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Host and Defense > EXAM 1 Intro to Antimicrobial Drugs > Flashcards

EXAM 1 Intro to Antimicrobial Drugs Flashcards

1
Q

how much do microbes contribute to total body weight (on or in the body)?

A

1-3 lbs

9 in 10 cells in the human body are microbial

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2
Q

compare the number of bacterial genes vs human genes

A

3.3 million bacterial genes

22,000 human genes

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3
Q

while all ___ are antimicrobials, not all antimicrobials are ___

A

antibiotics, antibiotics

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4
Q

what is an antibiotic?

A

a low molecular substance produced by a microorganism that inhibits or kills other microorganisms while causing little or no damage to itself

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5
Q

what is an antimicrobial?

A

any substance of natural, semisynthetic, or synthetis origin that kills or inhibits the growth of microorganisms while causing little or no damage to the host

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6
Q

describe classification of antimicrobial agents

A
  • which microorganisms the drugs are active against
  • the class and spectrum of microorganisms it effects
    • bacterostatic vs. bacterocidal
    • broad vs. narrow spectrum
  • the biochemical pathway or target on the microorganism with which it interferes
  • chemical structure of the pharmacophore
  • pattern of activity
    • type I, II, or III
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7
Q

describe broad spectrum antimicrobials

A
  • drugs that are active against a wide range of microorganisms
  • a drug’s “spectrum of action” is not the same as its “useful therapeutic range”
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8
Q

describe narrow spectrum antimicrobials

A
  • antimicrobials that have limited activity and are primarily only useful against particular species of microorganisms
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9
Q

T or F

no antimicrobial is effective against all microbes

A

true

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10
Q

describe clinical considerations before prescribing an antimicrobial therapy (AMT)

A
  • is it really an infection?
    • if so, is it benign and self-limiting?
  • is it a pathogen that calls for an antibacterial drug?
  • consider patient’s health, medications, and condition, and determine risk
  • can we treat it?
    • culture and test
    • is there an effective drug?
    • will the route get enough of the drug to the site of infection?
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11
Q

describe considerations in the choice of the appropriate antimicrobial drug

A
  • is it the most effective and least toxic?
  • does it have the narrowest spectrum?
  • is it the least expensive?
  • will it exacerbate the patients existing pathologies?
  • does it take into account the patient’s immune status?
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12
Q

what are some patient-related factors to consider before prescribing antimicrobials?

A
  • age
  • sex
  • weight
  • allergies
  • genetic factors
  • renal and hepatic function
  • concurrent medications
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13
Q

should specimens be collected and cultures started before beginning treatment?

A
  • yes
  • unless it is recognizable by characteristics signs/symptoms
  • it can be assessed by rapid test
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14
Q

when should treatment of serious infections begin?

A

ASAP

can make an educated guess using the handbook of antimicrobial therapy (HAT)

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15
Q

describe resistant, intermediate susceptibility, moderate susceptibility, and susceptible classifications of the disc diffusion test

A
  • resistant
    • no zone of inhibition
  • intermediate susceptibility
    • small zone of inhibition
  • moderate susceptibility
    • medium sized zone of inhibition
  • susceptible
    • large zone of inhibition
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16
Q

what is MIC?

A

the minimum concentration of an antibiotic that will inhibit the growth of a bacterial strain

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17
Q

what is the broth dilution test?

A

determines both the MIC and the MBC (minimum bactericidal concentration)

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18
Q

___ antibiotics usually have very similar MIC and MBC values

A

bactericidal

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19
Q

___ antibiotics have much higher (if any) MBC than MIC values

A

bacteristatic

20
Q

what is the difference between a prophylactic and a definitive antimicrobial treatment?

A

successful identification of the infective pathogen

21
Q

what are pharmacokinetics?

A

the relationship of the time course of drug absorption, distribution, metabolism, and excretion (ADME)

what the body does to the drug

22
Q

what are pharmacodynamics?

A

the relationship of the drug concentration at the site of action and the resulting effects, including the time course and intensity of therapeutic and adverse effects

what the drug does to the body

23
Q

MIC only provides a guide to therapy. describe.

A

must keep in mind that although MIC is compared to plasma concentrations, these concentrations may or may not reflect drug concentration at site of infection

24
Q

antimicrobial doses should provide “overkill” without causing toxicity to the host. describe the two goals associated with this.

A
  1. achieve a bactericidal concentration at the site
  2. discourage emergence of resistant bacteria
25
Q

which phase of a bacterial growth curve is most sensitive to antimicrobial intervention?

A

log phase (exponential growth phase)

26
Q

describe the difference between bactericidal vs bacteriostatic drugs

A

bactericidal antibiotics kill bacteria, while bacteriostatic antibiotics stop bacteria from growing or reproducing

27
Q

what are three pharmacodynamic properties of antibiotics that best describe activity? what is the rate of effect determined by?

A

I. concentration-dependence

II. time-dependence

III. time-dependent with persistent effects

  • the rate of effect is determined by either the length of time necessary to kill (time-dependent) or the effect of increasing concentrations (concentration-dependent)
28
Q

describe the persistent post-antibiotic effect (PAE)

A

provides suppression of bacterial growth following antibiotic exposure.

ie. delayed regrowth of the bacteria after complete removal of an antibiotic allowing less frequent dosing that with agents with no PAE

29
Q

what are 5 key rules for treating serious infections?

A
  1. begin treatment ASAP (remember to culture)
  2. use the safest effective drug
  3. use the largest reasonable dose
  4. monitor the plasma concentration of antibiotic if it is needed to guide dose or to avoid toxicity
  5. must continue treatment at least 2 days past apparent “cure”, but some infections require much longer
30
Q

describe AMT selectivity

A
  • should exhibit selective toxicity towards pathogen rather than host
  • when selectivity is high, the risk of adverse effects are reduced
  • the ideal AMT is defined by its specificity of action in host vs. bacteria
31
Q

describe AMT dose

A

while some antimicrobial activity is dose-dependent, dose can also be a limiting factor because many, but not all, adverse effects are dose-dependent

32
Q

describe the AMT therapeutic index (TI)

A
  • the ratio of the dose toxic to the host to the effective therapeutic dose
  • the higher (or wider) the therapeutic index, the better/safer the antibiotic
33
Q

describe adverse effects of AMTs analogous to antimicrobial action

A

an effect on human cells resulting from the same mechanism as the antimicrobial effect

34
Q

describe adverse effects of AMTs independent of antimicrobial action

A
  • irritation
  • allergy
35
Q

describe absorption of antmicrobial drugs

A
  • determines the compound’s bioavailability
  • route of administration is an important consideration
36
Q

describe distribution of antimicrobials drugs

A
  • will it pass the blood brain barrier? is it lipid soluble or water soluble?
  • is there systemic inflammation?
37
Q

describe the metabolism of antimicrobial drugs

A
  • usual routes of clearance are though the liver and kidneys
  • drugs begin to break down to metabolites as soon as they enter the body
  • metabolites may also be pharmacologically active
  • inactivation by bacterial enzymes
38
Q

describe inactivation of antimicrobial drugs by bacterial enzymes

A
  • augmentin - amoxicillin + clavulanate (inhibits beta-lactamase)
  • unasyn = ampicillin + sublactam (inhibits beta-lactamase)
  • primaxin = imipenem + cilistatin (inhibits dehydropeptidase-1)
39
Q

describe mechanisms of antimicrobial action

A

selectively target all essential microbial processes

40
Q

what are several reasons for using combination therapy?

A
  • for treatment of inherently mixed infections
  • to improve efficacy
  • for initial empiric therapy of uncharacterized serious infection
  • to enable use of lower drug concentrations
  • to delay emergence of resistance
41
Q

no new classes of antibiotics have been introduced since what year?

A

1987

42
Q

which qualified infections are included in the GAIN Act?

A
  • drug-resistant infections gram pos
  • multidrug resistant gram neg bacteria
  • multidrug resistant tuberculosis
  • any other WHO defined drug-resistant public health threats
43
Q

antimicrobial use can cause ___ by killing off large numbers of drug-sensitive organisms

A

a wide-spread alteration of the microbial ecosystem

44
Q

T or F

the current view is that pathogenic microbes interact with other bacteria to control growth of pathogens as well as of harmless bacteria

A

False:

nonpathogenic microbes

45
Q

what is the result of reducing the number of harmless microbes?

A

opens niches in the ecosystem in which drug-resistant organisms, some of which might be pathogens, can grow

46
Q

what is a superinfection?

A

the overgrowth of pathogens resulting from use of antimicrobial drugs

47
Q

what is superinfection usually caused by?

A
  • use of a broad-spectrum antimicrobial agent
  • use of a higher than normal concentration of even a narrower-spectrum antimicrobial drug
  • the larger the disruption of the microbiome, the greater the opportunity for pathogens to overgrow

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