Chapter 13- Antibiotic therapy Flashcards
Antibiotics (antibacterial) are a).. to bacteria without toxicity to eukaryotic organisms
Selectively toxic
What types of organisms do antibiotics effect?
antibacterial, antiprotozoal. antifungal and antiviral
spectrum of activity.
Penicillin has a a)… spectrum
narrow (GRAM + bacteria)
spectrum of activity.
Ampicillin has a a).. spectrum
broad (GRAM - and GRAM + bacteria)
What is the magic bullet concept?
an antimicrobial agent capable of selective destruction of pathogenic microorganisms.
spectrum of activity.
Isoniazid has a a)… spectrum.
Isoniazid aims at what type of bacteria?
a) very narrow
b) Mycobacterium tuberculosis. (mycolic acid)
bactericidal antibiotics do what
kill pathogens
good for immunocompromised
bacteriostatic do what
prevent or slow bacterial growth, which enables immune response to get rid of pathogen.
selective toxicity
The ability of a drug, at a given dose, to harm a pathogen without harming its host.
despite bacteria selectivity, abx’s still a)..
a) have unintended side effects
four unintended side effects of selective toxic antibacterials
-age dependent (toxicity depending on age)
-cell development (interferes with RBC in bone marrow)
-metabolism dependant (excreted/metablolized by kidney and liver)
-allergy (sensitivity)
The in vitro effectiveness of an antibiotic is determined by measuring what?
how little of it is needed to stop growth
minimum inhibitory concentration (MIC),
minimum inhibitory concentration (MIC), is defined as the?
lowest concentration of the drug that will prevent the growth of an organism
Kirby-Bauer assay
A method for determining antibiotic susceptibility.
zone of inhibition
A region of no bacterial growth on an agar plate owing to the diffusion of a test antibiotic
correlates to MIC
What is the flaw with Kirby-Bauer assay and tube dilution?
You can not tell if a drug is bactericidal because you can not tell if the cells within the zone of inhibition are dead or remain viable and just stopped growing.
minimum bactericidal concentration (MBC) is defined as a)..
a) The lowest concentration of a abx that kills bacteria
requires futher plating to determine if any cells survived.
For an antibiotic to stop bacterial growth in the patient, the drug’s concentration in tissue must a)..
remain higher than the MIC at all times.
The half life of a drug tells us what?
How long a drug will remain in the tissues.
To keep a drug level within the sufficient range, the clinician can do what?
Administer a higher dose (risk of SE)
or
Schedule mutiple doses to keep drug levels above lab determined MIC
therapeutic dose
Minimum dose per kg of body weight that stops growth
Toxic dose
Maximum dose tolerated by the patient
The ratio of the toxic dose to the therapeutic dose
chemotherapeutic index
The higher the chemotherapeutic index
the safer the drug
synergisitic drugs
have greater effectiveness when used together
(1+1=3)
example: aminoglycoside and vancomycin
Antagonist drugs
intere with each other and decrease effectiveness
example: penicillin and macrolides
What are the three ways of classifiying antibacterial agents?
- bactericidal or bacteriostatic
- target site
- chemical structure
What antibiotics are metabolic inhibitors?
intermediary metabolism
Sulfonamides
Trimethoprim
Metronidazole
What abx are protein synthesis inhibitors
Larger subunit (50S)
and
Small subunit (30s)
50s= macrolides (erythromycin)
30s= aminoglycosides (gentamicin)
what abx affects cell membrane integrity?
Polymyxins
What abx affect cell wall synthesis
cell wall inhibitor
penicillins, cephalosporins, vancoymycin, bacitracin, monobactams.
what abx effects mycolic acid synthesis?
Isoniazid
what abx effects DNA replication
Quinolones
What abx affects transcription?
RNA polymerase inhibitors
Rifampin and myxopyronins, fidaxomicin
Antibiotics targeting the cell wall biosynthesis generally only kill
growing cells
enzymes that produce peptide cross links in peptidoglycan
penicillin-binding proteins,
beta-lactam abx
penicillin and related abx bind to them
