Symbioses n Mutualism n Parasitism n Commensalism n

Symbioses n Mutualism n Parasitism n Commensalism n Opportunism 1

Infection and Disease n Contamination n Infection n Disease 2

Pathogenicity Concepts n Pathogenicity n Virulence/Avirulence 3

Normal Microflora n Population size n Resident n Transient – Hours to months – Even pathogens in an immune person 4

Koch’s Postulates n 1. Same microbe in every case of disease n 2. The agent must be isolated and grown in pure culture. n 3. Hosts must get the same disease when inoculated. n 4. The agent must be reisolated and show to be the same causative agent. n n EXCEPTIONS Microbes do not always cause the same disease n Microbes cannot be cultured in isolation n Many microbes cause the same disease 5

Kinds of Disease n Infectious/Non-infectious n Communicable/Non-communicable 6

How Microbes Cause Disease n Direct Action – Adhesins – Invasion enhancing enzymes • Hyaluronidase • Coagulase • Kinase n Bacterial Toxins – Endotoxins • Fever • Shock n Bacterial Toxins (cont. ) – Exotoxins • Hemolysins • Leukocidins • Neurotoxins • Enterotoxins n Cytopathic Effects (Viruses) – Inclusion bodies – Giant cells – Persistent infections (HBV) 7

Vocabulary Terms n Sign n Acute n Symptom n Chronic n Syndrome n Subacute n Sequelae (seen later) n Latent 8

Vocabulary Terms (2) n Local infection n Septicemia n Focal infection n Bacteremia n Systemic infection n Viremia 9

Vocabulary Terms (3) n Primary infection n Secondary infection n Superinfection n Mixed infection n Inapparent (subclinical) infection 10

Infectious Disease Stages n Incubation n Decline n Prodromal n Convalescence n Invasive 11

Control of Infectious Disease n Drugs n Immunization n Sanitization n Future Challenges 12