Antibiotics Review Flashcards
Beta Lactam Abxs
Includes penicillins, cephalosporins, carbapenems, aztreonam.
Beta lactams bind to the Penicillin Binding Proteins which are transpeptidases.
Bactericidal.
Center score for bacterial vs. viral pharyngitis
Absence of cough = 1 Age: 3-14 = 1 15-45 = 0 Older than 45 = -1 Anterior cervical lymphadenopathy = 1 Fever = 1 Tonsillar erythema or exudates = 1
If score is 2 or greater –> rapid antigen detection test.
Macrolide (erythromycin, azithromycin, clarithromycin)
MOA: Binds to23s subunit of the 50s ribosomal RNA near the peptidyltrasnsferase center blocking peptide chain elongation.
Spectrum: Broad coverage of respiratory pathogens
Resistance: methylation of 23S rRNA binding site and increased efflux
Adverse effects: GI discomfort, prolonged QT, Hepatic failure - inhibits CYP3A4
Clarithromycin - associated w/ miscarriages
Pharyngitis Treatment failure possibilities
- ABX resistance - rare for penicillins in S. pyo, but 5-8% are resistant to macrolides (methylation of 23s or efflux)
- ) Lack of compliance - patient feels better –> stops taking pills (patients worry they are becoming resistant, not bacteria –> education!)
- ) Pharyngitis is viral or other organism
- ) Superinfection w/ Candida
- ) Neighboring flora can impact treatment - H flu can secrete beta-lactamases
*Patients w/ rigors, shakes, chills, high fever, night sweats –> bacteremia
Oseltamivir
Neuraminidase inhibitors
AKA Tamiflu
Oral prodrug activated by hepatic esterases.
Modify for renal insufficiency, preferred for pregnant
Side effects: GI, headache, fatigue
Must be > 1 yr.
Zanamivir
Neuraminidase inhibitors
Inhaled –> useful if malabsorption or GI problems
Don’t use if other airway diseases like COPD, asthma
Must be >7 years
Peramivir
Neuraminidase inhibitorsI
V one dose
Must be >18 years old
Fluoroquinolones (Gemifloxacin, levofloxacin, moxifloxacin
MOA: Direct inhibitor of DNA replication by binding bacterial DNA topo II (gyrase) and IV
Bacteriocidal
Broad spectrum (Gram +, Gram -, and atypicals
Resistance: Overperscribed –> efflux of drug. Mutations in topoisomerases
Side effects: GI discomforts, tendinopathies, avoid pregnancy, lactating, children
Tetracyclines (Doxycycline)
MOA: binds 30s preventing attachment of aminoacyl- tRNA
Spectrum - limited by resistance (B. burgdorgeri, H. pylori, Mycoplasma pneumoniae, not good against GNRs)
Resistance: reduced uptake and increased efflux
Adverse effects: photosensitivity, discoloraiton of teeth, inhibits bone growth (avoid in preg, children), oral absorbtion limited by cations
Concentration dependent killing
Concentration dependent killing
Achieve more killing at a higher concentration.
Peak concentration > 10x over MIC
1 or 2 high daily doses
Aminoglycosides, fluoroquinolones
Time-dependent klling
t>MIC depending on the half life of the abx.
May need to dose multiple times per day
Beta-lactams and Vanco
ESKAPE Pathogens
Majority of US hosptial infections are able to escape the aresenal of currently available ABX
Enterococcus faecium Staph Aureus Klebsiella pneumoniae Acinetobacter baumannii Pseudomonas aeruginosa Enterobacter species
Polymixin E (Colistin)
Binds phosphatidylethanolamine in Gram-negative membrane to create holes in membrane
Extremely nephrotoxic
Used to treat KPC –> expresses extended spectrum Beta-lactamase (ESBL)
Vancomycin
Binds to the D-Ala D-Ala dipeptide and inhibits transglycosylation reactions to prevent cell well synthesis
Gram + only (need gram - coverage in empiric
Linezolid
Targets the 50s ribosome and inhibits initiation of protein synthesis
Used in MRSA
