EXAM 1 Intro to Antimicrobial Drugs

Question 1

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

Answer 1

1-3 lbs

9 in 10 cells in the human body are microbial

Question 2

compare the number of bacterial genes vs human genes

Answer 2

3.3 million bacterial genes

22,000 human genes

Question 3

while all ___ are antimicrobials, not all antimicrobials are ___

Answer 3

antibiotics, antibiotics

Question 4

what is an antibiotic?

Answer 4

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

Question 5

what is an antimicrobial?

Answer 5

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

Question 6

describe classification of antimicrobial agents

Answer 6

• 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

Question 7

describe broad spectrum antimicrobials

Answer 7

• 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”

Question 8

describe narrow spectrum antimicrobials

Answer 8

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

Question 9

T or F

no antimicrobial is effective against all microbes

Answer 9

true

Question 10

describe clinical considerations before prescribing an antimicrobial therapy (AMT)

Answer 10

• 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?

Question 11

describe considerations in the choice of the appropriate antimicrobial drug

Answer 11

• 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?

Question 12

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

Answer 12

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

Question 13

should specimens be collected and cultures started before beginning treatment?

Answer 13

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

Question 14

when should treatment of serious infections begin?

Answer 14

ASAP

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

Question 15

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

Answer 15

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

Question 16

what is MIC?

Answer 16

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

Question 17

what is the broth dilution test?

Answer 17

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

Question 18

___ antibiotics usually have very similar MIC and MBC values

Answer 18

bactericidal

Question 19

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

Answer 19

bacteristatic

Question 20

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

Answer 20

successful identification of the infective pathogen

Question 21

what are pharmacokinetics?

Answer 21

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

what the body does to the drug

Question 22

what are pharmacodynamics?

Answer 22

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

Question 23

MIC only provides a guide to therapy. describe.

Answer 23

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

Question 24

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

Answer 24

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

Question 25

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

Answer 25

log phase (exponential growth phase)

Question 26

describe the difference between bactericidal vs bacteriostatic drugs

Answer 26

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

Question 27

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

Answer 27

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)

Question 28

describe the persistent post-antibiotic effect (PAE)

Answer 28

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

Question 29

what are 5 key rules for treating serious infections?

Answer 29

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

Question 30

describe AMT selectivity

Answer 30

* 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

Question 31

describe AMT dose

Answer 31

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

Question 32

describe the AMT therapeutic index (TI)

Answer 32

* 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

Question 33

describe adverse effects of AMTs analogous to antimicrobial action

Answer 33

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

Question 34

describe adverse effects of AMTs independent of antimicrobial action

Answer 34

* irritation * allergy

Question 35

describe absorption of antmicrobial drugs

Answer 35

* determines the compound's bioavailability * route of administration is an important consideration

Question 36

describe distribution of antimicrobials drugs

Answer 36

* will it pass the blood brain barrier? is it lipid soluble or water soluble? * is there systemic inflammation?

Question 37

describe the metabolism of antimicrobial drugs

Answer 37

* 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

Question 38

describe inactivation of antimicrobial drugs by bacterial enzymes

Answer 38

* augmentin - amoxicillin + clavulanate (inhibits beta-lactamase) * unasyn = ampicillin + sublactam (inhibits beta-lactamase) * primaxin = imipenem + cilistatin (inhibits dehydropeptidase-1)

Question 39

describe mechanisms of antimicrobial action

Answer 39

selectively target all essential microbial processes

Question 40

what are several reasons for using combination therapy?

Answer 40

* 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

Question 41

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

Answer 41

1987

Question 42

which qualified infections are included in the GAIN Act?

Answer 42

* drug-resistant infections gram pos * multidrug resistant gram neg bacteria * multidrug resistant tuberculosis * any other WHO defined drug-resistant public health threats

Question 43

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

Answer 43

a wide-spread alteration of the microbial ecosystem

Question 44

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

Answer 44

False: nonpathogenic microbes

Question 45

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

Answer 45

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

Question 46

what is a superinfection?

Answer 46

the overgrowth of pathogens resulting from use of antimicrobial drugs

Question 47

what is superinfection usually caused by?

Answer 47

* 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