1. HOST-MICROBE RELATIONSHIPS AND DISEASE PROCESSES
CHAPTER 14
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2. Symbiotic Relationships
Mutualism
Microbe benefits
Host benefits
E. coli in intestine
Parasitism
Host is damaged
All pathogens
Commensalism
No effect on host
Corynebacterium in eye
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3. Host Invasion Contamination Presence of microbes Infection
Invasion or colonization by microbes
Disease
Change away from a normal state of health
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4. Pathogenicity Determinants
Microbial count
Virulence / Avirulence
Attenuation
Virulence Transposition via infection of novel hosts
Rabies vaccine
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5. Microflora 1014 microbes versus 1013 body cells Colonization
Non-sterile areas
Sterile areas
Resident microflora
Transient microflora
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6. Opportunism Host Defense failure Immune system Diabetes Burn victims
Microbes in unusual locations
Microflora disturbances
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7. Koch’s Postulates 1. Same microbe in every case of disease
2. The agent must be isolated and grown in pure culture.
3. Healthy hosts must get the same disease when inoculated.
4. The agent must be re-isolated and show to be the same causative agent.
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8. Exceptions to Koch’s postulates
Microbes do not always cause the same disease
Related to portal of entry
e.g. Strep throat, septicemia, flesh eating disease
Microbes cannot be cultured in isolation
Viruses, Chlamydia, Rickettsia
Many microbes cause the same disease
UTIs, pneumonias, meningitis
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9. Disease Types Infectious vs. non-infectious
Communicable vs. non-communicable
Contagious
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10. Bacterial Pathogenicity
Adherence factors permit attachment – Adhesins
Damage to Tissues
Invasive process directly
Enzymes /Toxins
Hyaluronidase
Coagulase
Kinase
WBC mediated damage
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11. Bacterial Toxins Endotoxins Exotoxins Gram negative
LPS cell wall component
Fever
Shock
Released at cell death
Gram positive
Proteins, usually enzymes
Potent effects
Specialized tissue damage
Hemolysins
Leukocidins
Neurotoxins
Enterotoxins
Secreted into bloodstream
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12. Exotoxin - Hemolysin
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13. Viral Pathogenicity Cytopathic effects Cell rupture Inclusion bodies
Giant cells
Latent infections
Persistent infections
HBV
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14. Eukaryotic Pathogen Effects
Algae
Toxins
Fungi
Toxins/enzymes
Direct damage
Protozoa
Helminths
Obstruction
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15. Vocabulary Terms Symptom Sign Syndrome Sequelae Acute disease
Chronic Disease
Subacute disease
Latent disease
Local
Focal
Systemic
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16. Disease Terminology Bacteremia Septicemia Viremia Primary infection
Secondary infection
Superinfection
Mixed infection
Inapparent infection
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17. Disease stages Incubation Prodromal Invasive (Disease) Decline
Convalescence
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18. Factors influencing Infectious Disease Prevention
Health care availability
Drugs
Immunization
Sanitization
Community Health
Emergence of new pathogens
Social migration/Change
Immigration
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