Principles of Infectious Disease

1
Principles of Infectious Disease
2
Terminology

• Pathology study of disease
• Etiology cause of disease
• Pathogenesis disease process
• Infection colonization by microbe
• Disease illness

3
Microbe-Host Interactions
4
Normal Microbiota/Flora

• Compete for living space and nutrients with
  pathogens
• Mutualism they get space and food, we get
  vitamins and protection from pathogens
• Biofilms of microbes cooperate in attachment

5
(No Transcript)
6
Opportunistic Pathogens

• Organisms that cause disease when they enter
  different environment
• Staphylococcus aureus enters break in skin
• Escherichia coli enters peritoneal cavity from
  burst appendix
• Clostridium difficile colonizes intestines when
  normal flora have been killed by antibiotics

7
Disease Etiology Kochs Postulates
8
Exceptions to Kochs Postulates

• Some bacteria and viruses cannot be cultivated in
  pure culture
• Some pathologies are caused by several organisms
  nephritis, pneumonia, meningitis, peritonitis
• -itis inflammation
• Some organisms cause several diseases
  (Staphylococcus aureus)
• Ethical considerations

9
Microbe of the Day

• Bacillus anthracis
• Gram positive rod
• Survives in soil as spores
• Infects hoofed animals
• First bacterium proven to cause specific disease

10
Anthrax

• Primarily a disease of domesticated and wild
  hoofed animals
• Human infection arises from contact with diseased
  animals or carcasses

11
Anthrax in Herbivores

• May be listless or without appetite
• After death, bleeding from body cavities
• In US, incidence higher along old cattle drive
  routes

12
Human Anthrax Infections

• Cutaneous
• Respiratory
• Gastrointestinal

13
Anthrax Disease

• Not spread person-to-person (not contagious)
• Most common in countries without veterinary
  public health programs
• NOW germ warfare threat

14
Infection
15
Portals of Entry

• Skin
• Gastrointestinal Tract
• Respiratory
• Urogenital
• Via Placenta
• Parenteral (injection, bite)

16
Attachment

• Fimbriae
• Glycocalyx
• Hooks
• Suction discs
• Viral spike

17
Surviving Host Defenses
18
Additional Virulence Factors
19
(No Transcript)
20
More Terminology

• Signs measurable changes
• Symptoms patient complaint

21
Portals of Exit
22

• Communicable disease transmitted from one host
  to another
• Contagious disease easily transmitted

23

• Acute disease
• Chronic disease
• Latent Disease

24

• Secondary infections
• Bacteremia, septicemia, toxemia, viremia

25

• Sporadic occasional cases
• Endemic constantly present
• Epidemic outbreaks
• Pandemic worldwide outbreaks

26

• Incidence number of infected people during a
  particular time period (i.e. year)
• Prevalence number of diseased people at any
  given time

27
Reported US AIDS Cases

• 1999 Incidence 45,000 prevalence 700,000

28
Spread of Disease

• Reservoir source of organisms
• Humans
• Animals (zoonoses)
• Environment

29
Spread of Disease

• contact
• direct
• indirect (fomite)
• droplet
• vehicle
• vector

30
Nosocomial Infections

• Hospital-acquired
• 5-15 of patients acquire infection

31
Control of Nosocomial Infection

• Handwashing
• Disinfection of surfaces
• Single-use materials
• Appropriate antibiotic use
• Surveillance infection control officer

32
Emerging Infectious Disease

• Mutation of organism to new serovar (antigenic
  type)
• Migration of humans and animals into new
  environments
• Travel
• War and natural disasters
• Decline in vaccination rates
• Climatic changes

33
What You Should Know About Principles of Disease

• All terminology covered in lecture
• Locations and importance of normal flora
• Kochs Postulates and exceptions
• Virulence factors
• Ways diseases are acquired and transmitted
• Importance of nosocomial infections
• Reasons for emerging infectious diseases