Lec21 Case Based Review of Antibiotics Flashcards
What is drug of choice for scarlet fever?
penicillin or amoxicillin [for strep A]
Which of these is a common side effect of penicillin?
A. allergic rxn B. bile sludging C. ototoxicity D. QTc prolongation E. tendonitis
A. allergic rxn
Which of these is a common side effect of ceftriaxone?
A. allergic rxn B. bile sludging C. ototoxicity D. QTc prolongation E. tendonitis
B. bile sludging
Which of these is a common side effect of aminoglycosides?
A. allergic rxn B. bile sludging C. ototoxicity D. QTc prolongation E. tendonitis
C. ototoxicity
Which of these is a common side effect of azithromycin?
A. allergic rxn B. bile sludging C. ototoxicity D. QTc prolongation E. tendonitis
D. QTc prolongation
Which of these are common side effects of fluoroquinolones?
A. allergic rxn B. bile sludging C. ototoxicity D. QTc prolongation E. tendonitis
QTc prolongation and tenodinits
How do you differentiate allergic rash vs rash not related to antibiotic?
allergic rash will have hives
What is the most important cause of septic arthritis?
staph aureus
What is empiric treatment for septic arthritis of the following
A. ceftriaxone B. cephalexin C. Nafcillin D. piperacillin-tazobactam E. vancomycin
C. nafcillin
What is mech of MRSA being reisistant?
altered PBP
What are 5 antibiotics most active against MRSA? 3 others that are pretty active?
most active
- vancomycin = first line
- daptomycin
- linezolid
- ceftaroline = only cephalosporin active against MRSA
pretty active
- clindamycin
- doxycycline
- trimethoprim-sulfamethoxazole
How is vancomycin administered? side effects? mech of action?
administered: IV
side effects: red man syndrome, nephrotoxicity
action: inhibits polymerization peptidoglycan
How is daptomycin administered? side effects? mech of action?
administered: IV
side effects: myositis, CPK elevation
action: disrupts bacterial membrane
notes: not active in lung because inactivated by surfactant
How is linezolid administered? side effects? mech of action?
administered: oral or IV [100% bioavaialbility]
side effects: bone marrow suppression, low platelets, serotonin syndrome
action: protein synthesis inhibitor
note: costly
How is clindamycin administered? mech of action?
administered: oral [good bioavailability]
action: protein synthesis inhibitor
note: excellent penetration to bone [good for osteomyelitis]
How is doxycycline administered? side effects? mech of action?
administered: oral, but absorption inhibited by Ca, Mg, dairy, antacids
side effects: photosensitivity, GI intolerance, staining of teeth in children
action: protein synthesis inhibitor [a tetracycline]
What is mech of action of trimethoprim-sulfmethoxazole administered? side effects?
side effects: steven-johnson syndrome = rash and blisters all over body, bone marrow suppression, kern-icterus in infants
action: folate pathway inhibitor
Which of the following is best definitive treatment for MSSA? Why?
A. amoxicillin B. azythromycin C. cefazolin D. cefepime E. penecillin
C. cefazolin
s. aureus usually produces penicillinase –> best to treat with penicillinase stable penicillin [nafcillin] or 1st gen cephalosporin [cefazolin, cephalexin]
other active but unnecessarily broad treatments:
4th gen cephalosporins: cefepime
5th gen: ceftaroline
beta lacam + betalactamase combo
What are the 3 beta lactam + betalactamase inhibitor combos?
Amoxicillin-clavulanic
Ampicillin-sulbactam
Piperacillin-tazobactam
What is empiric antibiotic regimen for infant with meningitis?
vancomycin + ceftriazone
vanc = some strains of strep pneumo resistant to cetriaxone ceft = strep pneumo, neisseria, h. influenzae
who gets listeria?
less than 1 month
pregnant
immunocompromised
What are causes of bacterial meningitis for less than 1 month old? empiric treatment?
GBS, E Coli, Listeria
treat: ampicillin + cefotaxime
What are causes of bacterial meningitis for 1 month to adulthood? empiric treatment?
N. meningitidis, S. pneumoniae, H. influenza type B
treat: cetriaxone + vancomycin
What are causes of bacterial meningitis in immunocompromised and pregnant? empiric treatment?
N. meningitidis, S. pneimoniae, H. influenzae type B, Listeria
treat: ceftriaxone + vancomycin + ampicillin
If you have kid with s pneumoniae meningitis which of the following would you choose to treat it?
A. ampicillin
B. cefazolin
C. cefuroxime
D. clindamycin
A. ampicillin
1st and 2nd gen cephalosporins don’t penetrate CNS [cefazlin, cefuroxime]
clindamycin = bacteriostatic so not strong enough for meningitis [prefer bacteridicidal since so serious], also doesn’t have great ability to penetrate CNS
What are the two first gen cephalosporins? how are they administered? what do they treat? Can they penetrate CNS?
cefazolin [IV], cephalexin [PO = oral]
- gram pos but not MRSA or enterococcus
- some gram neg [some E Coli, K pneumoniae]
= best cephalosporins for MSSA
Can’t penentrate CNS
What are the 3 main second gen cephalosporins? how are they administered? what do they treat? Can they penetrate CNS?
Cefuroxime [IV or PO], Cefoxitin, Cefotetan
treat:
- 1st gen spectrum + broader gram negative
- treat H. influenzae [sinusitis, otitis media]
- cefoxitin and cefotetan = only 2nd gen cephs with anaerobic spectrum
do not penetrate CNS
What are the main third gen cephalosporins? how are they administered? what do they treat? Can they penetrate CNS?
Ceftriazone [IV or IM], Cefotaxime [IV or IM]
- activity against most community acquired, broader gram neg than 1st or 2nd gen
- some s. pneumoniae are resistant
- no MRSA, enterococcus, pseudomonas, anaerobes
- penetrate all tissues including CNS
- good empiric treat for meningitis, pneumonia, urinary infections
What is side effect of ceftriaxone? who should avoid?
- can get bile sludging because excreted in bile
- avoid in infants and people with liver disease
What kind of coverage does ceftazidime have?
- no gram positive coverage
- good for pseudomonas
Is half life longer for ceftriaxone or cefotaxime?
ceftriaxone = longer half life, 1-2 daily admin
cefotaxime = shorter half life, 3x a day administration
What type of antibiotic used to empirically treat patient with leukemia, neutropenia? Hint: at high risk for bacterial sepsis including from pseudomonas?
- beta lactam with activity against gram +/gram-/pseudomonas
- levofloxacin
- add vancomycin to either if concerned for MRSA
What are betalactams with activity against psuedomonas?
penicillins: piperacillin +/- tazobactam, ticaracillin +/- clavulanic
cephalosporins: ceftazidime [3rd gen], cefepime [4th gen]
carbapenems: doripenem, imipenem-cilastatin, meropenem
monobactams: aztreonam
What is aztreonam useful against?
- against pseudomonas
- no gram + activity
- good for pt with beta-lactam allergy
what is ceftazidime useful against?
- against pseudomonas
- no gram + activity
What is cefepime active against? how is it administered?
- IV administration
treats:
- same gram post coverage of 1st gen cephalosporins [no MRSA or enterococcus]
- same gram neg coverage of 3rd gen cephalosporins
- pseudomonas
- other nosocomial gram neg
Why is shortcoming of piperacillin-tazobactam?
not good CNS penetration = don’t use for meningitis
What is imipenem [and carbapenems] active against? how is it administered? side effect?
- IV administration
treats:
- gram pos [no MRSA]
- gram neg [including borader nosocomial coverage than cefepime]
- anaerobes
side effect: associated with seizures
What are side effects of fluorquinolones? safe for kids? bioavailability? CNS penetration?
- side effect: tendonitis, QTc prolongation, CNS symptoms
- not first line drug for kids –> concern about effect on bone growth
- good bioavailability can give PO or IV
- good CNS penetration
What is mech of resistance to fluoroquinolones?
resistance by mutation in topoisomerase or DNA gyrase
What can ciprofloxacin treat of the following?
A. gram negative [including pseudomonas]
B. gram pos [MRSA and enterococcus not consistently]
C. anaerobes
D. atypicals [mycoplasma, chlamydia, legionella]
Yes: A and D
A. gram negative [including pseudomonas]
D. atypicals [mycoplasma, chlamydia, legionella]
Not:
B. gram pos [MRSA and enterococcus not consistently]
C. anaerobes
What can levofloxacin treat of the following?
A. gram negative [including pseudomonas]
B. gram pos [MRSA and enterococcus not consistently]
C. anaerobes
D. atypicals [mycoplasma, chlamydia, legionella]
Yes: A, B, and D
A. gram negative [including pseudomonas]
B. gram pos [MRSA and enterococcus not consistently]
D. atypicals [mycoplasma, chlamydia, legionella]
Not:
C. anaerobes
What can moxifloxacin treat of the following
A. gram negative [including pseudomonas]
B. gram pos [MRSA and enterococcus not consistently]
C. anaerobes
D. atypicals [mycoplasma, chlamydia, legionella]
All!
What is mech of action of aminoglycosides? Activity? side effects? CNS penetration?
mech: protein synthesis inhibitors
activity:
- mostly gram negatives, usully not used as single agents
- can be synergistic against some gram pos [with ampicillin against enterococcus]
side effects:
- ototoxic [auditory and vestibular]
- nephrotoxic
No CNS penetration!
What are the 3 aminoglycosides? what is broadest?
- Gentamicin
- tobramycin
- amikacin = broadest
What organism would you guess from:
24 yo male with AML, fever, neutropenia, on Cefepime. fever persisted and culture on day 6 grows gram + cocci in pairs and short chains
enterococci because gram + pairs and short chains that are common nosocomial pathogens and are not treatable by cephalosporins
What is the empiric treatment for serious enterococci infection? If resistant to this?
- vancomycin
- if resistant [VRE] use linezolid or daptomycin
What is the first line drug for susceptible enterococci strains?
ampicillin
What drugs cannot treat enterococci?
- cephalosporins have no activity
- fluoroquinolones have poor activity
- aminoglycosides have no activity on their own
What can ceftaroline treat?
- gram pos including MRSA
- gram neg narrower than 4th gen
- cannot treat pseudomonas or other resistant nosocomial negatives
Which of the following to treat pt with C difficile colitis? A. Ampicillin-sulbactam B. Piperacillin-tazobactam C. Imipenem D. Cefotetan E. Clindamycin F. Metronidazole
F. metronidazole
What can metronidazole treat? mech? type of administration? side effects?
treat: anaerobic bacteria, some parasites
mech: causes DNA damage
administration: IV or PO
side effects: disulfiram effect [vomiting, ab pain, headache combined with alcohol], metallic taste, CNS side effects
What can oral vancomycin be used to treat?
- C difficile colitis
- second line drug because of concerns for selection of VRE and cost
Clinical: pt on day 7 of levofloxacin treatment of pneumonia presents with fever, ab main, foul-smelling bloody loose bowel movements
What should you think?
C Diff colitis
What is cause of intra-abdominal abscess?
usually polymicrobial
- anaerobes, enteric gram neg, enterococcus, anaerobic streptococci
What treatment for intra-abdominal abscess?
- cephalosporin [for gram -] + metronidazole [for anaerobes]
- beta lactam/beta lactamase inhibitor
- carbapenem
also drain abscess
In order which is best for gram neg between: pip/tazo, imipenem, amp/sulbactam?
imipenem > pip/tazo > amp/sulbactam
Match the four main causes of pneumonia with the clinical situations?
A. most common
B. common after flu
C. common in COPD
D. common in alcoholic pt, older pts
A = s. pneumoniae B = s. aureus C = h. influenzae D = k. pneumoniae
What are causes of walking pneumonia?
- mycoplasma
- chlamydia
- legionella [sicker pts]
- viruses
How do you treat walking pneumonia?
- azithromycin
- fluoroquinolones [levofloxacin]
Treatment for v. sick pneumonia pt [inpatient]?
- ceftrioxone [to cover typicals] and azithromycin [to cover atypicals]
- levofloxacin
- if S aureus suspected –> vancomycin
Treatment for outpatient pneumonia?
- levofloxacin [for lobar PNA and atypicals]
- amoxicillin +/- azithromycin [preferred for peds]
What are the 3 macrolides?
- azithromycin
- clarithromycin
- erythromycin
What is a side effect unique to clarithromycin and erythromycin?
CP450 inhibitors, can elevate levels of drugs metabolized through that pathway
What are side effects of the macrolides?
all: QTc prolongation
erythromycin: GI discomfort
clarithro + erythro: CP450 inhibitors –> elevate levels of drugs metabolized through that pathway
