Battling the Enemy Flashcards
3 ways we classify microorganisms?
1) by structure
2) by pathogenicity
3) by outcomes of infection
3 ways we classify microogransims by structure?
1) Viruses: DNA or RNA surrounded by a protein coat
2) prokaryotes (bacteria) simple cell structure w/o nucleus or organelles
3) eukaryotic pathogens (fungi) complex cell structure with nucleus and specialized organelle
3 ways we classify microogransims by pathogenicity?
1) Commensal
2) Opportunistic
3) Pathogenic microbes
Commensal pathogenicity
- part of our normal flora- symbiotic relationship
- nonpathogenic
Opportunistic pathogenicity
- cause disease if our immune systems are weakened
- ex: immunocompromised from HIV or chemo can die from thrush
Pathogenic microbes pathogenicity
- cause disease in immune competent individuals
- ex: malaria
2 ways we describe outcomes of infection?
1) asymptomatic or symptomatic infection
2) acute or chronic infections
what is an outbreak and what are the two types?
- occur when a new pathogen is introduced to a new location, have no herd immunity
1) epidemic
2) pandemic
epidemic vs pandemic?
1) epidemic: occur over a larger geographic area into a naïve population
2) pandemic: a worldwide epidemic
Viruses
- smallest known infectious organisms
- are obligate intracellular pathogens (rely on host cell for replication and dissemination)
- contain a protein coat/capsid
How do we classify viruses (3 ways)
1) type of nucleic acid
2) presence/ absence of envelope
3) antigenic determinants
viruses & type of type of nucleic acid?
-can have RNA or DNA, ss or ds genomes
obligate intracellular pathogens
- relies on hot cell fo replication & dissemination
What does the protein coat/capsid do?
-protects the viral genome
Viral envelope?
- some have it some do not, a way we classify viruses
- made of lipid & protein, usually formed by virus budding through the cell membrane
5 routes viruses can use to get into the cell?
1) oral fecal route: rotavirus/ norovirus
2) respiratory route: influenza,
3) sexual transmisision:herpes
4) vectors
5) zoonoses
What is the route of transmission dependent on?
- the type of virus and where it is shed from and what cells it wants to infect
vector transmission of virus?
- arboviruses
- vectors are small bugs like ticks, mosquitoes and flies (arthropods)
zoonoses
the transmission of viral diseases from animal reservoirs to humans through direct contact with animals or through vectors
- some viruses can be eliminated in human pop but remain in animal reservoirs, then can resurface if in contact w/ humans
5 stages of viral life cycle?
1) Attachment
2) Penetration & uncoating
3) Genome replication
4) Assembly & maturation of virus
5) Release from infected cells
3 ways that viruses can be released from infected cells?
1) budding
2) secretion
3) burst out of cell
what are the 3 types of proteins encoded by the virus?
1) for replicating the genome
2) for packaging the genome & delivering it to host cells
3) for modifying the structure/function of host cell
4 ways viruses damage the host cell?
1) hijack cell trxn/trans machinery
2) cell lysis/ target for destruction
3) cell transformation (immortalization)
4) cause organ damage
Why is it bad for host cell when virus hijacks cell trxn/trans machinery for own use?
- means taking energy away from the normal cell functions
- also means that trxn/ trans viral & NOT normal proteins, so have a lack of proteins need to survive,
- proteosomes overloaded so dtysfunctioning
downstream consequence of viruses causes cell immortalization?
-can lead to cancer in some cases
viruses & effect of cell lysis on host cell
- cell lysis= cytopathic effect
- causes stress/inflamamtion response in the cell which is damaging
Bacteria
- Prokaryote; unicellular
- primitive nucleoid w/o membrane
- no cytoplasmic organelles
- reproduce asexually
- can/can’t cell walls
- most don’t cause disease, some beneficial
bacteria’s cell walls
- some cell walls contain peptidoglycan some don’t
- is basis of gram +/- staining
commensal organisms?
- bacteria that live on our bodies and have symbiotic relationships with us
- diff organisms prefer diff regions on the body due to bacteria’s specilization for certain habitats
what else can affect our microbiome?
- microbiome= all the bacteria naturally living on us
- lifestyle, diet, genetics can affect this
4 ways to classify bacteria?
1) Shape
2) Ability to retain dyes (gram vs. acid fast)
3) Ability to grow with/without air
4) Biochemical reactions
Shape of bacteria?
1) coccus – spherical
2) bacillus – rod shaped
3) spirillum – spiral shaped
4) virbrio – comma shape
what is it called when bacteria able to grow w/ air? w/o air?
1) Aerobes –best in the presence of oxygen
2) Anaerobes –best in the absence of oxygen
3 common biochemical reactions bacteria can perform?
1) nutrients
2) metabolites
3) antibiotic susceptibility
Gram stains used for?
- used to distinguish between 2 types of bacteria dependent on presence of peptidoglycan in their cell wall
Gram-positive bacteria
-have thick mesh-like cell wall made of peptidoglycan (50-90% of cell envelope)
-are stained PURPLE/BLUE by crystal violet
-
Gram-negative bacteria
-have a thinner layer of peptidoglycan (10% of cell envelope), so don’t retain the purple stain & are counter-stained PINK by safranin
staining process for Gram +/- ?
- have an initial staining step that both +/- take up, destaining removes gram - stain and leaves it clear.
- counter staining then occurs w/ safranin making the gram - cells pink
acid fast staining done on what bacterial cells?
- for bacteria w/ lipid rich cell walls that makes them resistant to Gram stain
- primarily mycobacteria and Nocardia
acid fast staining + vs - result?
- positive= RED/PINK
- negative= BLUE
- are staining the lipid (gooey) area
4 ways that bacteria cause tissue injury?
1) Byproducts of bacterial growth (acids; gases) are toxic
2) Degradative enzymes:
3) Toxins (end, exo, & super antigens)
4) Out-compete normal flora we require for tissue maintence
how do bacterial degradative enzymes cause tissue injury?
- they break down tissue allowing deeper penetration and spread
- can break down ECM, tight junctions,
super antigens
-are decoys that protect real antigen from being degraded
endotoxin
a toxin that is present inside a bacterial cell (or a part of the membrane) and is released when the cell disintegrates.
exotoxin
-a toxin released by a living bacterial cell into its surroundings
vacuolating toxin (vacA)
- an exotoxin
- causes gastric mucosal injury by making holes in the mucus lining
H. pylori and Type 4 secretion system?
- is a pill like structure that injects effectors into bacteria
- cause changes in cell structure & inhibit apoptosis so cell can keep producing bacteria
what kinds of things do effectors do?
1) actin remodeling
2) host cell growth proliferation
3) apoptosis inhibition
Parasites
- can be multicellular or unicellular
- are eukaryotic
4 eukaryotic kingdoms of parasites? what determines these kingdoms?
1) Protozoa (single cell)
2) stramernopilla (single cell)
3) Fungi
4) Animalia
- based on morphology, modes of locomotion, & reproduction*
Fungi
- type of parasite
- is eukaryotic
- have rigid cell walls
- have grouping based on morphology
why fungi have rigid cell walls?
- because they have chitin, glucans, & ergosterol instead of cholesterol in their walls
2 groups of fungi?
1) Molds – multicellular; reproduce by sexual & asexual spores
2) Yeasts – unicellular; reproduce by budding or fission
grouping based on morphology
5 classes of fungal infections?
1) Superficial mycoses
2) Cutaneous mycoses
3) Subcutaneous mycoses
4) Endemic/Systemic mycoses
5) Opportunistic mycoses
Superficial mycoses
localized on hair shafts & superficial skin cells
-non destructive; cosmetic only
Cutaneous mycoses
- keratin-containing tissues (hair, nails, and skin)
- elicit a host response and become symptomatic
Subcutaneous mycoses
- fungal infections deeper layers of the skin such as cornea, muscle and connective tissue
- elicit an immune response, symptomatic but tend to remain local
Endemic/Systemic mycoses
- occupy specific environmental/ecologic niches
- are pathogens
- e.g primary infection of the lung w/ spread to other organs in immune deficient individuals
Opportunistic mycoses
- caused by commensal fungi that are not usually pathogenic
- cause infection in individuals whose immune system is compromised
5 ways fungi can cause tissue damage
- not as well understood as bacteria*
1) fungi invasion leads to inflammatory response
2) subvert host immune system
3) Mucosal overgrowth compromises barriers
4) fungi + bacteria create biofilm
5) release toxins
what does “subvert host immune system mean”
- can mess up immune system & no longer kill other pathogens
- or can cause immune system to attack own body
biofilms
- a thin, slimy film of bacteria that adheres to a surface
- can be helpful or hurtful, can affect immune system functions
Protozoa
- single-celled eukaryotes
- do asexual or sexual reproduction
- can produce cysts, for protection during adverse env. conditions
- cabale of locomotion
trophozoite
is the vegetative form of protozoa
how do Protozoa do asexual reproduction?
-by fission, budding, or schizogomy
schizogomy
multiple fission events followed by separation into multiple daughter cells
how do Protozoa do sexual reproduction?
by conjugation where two haploid nuclei fuse to produce a zygote
how do Protozoa do locomotion (move around)
1) Pseudopodia
2) Cilia
3) Flagella
Pseudopodia
cell extensions that flow in direction of travel
Cilia
numerous, short, hairlike protrusions that propel organisms
Flagella
extensions that are fewer, longer, and more whiplike than cilia
how can parasites can tissue/cell damage?
1) adhesion to tissue can lead to damage
2) cause inflammation
3) nutrient sequestration
4) production of toxic substances
5) physical obstructions in tissues
