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FM2 > Basic concepts > Flashcards

Basic concepts Flashcards

1
Q

Pathogenicity vs virulence

A 
Pathogenicity= ability to cause disease
Virulence= extent of disease
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2
Q

Pathogen

A

organism causing damage and disease (symptoms / signs of illness) via interaction with host

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3
Q

List five broad classes of human pathogens

A 
viruses
bacteria
fungi
protozoa
helminths
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4
Q

Gram positive organisms stain ______ with Gram staining whereas gram negative organisms stain ______

A

purple/blue; pink/ red

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5
Q

Gram positive organisms have a thicker ________ layer than Gram negative organisms. This blocks the decolorization step of the Gram staining process

A

peptidoglycan (murein)

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6
Q

List the basic steps in Gram staining protocol

A
  1. fixation
  2. stain with crystal violet
  3. iodine treatment
  4. decolorization
  5. safranin counter stain
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7
Q

Findings of intracellular gram negative diplococci within PMNs on gram stain of urethral discharge in symptomatic men is diagnostic for ________

A

Neisseria gonorrhoeae

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8
Q

List features of Gram positive bacteria

A
  • two layers: thick peptidoglycan layer; cytoplasmic membrane
  • teichoic acids
  • adhesion to host cells by adhesions and teichoic acids
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9
Q

List features of Gram negative bacteria

A
  • three layers: outer membrane; thin peptidoglycan; inner membrane
  • endotoxin/ LPS
  • periplasmic space
  • porins
  • attachement to host cells by fimbriae, adhesins
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10
Q

Describe phases of standard bacterial growth curve

A
  1. Lag phase: little cell growth/ division as cells adapt
  2. Exponential phase: maximal division rate
  3. Stationary phase: nutrients exhausted, waste products accumulate, new cells= dying cells
  4. Death phase: number of nonviable cells > viable cells
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11
Q

Mesophiles grow best at ________ degrees celsius and include most human pathogens

A

20-45 C

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12
Q

_______ grow at temperatures below 20 C and are a major concern in _______ and blood products

A

Psychrophiles; refrigerated foods

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13
Q

Thermophiles grow at temperatures of 45-60 C and are a concern in _________

A

food processing/ canning

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14
Q

________ grow at temperatures greater than 60 C

A

Stenothermophiles

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15
Q

Why are anaerobes unable to grow in the presence of oxygen?

A

lack enzymes to detoxify reactive oxygen species

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16
Q

most human pathogens are ________ for oxygen

A

facultative

17
Q

_______ require reduced oxygen levels for maximal growth

A

Microaerophiles

18
Q

_______ grow best under conditions of increased carbon dioxide

A

Capnophiles

19
Q

Distinguish plasmids from transposons

A
  • Plasmids: 5-100 genes passed during cell division or transferred between bacteria during conjugation or transformation
  • Transposon: 1-10 gene element on plasmid or chromosome that can move to other sides in DNA; does not replicate independently
20
Q

Distinguish: transformation, transduction, and conjugation

A

Transformation – mediated by free (naked) DNA
Transduction – mediated by bacterial virus (bacteriophage)
Conjugation – mediated by transfer apparatus, e.g., pilus

21
Q

One way of maintaining transferred DNA is integration into a replicating DNA molecule via _______

A

genetic recombination

22
Q

Distinguish generalized transduction from specialized transduction

A
  • generalized transduction: mediated by lytic phase; any portion of degraded bacterial DNA can be repackaged into assembling phage head
  • specialized transduction: mediated by lysogenic phage, imprecise excision carries along bacterial DNA from areas adjacent to phage integration site
23
Q

Define lysogenic conversion

A

lysogenic phage infection changes the phenotype of the host bacterium, sometimes incurs new virulence factors. Ex diptheria toxin, cholera toxin

24
Q

Describe antigenic variation as a mechanism of escaping host defenses.

A

Organism expresses different phenotypes- homologous proteins-> antigenic variation. Change pilus so host response is no longer effective. Evade adaptive host response

25
Q

List three antibiotic classes that inhibit cell wall synthesis

A

penicillins, cephalosporins, vancomycin

26
Q

List three antibiotic classes that inhibit protein synthesis

A

tetracyclines, aminoglycosides, macrolides

27
Q

List the antibiotic class that inhibits DNA synthesis

A

Fluroquinolones

28
Q

List the antibiotic that is a folic acid inhibitor; contains two synergistic components

A

TMP-sulfa

29
Q

List three broad strategies for controlling antibiotic resistance

A
  1. reduce selective pressure: eliminate unnecessary use and improve quality of use
  2. improve nosocomial infection control: aseptic technique, surveillance
  3. aggressive control of outbreaks: identify, isolate

FM2 (11 decks)

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