Study Session December first

on

 Question 32

Card 1 — Correct prophylaxis choice

Label: Malaria prophylaxis — drug selection

The recommended medication for malaria prophylaxis for travel to East Africa is
Atovaquone–proguanil.




Chloroquine Resistant P Falciparum - atovaquone proguanil, doxy, mefloquine
Areas w/ chloroquine susceptible to P falciparum - chloroquine, hydroxychloroquine
needs to be started 1-2 weeks in advance, weekly dosing
w/o plasmodium falciparum primaquine

P falciparum - chloroquine
if resistant atovaquone proguanil
if no p falciparum - primaquine

Card 2 — Why this is correct

Label: Malaria prophylaxis — mechanism

Atovaquone–proguanil acts as a
hepatic schizonticide, targeting Plasmodium in the liver stage.

Card 3 — Timing of therapy

Label: Malaria prophylaxis — dosing schedule

Atovaquone–proguanil should be taken:

Start: 1–2 days before travel
Continue: for 7 days after leaving the endemic area

Card 4 — Why not ciprofloxacin?

Label: Traveler’s medicine — common confusion

Ciprofloxacin is used for traveler’s diarrhea, not malaria.

Card 5 — Why not clarithromycin?

Label: Opportunistic infections

Clarithromycin is used for prophylaxis against
Mycobacterium avium complex in patients with advanced HIV.

Card 6 — Why not mebendazole?

Label: Parasite specificity

Mebendazole treats intestinal helminths, not malaria.

Card 7 — Why not nifurtimox?

Label: Tropical diseases

Nifurtimox is used to treat Chagas disease caused by
Trypanosoma cruzi.

Card 8 — Classes of malaria drugs

Label: Malaria pharmacology

Malaria drugs are classified as:

• Hepatic schizonticides (Atovaquone–proguanil)
• Blood schizonticides (chloroquine, doxycycline, mefloquine)
• Hypnozoiticides (primaquine)

Card 9 — Hypnozoite coverage

Label: Malaria species differentiation

Primaquine clears hypnozoites in
Plasmodium vivax and Plasmodium ovale
(requires G6PD screening).

Card 10 — Special populations

Label: Malaria prophylaxis — pregnancy

Pregnant patients should receive:

• Chloroquine in sensitive areas
• Mefloquine in resistant areas




Contact precautions
C diff, MRSA, Varicella, HSV
droplet  Neisseria, influenza, mumps
Airborne TB, Measles, Varicella




Core diagnosis

Label: Transplant infections — CMV disease

Solid-organ transplant recipient with fever, leukopenia, transaminitis, diarrhea, and odynophagia most likely has cytomegalovirus (CMV) disease.

Card 2 — Why CMV fits

Label: CMV disease — classic presentation

CMV disease causes:

  • Low-grade fever & malaise

  • Leukopenia

  • Hepatitis (↑ AST/ALT)

  • GI involvement (diarrhea, esophagitis)

  • Occurs after rejection treatment or increased immunosuppression

Card 3 — Timing clue

Label: Transplant timeline — CMV risk

Peak risk for CMV disease is 1–6 months post-transplant, especially:

  • After stopping prophylaxis

  • After pulse steroids

  • After rejection therapy

Card 4 — Pathophysiology

Label: CMV in transplant — mechanism

CMV disease results from:

  • Reactivation of latent virus

  • Or superinfection from donor strain
    especially after immunosuppression escalation

Card 5 — Why not BK virus

Label: Transplant infections — BK vs CMV

BK virus presents with:

  • Progressive renal dysfunction

  • Tubulointerstitial nephritis
    NOT fever, diarrhea, or hepatitis.

Card 6 — Why not HSV

Label: Opportunistic infections — HSV vs CMV

HSV classically presents with:

  • Painful oral/genital ulcers

  • Localized disease
    Does NOT cause leukopenia or systemic illness like CMV.

Card 7 — Why not tacrolimus toxicity

Label: Immunosuppressant toxicity

Tacrolimus toxicity causes:

  • Nephrotoxicity

  • Neurotoxicity (tremor)

  • Hyperkalemia, hypertension
    Not fever, hepatitis, or diarrhea.

Card 8 — Why not Toxoplasma

Label: Post-transplant infections — Toxo

Toxoplasma gondii causes:

  • Brain abscess

  • Chorioretinitis

  • Pneumonitis
    Rare after kidney transplant and not GI-predominant.

Card 9 — Treatment

Label: CMV disease — management

Treatment includes:

  • IV ganciclovir or oral valganciclovir

  • Standard duration: 3 months (90–100 days)

  • Reduction in immunosuppression if possible



Card 10 — Exam pearl

Label: USMLE pearl — CMV

Any transplant patient with:

  • Leukopenia

  • Transaminitis

  • Diarrhea or odynophagia
    = Think CMV disease first.

BK virus - progressive renal dysfunction, tubulointerstitial nephritis
Not HSV - painful oral / genital ulcers, localized disease
CMV - occurs after reactivation of latent virus / superinfection from donor strain especially after immunosuppression escalation, leukopenia, transamanitis, diarrhea
Toxoplasma - Brain abscess, chorioretinitis, pneumonitis
CMV - IV ganciclovir / oral valganciclovir, reduction in immunosuppression if possible



Organisms that REQUIRE catheter removal:

  • Staphylococcus aureus

  • Pseudomonas aeruginosa

  • Fungal species (eg, Candida)

  • Mycobacteria

  • Persistent bacteremia despite therapy

  • Endocarditis, septic thrombophlebitis, or tunnel infection


Although coagulase-negative Staph forms biofilm, catheter salvage is allowed (with antibiotic lock) if the patient is stable and the organism is susceptible.

But Pseudomonas is aggressive and relapse-prone → salvage fails → remove.

Antimicrobial “lock” therapy involves placing a supratherapeutic antibiotic amount (100-1000 times higher than the normal dose) in the catheter lumen for hours to days to attempt catheter salvage in these cases.  However, Pseudomonas aeruginosa CRBSI usually has poor outcomes with catheter salvage, thus long-term catheters should be removed


Vomiting is s. aureus and bacillus cereus



Why this is norovirus:

This patient has the classic outbreak pattern and symptom profile of norovirus:

Key clues in the question

  • Multiple residents affected → common-source outbreak

  • Nursing home → classic risk environment

  • Vomiting > diarrhea → hallmark of norovirus

  • Negative stool culture → viral cause

  • Fever, myalgias, headache → systemic viral illness

  • Rapid onset, short duration → viral gastroenteritis


High-Yield Norovirus Profile

Transmission

  • Fecal–oral

  • Food and water

  • Fomites

  • Aerosolized vomitus (yes — airborne particles from vomiting)

Clinical Pattern

  • Sudden-onset vomiting

  • Watery diarrhea

  • Fever

  • Headache

  • Myalgias

Settings that scream Norovirus

  • Nursing homes

  • Hospitals

  • Cruise ships

  • Schools

  • Restaurants

  • Daycares

Course

  • Self-limited (48–72 hours)

  • Supportive care only




Why this is correct

This patient has a cat bite to the hand with a deep puncture wound → this is a high-risk bite and requires empiric antibiotics.

Cat bites are dangerous because:

  • They cause deep inoculation

  • They frequently introduce Pasteurella multocida

  • Hands have closed spaces → high risk for tenosynovitis, osteomyelitis, septic arthritis

First-line therapy for cat bites

✅ Amoxicillin–clavulanate

(covers Pasteurella + anaerobes + skin flora)

But…

She has a penicillin allergy → use an alternative

✅ Doxycycline + metronidazole

Provides coverage for:

  • Pasteurella multocida (doxycycline)

  • Anaerobes (metronidazole)

  • Streptococci & skin flora

Why the other answers are wrong

❌ A. Azithromycin + clindamycin

  • Macrolides (azithro) are unreliable against Pasteurella

  • Inadequate empiric therapy

❌ C. Primary closure

  • Never close animal bites on the hand

  • ↑ risk of abscess, tendon infection, osteomyelitis

❌ D. Tetanus immunoglobulin

  • Booster within 5 years → already protected

❌ E. Culture + observe

  • Cat bites need immediate prophylaxis, not watchful waiting

  • Pasteurella grows poorly on culture





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