Med Micro Exam I Flashcards by Ari B

Name the human pathogens

Virus and prions
Bacteria
Fungi
Protozoa
Helminths

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Describe Koch’s Postulate

To show that an organism causes specific disease

1) . Microbe present in every case
2) Microbe must be isolated from diseased host & grown in pure culture
3) Microbe must cause same disease when introduced into a healthy host
4) Microbe must be re-isolated from experimentally-infected host

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What factors influence the outcome of an infection?

Host Defenses and Microbe Pathogenicity

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What are the host defenses

Physical/chemical barriers
 Phagocytic cells
 Non-specific 
 Specific immunity
 State of the host

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What are the Microbe Pathogenicity ?

Virulence
 Attachment
 Capsule
 Enzyme &amp; toxin production
 Evasion of immunity

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Host Defenses > Microbe Pathogenicity =

health

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Host Defenses

disease

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Why re-emergence?

Lapses in vaccination 
Drug resistance and improper use of drugs 
increased travel and trade
changes in behavior 
increased immunosuppressed populations
increased poverty

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Main goal for parasites

survival and replication

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Classification is based on what?

Cell Structure
Life Cycle/Stratgey
DNA/RNA/PROTEIN (GENOME)

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Aceullular/Non cellular

genetic material but no cell membrane

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Describe virus

DNA/RNA with protein coat

uses host synthetic machinery

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Describe prions

infectious proteins

rely on normal cellular proteins to replicate

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Cellular

single vs multicellular

prokaryotes vs eukaryotes

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Describe prokaryotes

no nucleus 
single, circular chromosome, and plasmids 
couples tx and tl 
cell wall made of peptidoglycan 
uni/multi cellular goes to biofilms

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Describe eukaryotes

Fungi, Protozoans, Animalia
nucleus 
tx and tl separated
multiple chromosomes 
some have cell wall
membrane bound organelles 
ribosomes 
mitochondiria site of respiration

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Microscopic

bacteria, viruses, fungi, prions, protozoans
replicate within host
large number of progeny
overwhelming infection

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Macroscopic

worms and arthropods
infectious stage matures into reproductive form
number of progeny is controlled by number of organisms entering the host
life cycle continues after leaving the host

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Intracellular

viruses, chlamydia, rickettsias, all obligate intra parasites

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Advantages of Intracellular

access host machinery, intracellular nutrients, metabolite and ATP
protected from host immune response
protected against interaction with some drugs

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Disadvantage of Intracellular

resticted by the cell
to spread it must leave the cell
immune defenses that include intrracellular killing carried out by natural killer cells, cytotoxic T cell
may cause tissue damage which is damage can be from immune response and or lysis of cells by microbe

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Extracellular

all large macroparasites

most bacteria, fungi, protozoans

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Advantage of Extracellular

more rapid spread

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Disadvantage

must synthesize more things on its own

exposure to host envrionment that includes immune factors, various drugs

extracelular killing : antibodies, complement, phagocytes

pathogensis : extensive tissue damage die to immune response and physical size + motility microbe

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Classification is based on what?

genome sequencing

Eukaryote classification

species

Viruses classification

nucleic acid and life cycle / replication

Morphology of bacteria

cell wall | G+ and G-

Biochemical properties of bacteria is based on what?

subspecies

Subspecies

``` based on immunological properties serotype ot serogroup based on biochemical tests biotypes, strains, groups, mrsa phage typing genetics ```

Bacteria

dsDNA, no introns, no histones | plasmids , 70s ribosomes

Virus LifeCycle

``` Recognition/Attachment Penetration/Entry Uncoating Biosynthesis Assembly Release ```

Host range

the range of cells that can be infected | cell, tissue, species specific

Recognition/Attachment

viral attachment factors bind to host cellular receptor

Penetration/Entry | enveloped and naked viruses

fusion doesn't depend on pH during fusion w/ pm fusion depends on pH during receptor-mediated endocytosis/endosome entry through receptor-mediated, formation of endosome

Uncoating

happens for all viruses | trigger for uncoating varies

Biosynthesis

``` tx,tl,replication DNA viruses in nucleus RNA viruses in cp tx occurs as cascade tl dependent on host ```

Assembly

errors occur that result in non-infectious particles | particle-virion ratio is high

Release

Naked- lysis Envelope- budding,exocytosis,lytic lysis kill cells budding persistent infection and viral release

Viruses and Prions

acellular/cellular | obligate intracelluar parasites

Virion

infectious virus particle | 18-800 nm

Genetic material of Viruses

DNA or RNA ss or ds 1 chromosome vs multiple non segmented vs segmented

Polarity of RNA viruses

+ encodes final code - opposite polarity dsRNS +/- ambisense

simple virus

genome and single capsid

glycoprotein spikes

used for attachment may promote fusion major antigen

Non enveloped

more resistant to external environment

Enveloped

more susceptible to environmental (external) must be in a moist environment to remain intact

Transmission depends on

``` microbe number shed stability in environment microbe number required for infections route of transmission genetics of the strain ```

Phylum Nematoda

no attachment mature within host long lived infections thick cuticle layer- longer life

Class Trematoda

Flukes parasites of molluscs and vertebrates deposition of eggs lead to pathogen

Class Cestoda

``` flatworms have hooks and suckers on ends in larval stage lifecyle involves intermediate hosts grow in digestive tracks host generally not harmed ```

The three groups of pathogens

Phylum Platyhelminthes

Helminths

parasitic worms larval stage classify them as microbes adults can be meters long found in subtropics/tropic environments

Microspara

``` non motile obligate intracelluar parasites no mitochondria tubular structure at the end of cell asexual reproduction entercytozoans ```

sporozites | merozoites

attachment factors for liver | attahments factors for RBCs

intermmediate host | definite host

seen when more than one host - asexual reproduction | sexual reproduction

Ampicomplexa

``` organelle at apex of cell intracellular parasite non motile shizogony sexual repro = insect vector trophozoites ```

Cilliphora

``` cillia binary fission conjugation shizogony cyst and trophozoite stages Balatidium coli ```

Sarcomastigophora

ameboid and flagellated binary fission trophozoite

Phyla containing human pathogens are based on

morphology of cell structure motility reproduction

Protozoans

``` 2-100 um single celled no cell wall chemoheterotrophs faccultative anaerobes 20,000 species 57 cause pathogens ```

trophozoite

vegatative cell

asexual reproduction

binary fission, budding, shizogony

sexual reproduction

cojugatoin | gametocytes

cyst stage

protective against environment | frecal oral transmission