-
test to distinguish staph from strep
- catalase test.
- STAPH IS CATALASE POSITIVE
- strep is catalase negative
-
strep is gram [+ or -]
+ positive
-
poor availability oral antibiotics
- aminoglycosides
- vancomycin
-
40L Vd
40 liter volume distribution: drug distributes throughout the body fluids (gets to every single space in your body)
-
example: taking a drug q8, you won't be killing anymore by the end of each dose, but you won't be in the black long enough for the infection to take over. then comes the next dose.
what is this called, and what class of meds works like this?
- time-dependent antibiotic killing
- penicillins utilize this
-
drugs that kill when the concentration at the bacterial site is higher than the MIC of the organism, and 4 examples
time-dependent antibiotic killing.
examples: carbapenems, vancomycin, macrolides, clindamycin
-
highly bioavailable oral antibiotics (6)
- quinolones (ciprofloxacin, moxifloxacin)
- TMP-SMX
- clindamycin
- doxycycline
- rifampin
- azoles
-
combining beta lactases does this
increases the spectrum of activity
- gram + MSSA
- gram - H flu, E coli, Klebsiella
- anaerobes: B frag
-
these are antibiotics that expand the spectrum of specific beta-lactams by binding irreversibly to beta lactamase produced by the organism
beta lactamase inhibitors
-
3 beta lactamase inhibitors and what they do
- sulbactam
- tazobactam
- clavulanate
these get into the beta lactamase and keep it from working
-
half lives of oxacillin and nafcillin are
SHORT! 0.5 hrs. requires frequent dosing (q4 IV)
cleared hepatically (no need to adjust for renal, like you do with penicillin G)
-
side effects of ampicillin/amoxicillin
- rash
- diarrhea (diarrhea worse with ampicillin. amox better for diarrhea)
-
a semisynthetic penicillin
methicillin
-
semisynthetic penicillin good against gram + cocci:
S. pneumoniae
Groups A, B, C, G strep
viridans
S aureus
S epidermidis
methicillin
-
25-30L Vd
- 25-30 liter volume distribution
- drug distributes intracellularly
-
10-20L Vd
10-20 liter volume distribution
drug distributes into extracellular compartments
-
5L Vd
5 liter volume distribution
indicates antibiotic is restricted to circulatory system
-
piperacillin-tazobactam combined with this, is very powerful
vancomycin
*tazobactam does not cover MRSA
-
a ureido penicillin, similar to ampicillin against gram+. good against streptococci. expanded gram- coverage including Pseudomonas aeruginosa, Serratia marsescens, Enterobacter
good against B frag
piperacillin-tazobactam
-
pip-taz is short for
piperacillin-tazobactam
-
ampicillin-sulbactam and amoxicillin-clavulanate are better than amp/amox alone for:
- pneumonia
- H flu
- S aureus
- intra-abdominal infections (but needs better E coli coverage)
- skin and soft tissue
-
ampicillin-sulbactam is always given this way
IV
-
useful for nosocomial pneumonia, intra-abdominal infections, complicated wound infections, peudomonal infections, but very expensive
pip-taz
-
for Enterococci: ampicillin/amoxicillin vs penicillin
ampicillin and amoxicillin are 2x more active on Enterococci than penicillin
-
penicillin side effects
- rash
- anaphylaxis/urticaria
- hyperkalemia
- seizures
-
penicillin G repository (IM) formulations and why
1. procaine + Penicillin G delays onset of peak but gives a good 12 hour dose
2. benzathine penicillin combined with ammonium base: gives serum levels for 15-30 days. not powerful enough for CNS infections.
these are good for populations who 'don't come back' like travelers and careless teenagers
-
Penicillin G half life is
- very short! 0.5 hrs
- IV dosing q4
- cleared renally
- poor oral bioavailability
-
Penicillin G vs. spirochetes, cat bites
- penicillin G has good activity against
- T. pallidum (syphilis)
- B. burgdorferi (Lyme)
- Pasteurella multocida (cat bites)
-
Penicillin G vs. anaerobes
- good activity against oral anaerobes:
- Peptostreptococcus
- Prevatella
- Fusobacterium
- *Clostridium
not good for B frag and other B. therefore not good for intra-abdominal infections
-
how to measure MIC and why
millimeters of zone of inhibition (clear zone) correlates directly with MIC units (ug/ml)
to see if antibiotic is sensitive, intermediate or resistant
-
therapy for coagulase-negative staph infection
- remove implanted catheter or device
- vancomycin
(majority of these bugs are resistant to all beta-lactam agents)
-
therapy for VISA or VRSA staph infections
daptomycin, linezolid
-
therapy for HA-MRSA (healthcare-acquired MRSA staph infection)
- vancomycin
- daptomycin, linezolid or quinupristin-dalfopristin
-
therapy for CA-MRSA (community-acquired MRSA staph infection)
for minor/moderate: trimethoprin-sulfamethoxazole, clindamycin, doxycycline, minocycline, linezolid
for severe: vancomycin
-
therapy for MSSA staph infection
- oxacillin or nafcillin
- 1st or 2nd generation cephalosporins
- vancomycin
-
ampicillin half life
- short! 0.5 hours. frequent dosing q4-6
- cleared renally (must adjust)
- use amoxicillin for oral. this only has fair oral bioavailability
-
viridans vs Penicillin
very sensitive. PCN works great on viridans.
-
strep. pyogenes vs bacitracin
99% sensitive to it
-
7 diseases caused by s. pyogenes
strep throat, cervical lymphadenopathy, impetigo, nec fasc, rheumatic fever, scarlet fever, strep TSS
-
s pyogenes vs PCN
very sensitive to PCN
-
staph aureus vs penicillin G
NO. S. aureus contains a penicillinase
-
Penicillin G affects these gram +
- strep pneumoniae
- strep pyogenes (group A)
- strep agalactiae (group B)
- *viridans
-
Penicillin G affects this gram-
Neisseria meningitidis
note: not useful against gonorrhea
-
semisynthetic penicillins (methicillin) are not active against gram
gram negative
-
oral bioavailability of oxacillin, nafcillin
poor bioavailability! use dicloxacillin instead
-
aminopenicillins vs Klebsiella, serratia, acinetobacter, Pseudomonas, B frag
NO. these are resistant to aminopenicillins
-
aminopenicillins vs gram-
- YES.
- H flu
- E coli
- Proteus mirabilis
-
aminopenicillins are good for gram:
gram+
-
aminopenicillins vs penicillin-susceptible S. aureus
aminopenicillins are active against PCN-susceptible S. aureus
(BUT this is only 2% of all S. aureus)
-
3 factors affecting the bioavailability of oral antibiotics
- intestinal cytochrome enzymes
- intestinal transporter systems (P glycoprotein)
- decreased intestinal absorption (malabsorption, presence/absence of food, diarrhea)
-
some drugs need to be modified by this system to be biologically active
CYP (cytochrome P450)
-
a group of isoenzymes located primarily in the liver and GI tract
cytochrome P450 system
-
penicillin's mechanism
penicillins work by using BETA LACTAM to inhibit cell wall synthesis. bacteria produce beta lactamase enzymes and if the enzyme eats the beta lactam in the antibiotic, the bacteria becomes resistant to the medicine.
-
if CYP is being inhibited for a certain drug, this is called [up-regulation, down-regulation] and the drug level will be [increased, decreased]
down-regulation, and the drug level will be increased
-
if CYP is being induced for a certain drug, this is called
[up-regulation, down-regulation] and the drug level will be [increased,
decreased]
up-regulation, the drug level will be decreased
-
AUC
area under the curve: time above the MIC
-
covers MSSA, good for beta-lactamase producing Enterobacteriae (E Coli, Klebsiella) but 8% of E Coli are resistant
95% of B frag covered
tazobactam
-
pip-tazo half life
- short! 1 hr.
- frequent dosing q6 or q8 IV
- cleared renally (must adjust)
NO ORAL VERSION
-
concentration-dependent antibiotic killing
higher single dose better than smaller multiple doses
aminoglycosides and quinolones
-
strawberry tongue means
scarlet fever. sometimes accompanies strep throat. desquamating skin, too. caused by a phage.
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