Term
distinguish prokaryotes from eukaryotes |
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Definition
prokaryotes:
no nucleus or membrane bound organelles
less than 5 microns in size
70s ribosomes (eukaryotes 80s except in organelles which have 70s)
nucleic acid is a single circular molecule
replicate by binary fission
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Term
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Definition
thin peptidoglycan layer
have outer membrane and periplasmic space (pps)
porins transport hydrophilic molecules in/out of pps
LPS and lipid A major surface antigen
stain red or pink: lose crystal violet and get safranin red
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Term
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Definition
thick peptidoglycan
teichoic acids - major surface antigen
stain purple: retain crystal violet |
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Term
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Definition
1) crystal violet
2) gram's iodine - form complex in cells that have crystal violet
3) decolorizer (ex alcohol)
4) safranin red |
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Term
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Definition
Lipid A - endotoxin activity
core polysaccharide: link Lipid A to terminal PS, maintain cell wall integrity
terminal PS: repeating sugar subunits; O antigen |
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Term
bacterial cell membrane properties |
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Definition
no sterols (few exceptions: mycoplasma)
no organelles: cell membrane takes over these processes
(respiration, making macromolecules) |
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Term
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Definition
AKA glycocalyx, exopolysaccharide, slime layer
hydophilic, gel like simple polysaccharide covering
aid in identification
avoid phagocytic recognition
weak immunogen
can allow growth of microbial communities
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Term
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Definition
hair-like filamentous structures that extend outward through the capsular layer
anchor bacteria to solid surfaces
outer part: single repeating protein subunit
Additional fimbrial proteins are required for membrane transport, anchoring to the cell wall, filament assembly
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Term
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Definition
filamentous structures that extend outward from the cell to function in motility
single repeating protein subunit, flagellin
Additional proteins are involved in hook and basal body structures which anchor the flagellum to the cell wall and generate motion |
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Term
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Definition
made by bacillus and clostridium
extreme resistance: dipicolinic acid, high levels of calcium in the core wall
Parts:
core: contains components of live cell
inner membrane: semi crystalline, becomes fluid after germination. surrounded by thin PG layer
cortex: modified PG, special glycosidic bonds resist lysozyme, no teichoic acids or carbs
coat: impermeable to enzymes
exosporium: thin, complex membrane on outside
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Term
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Definition
takes several minutes
end dormancy: physical damage to the exosporium
germination is initiated by loss of dipicolinic acid and calcium and uptake of water.
Outgrowth through the spore coat and cell division: when nutrients are present |
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Term
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Definition
cell dies and releases an endospore
takes 8-10 hours |
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Term
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Definition
cells rapidly reproduce
produce metabolic enzymes
find growth rate by measuring colonies, or possibly spectrophotometry of samples, over time
"population doubling time"
if new nutrients are added and toxic products are removed
in a steady-state, bacteria can, theoretically, be maintained in logarithmic phase forever.
A laboratory device used to obtain a steady-state of bacterial growth is called a chemostat. |
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Term
pathogenic bacteria: nutrient source |
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Definition
tend to use macromolecules such as starch, proteins; don't produce own food source |
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Term
selective differential and selective enrichment media |
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Definition
Selective-enrichment and selective-differential media both select for a particular type of bacteria.
Selective-differential media differs in that it also contains some substance, such as a pH indicator, to assist in determining the identity of the bacteria.
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Term
types of oxygen requirements |
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Definition
Obligate aerobes
microaerophilic bacteria
capnophilic bacteria: carbon dioxide also must be high
aerotolerant
facultative anaerobes
obligate anaerobes |
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Term
reactive oxygen species (toxic oxygen radicals) |
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Definition
Superoxide, singlet oxygen, peroxides
found: where metabolism is occuring; especially high in phagolysosomes
Bacteria use enzymes (oxidase, catalase, superoxide dismutase) to convert them into less dangerous forms.
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Term
food storage methods to retard microbial growth |
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Definition
Refrigeration, freezing, treating with acid or salt, drying. Heating, radiation, and preservatives are intended to kill bacteria.
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Term
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Definition
Procedures (hand-washing)
equipment (gloves)
facilities (double sets of doors, autoclaves, security)
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Term
classification of infectious agents, risk |
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Definition
virulence and therapy groups:
1 – unlikely to cause disease.
2 – associated with non-serious disease, treatment available.
3 – associated with serious disease, treatment sometimes available.
4 – likely to cause serious disease, treatment unavailable or disease difficult to treat.
risk to individual and community:
1 – low risk.
2 – moderate individual risk.
3 – high individual risk, low community risk.
4 – high individual and community risk.
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Term
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Definition
likelihood (%) of true positives found by your test. |
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Term
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Definition
likelihood (%) of true negatives found by your test. |
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Term
positive predictive value |
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Definition
represents how likely a positive result is to be a true positive
varies with prevalence of the disease in the population
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Term
negative predictive value |
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Definition
represents how likely a negative result is to be a true negative.
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Term
preanalytical stage of testing |
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Definition
Proper test selection
proper sample collection
labeling
storage
transport |
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Term
methods to detect microbes in animal samples |
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Definition
Direct – Gross or microscopic
Gram stain and acid fast stain
Serology / fluorescent antibody
molecular analysis: PCR and DNA restriction comparisons.
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Term
using humoral / immune response in lab testing |
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Definition
Serology (ELISA testing)
skin hypersensitivity testing
lymphocyte proliferation
cytokine production assays
Limitations:
you have to know what you’re testing for.
not cheap enough to test for everything at once
some combined tests are available (e.g. Snap Tests for lyme, ehrlichia, and heartworm).
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Term
antibiotics: natural source and purpose |
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Definition
naturally produced by fungi and bacteria
purpose: "secondary metabolites" - not certain
vestiges of normal metabolism
could be used for signalling |
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Term
rate kinetics of antibiotics |
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Definition
1st order rate kinetics, i.e. one molecule of drug is consumed by one target molecule.
maintaining an optimal proportion of drug to target is important for treatment.
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Term
major subcellular targets of antibiotics and an example for each |
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Definition
Cell wall – beta lactams (penicillin)
Cell membrane – polymixin
Ribosomal action – tetracyclines (doxycycline)
Nucleic Acid:
sulfonamides (sulfamethazine) - folic acid synth
metronidazole - DNA structure
Quinolones (enrofloxacin) - DNA gyrase
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Term
two methods for susceptibility testing |
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Definition
Diffusion: diffuse drug through agar to form a gradient of drug concentrations
ex: disc diffusion
Dilution: contain uniform concentrations of drug in a broth or agar medium
ex: microbroth diluton |
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Term
disc diffusion: endpoint measured |
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Definition
diameter of zone of inhibition
compare to standard values for organism to classify as
Susceptible, Intermediate or Resistant |
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Term
broth dilution: endpoint measured |
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Definition
visible growth
MIC is reported as lowest concentration where all growth is inhibited |
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Term
standardization factors for testing susceptibility |
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Definition
composition of medium
ions / pH
depth and volume
concentration of drug
disk size and material
incubation time and conditions
preparation of inoculum, concentration
organism used
criteria for endpoints
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Term
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Definition
high likelihood of therapeutic success
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Term
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Definition
therapeutic outcome is uncertain |
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Term
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Definition
High likelihood of therapeutic failure |
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Term
how to determine resistance or susceptibility |
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Definition
MIC or zone diameter values compared to published “breakpoint” guidelines
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Term
Guidelines for drug/organism/host combination: determining factors |
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Definition
MICs from large, geographically diverse populations of the bacterium isolated in the field
pharmacokinetic and pharmacodynamic properties of the drug in the host
efficacy of the drug in clinical trials at standard dosage and dosing interval in the target infected host
inhibitory concentrations assume the drug is in the plasma
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Term
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Definition
the ability to kill or slow the growth of microbes while minimizing harm to the infected host |
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Term
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Definition
the lethality (in animal studies) divided by the effective dose
values are found for 50% of a representative population (LD50 and ED50)
high therapeutic index: drugs that are able to target a part of the bacteria not present or important in the host
ex: cell wall synthesis / beta lactams
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Term
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Definition
kills bacteria
ex: beta lactams (must have active growth) cephalosporins |
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Term
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Definition
slows the growth of bacteria without killing
ex: tetracyclines, sulfonamides |
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Term
factors for selecting an antimicrobial agent for treatment |
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Definition
1. species/age related adverse effects 2. fixed compounding (size/concentration/carrier) 3. restraint/feeding habits 4. compatibility with other medications 5. propensity for antimicrobial resistance |
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Term
factors that affect efficacy of treatment besides MIC result |
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Definition
1. physiological status of the bacteria (ex growth phase) 2. immuno-physiological status of the host 3. pharmacokinetic properties of drug in host (effect of host on drug - absorption, distribution, elimination, binding) 4. pharmacodynamic properties of drug (effect of drug on host/bacteria – principle of selective toxicity, post-antibiotic effect, sub-MIC effects, immunosuppression) |
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Term
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Definition
small, circular peices of DNA
do not code essential functions or products
Conjugative plasmids are self-transmissible from one bacterium to another in the process called conjugation
Some non-conjugative plasmids can be mobilized by conjugative plasmids, others cannot
plamids are replicated when the cell divides, can be integrated in the chromosome |
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Term
lytic bacterial infection |
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Definition
Recognition
Injection
Transcription of phage DNA
replication & protein synthesis
phage assembly
lysis and release Lysogenic cycle: viral DNA is integrated into the bacterial chromosome and coexists with it; no new viruses are made but DNA is replicated when host reproduces stress brings on the lytic cycle |
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Term
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Definition
small, extracellular DNA fragments
free DNA is rapidly degraded in extracellular environments and DNA is a large macromolecule that does not normally cross cell membranes.
competent cells are able to bind the DNA, translocate accross membrane and integrate into its chromosome
within one species
bacteria die and others are able to pick up their DNA to get that function
occurs in a limited number of pathogens; mostly within same species |
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Term
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Definition
moderate gene capacity
a DNA fragment is assembled in a bacteriophage nucleocapsid during lytic infection
Transduction occurs in different bacterial species but is limited by host range of the transducing phage
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Term
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Definition
moderate to large gene capacity
unidirectional plasmid transfer from a suitable donor to a recipient bacterial cell
encodes sex pilus so the recipient can go on to transfer it again
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Term
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Definition
site-specific recombination systems that recognize sites on 2 DNAs and promote the insertion of new DNA.
The most common integrons possess an antimicrobial resistance gene.
Integrons are important factors in multiple antimicrobial resistance in Gram-negative bacteria. |
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Term
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Definition
may move by excision from one location and insertion into another or by replication at one site and insertion of a new copy elsewhere.
sometimes referred to as jumping genes, can move large distances between DNA regions within a cell, eg. between plasmids and chromosome.
Many transposons possess genes for other traits such as antimicrobial resistance.
insertion may result in inactivation of genes in the target DNA region |
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Term
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Definition
genetic elements that are capable of moving, in a random fashion,from one place in a DNA molecule to another through site specific recombination
Each has terminal invert repeat sequences that encode enzymes for excision (transposase) and insertion (recombinase) and is flanked by direct repeats of the target sequence following insertion.
Insertion sequences are always excised from one region of DNA and inserted into another.
Insertion sequences do not move great distances and do not usually carry selectable genes. |
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Term
aquired resistance methods |
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Definition
1. Altered Targets (reduced drug binding affinity) 2. Enzymatic Inactivation of Drug (modifying enzymes ex beta lactamases) 3. Decreased Cell Permeability (porins, OMPs) (changes in LPS and outer membrane proteins can increase resistance to certain drugs) 4. Decreased Accumulation of Drug in Cell (efflux, antiport systems) |
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Term
innate resistance methods |
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Definition
a. structure b. alternate pathways c. environmentally regulated phenotypic variation |
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Term
solutions to antibiotic resistance issues |
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Definition
1. Prudent drug use
restrict extra label use, alternative therapy
2.Pathogen Control
hygeine, vaccination, food safety, understanding resistance methods
3. Policy
education, resisitance monitoring
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Term
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Definition
1) microbe must be associated with sick animals and not with healthy ones.
2) grow a pure culture of the microbe.
3) Infect a new host with the microbe and see disease take hold.
4) isolate the same microbe again from the new host.
Limitations:
some microbes are opportunistic (so they appear in healthy as well as sick hosts),
not all microbes can be cultured,
in culture the microbes could lose their virulence.
multi-species disease – a disease caused by the interaction of two or more parasitic microbe species.
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Term
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Definition
host: species, age, breed, sex, genetics, physiology, immune
pathogen: virulence, stability, route, dose
environment: stress, nutrition, trauma, immunosuppression, metabolic dysfunction, intercurrent disease, cilmate |
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Term
3 Types of virulence factors |
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Definition
- the ability to colonize and grow in or on the body
- the ability to avoid destruction especially after invasion
- the ability to cause tissue destruction
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Term
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Definition
1. enable a bacterium to reach a site of entry (bacterial motility and chemotaxis)
2. hold bacteria in place at the site of entry (bacterial adhesins – fimbriae, non-fimbrial
surface proteins, biofilm-forming exopolysaccharides)
3. support sufficient growth at the site of entry (preferred substrates, iron sequestering
components – siderophores, lactoferrin/transferring/heme receptors)
Colonization can involve complex relationships with other microorganisms. |
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Term
Avoiding destruction after invasion |
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Definition
possession of iron sequestering components (meet nutrient requirements)
avoiding destruction by host phagocytic cells and serum proteins:
1. evade phagocytosis
2. destroy or inactivate phagocytes
3. protect bacteria from phagocytic killing by escape from phagocytic vacuoles, prevention of
lysosomal fusion to phagosomes or resistance to hydrolysis in phagolysosomes.
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Term
tissue destruction methods |
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Definition
Toxins: act directly with mechanical or physiological alterations in cells
act indirectly by triggering exaggerated host inflammatory/immunological responses
that cause tissue damage
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Term
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Definition
1) a requirement for unfolding through enzymatic “nicking” to activate toxin
2) functional domains (binding and catalytic activity) that are physically separable either as different
proteins or different termini of a single protein. |
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