Term
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Definition
| An organism that causes disease |
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Term
| What is a primary pathogen? Examples? |
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Definition
Cause disease in healthy hosts
-influenza
-salmonella
-shigella |
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Term
| What is an opportunistic pathogen? What kinds of conditions do they occur in? |
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Definition
Cause disease in compromised hosts
-immunocompromised
-break in physical innate barrier
-break in normal flora
-candida albicans, pneumocysits jirovecii |
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Term
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Definition
| The degree of severity of a disease |
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Term
| How is virulence determined? |
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Definition
| By adherence, invasiveness, toxicity, persistence |
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Term
| How is virulence usually measured? |
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Definition
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Term
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Definition
-the number of microbes required to kill 50% of infected hosts
-the fewer the number of microbes required to cause disease, the more virulent |
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Term
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Definition
| the number of microbes required to infect 50% of a population |
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Term
| What is the relationship between LD50 and virulence? |
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Definition
INDIRECT
-a lower LD50 means the organism is more virulent (takes fewer organisms to cause disease) |
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Term
| What are portals of entry for a microbial pathogen into a host (2)? |
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Definition
Skin (integrity compromised)
Mucous membranes |
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Term
| What are different routes of entry of a microbe into a host (4)? |
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Definition
Ingestion: GI tract
Inhalation: Lung/Respiratory
Sexual Transmission: UG tract
Parental Route: microorganisms depostied directly into tissues beneath skin or mucous membranes (punctures, injections, bites, etc.) |
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Term
| How can infection spread? |
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Definition
| By either direct or indirect contact |
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Term
| What are some examples of indirect contact? |
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Definition
-contact with fomites
-horizontal transmission via vectors (mosquitoes, ticks, etc.)
-mode of entry depends on the pathogen |
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Term
| What are two examples of virulence factors? |
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Definition
| Virulence genes and pathogenicity islands |
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Term
| What are virulence genes? |
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Definition
encode factors allowing pathogen to cause disease (adherence, invasion, nutrient acquisition, modulation of immune system)
-toxins
-attachment proteins
-capsules |
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Term
| What are pathogenicity islands? |
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Definition
| Section of genome, may contain multiple virulence genes, often encode related functions (protein secretion system, toxin production) |
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Term
| How are pathogenicity islands transferred? |
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Definition
Transferred as a block from other organisms
-often flanked by phage or plasmid genes
-often have GC content different from rest of genome |
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Term
| How can you tell if there is a pathogenicity island in a host genome? |
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Definition
| by looking at the GC content |
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Term
| What are two common themes used by bacterial pathogens to cause disease? |
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Definition
| bacterial colonization and intoxication |
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Term
| How does intoxication cause disease? |
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Definition
| Due to production of a pre-formed toxin |
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Term
| What must a pathogen do before colonization can occur? |
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Definition
A pathogen must gain access to nutrients and appropriate growth conditions
-may grow locally at the site of invasion or may spread through the body |
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Term
| How do pathogens gain access to host tissues? |
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Definition
By adherence
-through interactions between pathogen and host macromolecules |
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Term
| what are some major adherence factors used to facilitate attachment of microbial pathogens to host tissues? |
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Definition
-capsules
-adherence proteins
-lipoteichoic acid
-fimbriae/pili |
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Term
| What is a pili (fimbriae)? What do they do? |
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Definition
-hollow fibrils with tips to bind host cells
-mediate initial "loose" binding
-can be followed by tighter bidning mediated by non-fimbrial adhesins |
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Term
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Definition
| surface proteins on pathogens that bind to host cells |
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Term
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Definition
-adhere to mannose (mannose sensitive)
-grows from outer membrane (sec dependent), new subunits added at base |
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Term
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Definition
-do not adhere to mannose (mannose resistant)
-grow from inner membrane (sec dependent), can grow and retract "twitching motility" |
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Term
| Which type of pili exhibits twitching motility? |
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Definition
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Term
| What is forced phagocytosis? |
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Definition
| An evolved mechanism for entering host cells that are not naturally phagocytic. This is done by attaching to host cell surfaces and causing changes in host cell cytoskeleton that results in engulfment by host cells |
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Term
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Definition
| Commandeers host cell machinery for intracellular movement |
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