Bullet points flashcards

True (Intrinsic) Antibiotic Resistance

Question:

What causes true (intrinsic) antibiotic resistance?

Answer:

• Inherent property of the bacterium

• Absence of the antibiotic target

• Low membrane permeability (e.g. Gram-negative outer membrane)

• Efflux pumps

• Naturally expressed inactivating enzymes

📌 Not due to mutation or plasmids → that is acquired resistance

Antibiotics active against Klebsiella and Pseudomonas

Question:

Which antibiotic groups are active against Klebsiella spp. and Pseudomonas aeruginosa?

Answer:

• Aminoglycosides

• Fluoroquinolones

• Ureidopenicillins (e.g. piperacillin)

• Antipseudomonal cephalosporins (ceftazidime, cefepime)

• Carbapenems (NOT ertapenem)

Treatment of Enterocolitis

Question:

What drugs are used to treat antibiotic-associated enterocolitis (C. difficile)?

Answer:

• Oral vancomycin

• Fidaxomicin

• Metronidazole (mild cases / older guidelines)

📌 Oral therapy only — IV vancomycin is ineffective in the gut

Cyclosporine & Tacrolimus – binding and mechanism

Question:

How do cyclosporine and tacrolimus work?

Answer:

• Cyclosporine binds cyclophilin

• Tacrolimus binds FKBP

• Both inhibit calcineurin

• ↓ IL-2 transcription

• ↓ T-cell activation

📌 Blocks Signal 1 + Signal 2 (Ca²⁺–calcineurin pathway)

Major antibiotic groups – when are they used?

Question:

Give typical clinical uses of major antibiotic groups.

Answer:

• Macrolides → atypical pneumonia, respiratory infections

• Lincosamides (clindamycin) → anaerobes, osteomyelitis

• Aminoglycosides → severe Gram-negative infections

• Tetracyclines → atypicals, Chlamydia, zoonoses

• Fluoroquinolones → UTIs, GI infections, bone infections

Cephalosporins excreted in bile

Question:

Which cephalosporin is excreted mainly via bile (not kidney)?

Answer:

• Ceftriaxone

📌 Safe in renal failure, caution in biliary disease

Antibiotics effective against MRSA

Question:

Which antibiotics are effective against MRSA?

Answer:

• Vancomycin

• Linezolid

• Daptomycin

• Clindamycin (if susceptible)

• Doxycycline

• Trimethoprim-sulfamethoxazole

Dexamethasone suppression test – interpretation

Question:

A woman receives dexamethasone and cortisol is 20 μg/dL the next day. What does this indicate?

Answer:

• Failure of suppression

• Suggests Cushing syndrome (ACTH-dependent or independent)

📌 CAH = LOW cortisol, not high

Antivirals requiring phosphorylation

Question:

Which of the following antivirals require phosphorylation for activation?

(Acyclovir, Foscarnet, Oseltamivir, Zanamivir, Zidovudine)

Answer:

• Acyclovir (viral thymidine kinase)

• Zidovudine (AZT)

❌ Do NOT require phosphorylation:

• Foscarnet

• Oseltamivir

• Zanamivir

Antibiotics NOT metabolized (excreted unchanged)

Question:

Which antibiotic groups are not significantly metabolized?

Answer:

• Aminoglycosides (renal excretion)

• Fluoroquinolones (mostly renal)

• Tetracyclines (variable, doxycycline via bile)

• Lincosamides → metabolized (NOT correct)

📌 Exam favorite: Aminoglycosides

Penicillins resistant to gastric acid

Question:

Which penicillins are acid-stable (resistant to gastric acid)?

Answer:

• Aminopenicillins (amoxicillin, ampicillin)

• Isoxazolyl penicillins (oxacillin, dicloxacillin)

❌ Ureidopenicillins are NOT acid-stable (IV only)

Rational antibiotic therapy – what must be considered

Question:

What factors must be considered in rational antibiotic therapy?

Answer:

• Identification of organism & susceptibility

• Site of infection

• Renal function

• Hepatic function

• Age

• Body weight

• Immune status

• Cost and toxicity

📌 Example: Renal failure → avoid aminoglycosides

Antibiotics active against atypical bacteria

Question:

Which antibiotics act against atypical bacteria?

Answer:

• Macrolides

• Tetracyclines

• Fluoroquinolones

❌ Beta-lactams do NOT cover atypicals

Histamine blockers – old vs new generation

Question:

When are antihistamines used and how do first and second generation differ?

Answer:

• Used in allergic conditions (rhinitis, urticaria)

First generation:

• Sedation

• Anticholinergic effects

Second generation:

• Minimal CNS effects

• Peripheral H1 selectivity

Monoclonal antibodies in asthma

Question:

A woman receives monoclonal antibodies for asthma. What mediator is inhibited?

Answer:

• IgE (e.g. omalizumab)

📌 Prevents IgE-mediated allergic response