Chapter 35

LPS (endotoxin)

-O polysaccharide side chains are antigenic and vary in composition between bacterial strains-core polysaccharide, charged sugars and phosphate-Lipid A, potent toxinLipids A: complex array of lipid residues; heat stable; toxic in small amounts; weakly immunogeniccauses septic shock: fever, blood vessel damage, weakness, diarrhea, inflammation, intestinal hemorrhage, fibromylosis-causes fever by causing macrophages to release endogenesactivates Hageman factor protein: blood clotting/multiorgan failure

ways to pathogens to evade host cell immune response

-make capsules that resemble host tissue components -change surface proteins (mutation or recombination) N. gonorrhaea -use phase variation to change gene expressional pili to adhere to host cells -produce proteases (IgA) to degrade host proteins

microbes avoid detection from the immune system by

-residing in cells that are supposed to destroy them -squeeze between host cells -make capsules to prevent phagocytosis -hide under mucus -take shelter in biofilm -produce enzymes to deactivate innate immune responses -have specialized protein secretion system to kill host cells

factors affecting pathogen entering a host

-virulence of the organism -number of invaders -presence of adhesion/invasion factors

active penetration of pathogens: production of lytic substances that alter host tissue by

1. attacking extracellular matrix/intestinal lining 2. degrading carb/protein complexes 3. disrupting host cell surface

2 steps of adhesion

1. nonspecific/reversible: hydrophobic, electrostatic, vibrational forces that encourage docking 2. specific/permanent: lock and key binding

AB exotoxin

A subunit: active toxin subunit; has an enzyme component that causes toxicity; causes harmful effects-usually have ADP ribosylation activity that catalyzes the transfer of adenosine diphosphate/ribose moieties of host NAD+ to target host molecules

ergots

Alkaloids with varying physiological effects, including hallucinations. One alkaloid in the group is lysergic acid, or LSD

aflatoxin

Approximately 18 different types; affect the liver, extremely carcinogenic, mutagenic, and immunosuppressive

Choose all of the following attributes that are necessary for any bacterial pathogen to attach to and colonize a host cell.

Capsule production, Utilize spikes to attach to host cells, Presence of fimbriae

strategy used to evade the immune responses of the host: changes surface proteins by genetic recombination

influenza virus

tumor necrosis factor

involved in the inflammation of autoimmune diseases-causes fever by releasing cytokines

endotoxins

lipid A portion of LPS of the outer membrane of gram-negative bacteria -complex array of lipid residues -heat stable, toxic in small amounts, weakly immunogenic -stimulate release of endogenous mediators of sepsis (damages endothelial cells, monocytes, macrophages, neutrophils, plasma cell precursors) -cause fever by causing macrophages to release endogenous pyrogens (IC-1 pyrogen) that reset the hypothalamic thermostat -tumor necrosis factor causes fever by cytokines released by macrophages small amounts may not cause problems; large problems arise when it becomes systematic

membrane disrupting exotoxins

lyse host cells by disrupting plasma membranes/form channels - do not have separable A and B subunitstwo types: pore-forming exotoxins and phospholipases

S. pneumoniae, meningitis, H. influenza ____ to prevent host cells from capturing them

make capsules

leukocidin

microbial toxin that kills leukocytes

Clostridium botulinum

neurotoxin

latent state

no symptoms or clinical signs evident

faculative intracellular pathogens

organisms that survive within host cells but also survive in the lab outside of host cell support -Brucella abortus -Histoplasma capsulatum

Pathogens produce virulence factors primarily to ________.

outcompete host cells for resources

Evaluate the statements below and choose those that are true regarding the exploitation of human cells by pathogens in order to survive.

pathogens can survive and replicate inside host defense cells -viruses can fuse host cells into large syncytia so they can spread undetected -liver cells are made to produce decoy HBY proteins that food antimicrobial proteins

Bactereima

presence of viable bacteria in the bloodstream

_____ stage of an infectious disease is the period after signs and symptoms have set in, but are not yet specific enough for formal diagnosis.

prodromal

C. purpurea

produce ergots (toxin) that produce alkaloids (LSD)

In an AB exotoxin molecule, the A portion ______.

produces the negative effect of the toxin inside the cell -A subunits have ADP ribosylation activity that catalyzes the transfer of adenosine diphosphate/ribose molecules of host NAD+ to target host molecules

droplets

saliva, bodily fluids, mucous; 2 mm diameter; direct transfer -travel short distance (< 1 meter)

Select three mechanisms by which pathogens can actively penetrate host mucous membranes and epithelial tissue.

secretion of enzymes that attack extracellular matrix and basement membranes secretion of enzymes that degrade the glycocalyx of cells disruption of host cell surface via microbe-secreted substances

exotoxins

soluble, heat-labile proteins secreted mainly by Gram positive bacteria (but also gram negative) -among the most toxic substances known heat-labile (inactivated at 60-80 degrees C) often encoded on plasmids or prophages -travel from infection site to other tissues -released by living bacteria -cytoplasmic protein -ex: AB toxin

Invasiveness can be defined as the ability of an organism to ______.

spread to adjacent or deeper tissues

toxin

substance that disrupts the normal metabolism of host cells

Which type of bacterial exotoxin stimulates a large proportion of the host T cell population to produce excessive amounts of cytokines (cytokine storm=low BP, vessel dilation)?

superantigens (exotoxins)--overstimulate immune sx

virulence

the degree of harm (pathogenicity) that an organism inflicts on its host The ability of an organism (usually a microbe) to cause disease

colonization

the establishment of a site of microbial replication on or within a host

Septecemia

the infectious disease process caused by bacterial or fungal toxins in the blood

resevoir

the natural environmental location where a pathogen normally resides; where the source acquires the pathogen -animate or inanimate -birds are reservoir to west Nile virus

period of infectivity

time during which source is infectious or is disseminating the organism

the ability of a microorganism to produce substances that alter host cell metabolism in a negative way

toxigenicity

Mycotoxins

toxins produced by fungi -contaminate food/water/damage buildings

dust

travels long distances; indirect transfer

Certain pathogens, often Gram-negative organisms, produce a Type VI secretion system that delivers lethal molecules from its cytoplasm to a competing organism through direct contact.

true

Staphylococcus aureus has a pathogenicity island that codes for several superantigens, including the toxin that is active in toxic shock syndrome, while Shigella flexneri encodes a Type III secretion system that acts as a cytotoxin.

true

One strategy for exploiting host cells that is used by certain bacteria such as Listeria, Shigella, and Rickettsia is to ________.

use the actin filaments of the host cytoskeleton to facilitate motility through the host cell thereby enhancing infection of neighboring cells

typical systemic effects of lipid A on host organisms

fever (pyrogenic), weakness, shock, diarrhea, damage to lining of blood vessels, intestinal hemmorhage

brucella abortus

grows and replicates within macrophages, neutrophils, and trophoblast cells (that surround the developing embryo) -facultative intracellular pathogen

HIV suppress the immune system by

hiding in immune system cells

vehicles in vehicle transmission

inanimate objects that indirectly transmit -usually a fomite (inanimate object that transfers pathogens between hosts) -ex: food, water, fluids, tissues--- spreads to multiple hosts

Stachybotrys trichothecene mycotoxins

Induce inflammation; potent inhibitors of DNA, RNA, and protein synthesis; disrupt surfactant phospholipids in the lungs, and may lead to pathological changes in tissues

intracellular pathogens

Microbial pathogens that are able to grow and replicate within a host cell

strategy used to evade the immune responses of the host: phase variation of pili proteins; also produces proteases

N. gonorrhoeae

passive penetration

Non-pathogen-related ways of bypassing host mucous membranes and epithelia

gram negative enteric bacteria that are in fierce competition for resources release a ______ to release lethal effector molecules through direct contact to a competing organism

T6SS

tropism

The microbe infects only specific cell or tissue types as dictated by the correct receptor being present on them

Hepatitis B virus (HBV) produces large amounts of proteins that are not associated with the complete, infectious virus. How do these these proteins benefit the virus?

They act as decoys for the host immune response.

Both Escherichia coli and Neisseria gonorrheae adhere to urethral epithelia using ________.

fimbriae

toxigenicity

ability of a pathogen to produce a toxin

Microorganism-secreted substances that alter host tissues allow for what type of penetration of host mucous membranes and epithelia?

active

Pseudomonas aeruginosa can form biofilms whereby the cells exhibit different characteristics to those of planktonic P. aeruginosa. Evaluate the statements below and choose those that correctly apply to biofilms.

antibiotics, antibodies, and hydrolytic enzymes are ineffective at killing cells in a biofilm -cells in a biofilm can suppress the actions of phagocytic leukocytes such as macrophages and neutrophils -pathogens are able to transfer plasmids, nutrients, and quorum-sensing molecules from cell to cell in the biofilm

Antibodies that recognize and inactivate bacterial exotoxins

antitoxins

pathogen

any organism that causes disease

L. monocytogenes, Shigella spp., and Rickettsia spp. are able to escape being digested by a phagocyte by triggering the assembly of an actin tail, which results in the bacteria ______.

being engulfed by an adjacent host cell

In an AB exotoxin molecule, the B portion ______.

binds to the target receptor on a host cell

septic shock

can result from exposure to relatively large amounts of the lipid A component of Gram-negative bacteria, and the subsequent release of large amounts of cytokines like IL-1 and tumor necrosis factor -fever, blood vessel damage, weakness, diarrhea, inflammation, intestinal hemorrhage, fibromylosis

obligate intracellular parasites

cannot live outside the host cell -viruses -rickettsias -Chlamydia spp. -malarial parasites

Most microorganisms do not usually cause disease when they enter a human host due to __________.

competition between resident microbiota and the potential pathogen, as well as successful attack by innate and adaptive immune cells

Bordetella pertussis

cytotoxin

vector

directly transfer pathogens -vector-borne illnesses: malaria, typhus, sleeping sickness

intoxications

disease caused by a specific toxin made by the pathogen; does not require actively growing bacteria (just the toxin)

Histoplasma capsulatum

fungus that grows within phagocytes -facultative intracellular pathogen

HIV, measles, cytomegalovirus ____ to jump between cells to go undetected by the immune system

fuse cells together

Congential infections

german measles, gonorrhea, herpes, syphilis, and toxoplasmosis

extracellular pathogens

grow outside cells in blood, tissue fluids -Aspergillus Yersinia pestis (black plague)

fomites

Inanimate materials (e.g. food, water, biological materials) that indirectly transmit pathogens to new hosts

strategy used to evade the immune responses of the host: produces a capsule that resembles host tissue components; also produces protein G

S. pyogenes

Which of the following organisms contain a pathogenicity island that encodes for Type III secretion proteins?

Salmonella enterica Shigella flexneri

strategy used to evade the immune responses of the host: produces protein A to interfere with immune system recognition

Staphylococcus

Pathogenic members of which bacterial species often carry a pathogenicity island that encodes several superantigen genes, including one for the toxic shock syndrome toxin.

Staphylococcus aureus

virbio cholerae

enterotoxin

passive penetration of pathogens

entrance through lesions/wounds, inflammation, arthropods that make wounds when feeding

Infectivity can be defined as the ability of an organism to ______.

establish a discrete focal point of infection

droplet nuclei

evaporation of larger droplets; 1-5mm diameter -travel long distances -survive longer (hours/days) -indirect transfer

Superantigens

exotoxin that causes an intense immune response of 30% of T cells due to release of cytokines from host cells-cytokine storm (low BP, blood vessel dilation)

infectious disease

When the presence of a pathogen or its products results in the impairment or loss of function of a host system

pathogenicity island

a large segment (10-200 kilobases) of bacterial chromosomal and plasmid DNA that encodes virulence factors

disease syndrome

a set of signs and symptoms that are characteristic of the disease