Study Q Flashcards
What is a prion composed of?
What about a virus?
prion= a polypeptide/protein ONLY virus= protein and nucleic acid
What do all viruses consist of? (2)
What are viruses called who only have these 2 things?
1.) a nucleic acid (either DNA or RNA but not both) *20-100 genes
2.) a protein coat known as a capsid
These viruses are known as Naked Viruses
what does a naked virus lack that other viruses have?
describe what this is (6)
an envelope outside outside the capsid (protein coat)
- Normally phospholipid mixed w. own lipids and proteins
- Viral encoded
- May project from the envelope as spikes or peplomers
- Involved in viral attachment to host cell
- May have enzymatic or other activity
- May play role in nucleic acid replication
What is attachment/adsorption? (3)
- specific recpetor-mediated attachment to complementary receptor on host cell
- receptor determines host preference (specific tissue, more than one host, more than one receptor)
- non covalent binding by induced endocytosis
True or false: ALL viruses are intracellular parasites
true
Is each of the following ss/ds or RNA/DNA?
A.) virus
B.) prokaryote/bacteria
A.) can be either RNA or DNA (not both), ss or ds
B.) ds DNA
What is the difference between gram + and gram - bacteria? (6)
Gram +:
- stain purple in gram stain (retain the dye)
- thick layer of peptinoglycan (multiple layers)
- no outer membrane
- no LPS content or lipids
- secretes exotoxins
- more susceptible to antibiotics
Gram -:
- stain pink in gram stain (doesn’t retain dye)
- thin layer of peptinoglycan (single layer)
- has an outer membrane that repels ions
- high LPS/lipid content
- secretes endotoxins (ALL DO)
- more resistant to antibiotics
Extra cellular or intracellular pathogens?
A.) Protozoans/eukaryotes
B.) Virus
C.) Bacteria/prokaryotes
A.) most are extracellular
B.) all are intracellular
C.) most are extracellular
What spores are more resistant/harder to eliminate?
Prokaryotic or Fungal?
prokaryotic (endospores)
-can’t get rid of with boiling- need sterilization
Many pathogenic fungi are dimorphic- which means in soil they are ____ and in the body they are _____
- ) mycelial in soil
2. ) yeast-like in body (mostly temperature dependent)
what is symbiosis?
what are the 3 types?
close relationship between 2 or more organisms of 2 or more different species
1.) Mutualism- both micro-org and host benefit
2,) Commensalism- micro benefits, host neither harmed or benefited *most bacteria
3.) Parasitism: micro-org benefits, host harmed *most pathogens
Name 2 normal flora micro-orgs found in the skin and nose
staphylococcus epidermidis
staphylococcus aureus
Name 2 normal flora micro-orgs found in the teeth
actinomyces
fusobacterium
Name 2 normal flora micro-orgs found in the throat
streptococcus pyogenes
streptococcus pneumoniae
Name 2 normal flora micro-orgs found in the mouth
streptococcus mitis
candida
Name 2 normal flora micro-orgs found in the urethra/vagina
staphylococcus epidermidis
streptococci
Name 2 normal flora micro-orgs found in the small and large intestines
lactobacilli
enterobacteria
where are majority of normal flora located?
large intestine (90-95%)
Strict/Obligate pathogen vs. Opportunistic
Strict/Obligate: causes diseases associated with the pathogen in most people when presented in the sufficient dose and transmitted in the correct manner
Opportunistic: micro-organism that normally does not cause disease except under certain circumstances (ie: E.Coli causing UTI)
what are the 5 stages of development of disease in a host?
- ) Incubation period: time from initial contact w/ pathogen to first s/sx (asymptomatic, variable time, person contagious for part of this period)
- ) Prodromal period: early, usually milder s/sx (not in all diseases, person contagious, short time)
- ) Period of Illness (variable time, person contagious for part of this period)
- ) Period of Decline: s/sx begin to decline (person usually not contagious)
- ) Convalescence: recovery
What is the Disease threshold? (2)
- minimum # pathogens and/or concentration of toxin which results in sufficient damage/dysfunction to cause S & S (disease)
- Varies among different pathogens and different hosts (age, general health, genetic background, body defenses)
What are the steps of pathogenesis? which one does not occur in all cases?
(see more information on each in handout)
- ) Maintain Reservoir
- ) Transmission to Host
- ) Attachment to Portal of Entry
- ) Invasion/Spread to deeper tissues (NOT ALL)
- ) Multiplication/Growth
- ) Evasion of host defenses
- ) Exit from host
What is a Portal of Entry?
- anatomic site where the pathogen first enters (or contacts) the body
- all pathogens have at least 1
What is ID50?
- Infectious dose (dose=# pathogens/toxins transmitted to host)
- Minimum # of pathogens/toxins which cause the associated disease in 50% of subjects
- Lower ID50= Higher Virulence (ability to cause disease)
what is a fomite? (4)
- an inanimate object that is capable of carrying infectious organisms
- transmits to few people
- NOT LIVING
- ie: tissues, utensils, clothing
What is a vector? what is the difference between a Biological and a Mechanical vector?
**SA
- Vector= animals that transmits pathogen from reservoir to host
- Biological vector = some part of pathogen’s life cycle occurs in vector (remove essential vector, stop disease transmission) *i.e., many mosquitos-> malaria
- Mechanical vector – no part of pathogen’s life cycle occurs in vector; not essential for transmission of pathogen, only accidental (i.e., mollusks, fly) -> fly lands in fecal material then goes and lands on food
What are the different ways a pathogen can be transmitted from reservoir to host? (8)
-Respiratory droplets
-Airborne
-Fecal Oral
-Direct contact (skin to skin; membrane to membrane)
-From Mouth via saliva to another mouth/skin
Indirect only:
-Fomites (few people)
-Vectors
-Vehicles (many people)
(also consider Horizontal Vs, Vertical transmission)
What are 3 mechanisms pathogens can employ to evade innate (non-specific) defenses?
- Interfere with/prevent phagocytosis–> survive phagocytosis or kill phagocytes
- Prevent dislodgement mechanisms–> stronger attachment to body surfaces
- Prevent action of complement proteins
A pathogen can avoid specific defenses by employing antigen variation. What are the 5 ways?
**SA
- ) Genetic Drift: antigenic properties are slightly changed
- gene mutation
- with viruses primarily (but also cells)
- reason why we change the flu vaccine every year - )Genetic Shift: radical changes in antigenic properties
- recombination between 2 different genomes
- seen with viruses
- causes a big pandemic outbreak
- not common - ) Gene Switching: multiple genes for slightly different, similar functioning proteins
- ) Immune Suppression/Interference
- ) Antibody destruction (enzymes)
describe the fever pathway
exogenous pyrogen (endotoxin)–> macrophages–> IL1 & TNF–> hypothalamus –> prostaglandins –> Fever
What is the difference between a persistent and a latent infection?
- Persistent/chronic infection: microbe remains in body and replicates at low level (+/- signs and symptoms)
- Latent Infection: recovery, but organism remains in latent state somewhere in body; reactivation possible at later time
Give definitions for the following: Epidemiology Morbidity Rate Mortality Rate Incidence of Disease Prevalence
Epidemiology – study of who, when, where, how of a disease in a population
Morbidity rate – # new cases/per time period/ # individuals in population
Mortality rate - # deaths/per time period/ # individuals in population
Incidence of disease - # new cases/time period/individuals in population
Prevalence - # total cases within population within a given time period
Give Definitions for: Sporadic disease Endemic Epidemic Pandemic
Sporadic Disease – occurs occasionally
Endemic – always present in population, usually at a low or moderate level
Epidemic – sudden occurrence of disease within population
Pandemic – world wide epidemic
What is a diseased acquired in a hospital or nursing home called?
What is the incidence of this happening?
What are common pathogens?
Nosocomial Disease
Incidence= 5-10% of all hospitalized pts (40-99k deaths a yr)
Common pathogens:
-E. Coli–> UTI
-S. Aureus–> surgical wound infections
-P. aeruginosa–> lower respiratory tract
-C. difficile–> GI tract
What are different ways to prevent/control disease (not cleansing, not globally) **3 things
- ) Exclude sources of infection
- Inanimate objects: use sterile instruments, disinfected materials; clean water, food
- People: ill employees stay home; no known carriers; minimize movements - ) Interrupt Transmission
- Control airborne/respiratory pathogen’s by proper ventilation, filtration; asceptic technique
- Minimize transmission by healthcare worker’s
- Wash hands - ) Enhance host’s ability to resist
- antibiotics, vaccines, immune boosters
What is the diffence between sterility/sterilization and disinfection? gives examples of each (sterile= 4; disinfectants=3)
Sterility= free of all viable microorgs
-autoclave (dry heat-ie: oven)
-gamma irradiation
-X irradiation (for things we can’t heat or get wet)
-filtration of fluids
Disinfectants= decrease the number of pathogens present but does not eliminate all
-inanimate objects/surfaces= chemicals (i.e., ethanol, chlorine) *Bleach is best!
-living tissues (Antisepsis)=chemicals that do not cause tissue damage
-liquids=Pasteurization (ie: milk)
what are 8 ways to prevent and control global aspects of infectious disease
- ) Limit people’s exposure to pathogen
- ) clean drinking water
- ) clean food
- ) personal cleanliness
- ) improved housing
- ) improved nutrition
- ) vector control
- ) Quarantine
Describe Active immunity (4)
- stimulate person’s own immune system to make the cells and antibody which can protect it and confer immunity
- memory cells (A and B cells)
- Naturally= get disease and recover (highest immunity)
- Artificially= vaccine (not as immunogenic as natural)
Describe Passive Immunity (5)
- person is given cells, antibody, or immunogenic chemicals from another source that provides quick, temporary protection
- no memory cells
- Natural=breast milk, colostrum
- Artificial= antiserum, antitoxin (antibody against toxin)
- Non-specific cellular immunostimulation: cytokines or other chemicals used to stimulate the immune system in a general way (interferons, some interkeaulin, BCG)
What makes a good vaccine? (4)
- ) High Immunogenicity (best ~90-95% efficacious)
- ) No or little pathogenicity
- ) Stable for reasonable time period
- ) Lowest cost possible
what are the 2 different types of vaccines? What their subtypes?
Whole Organism (Live attenuated or Killed/Inactivated) and Subunit (Recombinant, Toxoids, Adjuvants)
describe live attenuated vaccines (7)
- weakened, mutated, non-virulent form
- problem= weakened but not dead→ may cause infections w/o serious symptoms
- High immunogenicity (many antigens)
- Results in many memory cells being formed
- Results from mutations that can revert back to original, wild-type pathogenic form
- Used mostly for viral illnesses (measles, sabin polio, mumps, rebella)
- Not used much for prokaryotes→ difficult to attenuate
Describe Killed/Inactivated vaccines (6)
*compare to Live Attenuated vaccines
- Killed by heat or chemicals
- For pathogens that can’t be attenuated or are too dangerous
- Less immunogenic due to killing procedure (can denature antigens)
- May require a booster periodically
- Safe→ cannot revert bc it’s dead
- Used for many bacterial and some viral diseases (Pertussis, Hep A)
what is the difference between an antibiotic and a synthetic drug? (just describe what each is)
- Antibiotics are antimicrobial products made by one organism that inhibits or kills another (mostly fungi and soil proks, some plants)
- Synthetic drugs are not natural and are synthesized in a lab
what makes a good antimicrobial drug?
- ) Selective Toxicity: kills microbe, not patient –> drug binds to specific target in microorg
- ) Soluble in body fluids
- ) Minimum side effects (ie: allergic reactions)
- ) Low cost
- ) Microbes shouldn’t develop resistance to drug too soon
Name 2 Antibiotics that target Cell Wall Synthesis in Prokaryotes
beta-lactams
glycopeptides
Name 2 Antibiotics that target Nucleic Acid Synthesis in Prokaryotes
quinolones
sulfonamides
Name 2 Antibiotics that target Protein Synthesis in Prokaryotes
erythromycin
aminoglycosides
Name 2 Antibiotics that target =Synthesis of Key Metabolite in Prokaryotes
?
Name 2 Antibiotics that target Cell Membrane Function in Prokaryotes
polymixin (only one listed)
What are the mechanisms are drug resistance?
1.) Drug inactivation: Produce enzymes that destroy drugs (ie: penicillin resistant S. aureus)
2) Altered uptake: Change in permeability of CM to drug so can no longer enter OR pump out drug
3) Altered target -
a) Microbe develops alternative biochemical pathway
`b) makes new enzymes that no longer target
c) alters present target enzyme somehow so still functions
describe primary and secondary lymphoid tissues
Primary Lymphoid Tissues – bone marrow and thymus
-where B and T lymphocytes mature (learn to recognize non-self and respond (alloreactive), and to recognize self and not respond (not autoreactive); cells that fail to do this are eliminated
Secondary Lymphoid Tissues – lymph nodes, lymph nodules, MALT
–where B and T lymphocytes first meet epitope/antigen brought by antigen presenting cells.
-Lymphocytes circulate between the blood and secondary lymphoid tissues
how can you tell T, B, and NK cells apart?
cluster differentiation (have different antigens
primary vs secondary immune response
Primary response – first exposure to specific pathogen; typically takes 5-10 days to see any antibody; this will increase over several weeks until peak reached; first antibody seen is IgM; this then followed by IgG
If memory cells form as result of primary exposure, immunity will develop.
Secondary response (and subsequent exposure)- if memory cells formed and survive, each subsequent exposure to same pathogen should not reach the disease threshold due to stronger,quicker secondary response (mostly IgG
