Infectious Disease & Misc Agents – Master Q&A

This set of flashcards provides a comprehensive overview of key concepts related to infectious diseases and the various antimicrobial agents used in treatment, suitable for exam preparation.

What are the 4 major pharmacokinetic processes?

Absorption, Distribution, Metabolism, Excretion.

What alters pharmacokinetic processes?

Patient factors like renal/hepatic function, age, comorbidities.

Define bactericidal.

Bactericidal kills bacteria directly (e.g., penicillins, cephalosporins).

Define bacteriostatic.

Bacteriostatic inhibits bacterial growth (e.g., macrolides, tetracyclines).

What is the difference between time-dependent and concentration-dependent killing?

Time-dependent efficacy is based on duration drug level > MIC; concentration-dependent means higher peak equals more kill.

Which four bacteria account for ~70% of hospital infections?

Klebsiella spp, E. coli, Pseudomonas aeruginosa, Acinetobacter baumannii.

What practices accelerate antibiotic resistance?

Broad empiric coverage, failure to de-escalate, double coverage, prolonged therapy > 7 days, prophylactic misuse, antibiotic use in livestock.

What is the key structural feature of β-lactams?

The β-lactam ring which mimics D-Ala-D-Ala to irreversibly bind PBPs.

Which penicillin is the drug of choice for syphilis?

Penicillin G (IV).

Which oral penicillin is stable in stomach acid?

Penicillin V (Pen VK).

What differentiates aminopenicillins from natural penicillins?

Aminopenicillins have broader Gram-negative coverage.

What aminopenicillin has hepatic adverse effects?

Amoxicillin / Ampicillin.

Why are oral contraceptives less effective with amoxicillin/ampicillin?

Disruption of gut flora decreases enterohepatic estrogen recycling.

Which β-lactamase inhibitors are paired with penicillins?

Sulbactam with ampicillin, Tazobactam with piperacillin, Clavulanate with amoxicillin.

What infections are best treated with Augmentin?

Skin/soft-tissue infections, diabetic foot, animal/human bites.

Which penicillin covers Pseudomonas?

Piperacillin ± Tazobactam (Zosyn).

Describe the generation trend of cephalosporins.

Increasing Gram-negative coverage and decreasing Gram-positive coverage with generation increase.

What is the cross-sensitivity between PCNs and cephalosporins?

Less than 1%.

Which cephalosporin has no renal adjustment requirement?

Ceftriaxone.

Which cephalosporin is contraindicated in neonates under 30 days?

Ceftriaxone due to risk of calcium precipitation.

Which cephalosporin covers Pseudomonas?

Ceftazidime (3rd), Cefepime (4th), Ceftolozane/tazobactam.

Which cephalosporin covers MRSA?

Ceftaroline (5th).

Which 5th generation combination adds anaerobe coverage?

Ceftolozane/tazobactam (Zerbaxa).

What is a unique feature of Aztreonam (Azactam)?

Only Gram-negative coverage, safe in true PCN allergy.

Which carbapenem does not cover Pseudomonas?

Ertapenem (Invanz).

When are carbapenems the drug of choice?

For MDR Gram-negatives, ESBL producers, nosocomial infections, and meningitis.

What major adverse event should be monitored with imipenem?

Seizures, especially in patients with renal dysfunction.

What is the mechanism of action of vancomycin?

Binds D-Ala-D-Ala, blocking peptidoglycan cross-linking.

What is the coverage spectrum of vancomycin?

Gram-positive only, including MRSA and C. difficile (PO only).

What is the loading dose range for vancomycin?

25–30 mg/kg for critically ill patients.

What monitoring parameters should be used for vancomycin?

Trough concentration 10–20 mcg/mL, renal function, signs of toxicity.

What is the adverse infusion reaction for vancomycin?

Red Man Syndrome, which can be fixed by infusing slowly.

What is the mechanism of action of macrolides?

Bind the 50S ribosomal subunit and block transpeptidation.

What is a key atypical coverage provided by macrolides?

Mycoplasma, Chlamydia, Legionella.

What is the QT-risk order for macrolides?

Erythromycin > Clarithromycin > Azithromycin.

What are the major CYP interaction rankings for macrolides?

Erythromycin > Clarithromycin >>> Azithromycin.

What dietary caution is associated with tetracyclines?

It chelates with Ca/Fe; no dairy or antacids around dosing.

What is the age and pregnancy limitation for tetracyclines?

Avoid in children under 8 years and during the 2nd/3rd trimester.

Which tetracycline has the best oral absorption and less renal impact?

Doxycycline.

Which drug is known as Tigecycline (Tygacil)?

A glycylcycline that covers MRSA but not Pseudomonas.

What is the spectrum of aminoglycosides?

Gram-negative coverage, especially for Pseudomonas.

What is a unique pharmacokinetic feature of aminoglycosides?

Post-antibiotic effect and concentration-dependent killing.

What are the trough goals for aminoglycosides?

Gentamicin/Tobramycin < 1 µg/mL; Amikacin < 5 µg/mL.

What are the major toxicities associated with aminoglycosides?

Ototoxicity and Nephrotoxicity.

What is the mechanism of action of Linezolid (Zyvox)?

Inhibits the 50S ribosomal subunit.

What type of bacteria does Linezolid cover?

MDR Gram-positive bacteria, including MRSA and VRE.

What unique risk is associated with Linezolid use?

Serotonin Syndrome, particularly with SSRIs.

Why can’t daptomycin be used for pneumonia?

It is inactivated by surfactant in the lungs.

What is the dual mechanism of action for fluoroquinolones?

Inhibits DNA gyrase (Topo II) and Topo IV.

What is the generational pattern of fluoroquinolones?

2nd generation (Cipro - Gram-negative + Pseudomonas), 3rd (Levo - adds Gram positive), 4th (Moxi - no Pseudomonas).

Which fluoroquinolone should not be used for UTI?

Moxifloxacin.

What is a major boxed warning for fluoroquinolones?

Risk of tendinitis/rupture (Achilles) and QT prolongation.

What dietary caution is associated with fluoroquinolones?

It chelates with Ca/Fe/Mg; dairy and antacids decrease absorption.

What is the coverage provided by clindamycin?

Gram-positive aerobes including MRSA and Gram-positive anaerobes.

What unique toxicity is associated with clindamycin?

C. difficile pseudomembranous colitis.

What is the dual mechanism of action for sulfonamides (TMP-SMX)?

SMX blocks PABA to DHF, TMP blocks DHF to THF.

What is the drug of choice for PJP and Nocardia?

TMP-SMX.

What unique interaction does TMP-SMX have?

It increases INR of Warfarin via CYP2C9 inhibition.

What unique risk does metronidazole present?

Disulfiram-like reaction if alcohol is consumed within 48 hours.

What is the mechanism of action of metronidazole?

Breaks bacterial DNA strands leading to helical loss.

What is the drug of choice for C. difficile?

Metronidazole.

What is the mechanism of action for polymyxins (B & E)?

Detergent-like action binding LPS to disrupt Gram-negative membrane.

What is the coverage of amphotericin B?

Severe systemic mycoses such as cryptococcus and histoplasma.

What are the monitoring parameters for Amphotericin B?

Monitor K⁺/Mg²⁺ loss, nephrotoxicity, infusion fever.

Which antifungal enters the CNS?

Fluconazole (Diflucan).

Which azole is the only one active against Zygomycetes?

Posaconazole (Noxafil).

What are unique adverse effects of voriconazole?

Visual disturbances, hallucinations, elevated LFTs.

What is the mechanism of action of echinocandins?

Inhibit 1,3-β-D-glucan synthase to weaken the fungal cell wall.

What is unique about griseofulvin?

Deposits in keratin precursors and induces CYP1A2/2C9.

What is the mechanism of action of allylamine (Lamisil)?

Inhibits squalene epoxidase to reduce ergosterol.

What is the drug of choice for onychomycosis?

Allylamine (Lamisil).

What is the mechanism of action of albendazole and mebendazole?

Inhibit microtubule formation leading to glucose uptake block and worm death.

What is the mechanism of action of pyrantel pamoate?

Depolarizing neuromuscular blocker causing paralysis.

What is a unique tip for albendazole and mebendazole?

Both are available over-the-counter for pinworms.

What are key drug of choice patterns to remember?

Pen G for syphilis; Amp/Amox for enterococcus/listeria; Zosyn for Pseudomonas; Ceftriaxone for neonatal.

What are unique interaction alerts for macrolides?

Macrolides mainly interact with CYP3A4.

What unique toxicities should be monitored in vancomycin use?

Red Man Syndrome.

What unique toxicities should be monitored with aminoglycosides?

Nephrotoxicity and ototoxicity.

What unique toxicities should be observed with fluoroquinolones?

Risks of tendon rupture and QT prolongation.

What unique toxicities should be monitored with tetracyclines?

Effects on teeth and bone.

What unique toxicities should be observed with Amphotericin B?

Hypokalemia and hypomagnesemia, plus renal effects.