Antimicrobials- Purnuske Flashcards
What factors in presentation suggest it is bacterial pharyngitis?
Absence of cough Age 3-14 years Anterior cervical lymphadenopathy Fever Tonsillar erythema or exudates
Is the positive rapid antigen detection test more specific or sensitive?
Specific! (>95%)
Sensitivity = 80%
What color are gram + organisms on gram stain?
Purple!
What color are gram - organisms on gram stain?
Pink!
Describe the difference between treatments: Prophylactic Pre-emptive Empiric Definitive
Prophylactic: treating when there is risk, but no testing or symptoms
Pre-emptive: actively screening, treat if bug found, still asymptomatic
Empiric: SYMPTOMS! but don’t know what organisms is
Definitive: You know what’s up
What is empiric therapy of choice for community acquired pneumonia in a previously healthy outpatient w/ no prior antibiotic use?
Macrolide (50s) = azithromycin, erythromycin, clarithromycin
Doxycycline (30s)
What is empiric therapy of choice for community-acquired pneomnia in a patient with comorbities or previous antibiotic use?
Fluoroquinolone or high dose B-lactam + a macrolide
What are the respiratory fluoroquinolones? MOA?
Gemifloxacin
Levofloxacin
Moxifloxacin
MOA = direct inhibitor of DNA replication by binding bacterial DNA topo II and IV
Are fluoroquinolones bactericidal or bacteriostatic?
Bactericidial!
What is the main mechanism of resistance for floroquinolones?
Mutations in topoisomerase
Active efflux of durg
What is the spectrum for floroquinolones?
Gram +
Gram -
Atypical organisms like mycoplasma
What would you use to treat mycoplasma pneumonia?
Doxycycline, Azithromycin
What is the most likely mechanism for developing a multi-drug resistant infection?
Selection and replication of a colonizing organism that contained a PLASMID encoding SEVERAL resistance determinate genes
MOA of Polymyxin E
Binds phosphatidylethanolamine in gram negative membrane to create holes in membrane
Major side effect of polymyxin E?
Nephrotoxic!
What drugs are used to treat MRSA?
Vancomycin and Linezolid
MOA of vancomycin
Binds to D-ala-D-ala dipeptide and inhibits TRANSglycosylation reactions to prevent cell wall synthesis
**binds precursors!
MOA of Linezolid
Inhibits protein synthesis by binding to 50S subunit and preventing formation of the initiation complex
Why do you administer tazobactam with piperacillin?
Tazobactam is a B-lactamase inhibitor
Why do you administer cilastatin with imipenem?
It protects the kidney by inhibiting the enzyme that makes toxic metabolites
What is the treatment for a local fungal infection?
Itraconazole
Voriconazole
What is the treatment for a systemic fungal infection?
Amphotericin B
MOA of Amphotericin B?
Binds ergesterol (unique to fungi)
Forms membrane pores that allow leakage of electrolytes
MOA of “azoles”
binds fungal P450 enzyme blocking production of the membrane protein ergosterol and causing the accumulation of Ianosterol
What fungal infection is common east of the Mississippi River and Central America and cause an inflammatory lung disease?
Blastomycosis
Can blastomycosis be transmitted person-to-person?
Nope!
What fungal infection is associated with bird and bat droppings in the mississippi and ohio river valleys?
Histoplasma capsulatum
What fungal infection found in the southwestern united states can causes pneumonia and meningitis?
Coccidioidmycosis
Where do systemic fungal mycoses disseminate to?
Bones
Joints
CNS
If there is CNS involvement during a fungal infection what should you treat with?
Amphotericin B and follow up with itraconazole
What are the major adverse side effects of Amphotericin B?
Toxic because binds to cholesterol!
Decreases renal blood flow and can cause permanent BM destruction.
80% patients have nephrotoxicity
What fungus primarily infects the lungs and causes a hypersensitivity with brown mucus plugs?
Aspergillus fumigatus causes allergic bronchopulmonary aspergillosis
Can causes systemic disease in immunocompromised
What is the main mechanisms of resistance of the azoles?
- Altered cytochrome P450
- Upregulation of efflux pump transporters
MOA of B-lactams?
Binds to transpeptidases and block cross-linking of peptidoglycan in cell wall
MOA of doxycycline?
Binds to 30S and prevents attachment of aminoacyl-tRNA
MOA of Macrolides?
Azithromycin
Clarithromucin
Erythromycin
Binds to 23s rRNA of 50S inhibiting translocation
What is the main mechanism of resistance for macrolides?
Methylation of the 23S rRNA binding site prevents binding of drug.
Increased efflux also
MOA of fluoroquinolones?
Gemifloxacin
Levofloxacin
Moxifloxacin
*Inhibits Topo II and Topo IV
MOA of Oseltamivir, Zanamivir, Peramivir?
Oral prodrug activated by hepatic esterases
inhibits influenza (A & B) neuraminidase thus decreasing release of progeny virus
When are the neuraminidase inhibitors most active?
48 hours after infection
