Chapter 8 of 157% of exam

Infectious Diseases

The infectious disease block is organized by organism class: bacterial, fungal, mycobacterial, parasitic, spirochetal and viral, plus prion disease, sepsis and perinatal transmission. Treatment choices change as national guidelines update, so name the current guideline.

Bacterial and spirochetal infections

Several bacterial infections have one clearly preferred regimen, set by national guidelines that update over time. Older regimens still circulate in study materials, so name the current guideline edition. Partners of patients with sexually transmitted infections need evaluation too.

C. difficile

Oral fidaxomicin or oral vancomycin is first-line for an initial episode; metronidazole is no longer first-line.

IDSA/SHEA 2021 Focused Update on C. difficile Infection

Syphilis

Benzathine penicillin G is the treatment of choice for most stages; partners are evaluated.

CDC STI Treatment Guidelines, 2021

Gonorrhea

Ceftriaxone 500 mg IM once (1 g if 150 kg or more), plus doxycycline if chlamydia is not excluded.

CDC STI Treatment Guidelines, 2021

Tick-borne and vaccine-preventable infections

Clinical diagnosis and prompt empiric treatment prevent the worst outcomes of tick-borne disease. Serology often lags behind early disease and should not delay therapy. Vaccine-preventable diseases carry specific isolation requirements.

Lyme disease

Erythema migrans is diagnosed clinically because serology is often negative early; doxycycline is standard.

Merck Manual Professional Edition, Lyme Disease

Rocky Mountain spotted fever

Fever, headache and a rash starting at wrists and ankles; doxycycline for all ages, started on suspicion.

Merck Manual Professional Edition, Rocky Mountain Spotted Fever

Measles

Fever, cough, coryza, conjunctivitis, Koplik spots and a head-to-trunk rash; airborne precautions.

Merck Manual Professional Edition, Measles

Sepsis and HIV-related infection

Sepsis management is time-sensitive and built on early antibiotics, fluids and vasopressors. Definitions use mean arterial pressure and lactate. In HIV, opportunistic infection prophylaxis follows CD4 thresholds and can stop with immune recovery.

Septic shock

Sepsis needing vasopressors for MAP of 65 mm Hg or more with lactate above 2 mmol/L after fluids.

Surviving Sepsis Campaign 2021

Initial fluids

Many patients need at least 30 mL/kg of crystalloid in the first 3 hours, guided by perfusion.

Merck Manual Professional Edition, Sepsis and Septic Shock

Pneumocystis prophylaxis

Can stop once ART raises the CD4 count to 200 or more for at least 3 months.

Merck Manual Professional Edition, Pneumocystis jirovecii Pneumonia

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