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Clin Microbio > Study Q > Flashcards

Study Q Flashcards

1
Q

What is a prion composed of?

What about a virus?

A 
prion= a polypeptide/protein ONLY
virus= protein and nucleic acid
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2
Q

What do all viruses consist of? (2)

What are viruses called who only have these 2 things?

A

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

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3
Q

what does a naked virus lack that other viruses have?

describe what this is (6)

A

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
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4
Q

What is attachment/adsorption? (3)

A
  • 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
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5
Q

True or false: ALL viruses are intracellular parasites

A

true

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6
Q

Is each of the following ss/ds or RNA/DNA?

A.) virus
B.) prokaryote/bacteria

A

A.) can be either RNA or DNA (not both), ss or ds

B.) ds DNA

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7
Q

What is the difference between gram + and gram - bacteria? (6)

A

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
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8
Q

Extra cellular or intracellular pathogens?
A.) Protozoans/eukaryotes
B.) Virus
C.) Bacteria/prokaryotes

A

A.) most are extracellular
B.) all are intracellular
C.) most are extracellular

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9
Q

What spores are more resistant/harder to eliminate?

Prokaryotic or Fungal?

A

prokaryotic (endospores)

-can’t get rid of with boiling- need sterilization

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10
Q

Many pathogenic fungi are dimorphic- which means in soil they are ____ and in the body they are _____

A
  1. ) mycelial in soil

2. ) yeast-like in body (mostly temperature dependent)

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11
Q

what is symbiosis?

what are the 3 types?

A

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

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12
Q

Name 2 normal flora micro-orgs found in the skin and nose

A

staphylococcus epidermidis

staphylococcus aureus

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13
Q

Name 2 normal flora micro-orgs found in the teeth

A

actinomyces

fusobacterium

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14
Q

Name 2 normal flora micro-orgs found in the throat

A

streptococcus pyogenes

streptococcus pneumoniae

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15
Q

Name 2 normal flora micro-orgs found in the mouth

A

streptococcus mitis

candida

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16
Q

Name 2 normal flora micro-orgs found in the urethra/vagina

A

staphylococcus epidermidis

streptococci

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17
Q

Name 2 normal flora micro-orgs found in the small and large intestines

A

lactobacilli

enterobacteria

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18
Q

where are majority of normal flora located?

A

large intestine (90-95%)

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19
Q

Strict/Obligate pathogen vs. Opportunistic

A

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)

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20
Q

what are the 5 stages of development of disease in a host?

A
  1. ) Incubation period: time from initial contact w/ pathogen to first s/sx (asymptomatic, variable time, person contagious for part of this period)
  2. ) Prodromal period: early, usually milder s/sx (not in all diseases, person contagious, short time)
  3. ) Period of Illness (variable time, person contagious for part of this period)
  4. ) Period of Decline: s/sx begin to decline (person usually not contagious)
  5. ) Convalescence: recovery
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21
Q

What is the Disease threshold? (2)

A
  • 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)
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22
Q

What are the steps of pathogenesis? which one does not occur in all cases?
(see more information on each in handout)

A
  1. ) Maintain Reservoir
  2. ) Transmission to Host
  3. ) Attachment to Portal of Entry
  4. ) Invasion/Spread to deeper tissues (NOT ALL)
  5. ) Multiplication/Growth
  6. ) Evasion of host defenses
  7. ) Exit from host
23
Q

What is a Portal of Entry?

A
  • anatomic site where the pathogen first enters (or contacts) the body
  • all pathogens have at least 1
24
Q

What is ID50?

A
  • 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)
25
Q

what is a fomite? (4)

A
  • an inanimate object that is capable of carrying infectious organisms
  • transmits to few people
  • NOT LIVING
  • ie: tissues, utensils, clothing
26
Q

What is a vector? what is the difference between a Biological and a Mechanical vector?

**SA

A
  • 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
27
Q

What are the different ways a pathogen can be transmitted from reservoir to host? (8)

A

-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)

28
Q

What are 3 mechanisms pathogens can employ to evade innate (non-specific) defenses?

A
  • Interfere with/prevent phagocytosis–> survive phagocytosis or kill phagocytes
  • Prevent dislodgement mechanisms–> stronger attachment to body surfaces
  • Prevent action of complement proteins
29
Q

A pathogen can avoid specific defenses by employing antigen variation. What are the 5 ways?

**SA

A
  1. ) Genetic Drift: antigenic properties are slightly changed
    - gene mutation
    - with viruses primarily (but also cells)
    - reason why we change the flu vaccine every year
  2. )Genetic Shift: radical changes in antigenic properties
    - recombination between 2 different genomes
    - seen with viruses
    - causes a big pandemic outbreak
    - not common
  3. ) Gene Switching: multiple genes for slightly different, similar functioning proteins
  4. ) Immune Suppression/Interference
  5. ) Antibody destruction (enzymes)
30
Q

describe the fever pathway

A

exogenous pyrogen (endotoxin)–> macrophages–> IL1 & TNF–> hypothalamus –> prostaglandins –> Fever

31
Q

What is the difference between a persistent and a latent infection?

A
  • 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
32
Q 
Give definitions for the following:
Epidemiology
Morbidity Rate
Mortality Rate
Incidence of Disease
Prevalence
A

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

33
Q 
Give Definitions for:
Sporadic disease
Endemic
Epidemic
Pandemic
A

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

34
Q

What is a diseased acquired in a hospital or nursing home called?
What is the incidence of this happening?
What are common pathogens?

A

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

35
Q

What are different ways to prevent/control disease (not cleansing, not globally) **3 things

A
  1. ) Exclude sources of infection
    - Inanimate objects: use sterile instruments, disinfected materials; clean water, food
    - People: ill employees stay home; no known carriers; minimize movements
  2. ) Interrupt Transmission
    - Control airborne/respiratory pathogen’s by proper ventilation, filtration; asceptic technique
    - Minimize transmission by healthcare worker’s
    - Wash hands
  3. ) Enhance host’s ability to resist
    - antibiotics, vaccines, immune boosters
36
Q

What is the diffence between sterility/sterilization and disinfection? gives examples of each (sterile= 4; disinfectants=3)

A

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)

37
Q

what are 8 ways to prevent and control global aspects of infectious disease

A
  1. ) Limit people’s exposure to pathogen
  2. ) clean drinking water
  3. ) clean food
  4. ) personal cleanliness
  5. ) improved housing
  6. ) improved nutrition
  7. ) vector control
  8. ) Quarantine
38
Q

Describe Active immunity (4)

A
  • 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)
39
Q

Describe Passive Immunity (5)

A
  • 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)
40
Q

What makes a good vaccine? (4)

A
  1. ) High Immunogenicity (best ~90-95% efficacious)
  2. ) No or little pathogenicity
  3. ) Stable for reasonable time period
  4. ) Lowest cost possible
41
Q

what are the 2 different types of vaccines? What their subtypes?

A

Whole Organism (Live attenuated or Killed/Inactivated) and Subunit (Recombinant, Toxoids, Adjuvants)

42
Q

describe live attenuated vaccines (7)

A
  • 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
43
Q

Describe Killed/Inactivated vaccines (6)

*compare to Live Attenuated vaccines

A
  • 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)
44
Q

what is the difference between an antibiotic and a synthetic drug? (just describe what each is)

A
  • 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
45
Q

what makes a good antimicrobial drug?

A
  1. ) Selective Toxicity: kills microbe, not patient –> drug binds to specific target in microorg
  2. ) Soluble in body fluids
  3. ) Minimum side effects (ie: allergic reactions)
  4. ) Low cost
  5. ) Microbes shouldn’t develop resistance to drug too soon
46
Q

Name 2 Antibiotics that target Cell Wall Synthesis in Prokaryotes

A

beta-lactams

glycopeptides

47
Q

Name 2 Antibiotics that target Nucleic Acid Synthesis in Prokaryotes

A

quinolones

sulfonamides

48
Q

Name 2 Antibiotics that target Protein Synthesis in Prokaryotes

A

erythromycin

aminoglycosides

49
Q

Name 2 Antibiotics that target =Synthesis of Key Metabolite in Prokaryotes

A

?

50
Q

Name 2 Antibiotics that target Cell Membrane Function in Prokaryotes

A

polymixin (only one listed)

51
Q

What are the mechanisms are drug resistance?

A

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

52
Q

describe primary and secondary lymphoid tissues

A

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

53
Q

how can you tell T, B, and NK cells apart?

A

cluster differentiation (have different antigens

54
Q

primary vs secondary immune response

A

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

Clin Microbio (3 decks)

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