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MCM Test 3 > B2.052 The Microbial World > Flashcards

B2.052 The Microbial World Flashcards

1
Q

what are Koch’s postulates?

A
  1. the organism is regularly found in the lesion of the disease
  2. the organism can be isolated in pure culture on artificial media
  3. inoculation of this pure culture produces a similar disease in experimental animals
  4. organisms can be recovered from the lesions in the animals
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2
Q

what did threat of ID decline in the 1900s?

A 
sanitation and hygiene
chlorination of water
antibiotics
vaccination
animal and pest control
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3
Q

why can diseases re-emerge?

A

evolution of microorganisms
intensive misuse of antibiotics (selection for the proliferation of resistant organisms)
increased globalization
decline in public health in some regions
increase in people with decreased immune function

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4
Q

what are the classes of infectious agents?

A 
priors (infectious proteins)
viruses (acellular)
bacteria (prok)
fungi (euk)
parasites (euk)
-protozoans (unicellular)
-helminths (multicellular)
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5
Q

rank microorganisms by size

A

viruses

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6
Q

what is the requirement in bacteria to be classified as the same species?

A

> 97% identity in 16s rRNA
high degree of DNA sequence identity
more arbitrary than eukaryotes

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7
Q

bacillus

A

oval

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8
Q

coccus

A

circle

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9
Q

diplococcus
streptococcus
staphylococcus

A

2 cocci
chain of cocci
collection of cocci

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10
Q

funky shaped bacteria

A

coccobacillus: halfway between coccus and bacillus
curved rod
club shaped
spirochete

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11
Q

what is unique about the spirochete shape?

A

very thin

predestined to penetrate tissues

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12
Q

what is a spore?

A

formed under stress conditions
can survive in suboptimal circumstances better than the bacteria themselves
allow colonies to survive

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13
Q

what is the function of a capsule?

A

antiphagocytic

more chronic infection

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14
Q

gram positive

A

thick peptidoglycan cell wall

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15
Q

gram negative

A

thin PG layer with a second membrane

lipopolysaccharides acyl chain linkages with second membrane

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16
Q

spirochetes

A

have lipoproteins expressed on membrane
thing PG layer
flagella in between membranes

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17
Q

acid-fast

A 
cant be stained by gram staining
waxy surface 
-mycolic acids
-porins
-arabinogalactan
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18
Q

commensal

A

microorganism in symbiotic relationship with host

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19
Q

virulence

A

degree of pathogenicity

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20
Q

etiology

A

cause of disease

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21
Q

epidemiology

A 
factors of disease spread
sporadic- small isolated cases
endemic- continually prevailing in a region
epidemic- outbreak
pandemic- worldwide outbreak
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22
Q

stages of infection disease

A

incubation period
prodrome
specific illness (localized or systemic)
convalescence

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23
Q

what is prodrome

A

nonspecific symptoms

24
Q

what is convalescense

A

after resolution of symptoms to complete recover there can be complications

  • chronic carriers
  • latent infections
  • permanent tissue damage
25
Q

how do you measure virulence

A

ID50

LD50

26
Q

microbiome of skin

A

gram+

27
Q

microbiome of respiratory tract

A

nares- staphylococci

28
Q

microbiome of GI

A

anaerobes

29
Q

microbiome of GU

A

anterior urethra- lactobacilli

vagina- lactobacilli, others

30
Q

what parts of the body are generally sterile

A

upper GU

lower respiratory tract

31
Q

what is an example of a beneficial intestinal bacteria

A

E.coli producing vitamin K and B

32
Q

what are types of gut flora restoration therapy and when are they necessary?

A

fecal transplants
probiotics
need in C.difficile treatment

33
Q

what are 5 common transmission patterns

A 
oral/aerosol
fecal-oral
venereal
vector-borne (Lyme disease)
zoonotic
34
Q

what are portals of entry for a pathogen

A 
skin, soft tissue (trauma)
skin, bloodstream (bite)
respiratory (inhalation)
GI (ingestion)
GU (sexual transmission)
transplacental
35
Q

what are primary pathogens?

A

if present, they have a high probability of causing disease

immunizations common

36
Q

what are opportunistic pathogens?

A

some commensals

cause disease under certain conditions only

37
Q

what are nonpathogens?

A

rarely cause disease

38
Q

what are the stages of bacterial pathogenesis

A 
transmission
adhesion
colonization
spread
damages to host (direct or indirect by immune response)
evasion of immunity
transmission
39
Q

what are virulence factors?

A

help bacteria to invade the host, cause disease, and evade host defense
some are targeted by vaccines or detected by specific diagnostic tests

40
Q

what are some virulence factor examples?

A 
motility
adhesins
invasins
exotoxins
endotoxin (LPS)
degradative enzymes
capsules
siderophores
resistance to antibiotics
41
Q

what are adhesins?

A

surface virulence factors that confer ability to adhere to host surfaces

42
Q

what are examples of adhesins

A 
pilli
-type 1: adhere to mannose receptors
-p pilli: adhere to Gal-Gal receptors
protein adhesins
biofilms: bacterial polysaccharides allow bacteria to stick to each other and attach to a surface
43
Q

what are the 2 types of intracellular bacterial growth?

A

obligative- always require host cell

facultative- can also grow extracellularly

44
Q

what are some mechanisms of systemic disease?

A

destruction of tissue barrier by tissue damaging enzymes

penetration of cell membrane

45
Q

what are the 3 mechanisms of invasion of intracellular pathogens?

A

passive uptake: bacteria opsonized by complement are taken up by phagocytic cells
active invasion: invasins on bacterial cell surface induce uptake by non-phagocytes
transcytosis: intracellular motility by actin polymerization

46
Q

what are exotoxins?

A

bacteria mediated pathogenesis

47
Q

what are endotoxins?

A

host mediated pathogenesis
released when cells dies
LPS, gram negative and nonspecific immunity

48
Q

what makes up the syringe complex in “syringe” secretion systems?

A

T3SS

49
Q

what are examples of exotoxins?

A

enzymes (act on ECM, collagenase)
A-B type toxins (2 subunits)
membrane damaging toxins (phospholipases, pore forming toxins)
superantigens

50
Q

depict A-B toxins

A

B portion binds to cell surface receptor

A portion is enzymatically active and is transported into cell interior

51
Q

give examples of A-B toxins

A
  1. ADP ribosylating toxins
    - diphtheria toxin inactivated elongation factor
    - cholera/pertussis toxins activate adenylate cyclase (increase cAMP)
  2. others
    - shiga EHEC cleaves rRNA
    - tetanus blocks release of neurotransmitter
52
Q

describe host mediated pathogenesis

A

inflammation is mediated by microbial products (LPS, cell wall, some toxins), antibody and complement, and cell-mediated immunity
enhances microbial killing at the expense of the host tissue
autoimmunity in some chronic diseases

53
Q

what are superantigens?

A

lock antigen presenting cell and lymphocytes together

results in continuous stimulation of the immune system

54
Q

what is the mechanism of the endotoxin LPS?

A

released by cell lysis (not secreted)
toxic due to lipid A component
causes septic shock
binds to LPS binding proteins and interacts w host receptor CD14

55
Q

what are 3 ways pathogens evade host immune responses?

A

defense (capsules, serum resistance due to LPS modifications)
offensive (toxins degrade immune components, killing of phagocytes)
stealth (antigenic variation)

56
Q

how do bacteria obtain iron for growth?

A

siderophores

57
Q

where are virulence factors encoded?

A

chromosome: stable
pathogenicity island: region of DNA
plasmid: extrachromosomal smaller DNA replicon, can be transferred, dispensable for growth
bacteriophage: bacterial viruses, can transfer DNA between bacteria
transposons: highly mobile DNA element

MCM Test 3 (23 decks)

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