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30 Cards in this Set

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What are the 6 host-microbe ecosystems?
1. Normal flora (microbiota): associated with healthy tissue
2. Commensalism: microbe +, host not +/-
3. Mutualism: both microbe and host +
4. Parasitism: microbe +, host -
5. Infection: growth within host
6. Disease: injury to host
Where are most normal flora found in the body and how much of the body does that surface comprise?
1. Skin: 2m2
2. Mucous membrane: 400m2
What are the three importances of normal flora in the body?
1. Physiologically important commensal organisms
2. remove or out-compete microbes that become harmful
3. keep harmful microbes out
What are mucous membranes and where are they found?
Single layer epithelial cells in direct contact with external environment; covered by protective mucous layer; major site of infection; found in areas with direct contact to external environment
How do microbes interact with mucous membranes?
bind through ligand on microbe surface to receptors on epithelial cells
What is a biofilm and what is their significance?
microbial colony attached to a surface (often external like catheters)and encased in a polysaccharaide material; contains different kinds of microbes; causes 2/3 of human bacterial infections; provide protective environment to microbes shielding against immune system and antibiotics
Why does the mouth make a perfect microbial niche?
moist with tons of nutrients and a good pH; 10^6 microbes per 1mL saliva, mostly bacteria with some fungi; microbes can adhere to teeth fighting silivary flow
How do microbes colonize the mouth from birth?
sterile at birth, acquire aerobes, teeth growth, acquire anaerobes; form a pellicle, a film of salivary glycoproteins, on tooth surface; streptococci are first to colonize, followed by fusobacteria, then actinomyces, forming biofilm on tooth surface (dental plaque)
Discuss dental caries
1. Etiological agent: stept mutans et al
2. Virulence factor: sugar polymer dextran and pili allow biofilm formation on tooth
3. Susceptibility: high sugar diet, sugar broken down by s. mutans into fructose and glucose for food for microbes
4. Prevention: brush and floss, floridated toothpaste and water
Discuss normal flora of the GI tract and the effect of oral antibiotics on them
Most sterile towards the upper tract; bacteriodes exist in large intestine; composition changes during early development; oral antibiotics kill all normal flora allowing resistant species to overgrow (opportunistic pathogens), normal flors regrow once AB stop
What contributions do intestinal micorbes provide?
Vitamin synthesis, gas production, odor production, organic acid production, glycosidase reactions, and steroid metabolism; probiotics are said to displace harmful microbes
Discuss normal flora of the skin and how their number and type are affected
susceptible to change, mostly gram + bacteria and fungi (propionibacterium causes acne), most having to do with sweat glands; type and # affected by age, weather and personal hygiene
What are the main normal flora of the respiratory tract?
Staphylococcus, streptococcus, candida; lower tract usually devoid because of constant clearing by antibodies and ciliary action
Discuss normal flora of UG tract and how they change
upper regions normally sterile, urethra have facultative gram - (e. coli adn proteus mirabilis); lactobacilius exist in the female; typpes in vagina change with age/development
What is a pathogen and what are the two different kinds?
an organism that causes disease;
1. primary: affects health host
2. opportunistic: affects compromised host
What is the difference between pathogenicity and virulence?
ability to cause disease versus the degree at which it diseases
What are virulence factors?
traits connected with pathogenicity, often carries on plasmids or regions of chromosome called pathogenicity islands; pathogens usually contain multiple VFs
What are the major problems with Koch's postulates?
assumes virulence is independednt of host, not all organisms can be cultured, some are not virulent alone (bioflims), cultivation can lead to loss of virulence, cannot test in humans
Explain portals of entry
pathogens must gain access to the host to cause disease, either through natural opening in the body or parenteral means like needles or surgery
Discuss adherence factors (adhesins) as virulence factors
ligands that bind to host cell receptors and can determine specificity of infection for pathogen (certain pathogens affect certain cells); glycocalyx, capsule, slime layer bind to surfaces, adherence proteins bind to receptors (M and Opa protein), lipoteichoic acid binds to receptors, fimbriae, pili bind to surfaces
Discuss extracellular enzymes as virulence factors
secreted by pathogen to dissolve structural chemicals of host cells to maintain infection, invade and spread, and avoid host defenses; hyaluronidase (degrades hyaluronic acid in extracellular matrix); collagenase (degrades collagen); coagulase forms blood clots for protection, kinases digest clots and release microbes (occurs near or in blood vessels)
Discuss toxins as virulence factors
chemicals or proteins produced by pathogen to harm tissue or trigger host immune responses that cause damage to hose
Disuss exotoxins as virulence factors
proteins released by growing pathogen that cause damage in distal areas of host (cytotoxin, neurotoxin, enterotoxin); can be cytolytic by putting pores in cell membrane, or A-B toxins, two subunits, A is enzyme, B is adherent, act on intracellular targets
-Botulinium: blocks release of acetocholine, preventing muscle contraction causing flaccid paralysis
-Tetanus: blocks release of contractile inhibitors causing rigi paralysis and respiratory failure (tetanus vaccine and antitoxin both inhibit tetanus toxin)
-Enterotoxin: act on small intestine by causing massive water secretion into lumen; cholera is A-B toxin (1A, 5B), A activates adenylate cyclase which makes cAMP, which stimulates secretion of Na and Cl leadig to water loss in cells
Discuss endotoxins as virulence factors
lipid A portion of LPS on Gram - is released into circulation when bacteria lyses, activates complement which leads to inflammation, high [] of cytokines activates immune system and leads to septic shock (antitoxins inhibit action, toxoids inactivate by heat or chemical treatment and are used as vaccines)
What are superantigens and what are two examples?
toxins that over-stimulate immune system leading to cell damage and toxic shock; staph aureus is toxic shock syndrome toxin and causes fever and TSS; strept pyogenic exotoxin causes TSS like symptoms and fever
Discuss antiphagocytic factors as virulence factors
used to elude macrophages; two ways:
- bacterial and fungal capsules: made of polysaccharides common in the body so not seen as foreign, slippery making engulfment difficult
-antiphagocytic chemicals: some prevent phagolysosome fusion, some resist phagocytosis, some make leukocidins that destroy phagoctyic WBC
What are T cells, where are they produced, and how do they work?
they are a kind of lymphocyte that are produced in red bone marrow, mature in the thymus, and circulate in the blood and lymph to the lymph nodes, spleen, and Peyer's patches; they are a cell-mediated immune response and do not secrete antibodies, the act directly on endogenous invaders, cells that have intracellular pathogens, abdormal host cells with abdornal surface proteins
What are the three types of T cells?
1.cytotoxic: contain hundreds of T cell receptors, have CD8 glycoprotein on cell surface, directly kill virus/pathogen-infected cells and abdormal cells
2. helper type 1: CD4 glycoprotein, assist Tc, express cytokine receptor CCR, secrete cytokines that determine which immune response to activate
3. helper type 2: CD4 glycoprotein, activate B cells to make and secrete ABs, have cytokine receptors CCR3 and CCR4, secrete cytokines that determine which immune response to activate
What are cytokines and which types are found in the immune system?
-soluble regulatory polypeptides that act as intercellular signals to leukocytes when released in immune system
-interleukins: signal to leukocytes (27 found)
-interferons: antiviral proteins that may act as cytokines
-GF: stimulate stem cells to divide maintaining supply of leukocytes
-tumore necrosis factors: secreted by macrophages and T cells to kill tumor cells and regulate immune responses and inflammation
-chemokines: signal leukocytes to inflammation or infection sites and stimulate other leukocytes
What is the MHC?
major histocompatibility complex: anitgens of glycoproteins found in membranes of most cells; first IDed in graft patients, important in determining the compatibility of tissues in successful grafting; function in presenting antigenic determinants to T cells; antigens bind in antigen-binding groove of MHC molecules; two classes:
-class I: found on all cell membranes but RBC
-class II: only found on B cells and antigen-presenting cells like macrophages, leukocytes, and monocytes