Chapter 3 Flashcards
what is defined as a low molecular weight substance produced by a microorganism that at low concentrations inhibits or kills other microorganisms
antibiotic
what includes any substance of natural, semisynthetic, or synthetic origin that kills or inhibits the growth of a microorganism but causes little or no damage to the host
antimicrobial
true or false:
there are no specific guidelines for dose adjustments on antibiotics
true
what are the practical uses of antibiotics
-right antibiotic
-right patient
-right dose
-right duration of action
-right route of administration
-monitor the patient throughly
what should be one of the most important considerations when you are choosing an antibiotic
if its effective against the bacteria
what type of antibacterial agent only inhibits gram + or gram -
narrow-spectrum
what type of antibacterial agent inhibits both gram + and gram -
broad-spectrum
true or false:
a pathogen’s susceptibility should be a main point when deciding on the selection of an antibiotic
true
what are some differences to consider when setting MIC measurements for drugs
- concentrations are fixed over time in incubation
- growth medium may differ physiologically
- testing doesn’t include host factors
- growth inhibition is the end point
- no info on persistent effects
- virulence factors
when designing treatments, what is considered the most important factors governing the selection for clinical veterinary use
Antimicrobial Susceptibility Testing (AST)
what may AST results not always provide
accurate prediction of clinical outcome
when is there the most concern for AST
no animal species and infection-specific veterinary clinical breakpoints are available
what are the 3 parameters to assess a clinical breakpoint
- epidemiological cut-off value (ECOFF)
- MIC to define a PK/PD cut off
- clinical cut-off value
what does the epidemiological cut-off value mean
highest MIC for bacteria free of detectable aquired resistance mechanisms
what data is combined to result in clinical breakpoints
MIC values
PK/PD indices
clinical outcome results
what type of antibiotic kills bacteria
bactericidal
what type of antibiotic inhibits bacterial growth without killing them
bacteriostatic
what is the lowest concentration of an antimicrobial agent required to prevent the growth of the pathogen
minimum inhibitory concentration
what is the lowest concentration of an antimicrobial agent required to kill the pathogen
minimum bactericidal concentration
what are the most important drivers of drug efficacy
optimal dosing
pharmacokinetics
tissue penetration
at concentrations equal to the MIC of a pathogen, which drug acts bacteriostatic rather than as bactericidal
fluoroquinolones
which drug, normally bacteriostatic against most gram-negative bacteria, is bactericidal against Haemophilus influenzae and strep.
chlorampheniol
what can vary a drug’s bactericidal activites
intracellular pH
oxygen content
intracellular enzymatic activity
which chemical groups of antibiotics are concentration dependent
fluoroquinolones
aminoglycosides
nitroimidazoles
polymixins
which chemical groups of antibiotics are time-dependent
penicillins
cephalosporines
macrolides & triamilides
lincosamides
phenicols
sulfonamides
diaminopyrimidines
which chemical groups of antibiotics are co-dependent for killing needing duration of exposure and maintained drug concentration
tetracyclines
ketolides
glycopeptides
what are the 2 ways antimicrobial agents are often classified
time-dependent
concentration-dependent
what can the combination of AUC and MIC values be used to predict
probability of bacterial eradication
clinical success
what does T/MIC mean
increasing the concentration over the MIC curve will not increase the efficacy of a drug. This drug needs to have a longer time limit at a constant concentration
what does AUC/MIC or Cmax/MIC mean
these drugs will need increased drug concentrations above the MIC
what can control the achieved concentration
systemic availability
what is systemic availability variable by
dosage form
route of administration
ability of drug to gain access
volume distribution
true or false:
parenteral therapy should never be used in the treatment of severe infections
false
it should always be used
when would it be most appropriate to use an oral therapy in dogs and cats
mild to moderate infections
what will enhance passage of a drug across barriers
inflammation
define a synergistic antibacterial combination
combined effects are significantly greater than the independent effects
define an antagonistic antibacterial combination
combined effects are significantly less than their independent effects
which type of antibiotic interferes with the final stage of peptidoglycan synthesis
beta-lactams
what do beta-lactams prevent
formation of bacterial cell wall (inhibit activity of PBPs)
what type of action do beta-lactam drugs have on bacteria
bactericidal
what causes a difference in susceptibility between gram-positive and gram-negative bacteria
differences in receptors sites (PBPs)
relative amount of peptidoglycan present
ability of drug to penetrate the outer cell membrane
resistance to beta-lactamase enzymes
which group of penicillin has procaine as a derivative
benzyl penicillin
which group of penicillin has a derivative of cloxacillin, dicloxacillin & oxacillin
anti-staphylococcal isoxazolyl penicillins
which group of penicillins has a derivative of ampicillin & amoxicillin
extended - broad spectrum penicillins
which group of penicillins has a derivative of ticarcillin
antipseudomonal penicillins
which penicillin is the only one whose oral bioavailability is great enough to warrant oral administration
amoxicillin
where are penicillins predominantly ionised
plasma
how are penicillins eliminated from the body
almost entirely from the kidneys
true or false:
since penicillin is eliminated through the renal system, glomerular filtration and tubular secretion need to be intact to maintain safe concentrations within the body
true
what can be used to increase penicillin resident time in the body
probenecid - inhibits tubular secretion
what are penicillins normally synergistic with
aminoglycosides - enhance the penetration of the aminoglycoside of the bacteria
what are the possible adverse effects of penicillins
acute anaphylaxis
collapse
mild hypersensitivity reactions
true or false:
penicillins are not cross-sensitising or cross-reactive
false
what is a possible consequence when taking broad-spectrum penicillins
disturbance of the normal intestinal flora
what animals should not be given ampicillin due to their intestinal normal flora containing clostridial colitis
small rodents - rabbits, hamsters, gerbils ect.
which antibiotic is inherently more resistant to beta-lactamases than penicillin
cephalosporins
which groups of cephalosporin primarily only have gram-positive activity
group 1
group 2
which group of cephalosporins have gram-positive and gram-negative activity
group 3
which group of cephalosporin has decreased gram-positive but increase gram-negative activity
group 4
group 5
group 6
which group of cephalosporin has increased gram-positive and gram-negative activity
group 7
what are the 3 mechanisms of resistance to cephalosporins can create
PBP modification
reduced permeability
increased efflux
enzymatic degradation by beta-lactamases
what antibiotic are cephalosporins synergistic with
aminoglycosides
