Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
58 Cards in this Set
- Front
- Back
|
colonization |
microbe establishing itself in the host |
|
|
infection |
pathogen establishing itself in the host |
|
|
ID50 |
infectious dose required to produce infection in 50% of a population |
|
|
incubation period |
time between infection and onset |
|
|
prodromal phase |
vague symptoms |
|
|
convalescence |
recuperation, recovery from disease |
|
|
acute infection |
illness is short term because the pathogen is eliminated by host defenses; person is usually immune to reinfection |
|
|
chronic infection |
illness persists over a long time period |
|
|
latent infection |
illness may reoccur if immunity weakens |
|
|
-emia (bactermia, toxemia, viremia) |
-emia = condition of the blood |
|
|
septicemia or sepsis |
acute, life-threatening illness caused by growing infectious agents or products in bloodstream |
|
|
Koch's postulates |
1. microorganism must be present in every case of the diesease 2. organism must be grown in pure culture from diseased host 3. same disease must be produced when pure culture is introduced into susceptible hosts 4. organisms must be recovered from experimentally infected hosts |
|
|
limitations of Koch's postulates |
1. some organisms cannot be grown in laboratory medium (syphilis) 2. infected individuals do not always have symptoms (cholera, polio) 3. some diseases are polymicrobial (periodontal) 4. suitable animal hosts not always available for testing |
|
|
steps to establishing infection |
adherence, colonization (growth in biofilms), invasion |
|
|
adhesins |
attach to host cell receptor, located at tips of pili (called fimbriae), can be component of capsules or various cell wall proteins |
|
|
invasion-breaching the anatomical barriers |
penetrating the skin penetrating mucous membranes |
|
|
penetrating the skin |
difficult to penetrate-bacteria rely on injuries -Staphylococcus aureus enters via cut or wound -Yersinia pestis is injected by fleas |
|
|
penetrating mucous membranes |
1. directed uptake by cells 2. exploiting antigen-sampling processes |
|
|
directed uptake by cells (penetrating mucous membrane) |
pathogen induces non-phagocytic host cells to engulf them via endocytosis 1. salmonella uses type III secretion system (injectisome) to inject effector proteins into host cell 2. effector proteins induce changes 3. membrane ruffling 4. ruffles enclose bacterial cells bringing them inside |
|
|
exploiting antigen sampling processes (penetrating mucous membrane) |
1. some pathogens use M cells to cross intestinal barrier 2. shigella survives phagocytosis by macrophages; induces apoptosis 3. binds to base of mucosal epithelial cells and induces uptake |
|
|
avoiding host cell defenses: hiding within a host cell |
allows avoidance of complement proteins, phagocytes, and antibodies -shigella directs transfer from intestinal epithelial cell to adjacent cells (actin polymerization) -Listeria monocytogenes (meningitis) does the same |
|
|
avoiding host defenses: avoiding killing by complement system proteins |
serum resistant bacteria avoid killing by complement proteins -Neisseria gonorrhoeae hijacks host mechanism, binds complement regulatory proteins to avoid activation of complement, thereby postponing membrane attack complex (MAC) formation |
|
|
avoiding host defenses: avoiding destruction by phagocytes: 3 mechanisms |
1. preventing encounters with phagocytes 2. avoiding recognition and attachment 3. surviving within phagocytes |
|
|
Preventing encounters with phagocytes |
1. C5a peptidase: degrades chemoattractant c5a -streptococcus pyrogenes 2. membrane-damaging toxins: kill phagocytes, other cells -s. pyrogenes makes streptolysin O |
|
|
avoiding recognition and attachment |
1. capsules: interfere with opsonization; some bind host's regulatory proteins that inactivate c3b (streptococcus pneumoniae) 2. m protein: in cell wall of streptococcus pyrogenes; binds regulatory protein that inactivates c3b 3. Fc receptors: bind Fc region of antibodies (staphylococcus aureus, streptococcus pyogenes) |
|
|
surviving within phagocytes |
1. escape from phagosome: prior to lysis with lysosomes Listeria monocytogenes produces molecule that forms pores in phagosomal membrane; shigella species lyse phagosome 2. prevent phagosome-lysosome fusion: avoid destruction; salmonella sense ingestion by macrophage, produce protein that blocks fusion process 3. survive within phagolysosome: few can survive destructive environment; coxiella burnetti (Q fever) can withstand; delays fusion, allows time to equip itself to survive |
|
|
avoiding antibodies: |
1. IgA protease: cleaves IgA, found in mucus secretions 2. antigenic variation: alter structure of surface antigens, stay ahead of antibody production 3. mimicking host molecules: cover surface with molecules similar to those found in host cell, appear to be "self" (streptococcus pyogenes form capsule from hyaluronic acid, a polysaccharide found in tissues) |
|
|
damage to the host: direct effects |
toxins produced |
|
|
damage to the host: indirect effects |
immune response |
|
|
exotoxins: proteins with damaging effects |
1. secreted or leak into tissue following bacterial lysis, foodborne intoxication results from consumption, destroyed by heating, most exotoxins are heat sensitive 2. can act locally or systemically 3. proteins, so immune system can generate antibodies, many fatal before immune response mounted, vaccines critical, toxoids are inactivated toxin, antitoxin is suspension of neutralizing antibodies to trat, neurotoxins damage nervous system, enterotoxins cause intestinal disturbance, cytotoxins damage variety of cell types |
|
|
damage to the host: endotoxin, other bacterial cell wall components |
1. endotoxin is lipopolysaccharide (LPS) 2. Lipid A triggers inflammatory response, when localized, response helps clear, when systemic, causes widespread response: septic shock or endotoxic shock 3. heat stable, autoclaving does not destroy |
|
|
attack rate |
% of people who become ill in population after exposure, reflects ID and immune status of population |
|
|
incidence rate |
risk of an individual contracting a disease |
|
|
prevalence |
overallimpact pf disease on society |
|
|
morbidity |
incidence of disease in population at risk |
|
|
mortality |
overall death rate in population |
|
|
case-fatality rate |
% of population that dies from a specific disease |
|
|
endemic diseases |
constantly present in populationiat low levels ex. common cold |
|
|
epidemic |
sudden, unusually large number of cases in a given period of time, in a given population, can be endemic or introduced to a population |
|
|
pandemic |
GLOABEL (AIDS) |
|
|
human reservoirs |
often easier to control, symptomatic (obvious source of pathogens) or asymptomatic(harder to identify, may not realize, can spread to others) |
|
|
non-human animal reservoirs |
common (rabies), zoonoses primarily exist in animals but can be transmitted to humans, |
|
|
environmental reservoirs |
difficult/impossible to eliminate (clostridium), soil and water (NOT AIR) |
|
|
vertical transmission |
woman to fetus or mother to nfant during birth & breast feeding |
|
|
horizontal transmission |
person to person via air, physical contact, ingestion of food or water, or vector |
|
|
direct contact |
handshake, sex 1. fecal-oral transmission droplet transmission 1. densely populated buildings 2. spread minimized by covering mouth when sneezing |
|
|
food and water disease transmission |
1. animal products (meat, eggs) from animals intestines 2. cross-contamination: transfer from one food to another 3. municipal water systems can distribute to large numbers |
|
|
Air: disease transmission |
respiratory diseases commonly transmitted talking, laughing, singing, sneezing, coughing generate droplet nuclei (microbes attached to dried material), most difficult to control |
|
|
vectors: disease transmission |
living organisms that can carry pathogen, most commonly arthropods, can be mechanical or biological |
|
|
descriptive studies: the person |
age, gender, ethnicity, occupation, personal habits |
|
|
descriptive studies: the place |
geographic location |
|
|
descriptive studies: the time |
season, rate of spread |
|
|
common source epidemic |
rapid rise in cases suggests exposure to single source of pathogen |
|
|
propagated epidemic |
slow rise in cases suggests contagious disease in population |
|
|
factors contributing to emerging or reemerging diseases |
1. population expansion-increased contact with reservoir 2. mass production, widespread distribution, and importation of food 3. climate changes-warmer temps favor reproduction of some vectors |
|
|
nosocomial infections |
hospital associated infections |
|
|
reservoirs of infectious agents in healthcare settings |
other patients patient microbiota healthcare workers |
|
|
transmission of infectious agents in healthcare settings |
fomite transmission: medical devices-often breach first-line barriers of defense, inadequately sterilized invasive instruments direct transmission: Healthcare worker airborne transmission |
