Antibiotics Flashcards
What are the MC and second MC antibiotic MOAs?
1 = inhibition of cell wall synthesis
Important aerobic gram positive cocci
1) Staphylococci (S. aureus, Coag-negative staph)
2) Streptococci (S. pneumoniae,Group B Strep, Viridans Strep)
3) Enterococci (E. faecalis, E. faecium)
Important aerobic gram negative rods
1) E. coli
2) K. pneumoniae
3) Serratia (Enterobacteriaceae)
4) H. influenza
5) . P. aeruginosa
Important aerobic gram negative cocci
1) Moraxella catarrhalis
2) N. gonorrhoeae
3) N. meningitidis
Important atypical respiratory aerobes
1) Legionella spp.
2) Mycoplasma pneumoniae
3) Chlamydia pneumoniae
Important anaerobes
1) True anaerobes (gut): Bacteroides fragilis and C. diff
2) Oral anaerobes: Prevotella and Peptostreptococcus
MIC
minimum inhibitory concentration
(dilution test to determine microbial sensitivity)
Note: many drugs will not reach their MIC in certain tissues
MBC
minimum bactericidal concentration
-cidal = kills bacteria
(dilution test to determine microbial sensitivity)
Penicillins MOA
B-Lactam
inhibit cell wall synthesis by binding to penicillin binding proteins (PBPs)
How are Penicillins differentiated?
By their side chains
different penicillins target different bacteria and have different resistance profiles
Penicillins resistance
1) B-lactamases - can cleave beta-lactam ring in center of Penicillins and render them inactive; doesn’t affect all penicillins
2) Altered PBPs
Natural penicillins
1) Penicillin G (IV)
2) Penicillin VK (PO)
Aminopenicillins
1) Amoxicillin
2) Ampicillin
3) Amoxicillin + Clavulanate (Augmentin)
Penicillinase-resistance penicillins
1) Methicillin
2) Nafcillin
3) Cloxacillin
4) Dicloxacillin
Extended-Spectrum Penicillins
1) Piperacillin
2) Ticarcillin
**These are IV only
Natural Penicillins spectrum
1) Gram-positive cocci
2) Neisseria
3) Most oral anaerobes
*Not effective against gram-neg aerobes or beta-lactamase producing organisms
What is Penicillins the DOC for?
N. meningitidis
Syphilis
Penicillinase-resistance penicillins spectrum
1) Gram-positive cocci (including B-lactamase producers)
2) some Streptococci
3) Oral anaerobes
*Not effective against gram-negative aerobes
Penicillinase-resistance penicillins are DOC for
MSSA (methicillin sensitive Staph. aureus)
Aminopenicillins MOA
binds to PBPs and inhibits synthesis in bacterial cell wall
Aminopenicillins spectrum
1) Some gram negative organisms
2) some gram positive organisms (Strep, Enterococci)
3) oral anaerobes
*Note effective against B-lactamase producing organisms
T/F: Aminopenicillins are the DOC for UTIs
FALSE
only use for UTI if you know its caused by enterococci
Extended-Spectrum Penicillins
1) Gram negative infx (esp. good again Pseudomonas aeruginosa)
2) Some gram positive (Strep, Staph, Mb Enterococci)
3) Oral anaerobes
4) some true anaerobes
Extended-Spectrum Penicillins are indicated for
severe infections
esp. useful for tx Pseudomonas
Broad Spectrum
Penicillin + B-lactamase inhibitors
1) Amoxicillin + Clavulonic acid (Augmentin) (PO)
2) Piperacillin + Tazobactam (IV)
T/F: Penicillin + B-lactamase inhibitors work very well to treat all anaerobes
TRUE
Penicillins ADRs
1) Allergic rxn - anaphylaxis, rash, urticaria, fever
2) Diarrhea
3) Hematologic - anemia, thrombocytopenia
4) Hepatitis (nafcillin, oxacillin)
5) Interstitial nephritis (nafcillin, oxacillin)
6) Seizures
7) Renal failure
If pt. have a true Penicillin allergy, there is a 5% cross reactivity with _____________
cephalosporins
Amoxicillin + Clavulanate (Augmentin) s/e
-notable GI s/e (diarrhea is very common)
What is the most severe cause of antibiotic induced diarrhea?
Pseudomembranous colitis (C. diff colitis)
Most penicillins are renally cleared so you have to adjust dosage for renal fn changes. What are the exceptions?
Nafcillin, oxacillin, dicloxacillin
What natural product does amoxicillin have a major interaction with?
Acacia
Cephalosporins MOA
disturbs cell wall synthesis of bacteria
B-lactam binds PBPs
T/F: Cephalosporins not, ever cover enterococcus
TRUE
Cephalexin (Keflex) (PO) and Cafazolin (IV) class
1st generation cephalosporins
Cephalexin (Keflex) (PO) and Cafazolin (IV) spectrum
1st gen
1) Gram pos = Strep and MSSA
2) Gram neg = some E.coli and Kleb
3) oral anaerobes
Cephalexin (Keflex) (PO) and Cafazolin (IV) indications
1st gen
UTIs, skin infx, some respiratory infx, surgical prophylaxis
*alternative to penicillins in allergic pt.
Cefuroxime, cefotetan, cefoxitin class
2nd generation cephalosporins
more resistant to beta-lactamase activity than 1st gen
Cefuroxime, cefotetan, cefoxitin spectrum
2nd gen
1) Gram pos = Strep, MSSA
2) Gram neg = good coverage
3) Anaerobes = oral and B. fragilis (cefoxitin, cefotetan)
*None are effective against pseudomonas
Ceftriaxone (IV), cefotaxime,ceftazidime, cefixime class
3rd generation cephalosporins
Ceftriaxone (IV), cefotaxime,ceftazidime, cefixime spectrum
3rd gen
1) Gram pos = Strep, MSSA
2) Gram neg = very good; P. aeruginosa (Ceftazidime)
3) oral anaerobes
Ceftriaxone (IV), cefotaxime,ceftazidime, cefixime indications
(3rd gen)
- respiratory infx
- serious infx
- some are able to cross BBB
Cefuroxime, cefotetan, cefoxitin indications
2nd gen
some respiratory (oral) GI infx (B. fragilis)
Cefepime (IV) class
4th generation cephalosporins
Cefepime indications
4th gen
serious hospital infx
Cefepime spectrum
4th gen
1) Gram pos = Strep, MSSA
2) Gram neg = Excellent; P. aeruginosa
3) Oral anaerobes
What is the only cephalosporin that can tx B. fragilis?
Cefoxitin (2nd gen)
Which cephalosporin(s) can tx Pseudomonas?
Ceftazidime (3rd gen)
Cefepime (4th gen)
What is the newly approved ‘5th generation’ cephalosporin and what can it tx?
Ceftaroline
Tx: MRSA (the only one), Strep. pneumo, GNR
Does NOT tx pseudomonas
Most cephalosporins are renally cleared and doses need to be adjusted for renal function changes. An exception to this is _______
ceftriaxone (3rd gen)
Cephalosporin ADRs
1) Allergic - anaphylaxis, rash, urticaria, fever; 3-7% cross resistance with PCN allergy
2) Diarrhea
3) Hematologic - anemia, thrombocytopenia
4) Seizures (high doses)
Macrolides MOA
inhibition of bacterial protein synthesis by binding to the 50s subunit
mostly bacteriostatic
Macrolides resistance
plasmid mediated changes or inactivation of ribosomal response
Erythromycin, Azithromycin, and Clarithromycin class
Macrolides
Erythromycin, Azithromycin, and Clarithromycin (i.e. Macrolides) spectrum
1) Gram pos = Strep, pneumococci, Mb MSSA
2) Gram neg = minimal (H. flu)
3) oral anaerobes
4) Atypical respiratory pathogens (legionella, chlamydia, mycoplasma)
Which class of antibiotics do well at tx atypical respiratory pathogens such as Legionella sp., Chlamydia pneumoniae, and Mycoplasma pneumonia?
Macrolides**
Tetracyclines
Fluoroquinolones
Erythromycin, Azithromycin, and Clarithromycin (macrolides) ADRs
1) GI - N/V, diarrhea (Erythro > clarithro > azithro)
2) Phlebitis (IV erythro)
3) Prolonged QT interval (Erythro > clarithro»_space; azithro)
4) Hepatotoxicity (erythro)
Macrolides have multiple drug interactions because they
inhibit liver CYP3A4
Erythro»_space; clarithro»_space; azithro
Tetracyclines MOA
inhibits protein synthesis by binding to the 30s ribosomal subunit
bacteriostatic
Tetracyclines spectrum
1) Gram pos = Strep, MSSA (SSTI)
2) Gram neg = H. flu, rickettsiae; other gram neg often resistant
3) mostly oral anaerobes
4) atypical respiratory pathogens (Legionella, chlamydia, mycoplasma)
Tetracyclines ADRs
1) **Photosensitivity
2) nausea and diarrhea
3) **tooth discoloration in children (C/I in children and pregnancy)
4) esophagitis
5) leukocytosis
Macrolides natural product interactions
cesium, ephedra, oleander, sida cordifolia
Tetracyclines natural product interactions
oleander, hypericum, p-glycoprotein substrates
T/F: tetracyclines are more effective when given with calcium supplements or dairy products
FALSE
they should NOT be given with Ca++ or dairy products
Sulfonamides (Sulfa Drugs) MOA
inhibits folic acid synthesis via enzyme inhibition
bacteriostatic
Sulfamethoxazole with Trimethoprim/Bactrim MOA
synergistically inhibits two steps in folic acid synthesis
Sulfamethoxazole with Trimethoprim/Bactrim spectrum
1) Gram pos = Strep, MSSA, CAMRSA
2) Gram neg = most enterobacteriacae
3) Oral anaerobes
T/F: Sulfamethoxazole with Trimethoprim/Bactrim can treat community acquired MRSA
TRUE
Bactrim ADRs
1) Allergic rxn (sulfonamide moiety) - rash, fever, photosensitivity, urticaria
2) GI effects
3) Neutropenia, thrombocytopenia (folate deficiency)
4) Steven Johnsons Syndrome (rare)
Bactrim increases effects of which drug?
warfarin
Fluoroquinolones MOA
inhibit bacterial DNA gyrase, inhibiting DNA replication and transcription
***Bactericidal
Levofloxacin, Ciprofloxacin, and Moxifloxacin class
Fluoroquinolones
Fluoroquinolones spectrum
potent broad-spectrum that can tx most gram neg and some gram pos
1) gram pos = Strep, MSSA (cipro poor)
2) gram neg = majority, P. aerugonisa
3) minimal anaerobes
4) atypical respiratory pathogens (CA pneumonia - legionella, chlamydia, mycoplasma)
Fluoroquinolones ADRs
1) GI - nausea
2) CNS - HA, dizziness, insomnia, confusion, seizures; esp. in elderly
3) Cartilage toxicity (C/I children and pregnancy)
4) Prolonged cardia QT interval
Levofloxacin (Fluoroquinolone) natural product interactions
1) cesium
2) ephedra
3) grapefruit
4) sida cordifolia
5) sweet orange
What are our main anti-anaerobe drugs?
Metronidazole and Clindamycin
Metronidazole (Flagyl) MOA
inhibiting nucleic acid synthesis
Clindamycin MOA
ribosomal protein synthesis inhibitor
Metronidazole (Flagyl) spectrum
ONLY ANAEROBES!
Which antibiotic tx C. diff associated diarrhea and intra-abdominal abscess?
Metronidazole (Flagyl)
Clindamycin spectrum
1) Gram pos = Step, MSSA, Mb CAMRSA
2) Gram neg = none**
3) Good coverage for anaerobes (o.k. B. fragilis)
Metronidazole (Flagyl) ADRs
1) GI - nausea, diarrhea
2) metallic taste
3) “Disulfiram rxn” - flushing, sweating, nausea w/ alcohol; can persist for a few days post drug
Clindamycin ADRs
1) GI - Diarrhea, nausea, C. diff
Nitrofurantoin (Macrobid) indication
lower UTI
- *not for pyelonephritis
- considered safe in pregnancy prior to 38 wks of gestation
Nitrofurantoin (Macrobid) MOA
disrupts both DNA and RNA of bacteria which are sensitive to the drug
Nitrofurantoin (Macrobid) ADRs
1) GI - N/V, diarrhea
2) fever and chills (LC)
3) pulmonary fibrosis (LC)
Gentamicin, Tobramycin, and Amikacin class
Aminoglycosides
when would you use aminoglycosides?
severe infections caused by gram negative, pseudomona auerginosa
aminoglycosides ADRs
nephrotoxicity and ototoxicity (monitoring required)
only use in hospital severe infx
What is the primary drug used to treat MRSA?
IV Vancomycin
What is the ‘triple antibiotic cream’
Neosporin OTC
Bacitracin + Neomycin + Polymyxin B
T/F: Most pharyngitis cases are bacterial
FALSE
90% of cases are viral (however, about 60% of OV result in antibiotic rx)
MC bacterial cz of pharyngitis
Group A B-hemolytic streptococci (GABHS)
*S. pyogenes
DOC to tx GABHS
penicillin
if PCN allergy/resistance, tx w/ azithromycin or cephalosporins
What is the leading indication for outpatient antimicrobial use in the U.S.?
otitis media
25-50% are viral in origin, however, 80% are rx antibiotics
MC bacterial etiologies of otitis media
1) Step. pneumo (~35%)
2) Haemophilus influenzae (~25%)
3) Moraxella catarrhalis (~15%)
guidelines state that it is appropriate to observe pt. with otitis media in children 2-12 y/o with non-severe symptoms for ______ hours
48-72 hrs (or start if child worsens)
**70-90% of children have spontaneous resolution with 7-14 days
T/F: if child has AOM with otorrhea you should not observe and go right to tx with antibiotics
TRUE
DOC for otitis media
#1 Amoxicillin #2 Amoxicillin-clavulante (2nd line used for more gram neg)
(alternative for PCN allergy or tx failure are Cephalosporins, Macrolides, and Clindamycin)
Treatment failure with otitis media is defined as
no improvement after 48-72 hours of initial tx (switch drugs!)
T/F: Purulent nasal secretions or sputum do not predict bacterial infection
TRUE
____% of sinusitis cases are viral and ____% of sinusitis cases are bacterial
25% viral
75% bacterial
What are the MC bacterial cz of sinusitis?
S. pneumoniae, H. influenza, and M. catarrhalis
First-line tx for sinusitis
- amoxicillin
- doxycycline
- TMP/SMX
Second-line tx for sinusitis
- amoxicillin/clavulanate
- cephalosporins
- azithromycin or clarithromycin
MC bacteria involved in community-acquired pneumonia
S. pneumoniae
H. influenzae
For pt. with CA pneumonia that were previously healthy have not use of antimicrobials w/in past 3 mo., tx with
- a macrolide (strongly recommended)
- doxycyline (weakly recommended)
*risk of resistance to S. pneumo is high for these drugs
MC bacterial cz of uncomplicated cystitis
1) E. coli (75-95% cases)
2) Klebsiella pneumonia
3) Staph. saprophyticus (post-coital UTIs)
4) Enterococcus
5) Strep. agalactiae (group B strep)
If Enterococcus is expected as causative organism in uncomplicated cystitis, tx with
Amoxicillin
Ampicillin
(otherwise avoid these drugs)
Tx for Gonorrhea
Single dose tx of:
1) Ceftriaxone 250 mg IM x 1
PLUS
2) Azithromycin 1g PO x 1
(fluoroquinolones are no longer used d/t resistance)
Tx for Chlamydia trachomatis
1) Doxycycline 100 mg po BID x 7 days
OR
2) Azithromycin 1 g po x1 (used in tx of gonorrhea anyway)
Mild-cellulitis is most often d/t
Group A Strep or Staph aureus (MSSA)
Cellulitis that is uncomplicated & non-MRSA infx can be tx with
1) Amoxil-clavulanate
2) Dicloxacillin
3) Cephalexin
Cellulitis with a suspicion of MRSA infx requires empiric tx with
1) TMP-sulfa
2) Clindamycin
3) Doxycycline
