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56 Cards in this Set
- Front
- Back
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What is a good serologic indicator of an acute infection?
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High IgM titer
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What is a good serologic indicator of a chronic infection?
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IgG
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Does the IgG titer always increase with time after infection?
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No it may decrease
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What is PCR not capable of distinguishing?
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Between live or dead organisms
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What are 3 general mechanisms by which organisms cause disease?
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-Direct tissue injury
-Injury 2ndary to inflammation -Immune cross-reactivity to host tissues |
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Why do we want to understand how organisms cause disease?
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It allows us to develop specific therapies - vaccines, and also to determine drug resistance.
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What is Empiric therapy?
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Treating based on the clinical presentation, complicating factors, and Gram stain.
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What is Definitive therapy?
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Treatment based on in vitro susceptibility test results.
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What organisms are Obligate intracellular?
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-Viruses
-Chlamydiae -Rickettsiae -Leishmania donovani (protozoan) -Trichinella spiralis |
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What organisms are Extracellular?
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-Mycoplasma
-Strep pneumoniae -Sporothrix schenkii -Trypanosoma gambiense -Wuchereria bancrofti |
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What organisms are cutaneous?
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-Staph epidermidis
-Trichophytan species |
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What organisms are mucosal?
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-Vibrio cholerae
-Candida albicans -Giardia lamblia -Enterobius vermicularis |
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What organisms are facultative intracellular?
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-Mycobacterium tuberculosis
-Histoplasma capsulatum -Trypanosoma cruzi |
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What are Prions?
What disease do they cause? |
-Abnormal proteins that resist proteases
-Chronic wasting disease - transmissible spongiform encephalopathy |
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What characterizes viruses?
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Dependent on host cell metabolism for replication
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What is the viral structure?
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-Nucleic acid genome
-Surrounded by protein capsid |
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What are bacteriophages, plasmids and transposons?
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Mobile genetic elements that encode bacterial virulence factors
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What are chlamydiae?
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Something in between bugs and viruses
-Divide via binary fission -Susceptible to antiobiotics -Cannot synthesize ATP |
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What morphology do Chlamydiae exhibit?
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Intranuclear inclusions containing elementary bodies
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What is the target cell for Rickettsiae?
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Endothelial cells
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What are Rickettsiae similar to?
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Chlamydiae
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So the main obligate intracellular pathogens are:
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-Viruses
-Chlamydiae -Rickettsiae |
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What are the 2 defining hallmarks of Mycoplasma?
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-Lacks a cell wall
-Smallest free living organisms capable of growing on an agar plate. |
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Can viruses grow on agar plates?
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No; viruses depend on eukaryotic cells in order to divide and grow.
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What is the most frequent and diverse group of human pathogens next to viruses?
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Bacteria
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What is the main structure of bacteria?
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-Have cell membrane
-Lack nuclei -Lack ER |
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What type of organism are Fungi? What is in their cell wall?
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-Eukaryotes
-Ergosterol |
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What are the 2 categories of fungi?
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-Budding yeasts
-Filamentous hyphae |
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What organism shows germ tube production in serum?
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Candida albicans
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What are the single-celled motile organisms with complex cytoplasmic organelles?
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Protozoa
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What are helminths?
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Parasitic worms
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How do we diagnose most of the helminths?
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By their eggs or larvae in stool samples.
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What are 2 common types of ectoparasites?
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-Lice
-Ticks |
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What are 3 tick transmitted diseases?
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-Lymes
-Babesiosis -Ehrlichiosis |
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With all of the bugs and viruses and pathogens floating around why aren't humans all sick?
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Because they have host barriers to infection - immune system, skin and mucosal surfaces, etc.
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What factors will result in pathogens being able to evade host defenses?
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-If the inoculum is very high
-If the host is immunosuppressed |
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Does the route of entry of an organism always indicate where the ultimate disease will develop?
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No; polio virus is SWALLOWED but is tropic for the brain.
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What type of pathogen invasion is usually quickly suppressed?
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Bloodstream invasion
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minute 22, slide 24
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ok
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What determines viral tropism for a host cell?
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Specific receptors
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What are the 6 general steps in viral infection of a host cell?
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1. Attachment
2. Penetration of host membrane 3. Viral uncoating 4. Replication of nucleic acid via host cell machinery 5. Viral assembly 6. Release |
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What are 5 major effects of the viral proteins made by the host cell machinery?
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1. Reduced host cell synthesis of DNA, RNA, and protein
2. Metabolic derangements 3. Cell lysis/fusion 4. Neoplastic transformation 5. Viral inclusions in host cell |
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What are the 2 things that can be done with viral proteins by a host cell?
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-Viral assembly (of new viruses)
-Processing for presentation on MHCI |
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What happens as a result of viral presentation on MHC I?
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-Immune damage to the host cell via Tc cells
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What mechanism is used by many viruses to decrease immune recognition?
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Blocking MHC I loading and synthesis at various points along the way (TAP transporter, Proteosomal activity, etc)
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What is the inflammatory stimulator in gram neg bacteria?
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LPS
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What is the predominant component of gram pos cell walls?
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Peptidoglycan + teichoic acid
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What is the main effect of endotoxin?
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Stimulation of cytokines
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What cytokines are stimulated by LPS?
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-TNF
-IL1, 6, 8 -Nitric oxide and PAF |
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What are the effects of LPS in low amounts?
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-Leukocyte activation
-Endothelial cell activation -Complement activation |
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What are the effects of LPS in moderate amounts?
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-Fever
-APR production in the liver -Leukopoeisis in the BM |
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What are the effects of LPS in high amounts?
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-Decreased CO and PVR
-Vascular injury, thrombosis, DIC -ARDS |
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What do we call the response to LPS in low/mod/high amounts?
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Low = local inflammation
Mod = systemic effects High = septic shock |
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Is giving an antibiotic to kill the gram neg organisms causing a septic infection sufficient to STOP the sepsis?
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No - the endotoxin is still prsent and you have to get it cleared.
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What are the pathogens capable of significant antigenic variation?
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PRINTBG
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What does PRINTBG stand for?
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-Plasmodium falciparum
-Rhinovirus -Influenza virus -Neisseria gonorrhoeae -Trypanosoma brucei -Borrellia species -Giardia lamblia |
