Epidemiology and Disease Processes Chapter 17, examples from Chapter 19 Fields of Microbiology
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Transcript of Epidemiology and Disease Processes Chapter 17, examples from Chapter 19 Fields of Microbiology
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Pathology 1
Epidemiology and Disease Processes
Chapter 17, examples from Chapter 19
Fields of Microbiology
Epidemiology-- Population focus
-- disease spread & containment
Microbial pathology-- Disease focus
-- ‘etiology’ of disease-- Biology of pathogen & effects on host
Clinical Microbiology-- Patient focus
-- ID of pathogen and treatment
John Snow’s classic search for source of cholera – London, 1854
Germs
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Pathology 2
Roles of the the CDC
Epidemiological studies
the MMWR
Notafiable diseases (see tables 15.3 & 15.4)
Recommendations:antibioticsdrugsvaccine
The WHO
based in Geneva, Switzerland
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Our bodies sustain diverse microbial ecosystemsMicrobiota
= all the species
Microbiome: = where they liveor all their genes
Over 100 trillion cells~90% of the cells in our body~3 – 5 lbs of body weight1000s of species - from all domains~3,000,000 microbial genes - vs ~25,000 human genes
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How does our microbiome influence our lives?
We are a meta-organism Mutualistic symbiosis
Microbiome effects our biology
Disruption can lead to disease-- introduction of pathogens
-- changes in immune tolerance
-- crossing the epithelium
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Pathology 5
What are the clinical stages of a disease?Incubation
Prodromal
Invasive
Acme
Decline
Convalescence
Symptom can be:Acute
Chronic
Latent
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Pathology 6
What are disease ‘Reservoirs’?Nonliving (usually noncommunicable, opportunistic)
tetanusfungi
LivingAnimal (‘zoonotic’) (generally noncommunicable)
rabiesanthraxlyme disease
Human (may be ‘contagious’)choleraPneumoniaHIV
‘Carriers’ (read essay about Typhoid Mary, p 376)
Nosocomial
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Pathology 7
What are “modes of transmission:”?The “Five F’s”
A. Contact transmission
Direct Contact transmission-- includes ‘aerosols’-- respiratory infections
Indirect Contact transmission involves ‘fomites’Haemophilus
B. Vehicular transmission (disseminates)water, food, dustcholera, salmonellosis
C. Vector transmission
Reservoirs, Vehicles and Vectors are not the same!
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Pathology 8
Entering and exiting the body
Portals of entrySkin
Mucous epithelia (‘membranes’) -- respiratory -- eye -- reproductive -- digestive
Placental
Parenteral
Portals of exit
SkinFecesWoundsAerosolsVectors
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Pathology 9
Case study: Lyme disease
An “Emerging Disease”
New Lyme, Conn, 1982
Borrellia burgdoferi
White-tailed deer & mice
Ixodescomplex life cycle
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Pathology 10
Lyme disease, con’t
Distibution
Stages of disease
Acute symptoms:
“Bulls-eye rash”
flu-like symptoms
Chronic symptoms:
arthritis
neurological disorders
etc
Treatmentantibiotics (yes and no)
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Pathology 11
Patterns of disease occurrenceepidemic
pandemic
endemic
sporadic
cyclic
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Pathology 12
Case study: Tuberculosis -- A ‘reemerging’ disease
Mycobacterium tuberculosis
Intracellular pathogenlungsWBCsimmune responsegranulomas
Spread/control linked to clinical and social factors:
1) Diagnosis and treatment difficult
2) Slow growth
3) Poverty-- developed & developing nations
4) AIDS
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Pathology 13
What are the stages of an infection?Adherence
Colonization
Invasion
1. Adherenceglycocalyx
fimbriae
receptors
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Pathology 14
Colonization and Invasion are often coupled
Many ‘strategies’
Enzymes (‘virulence factors’)collagenase
hemolysin
streptokinase
Phagocytosis
Intracellular and extracellular infections
collagenase hemolysin
Penetration
Actin Tails
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Pathology 15
What causes the symptoms of infection?
Altered physiologye.g., fever; lethargy; loss of appetite
-- altered blood chemistry;-- effects on hypothalamus
Immune responses – some damaginge.g., many diseases; tuberculosis, leprosy
rheumatic fever, etc
Toxins -- damage to cells, tissues and organsExotoxins
Gram-Positive sp.proteins, Secreted from cellsHighly toxic, specific effects
EndotoxinsGram-negative lipopolysacchraridesLess toxic, more general effects
pyrogenic, hypotension
Syphilis lesions in liver
Endotoxins Enteric Virulence
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Pathology 16
Toxicity of Some Exotoxins Toxicity compared with: Toxin Lethal Dose (mg) Strychnine Snake Venom
Botulism Type D 0.8 x10-8 (mouse) 3x106 times 3x105 X Tetanus 4 x10-8 (mouse) 1x106 X 1x105 X Shigella Neurotoxin 2.3 x10-6 (rabbit) 1x106 X 1x105 X Diphtheria 6 x10-5 (guinea pig) 2x103 X 2x102 X
Some Effects of Exotoxins
1) Cell destruction (hemolysins)
2) Hemorrhaging (anthrax, Streptococus toxins)
3) Effect intestinal function (enterotoxins)water balance (cholera toxin)
4) Nerve function (botulism & tetanus toxins)Anthrax lesion
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Pathology 17
Botulism and TetanusClostridium botulinum vs C. tetani
obligate anaerobes
Botulismfood borne
flaccid paralysis
Tetanussoil borne
rigid paralysis
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Pathology 18
A Botulism Case History
- Food risks
- Antitoxins
Birds, Babies, Botox and Bioweapons…
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Pathology 19
Case study:Helicobacter pylori causes peptic ulcers
Only discovered 1982
Dimorphic
causes60-80% of stomach ulcers90% doudenal ulcersStomach cancers
Immune response plays important roles
Good news: treatable
Bad news: 25% in U.S. infected
More bad news: antibiotic resistanceis spreading
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Pathology 20
Gonorrhea
agent Neiserria gonorrhoeae-- Gram-negative dipplococcus-- attaches via fimbriae
Endotoxin
Infection in males
“thick, copious & yellowish” pus
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Pathology 21
Gonorrhea Infection in females
cervix
fallopian tubes
PID
ectopic pregnancy
neonatal prophylaxis
epidemiology
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Pathology 22
A Souvenir of London
Bought a souvenir in Londongot to hide it from my mum.
Can't declare it at the customs,but I'll have to take it home.Tried to keep it confidential,but the news is leaking out.Got a souvenir of London.There's a lot of it about.
Yes I've found a bit of London,and I'd like to lose it quick.Got to show it to my doctor,'cos it isn't going to shrink.
Want to keep it confidential,but the truth is leaking out.Got a souvenir of London.There's a lot of it about.
by Procol Harum, 1973
ASoL
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Pathology 23
What causes the symptoms of Syphilis?
AgentTreponema pallidumspirochete
Stages of the infectionIncubation
Primary (1O) syphilischancre
(clinical latency)
Secondary (2O) syphilisimmune hypersensitivity
(clinical latency/ recurrent 2O)
Tertiary syphilisgumma lesions
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Pathology 24
Syphilis, con’t.
Tertiary syphilisgumma lesions
autoimmunity?
Treatment
Congenital syphilis
Saddle nose
Notched teeth
Saber shin nose