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
Germs
John Snow’s classic search for source of cholera – London, 1854
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
Pathology 3
What are disease ‘Reservoirs’?Nonliving (usually noncommunicable, opportunistic)
tetanusfungi
LivingAnimal (‘zoonotic’) (generally noncommunicable)
rabiesanthraxlyme disease
Human (may be ‘contagious’)choleraleprosyHIV
‘Carriers’ (read essay about Typhoid Mary, p 376)
Nosocomial
Pathology 4
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!
Pathology 5
Case study: Lyme disease
An “Emerging Disease”
New Lyme, Conn, 1982
Borrellia burgdoferi
White-tailed deer & mice
Ixodescomplex life cycle
Pathology 6
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)
Pathology 7
Patterns of disease occurrenceepidemic
pandemic
endemic
sporadic
cyclic
Pathology 8
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
Pathology 9
What are the stages of an infection?Adherence
Colonization
Invasion
1. Adherenceglycocalyx
fimbriae
receptors
Pathology 10
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
Pathology 11
Gonorrhea
agent Neiserria gonorrhoeae-- Gram-negative dipplococcus-- attaches via fimbriae
Endotoxin
Infection in males
“thick, copious & yellowish” pus
Pathology 12
Infection in females
cervix
fallopian tubes
PID
ectopic pregnancy
neonatal prophylaxis
epidemiology
Pathology 13
Colonization and Invasion are often coupled
Many ‘strategies’
Enzymes (‘virulence factors’)collagenase
hemolysin
streptokinase
Phagocytosis
Intracellular and extracellular infections
Listeria and actin tails
collagenase hemolysin
Pathology 14
What are the clinical stages of a disease?
Incubation
Prodromal
Invasive
Acme
Decline
Convalescence
Infections can be:AcuteChroniclatent
Pathology 15
What causes the symptoms of infection?
Altered physiologye.g., fever; hormones; blood chemistry
Damage to cells, tissues and organse.g., respiratory infections, syphilis, etc
Damaging immune responsese.g., many diseases; tuberculosis, leprosy
rheumatic fever, etcToxins
exotoxinsGram-Positive sp.proteinsSecreted from cellsHighly toxic, specific effects
endotoxinsGram-negative LipopolysacchraridesLess toxic, more general effects
pyrogenic hypotension
Syphilis lesions in liver
Pathology 16
What causes the symptoms of Syphilis?
AgentTreponema pallidumspirochete
Stages of the infectionIncubation
Primary (1O) syphilischancre
(clinical latency)
Secondary (2O) syphilis
immune hypersensitivity
(clinical latency/ recurrent 2O)
Tertiary syphilisgumma lesions
Pathology 17
Syphilis, con’t.
Tertiary syphilisgumma lesions
autoimmunity?
Treatment
Congenital syphilis
Saddle nose
Notched teeth
Saber shin nose
Pathology 18
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
Pathology 19
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
Pathology 20
Botulism and TetanusClostridium botulinum vs C. tetani
obligate anaerobes
Botulismfood borne
flaccid paralysis
Tetanussoil borne
rigid paralysis
Pathology 21
A Botulism Case History
Food risks
Antitoxins
Birds, Botox and Bioweapons…