penicillin develop
find fungi that produced most penicillin - need huge culture, stabilize it - go to markets and collect mouldy fruits
how did Howard Florey and Ernst Chain contribute to antibiotics and when
1930s/1940s
- increased productivity by 4 orders of magnitude
- developed submerged cultures
what do bacteria do and how are they able to
grow and divide - continually make cell wall - defence against the extracellular environment/organisms
how is bacterial cell wall made
PEPTIDOGLYCAN - numerous glycan backbones connected by peptides
gram-positive
thick wall of peptidoglycan
gram-negative
peptidoglycan between membranes = defend better, substance don’t reach it easily (outer membrane)
how do beta-lactam antibiotics work (include penicillin and derivatives)
bacteria make glycan backbones then move to surface - enzyme allows peptide bonding - part of penicillin structure that enzyme recognizes = enzyme binds to penicillin = irreversible
effect of penicillin on bacteria
gram-positive = enough kills them gram-negative = variable, far less effective
did we conquer all infectious diseases with antibiotics
no, gram-negative bacteria diseases are not treated
bacteria causing infections (wound/following surgery)
all gram-positive
some gram-positive bacteria form spores which are very resistant, how did Flemming detect this
took swatches from soldiers uniform, put them on cultures = clostridium
antiseptics
kill bacteria
how did Flemming show antiseptics don’t work on battlefield wounds
- two sterile tubes: smooth.cracked
- pollute with bacteria
- disinfect tubes
- apply a culture medium to tubes
= disinfectant work on smooth surfaces (reach all bacteria) not on rough edges
was evolution to antibiotic resistance expected
and how do multicellular/eukaryotic organisms get new info
expected but didn’t know the different ways bacteria could acquire new info - bacteria evolve resistance to one antibiotic, may develop for everything that has the same mode of action - (humans only get new genetic info by mutation)
different antibiotics have
MODES OF ACTION
how does natural selection work (penicillin)
- original population = variation of bacteria
- change the environment by adding penicillin - ones that die fist = make least cell wall making enzyme
- some bacteria resistant to antibiotic = natural selection population favours this bacteria
(changing env = favours surviving bacteria)
why do antibiotics have trouble reaching mycobacteria
thick waxy coat outside layer
what year did we antibiotics against all bacteria
1950s
how do genes for resistance appear
bacteria can acquire new info by 1. transformation 2.transduction 3. conjugation AND MUTATION
transformation
some bacteria can take up DNA from the environment and incorporate into own genetic sequence
competence (for bacteria)
the ability of a cell to take up extracellular DNA from its environment
transduction
the process by which bacterial DNA is moved from one bacterium to another by a virus
conjugation
transfer of genetic information between bacteria through direct cell-to-cell direct
. plasmids replicate and pass info
. can occur between different species
what are some resistance mechanisms of bacteria
- degrade antibiotics (penicillinase)
- make more product
- alter antibiotic
pump out antibiotic
where do antibiotics come from
not invented, come from the natural world - pencilin came from a fungus
bacteria competing in soil (grow and divide)
types of antibiotic misuse
- inappropriate prescription (antibiotics only kill bacteria, not viruses)
- use of broad-spectrum antibiotics - affect range of bacteria (patient, doctor, company = happy ) * all bacteria get affected - some resistant - selected in that population
- agricultural use (pigs grew 50% faster)
- incorrect use (incomplete course/Tb thicky waxy layer = harder to reach)
- water contamination (urinate antibiotics - water sources not regulated)
why are we ‘back in the nineteenth century’
Tb - strains we can’t deal with > back to sanitariums/accept the transmission of an incurable disease
MDR-TB
multi-drug-resistant Tb - any strain of Tb that is resistant to both of the two main first-line antibiotic drugs
how many antibiotics do you get prescribed for Tb and why
cocktail of antibiotics - mutation can develop resistance
problems between the first and second-line drugs
cost and severe side effects
XDR-TB
extreme drug-resistant Tb - any strain of Tb that is resistant to both of the two main first-line antibiotic drugs AND two more of the second-line drugs
antibiotic resistance strains are a big problem before antibiotics resistant to everything why
- drugs of last resort - more expensive
- inconvenience - drugs may need to be given intravenously and over longer period
- side effects - much more severe
why are we still heading in the wrong direction
no new antibiotics being made
antibiotics
chemical substance that kills/suppresses the growth of microorganisms
antibiotic resistance
ability of a microorganism to withstand the effects of an antibiotic
latent/dormant infection
asymptomatic infection only capable of manifesting symptoms if activated
Describe the work of Fleming, and Florey and Chain, and how this work was important
Fleming isolated penicillin from a fungus that was killing bacteria, the first antibiotic
Florey and Chain found more productive strains of penicillin to increase productivity
This work allowed widespread use of ABs, reducing mortality from infection in WWII and paving the way for widespread use of ABs throughout the world
