Block 3 Flashcards
what is selective toxicity
a drug that kills harmful microbes without damaging the host
how do bactericidal agents work
kill bacteria leading to a faster decline in bacteria cell number
what are 4 examples of bactericidal drugs
penicillin
cephalosporins
aminoglycosides
fluoroquinolones
how do bacteriostatic agents work
inhibit bacterial growth
why are bacteriostatic agents not preferred in immunocompromised patients
bacteria will resurface because intact immunity is required to get rid of the static bacteria
what are 3 examples of bacteriostatic agents
sulfonamides
tetracyclines
erythromycin
what is an example of a drug which is bactericidal against one set of bacteria but bacteriostatic against another
chloramphenicol
what is the downside of use of broad spectrum drugs
they can cause superinfections by organisms whose growth is normally kept in check by presence of normal flora
what is minimum inhibitory concentration of drugs
the lowest antibiotic concentration that prevents visible growth of an organism after 24 hours of incubation
based on minimum inhibitory concentration, how can you determine if a bacteria is resistant or susceptible
low MIC to suppress growth= sensitive
high MIC to suppress growth= increased resistance= increased risk of toxicity
what is antibiotic concentration dependent killing
as concentration of the drug increases from 4 to 64 fold, there is an increase in bacteria killing
what type of antibiotic dosing and frequency do you use for concentration dependent killing
(high/low dose, frequent/less frequent)
high dose
less frequent
do daptomycin, aminoglycosides, and fluoroquinolones exhibit a concentration or time dependent killing
concentration
what is antibiotic time dependent killing
killing continues as long as the concentration is above MIC (increasing concentration very high above MIC does not result in proportionate increase in killing)
what type of antibiotic dosing and frequency do you use for time dependent killing
(high/low dose, frequent/less frequent)
low
more frequent
beta lactams (such as penicillin) and vancomycin use what type of dependent killing (concentration or time)
time
what is post antibiotic effect
suppression of bacterial growth persists following removal of the antibiotic
what type of drug shows a post antibiotic effect against gram + cocci
penicillin
what type of drugs show a post antibiotic effect against gram - bacilli
aminoglycosides
the higher the lipid solubility of a drug the __ better it will be able to reach the BBB
higher
are 2 examples of drugs that are able to pass the BBB due to their high lipid solubility
chloramphenicol and metronidazole
bactericidal drugs are used in __ (larger/smaller) dose for a __ (longer/shorter) duration in immunocompromised patients
larger
longer
what are 2 drugs that are contraindicated for patients with hepatic dysfunction
erythromycin
doxycycline
*primarily cleared by liver
what are 6 main drugs to avoid during pregnancy
tetracycline (impaired bone growth, teeth dysplasia)
aminoglycosides (ototoxic effects-ear)
erythromycin estolate
clarithromycin
fluoroquinolones
sulfonamides
what route of administration is used for serious infection
parenteral (other than GIT)
what is pre-emptive therapy
treatment of an infected but asymptomatic patient
what is specific (definitive) therapy
treatment started after identifying the organism and finding out what drug it is sensitive to
what is empiric therapy
treatment after speciman has been obtained but before results of culture are available
what in an example of when empiric therapy is used
in patients in meningitis where delay could be fatal
what are 4 factors that determine choice of drug for empiric therapy
hospital vs community acquired
immune status of patient
patient’s travel record
age
why are antibiotics used prophylactically in acute rheumatic fever
for the prevention of streptococcal reinfection and rheumatic heart disease
how can you identify a cell wall synthesis inhibitor based on the name
ceph-
cef-
-cillin
-vancin
how do beta lactam drugs work
they interfere with cell wall synthesis by binding to penicillin binding protein and inhibiting transpeptidase
what are the 2 mechanisms of antibiotic resistance with beta lactam antibiotics
beta lactamase
structural change in penicillin binding protein
what penicillins are included in standard/natural penicillins
penicillin G (IM) and phenoxymethyl penicillin V (oral)
anti-staphylococcal penicillins are resistant to what
beta lactamase
what are 5 examples of anti-staphylococcal penicillin drugs
methicillin
nafcillin
oxacillin
cloxacillin
dicloxacillin
what are 2 examples of aminopenicillins
ampicillin
amoxicillin
what are 3 examples of antipseudomonal penicillins
carbenicillin
ticarcillin
piperacillin
how is penicillin G administered, why
parenterally, it is destroyed by gastric acid
when does penicillin G cross the BBB
during inflammation in meningitis
does penicillin G have a short or long half life
short (30 minutes)
90% of penicillin G is eliminated by __
tubular secretion in urine
how can the concentration of penicillin G in plasma be increased
addition of probenecid
penicillin G is also known as what
benzyl penicillin
penicillin G is used against what 6 bacteria
staphylococci
neisseria meningiditis
corynebacterium diptheriae
clostridium tetani
clostridium perfringes
treponema (syohilis)
how do beta lactamases work
they hydrolyze of beta lactam rings, making them ineffective
penicillin G is used for prophylaxis for what infection
acute rheumatic fever
what is an advantage of nafcillin
it’s excreted in the bile so it can be given to patients with renal impairment
what penicillinase is no longer used due to it’s nephrotoxicity
methicillin
what drugs are used for methicillin resistant staph aureus
vancomycin/daptomycin
what is the preferred antibiotic for listeria infection
ampicillin
what in interferes with ampicillin absorption
food
how is ampicillin excreted
in the bile and partially undergoes enterohepatic circulation
what is a side effect of ampicillin
diarrhea
what are the advantages of amoxicillin use over ampicillin use
less diarrhea
less risk for pseudomembranous colitis
ampicillin and amoxicillin are used for what therapeutic uses
upper respiratory tract infections
urinary tract infections
meningitis
salmonella (ampicillin)
what drug is given for prophylactic use in patients with abnormal or prosthetic heart valves undergoing dental surgery/procedure
amoxicillin or ampicillin
high doses of what drug can cause bleeding by interfering with platelet formation
antipseudomonal penicillins (piperacillin, carbenicillin, ticarcillin)
antipsudomonal penicillins are used against what bacteria species
pseudomonas aeruginosa
enterobacteriaceae
klebsiella
piperacillin is used in combination with what other drug
tazebactam
antipseudomonal penicillins are used in __ infections by gram - bacteria (what type of setting)
nosocomial (hospital acquired)
what is the Jarisch-Herxheimer reaction
penicillin is injected in a syphilitic patient and produces fever, chills, headache, hypotension, etc
are penicillins safe to use in pregnancy
yes
do penicillins have high or low therapeutic index
high
they are safe drugs
clavulanic acid is used in combination with what 2 drug
amoxicillin
ticarcillin
sulbactam and tazobactam are used in combination with what drugs
ampicillin
piperacillin
what are 5 mechanisms of drug resistance
inactivation of microbial enzymes (beta lactamases)
decreased accumulation (decreased uptake, increased efflux)
reduced affinity of the target macromolecule for the drug
altered metabolic pathway
what inactivated aminoglycosidases and chloramphenicol
acetyltransferases
what spectrum type of antibiotics can cause superinfection
broad
