Infectious Diseases Lecture Review

Collection of key review questions and concise answers covering fungal, protozoal, viral, bacterial, and systemic infectious diseases discussed in the lecture.

What organism causes Pneumocystis pneumonia (PCP) and which patient population is most at risk?

Pneumocystis jirovecii; most common opportunistic infection in AIDS patients (HIV with CD4 <200) and other immunosuppressed states.

What are the classic clinical features and exam findings of PCP?

Subacute fever, dyspnea, tachypnea, nonproductive cough; exam often shows desaturation that is out of proportion to clinical appearance.

How is PCP diagnosed and when is prednisone added to therapy?

Silver stain on sputum/bronchoscopy sample historically (gold standard); now PCR is more sensitive; treat with TMP-SMX and add prednisone taper if PaO2 on ABG <70 mmHg.

Which Candida species typically responds to fluconazole?

Candida albicans (non-albicans species may be resistant to fluconazole).

What is the typical presentation and treatment for vulvovaginal candidiasis?

Preceding antibiotic exposure; vulvar itching, erythema, white discharge without odor; diagnosed by KOH showing hyphae; treated with topical azole (e.g., miconazole) or oral fluconazole 150–200 mg.

What is the typical presentation and management of candidal esophagitis?

Immunosuppressed state or prior antibiotics; dysphagia and odynophagia; diagnosed by EGD/biopsy; treat with IV fluconazole if swallowing is difficult; otherwise oral fluconazole.

Name the five Plasmodium species and identify the two most common worldwide.

Vivax, malariae, ovale, nolesi, falciparum; falciparum and vivax are the most common worldwide.

What is the vector for malaria and where is chloroquine resistance most common?

Female Anopheles mosquito; chloroquine resistance worldwide except in Mexico and Central America.

What are common malaria prophylaxis options in chloroquine-resistant areas and key considerations?

Atovaquone-proguanil (Malarone) preferred; mefloquine; doxycycline; primaquine/tafenoquine added in some regions (e.g., SE Asia) but can cause hemolytic anemia in G6PD deficiency; test and use cautiously.

Where does varicella-zoster virus (VZV) lie dormant and what disease results from reactivation?

Dormant in dorsal root ganglia; reactivates as herpes zoster (shingles).

When is Shingrix recommended and what are its characteristics?

Recommended starting at age 50; two-dose non-live vaccine; high efficacy and immunogenicity; Zostavax was the older live vaccine with lower immunogenicity.

What are the two main coronavirus vaccine platforms and give examples?

mRNA vaccines (Pfizer-BioNTech, Moderna) approved 6 months and older; protein nanoparticle vaccine (Novavax) approved 12 and older; older viral vector vaccine (J&J) previously used.

What outpatient SARS-CoV-2 therapies exist and what are key timing/interactions notes?

Paxlovid (nirmatrelvir/ritonavir), molnupiravir, and remdesivir (IV); start oral agents within 5 days of symptom onset (remdesivir within 7 days); Paxlovid has important drug interactions (e.g., with statins and NOACs).

What are the two testing platforms for influenza and their relative sensitivity?

RIDTs (rapid antigen tests) with ~70% sensitivity; PCR with ~95% sensitivity; testing needed to distinguish from COVID-19 infection.

What are the main antivirals for influenza and when should they be started?

Oseltamivir, baloxavir, and zanamivir; initiate within 48 hours of symptom onset for best effect.

What is a key risk feature of rubella in pregnancy and what vaccine prevents it?

Congenital rubella can cause cataracts, heart defects, and hearing impairment; prevented by MMR vaccination.

What is a common complication of mumps and what route of transmission is typical?

Orchitis is a common complication; mumps is transmitted via respiratory droplets and salivary gland infection.

Which HPV types are high risk and what vaccine covers them?

High-risk types 16 and 18 (cancer risk); Gardasil 9 covers 6, 11, 16, 18, 31, 33, 45, 52, 58; recommended 9–26 years old, shared decision-making 27–45.

What is the test of choice for diagnosing HSV and how do HSV-1 and HSV-2 differ clinically?

PCR from lesion is the test of choice; HSV-1 is mainly oral but can cause genital lesions; HSV-2 mainly genital and more likely to recur; suppressive therapy considered for frequent outbreaks.

What are the major pathogens and diagnostic criteria for infective endocarditis?

Major Duke criteria include positive blood cultures and evidence of endocardial involvement on echocardiography (TEE is most sensitive; TTE first).

What is the initial empiric management for suspected meningitis in ages 1 month to 50 years?

Empiric antibiotics: ceftriaxone + vancomycin; add ampicillin if Listeria coverage is needed (e.g., neonates, elderly, or immunocompromised). Dexamethasone is often given adjunctively.

What CSF findings differentiate bacterial meningitis from aseptic meningitis?

Bacterial: high opening pressure, WBC high with neutrophil predominance, low glucose, high protein; aseptic: lymphocytes, normal or mildly elevated opening pressure, normal glucose, negative cultures.

What is the first-line treatment for typical osteomyelitis and what imaging is most useful?

Long-term IV antibiotics (4–6 weeks) targeting the organism; MRI is the preferred imaging modality; blood cultures and bone biopsy may be needed for culture-directed therapy.

What is the typical presentation of infectious arthritis and how is it managed initially?

Usually a single hot, swollen joint; rule out crystal arthritis; diagnose with joint aspiration and cultures; initial empiric therapy often includes vancomycin + ceftriaxone until cultures guide therapy.

What is Fitz-Hugh-Curtis syndrome and with which infection is it associated?

Acute perihepatitis associated with gonorrhea (disseminated gonococcal infection can involve the liver capsule).

What is the recommended tetanus vaccination strategy and post-exposure management?

Boosters with TD or Tdap every 10 years; for wounds, tetanus immune globulin (TIG) and penicillin G may be given to neutralize toxin and eradicate bacteria.

What is the recommended approach to sepsis management in the initial hours?

Early recognition via SIRS/qSOFA, obtain lactate and cultures, start crystalloids 30 mL/kg within 30–60 minutes, and administer broad-spectrum antibiotics (e.g., vancomycin + piperacillin-tazobactam) if source is unknown.