Environments Flashcards
pathogen
MO able to cause disease in plant/animal/insect
pathogenicity
ability to produce disease in host
virulence in microbes (genetic,biochemical,structural)
outcome of pathogen + host depends on…
virulence and resistance/susceptibility of host
mechanisms of pathogenicity
invade
colonise
toxins
invasiveness
colonisation, bypass defence mechanisms, substances that facilitate invasion
toxigenesis
exotoxins released from bacteria and act away from bacteria
endotoxins are cell -associated like part of cell walls of Gram -ve (capsule, LPS)
opportunistic pathogen
part of normal flora
infection in compromised host
primary pathogens
cause disease as a result of their presence or activity within the normal, healthy host
regardless of microbiota/immune system
how does the environment affect pathogens?
ability to survive in diff environments affect ability to transmit to us and determines reservoirs and modes of transmission
can change physiology if in undesirable env. (like Gram +ve spores) so improve survival
3 constraints of env.
temperature
pH
anaerobiosis
psychrophile
best at low temperature
psychotroph
best at moderate temperature but can live at low temp
phile vs troph
phile loves while troph tolerates
mesophile
most bacteria
in warm-blooded animals
thermophile
wide variation, not pathogens
what temperature range do most microbes grow at?
over range of 30 degrees with diff mins maxs and optimums
relationship between growth rate and temperature
steady linear increase from min to opt
not linear at optimum
rapid plunge of growth after optimum
cold shock adaptation
e.g. E.coli
downshift in temperature so inhibition of protein synthesis and modified ribosomes
growth lag, acclimation phase and cold shock proteins (Csp) induced so adapt ribosomes to cold and resume growth
chaperones are used so ribosomes don’t damage
types of cold shock proteins
Class I = >10 fold induction
Class II = <10 fold induction
on word
Listeria
non-spore forming Gram +ve bacilli
Listeriosis is quite rare and only in pregnants and immunocompromised
widespread in environment
from contaminated food
can grow in low temps of fridge
invade intestinal mucosa and systemic spread from macrophages to liver
Legionella pneumophila
motile, aerobic, Gram -ve rod
disrupt IS in phagocytic cells and avoid destruction
forms biofilm in air-conditioning but not in humans
causes bacterial pneumonia
temp affects motility, piliation, virulence
most physiological attributes like flagella are better at lower temp
adhesion more effective at 25 degrees but more virulent at 37 degrees
dominant role for aquatic env so humans accidental host maybe from heat shock response
pH of natural environment
0.5 acidic soils to 10.5 alkaline lakes
pH range for most free-living prokaryotes
grow over 3 pH units
pH growth changes are…
symmetrical
acidophile
optimum below neutral
usually archaea, many fungi
for membrane stability
some obligate acidophiles need low pH because membrane dissolves otherwise
some Thiobacillus species
neutrophils
grow best at neutral
alkaliphiles
grows best at alkaline like soda lakes, high carbonate soils
abligate alkaliphiles grow around pH10
Bacillus - alkaliphile
has sodium gradient not pmf (pH proton) gradient because high pH
intracellular pH
optimal pH of organism refers to external pH of env. because intracellular needs neutrality
some can vary internal pH in extreme acidophiles/alkaliphiles
why are buffers used in cultures?
maintain pH so not changed by MO growth and waste
pH of most pathogenic bacteria
narrow pH range, most pH7
acidic conditions
need neutral pH inside - cytoplasmic homeostasis to protect proteins and DNA,
affect capacity for nutrient acquisition and energy generation,
chaperones and aklalisation of periplasm stops denature
Helicobacter pylori (detail on word)
gastric and duodenal ulcers
lining of stomach
virulence factors: flagella, urease, adhesins, vacuolating toxin
H.pylori urease
neutralise acidic pH of stomach
Koch’s postulates
how we know H.pylori causes ulcers
organism from animal put in culture and to another animal from this - should be same as original organism
no animal model for evidence so Marshall drank it himself and got lesions
how does H.pylori survive the acidic pH of the stomach? (what does it colonise, motility, VacA, BabA, UreI)
colonise mucin layer not lumen - mucus resists diffusion of protons from stomach acid because composed of negatively charged sulphated polysaccharides which act as buffer so alkaline pH
motility important to reach mucin, but requires short term protection with urease - hydrolyses urea secreted by gastric cells (ammonia + Co2 = neutralise)
VacA - vacuolating cytotoxin produces large vacuoles in mammalian cells
BabA - adhesin recognising LewisB antigen, binds sulphated mucin sugars on epithelial cells
UreI pH sensor - inner membrane protein facilitates urea entry only when acidic pH
Salmonella typhimurium virulence factors
adhesins
invasion of mucosal cells of small intestine
type III secretion system (contact dependent)
type II secretion system on Salmonella t
acid tolerance and virulence factor
contact dependent - only when contact target cell,
secrete molecules and change cell physiology,
only induced in acidified phagosomes of macrophages
Salmonella acid tolerance
grows at neutral pH but survives well till pH 4/5 only if gradual changes
can survive at pH3 if allowed to adapt before exposed, in next generation
Salmonella Fur protein
2 regulatory domains, 1 senses iron and 1 senses pH (sensed separately)
iron important virulence factor - hard to get from host, haem full of iron so major toxins haemolysin lyse RBCs for iron
Gram +ve proton pumps
F1Fo-ATPases (tolerant bacteria) less sensitive to low pH
GAD consumes protons via glutamate decarboxylation - GABA release
Gram +ve pH tolerance
regulator cell density - quorum sensing and biofilm growth altered metabolism envelope alterations production of alkali like urease
obligate aerobes
require O2 for final electron acceptor in aerobic respiration
a lot of bacteria
obligate anaerobe
aerophobes so don’t need O2 and it is toxic,
live by fermentation, anaerobic respiration, bacterial photosynthesis, methanogenesis,
facultative anaerobes/aerobes (+ e.g.)
can switch between anaerobic/aerobic metabolism
e.g. E.coli
aerotolerant anaerobes
anaerobic metabolism but insensitive to O2 so don’t care
microaerophile
obligate aerobe
require O2 but can grow at low levels like below 2 atm
effect of O2 on growth
O2 radicals can damage enzymes (H2O2 peroxide or O2- superoxide)
chlorophyll react with O2 in light to produce singlet oxygen radical
how MOs deal with oxygen?
aerobes and aerotolerants solve radical accumulation by superoxide dismutase (SOD) which detoxifies radicals)
also catalase - decompose H2O2, almost all have this
and those w/o catalase have peroxidase to decompose H2O2 - electrons from NADH2 reduce peroxide to H2O
obligate anaerobes don’t have these enzymes
photosynthetic MOs protected by carotenoid pigments which react with singlet O2 radicals and lower to non-toxic ground state so detoxify
which MOs contain superoxide dismutase, peroxidase and catalase?
SOD: obligate aerobes, most facultative, most aerotolerant
peroxidase: only most aerotolerant
catalase: only obligate aerobes, most facultative
clostridium species are… so…
obligate anaerobic pathogens
lack respiratory chain cytochromes, catalase, peroxidase, superoxide dismutase
ATP by substrate-level phosphorylation
substrate-level phosphorylation
high energy phosphate bonds from organic intermediates transferred to ADP to form ATP (phosphorylated intermediate not Pi)
lysogenic bacteriophage in C.botulinum
virus infects bacteria and remains dormant in DNA, some toxins encoded by these and alter phenotype - lysogenic conversion
exotoxins from C.botulinum
released in inactive form, proteolytic cleavage activates it
2 subunits light/heavy linked by disulphide bridge
type A most potent
block release of ACh NT
botulinum toxin mode of action
heavy chain (HC) binds toxin to presynaptic receptor so take in by vesicle,
disulphide bond cleaves so chains separate,
LC to cytoplasm and endosomal compartment,
affect proteins for vesicle fusion so can’t release ACh,
zinc endopeptidase LC cleaves synaptosomal-associated protein (SNAP), and vesicle-associated membrane protein (VAMP) and syntaxin
clostridium tetani
tetanus - lockjaw
on rust
release antigenic exotoxin which circulates blood, adheres to neuronal receptors and fixes to gangliosides to block glycine NT and GABA release so can’t stop ACh release and causes muscle spasms
C.tetani mode of action
HC for cell entry,
C-terminal of HC binds gangliosides, N-terminal allows LC to cross cytoplasm,
LC is a zinc metalloprotease so cleaves synaptobrevin2 (SNARE protein) so vesicles with GABA/glycine can’t dock,
so respiratory paralysis
death so cause anaerobic env for growth
Clostridium difficile
antibiotics disturb gut microbiome and reduce conc. of difficile so overgrows and produce toxins A and B
diarrhoea, lesions on colon surface
rapidly fatal because toxins modify host G proteins (glucosyl group added to specific threonine on G protein) and alter actin cytoskeleton
antibiotics not effective so faecal transplantation restores normal microflora
Chagas disease
American trypanosoma cruzi
trypanosome types
American - cruzi (chagas disease)
African - brucei
mechanical vs biological vectors
mechanical - no development in vector e.g. trachoma in bazaar fly
biological - important in life cycle, needs vector, e.g. malaria mosquito, trypanosomiasis tsetse fly
structure of trypanosoma (diagram on paper lecture 4-5 first page)
kinetoplastids - flagellated forms, have kinetoplast (modified mitochondria, DNA-containing structure) and nucleus
African tryp. longer and more wavy
trypanosoma life cycle
morphological changes in hemoflagellates inside vector and humans
amastigote (circle, almost no flagella) in vertebrate host
paramastigote (more round, flagella begins) in invertebrate hosts
promastigote (longer body and flagella) in invertebrate host
epimastigote invertebrate
trypomastigote in vertebrate host, diff position of nucleus and kinetoplast, important in transmission to and from vector
all stages not infectious until metacyclic trypomastigote in invertebrates and trypomastigote in humans
development for transmission of T.brucei and T.cruzi
T.brucei: salivary gland transmission, metacyclic trypanosome only in gland, development then migrate to gland
T.cruzi: in gut, through faecal contamination
Chagas disease vectors
reduviid or Triatominae bugs (kissing bugs)
no larvae stage
every stage needs blood
1 meal can be enough for 1 stage
can be long lived - 12 months of starvation
take up to 1ml of blood
Chagas disease transmission cycle
in bug faeces - scratch bite and get everywhere
1) metacyclic trypomastigote penetrate various cells
invade IS when invade macrophages, not affected by lysosomes
2) transform to amastigote, to cytoplasm to divide
3) transform to trypomastigotes - movement so bursts out cell to blood to infect more
8 days from infected to infectious
0.6% contact cause infections so contact must be v high for high infections
Chagas disease route of transmission
vector-borne kissing bugs (80%)
transfusion of infected blood (<4%-20%)
congenital - regionally high
ingestion of infected sources
2 phases of Chagas disease pathology
acute and chronic
acute phase of Chagas
symptomatic, 4-8 weeks
usually children or 1st exposure because adults will have chronic if already exposed
fever, gland swell, liver/spleen enlarge, mostly mild but some mortality and severe symptoms
chronic phase of Chagas
life long
clinically silent
can progress after 10-20yrs to 20-30% cardiac disease and 8-10% gastrointestinal
genetic variation so diff geographical diff in cardiac/gastro
parasitaemia (levels in blood) drops so harder to detect, not circulating but in cardiac muscle/macrophages
treatment of Chagas?
not effective so need prevention
how do you prevent Chagas?
vector control
why is vector control hard for Chagas?
20 species with diff niches but main 3 in human transmission
Southern Cone Initiative 1991
improve housing to reduce vectors and introduce blood screening before transfusions
housing and Chagas disease
poorly constructed and deforestation and colonisation means more blood source and habitat
re-infection rates high because of peridomestic vectors (just outside house)
white washing (Chagas)
plastering walls so no gaps in bricks reduces risk because change vector niche and easier to spot
why might insecticide spraying homes not work?
have to move all belongings out but might live in there,
lack expertise
might be in farm as well
insecticides for Chagas disease
DDT not effective and bad
Formulations for walls
paints in development but may be hard to apply
insecticide impregnated materials (ITNs)
what is the water droplet in the tsetse fly photo?
water droplet so blood more concentrated
disease of T.brucei
sleeping sickness
T. brucei vector
Tsetse fly (Glossina spp)
large blood meal
K-strategists - lots effort into producing young and not a lot of them
good vision but need light
salivarian transmitters - multiply in blood stream and migrate and can cross blood brain barrier
tsetse fly life cycle
don’t lay eggs
larvae develop in females and lay developed larva into soil
tsetse transmission cycle
morphological changes in vector
procyclic trypomastigote multiplies
epimastigote multiply in salivary gland
blood meal by tsetse so trasmit to humans
3 weeks from infection to infectious and live 6-14 weeks (can reduce transmission if reduce life expectancy of vector)
T.brucei diagnosis
diagnose later stages with cerebral spinal fluid
chancre circle blisters
pathology of HAT (brucei) - early and late stage
early stage (haemolymphatic): chancre in 50% rhodesian, through lymphatic system and blood, swollen glands and spleen, local oedema, cardiac abnormalities, headache, fever
late stage (encephalitic): crossed blood brain barrier, sleeping sickness, invade CNS, headache, sleeping pattern, personality, mental function, weight loss, coma and death acute haemorrhagic leucoencephalopathy (AHL) - brain inflammation and necrosis from O2 starved vessels
chancre
circle blister from T. brucei
heal to altered pigmentation
T. brucie Gambiense vs Rhodesiense
phases slightly different
G: long asymptomatic and advanced disease, need early diagnosis
R: acute infection, 1-4 weeks incubation, quickly detectable
VSG
variable surface glycoprotein on surface of T. brucei
produces strong Ab response
stage-specific: only in trypomastigotes
switch proteins so the ones not detected will proliferate and be selected for
after IS, parasite levels decrease but switches VSG so increased number again (waves)
T. brucei treatment
4 licensed drugs (on word)
morsitans group flies
savannah
highly motile
visual and olfactory (smell) cues
Palpalis group flies
riverine woodlands
less mobile
visual cues
Nagana disease in cattle
from 3 trypanosomes:
T.b.brucei (chronic to mild)
T.congolense (severe)
T.vivax (less pathogenic) - severe emaciation (blood cells reduced), infertility, reduced milk, weight loss
Gambiense control
vector control not cost effective
case detection and treatment needed to reduce transmission
Rhodesiense control
vector control, cattle treatment, so reduce transmission from zoonotic reservoirs, treat to reduce circulation
vector control rationale for T. brucei
tsetse flies are K-strategists so get rid of few female to to have big impact
vector control options for T. brucei
destroy larvae sites - not long term
tsetse traps - attracted to dark shapes, electrified, impractical over large areas
insecticide - on traps/animals, effective in open areas
SLT (sterile insect technique) - in Zanzibar, release sterile males but can store sperm so useless if already mated, expensive + intensive
problem with using insecticides on cattle to reduce T. brucei (problem, breed selection, solution)
would kill tsetse but ticks as well (involved in babesiosis disease) but TBD (tick borne diseases) more severe in older cattle so need to keep exposure to ticks when young so insecticide not helping this
breed selection - Bos tauras susceptible to Babesia but trypanotolerant
Bos indicus resistant to Babesia but susceptible to trypanosomiasis
95% ticks on upperside/bum so diff site from tsetse on legs so only spray legs,
target big ones (at risk - blood meals increase with cattle weight) so leaves young exposed to ticks
tiny target traps
fly target with mesh with deltamethrin
significantly reduced tsetse population but need combination with case detection and treatment
tiny target traps edge effect
much stronger effect in centre than edge so re-invasion into centre after removal
apicomplexan parasite structure
apical complex with secretory organelles
apical organelles expressed during invade/attachment to host cells
life cycle of apicomplexan parasites in humans (e.g. malaria)
secrete proteins at apical pole to invade (triggered by free Ca in parasite cytoplasm)
conoid in centre of polar rings protrudes so sensitive to Ca
rhoptries (club shaped) near apical end is secreted during invasion
3 processes of apicomplexan parasites (development, life cycle)
1) SPOROGONY: after sexual phase comes asexual reproduction forming sporozoites
2) MEROGONY: another asexual reproduction to form merozoites, can have many cycles
3) GAMETOGONY: merozoites become gametes by asexual R then sexual R to zygote and differentiate to sporozoites
4 distinct Plasmodium species in humans
P. falciparum (most virulent, most morbidity + mortality)
P. vivax (concurrent infection, most morbidity in under 10s)
P. malariae
P. ovale
malaria vector
FEMALE Anopheles mosquito (only females take blood meals)
where is malaria mostly?
African and South America
malaria mechanism
1) infected female takes blood meal
2) sporozoites into blood and then infect liver cells
3) to merazoites, buds to merasome to blood
4) merazoites released from marosome to infect RBCs
5) consumes Hb and multiplies to produce symptoms (2 days)
6) RBCs adhere to walls so block flow so affect brain and kidney and avade IS
7) RBCs burst so merazoites infect new cells
8) some into gametocytes (10-12 days) to another mosquito to develop to gametes and zygote, fertilisation and develop to ookinete which invades gut wall of mosquito and form oocyst, mature and divide to sporozoites to salivary gland (survive 59 days)
symptoms in malaria are due to?
asexual erythrocytic stage
P. falciparum
cerebral malaria
often fatal
treatment as cost effective as measles vaccine
insecticide bednets (ITNs) for malaria
reduced mortality by 20%
low mammalian toxicity
high residual effect
LLINs - preffered form, long lasting
how does P. falciparum evade host immunity?
60 var genes encode hypervariable erythrocyte membrane protein 1
express 1 at a time in erythrocyte stage so evade is switch var during infection
why are vaccines not effective for P. falciparum?
protective immunity only as long as residual population of parasites present, if curved then susceptibility returns
who is immune to P. vivax?
it enters through RBC receptor in people with Duffy blood groups
West Africa evolved without this receptor so immune
sickle cell anaemia and malaria?
protective against malaria because glutamic acid in Hb replaced with valine so reduces O2 carrying capacity and 80-95% protection against P. vivax
malaria drug treatments
work in 3 ways: kill in liver, kill asexual parasites in RBCs, kill sexual in RBCs
antifolates - malaria drug
target folate metabolism so reduces folates which are co-factor for biosynthesis of AAs/nucleotides important for malaria to make DNA
why does malaria treatment fail?
self-treatment - lower doses to save money and stop when feel better
poor compliance
long drug 1/2 life, don’t clear from system
re-infection
expensive
sterile insect technique for malaria
GM spermless males
ethics of releasing GM
cryptosporidium oocytes resistant to what?
why?
water treatment e.g. in filtration of pools
because so small
resistant to chlorine and bleach
have double layer protein-lipid-carb matrix
filtration of cryptosporidium oocytes
can’t remove with sedimentation: small and low density oocytes have low rate of settling
flocculation: surface charge low so clump from chemicals then can use sedimentation
rapid filtration: after flocculation and sedimentation
slow sand filtration: aerobic bacteria on top produce extracellular polymers for natural biological filter
membrane filtration: final, not often in public water supplies
disinfection of cryptosporidium oocytes
resistant to chlorination and survive bleach for hours
Uv light no evidence
ozonisation
cryptosporidium life cycle
trophozoite to merogony to meront I to meront II to microgamont to macrogamont to microgametes to zygote to oocyte (infective stage) to faeces to thick walled oocyte to thin oocyte to sporozoites to released and attach to epithelial wall to become merazoite
feeds off host
some form gametes and zygote and oocyte which goes ti faeces
invasion by C. parvum
free parasite enter intestinal lumen and attach to epithelium surface among microvilli,
microvilli elongate along surface of parasite to form dense band in cytoplasm of host cell, parasite covered by microvilli
where feeding happens
therapy for cryptosporidium
no safe or effective
supportive care for immuno-competent
some antibiotics (on word)
toxoplasmosis
T. gondii chronic infection in 1/3 humans and animals
mild in healthy,
life threatening in immunocompromised and foetus
complex life cycle: intestinal/tissue phases
intestinal only in felines, merogony and gamogony,
sexual cycle produce oocytes excreted in faeces
toxoplasmosis life cycle
feline host
cats eat rodents so tachyzoites ingested and oocyst in cat faeces not infectious but sporozoites later released which infects people and penetrates intestinal epithelium and invades macrophages where binary fission occurs to produce tachyzoites causing host cell rupture and release
cats only infected once so need fresh host
toxoplasmosis human infection
congenital/blood transfusion/from cats liver tray/other meat
dormant/resting toxoplasmosis
slow replication, host cells encapsulated (tissue cysts),
bradyzoites secrete chitin and other to form cyst wall to hide from IS
reactivation from waning IS
starts tachyzoite fast stage so tissue damage and inflammation
toxoplasmosis and rodent psychology
less cautious of cats, reduce fear to complete life cycle
toxoplasmosis and human psychology
increased risk traffic accidents because prolong reaction times
suicide attempts - personality type increase chance
toxoplasmosis and schizophrenia
details in notes
42% Sch were T.gondii +ve
some Sch meds inhibit replication
toxoplasmosis vaccine
for sheep not humans because could become pathogenic
cat vaccine would be useful
small colony variants (SCV) of mycobacteria
mutations
variant phenotype of S.aureus, normally fast growing but slow in biofilms so hard to kill with antibiotics
get SCvs with other like E.coli., P.aeruginosa, salmonella, gonorrhoea etc.
antibiotics for SCV
normally target growth but biofilm-mediated infections and TB are slow growing/dormant so hard to treat
ionophores (mycobacteria)
reversibly bind ions,
chemical structures of various membrane-active agents,
molecules perturb membrane and vary in size/chemical structure - determine if bactericidal and how rapid
high lipophilic content interact with hydrophobic membrane
(clofazimine exception - kills latent mycobacteria but all others have anti-biofilm properties)
intracellular pathogens
protected from IS/antibiotics,
s. aureus is extra/intracellular,
uptake by non-professional phagocytes,
SCV internalisation mediated by fibronectin bridging between FnBPs and alpha5beta1-integrin receptor
leprosy
can’t catch easily
chronic disease of skin/nerves - lose sensation
prefers 30 degrees but extremeties like cool nose
migrate to Schwann
facial deformity, ears curl, lose fingertip feeling
high infection dose - 1 cell to infect
cause chronic granulomatous (inside macrophages)
leprosy treatment
MDT (multidrug therapy) - Clofazimine, Rifampicin, Dapsone, early diagnosis prevents permanent disability, some side effects
leprosy structure
unique cell wall - capsule like material, mycolic acids up to 20 carbon lengths like wax, peptidoglycan linked to mycolic acids with Arabinan Galactan polymers
leprosy diagnosis
Ziehl Neelsen stain (red)
leprosy mechanism
1) inhalation and migration to macrophages
2) can subvert infection with cellular immunity
3) humoural response (Ab) not effective because of wax and because intracellular
4) tuberculoid pole - aggregation of macrophages, cells break out to nerve cells, to Schwann, cause ischemia so die
5) bacteria has laminin like projections (LBP21) that bind laminin (LAMA2) on schwann outer membrane
6) Tol receptors 1/2 important in resistance, not work so stimulate infection and don’t trigger T cells properly
TLR1 (leprosy)
wild type 6021
mutant TLR1 I602S to resistant to leprosy
so TLR1 involved in pathogenesis
M.leprae genome
reduced genome, lost key genes but still have all essential ones and pseudogenes
Clofazimine for mycobacteria
membrane-disrupting agent, bad side effects,
impact healthy cells but prefer bacterial cell walls,
aggregation of antimicrobial bends lipid bilayer of mycobacteria to form Toroidal pore
1) barrel-stave pore: hydrophobic part of antimicrobial align with membrane lipids and hydrophilic face in
2) carpet-like pore: coating of bilayer, micelle formation, membrane dissolution
so leaky membrane and cells die
treatment for mycobacteria
clofazimine
rifampicin
sulphones and sulphonamides
mycobacterium tuberculosis
disease of immunocompromised
burden in poor countries
aerosol - spreads by inhalation of 1-3 bacilli
1/3 population has dormant/latent TB that can reactivate
mycobacterium tuberculosis genome
reductive evolution so reducing genome because don’t need,
evolutionary tree useful for diagnostics
mycobacterium tuberculosis life cycle (similar to leprosy)
1) macrophages eat it, signals attract monocytes, forms big pus granuloma (aggregation of infected macrophages, producing lipids so foamy macrophages)
2) macrophages respond to infected macrophages, lymphocytes surround structure as well
3) vascularisation, more vessels around granuloma
4) fibrous cuff if cells not cleared, can’t get antibiotics in granuloma
5) macrophage in middle dissolved by TB to form caseum (impenetrable)
6) loss vascularisation, TB multiplication, opens up, to lymph and blood to infect more macrophages
immune response to TB
5% massive progression and proliferation
90% have elimination and latent and 5-10% of these will re-activate
suppression of T cell activation and toll cell activation
pH tolerant so survive macrophages
BCG vaccine
widely used but controversial
80-90% efficacy
no new vaccine since this one, had to stick with live attenuated (expensive)
northern hemisphere has low IFN-gamma response before vaccine so it significantly increases it
southern hemisphere has high IFN-gamma before so not much response after vaccine
can’t treat during latency
TB diagnosis
biomarkers in peripheral blood
signals from transcription
metabolites in urine/breath/sputum
x-ray/scan
Zhiel Neelson stain (resists acid rinse so stays coloured)
smear microscopy (only works 5 months with TB but infectious by 3rd month so can’t early diagnose)
hard to diagnose because feels like bad cold
TB treatment
5 antibiotics
environmental mycobacteria (EM)
opportunistic pathogen
risk to immunocompromised (HIV) and with pre-existing lung disease and Helminth infections
EM and BCG
EM may interfere with BCG vaccine - by blocking (immunity restricts BCG growth) or masking (can’t give additional immunity to already induced by EM)
diseases by EM
pulmonary disseminated lymphadenitis - enlargement of nodes cutaneous disease - skin nosocomial
evolution of EM
M. marinum (amphibia/fish pathogen) closely related to M. ulcerans (human pathogen) - both produce mycolactone toxin
high G and C content (bases), need to survive outside host and adapt to many diff env.
mycolactone toxin
large gene cluster on large plasmid, came in before split into marinum/ulcerans
immunosuppressive and analgesic - don’t feel infection
induce apoptosis, inhibit inflammatory cytokine, inhibit T from skin to lymphoid organs, damage nerve cells
cutaneous disease (EM)
Buruli ulcer by M. ulcerans
necrotising, subcutaneous
3rd most common human mycobacteria (after TB & leprosy) and least understood
subverts IS, kills pains, develops in bone so irreversible deformity
mostly Africa, some Australia
maybe possums
low prevalence but bad where prevalent
similarities of M. ulcerans to mycobacteria
subvert macrophage response
IFN-g protect (from non-tuberculous)
mycolactone unique to ulcerans
target scaffolding proteins
MHC reduced so no T cell response
ulcerans no tropism for schwann but diffuses into them
BCG against TB + leprosy + buruli ulcer
buruli ulcer pathology
primary infection turns to latency - lesion in immunocompromised
disseminated - spread so worse, or localised
clearance and self-healing can happen depending on mycolactone
can progress to osteomyelitic - bone, permanent damage because bone stays in that position
buruli ulcer pathogenesis
low optimal temp
mycolactone high cytotoxicity
BCG against osteomyelitis
mycolactone biosynthesis (BU)
like fat synthesis but without reduction
repeating units of polyketide causes necrosis
build up fat but keto groups not reduced but cyclise,
polyketide secondary metabolism
BU in possums in Australia
found in faeces
1) possums ingest from env/insect vector
2) amplify and shed
3) insect contaminated
4) transmit to humans via insect or direct from env.
BU vector
strong evidence of biting amphibious beatles
Notonectidae carry disease in mouth
found M. ulcerans DNA in insects, mainly in July
disease most prevalent when lots notonectidae
BU epidemiology
endemic where human activity - deforestation etc so not much to bite except humans
no difference with water bugs
BU evolution
M. ulcerance close to M. tuberculosis but diff disease
BU treatment
antimycobacterial drugs but no evidence and lack clinical trials and too late for irreversible damage
monotherapy could cause drug resistance so multiple is better to use
Crohn’s disease(CD)
EM
association with cattle MAP disease
evidence for and against MAP causing Crohn’s: lecture 13 slide 22
pasteurised milk doesn’t kill so MAP pass to milk to humans
MAP detected in Crohn’s patients but also MAP in humans without Crohn’s
humans with MAP animals don’t have higher CD prevalence
intracellular vs extracellular mycobacteria, how?
free-living amoeba may have conditioned mycobacteria to be intracellular and subvert IS
mycology
study of fungi
fungi characteristics
eukaryotic
chemoheterotroph
rigid cell wall, layers of polysaccharides, rigid matrix,
feed: saprophytes (decaying matter) or parasites (living matter),
osmotrophic (absorb food)
disease mostly skin/hair/nails
can hydrolyse keratin
lichens
fungi
on walls, pollution indicators
fungal pathogen mechanisms (3)
1) allergic hypersensitivity reactions
2) toxins like mycotoxins
3) infection, growth in/on body = mycosis
3 main types of fungal infections
1) cutaneous (superficial) mycoses: surface of skin
2) subcutaneous mycoses: beneath skin, localised, spread by mycelial growth
3) systemic mycoses: not common, whole body, can kill
why is cutaneous fungi called superficial?
where no living cells so no cellular response
dermatophytes
cutaneous fungi that use keratin as nutrient source so digest it
treatment/prevention of cutaneous fungal infections
topical therapy - creams
oral antifungals - fluconazole
what type of infection is yeast?
superficial (cutaneous) or systemic fungi
how does yeast affect the IS?
body recognises PAMPs, yeast cell wall binds PRRs and causes inflammation, fever, phagocytosis, activates alternative complement pathway and lectin pathway
yeast candida albicans
produce pseudohyphae
buds elongate - tube like structure - filament (pseudohypha) - help invade deeper tissues after colonises epithelium
dimorphic so diff form in env and body
candidiasis infection
from lots diff types of yeasts some only in immunocompromised vaginitis thrush less commonly infects lungs/blood/heart/brain
10% septicaemia - enters blood
diagnosis of superficial fungal infections
1) collect sample - where most viable fungus, with blunt scalpel
2) direct microscopy - presence of small, round to oval, thin walled clusters of budding yeast cells and branching pseudohyphae, colonies are white/cream with smooth waxy surface
treatment of superficial fungal infections
topical imidazole compound
azoles
polyenes
oral fluconazole
prolonged therapy may cause resistance
subcutaneous fungal infection examples
more detail on word
chromobloastomycosis
sporotrichosis
treatment of systemic fungi
chemotherapy - difficult
amphotericin B antibiotic - affect cell membrane but side effects
exposure rarely eliminated except with air filtration
fungal pathogenicity
1) promote fungal colonisation:
adhere to host cells,
capsules resist phagocytosis,
candida albicans - cytokine GM-CSF suppress complement for chemotaxis of phagocytes and acquire iron from RBCs so haemolysins.
2) damage host:
enzymes digest cells - proteases and host cytokines,
mycotoxins - lose muscle coordination, weight loss, tremors, aflatoxins are carcinogenic
GM-CSF
granulate-macrophage colony-stimulating factor
