Infectious Diseases

A

• Acute Bacterial Meningitis (Adults) — Early Antibiotics, Dexamethasone, and LP/CT Algorithm

  Suspect with fever, neck stiffness, and altered mental status. Give empiric antibiotics immediately after blood cultures; add dexamethasone before or with first dose for suspected pneumococcal meningitis. CT before LP only if focal deficit, papilledema, new seizure, immunocompromise, or altered consciousness.
• Acute Bacterial Meningitis (Adults) — Empiric Therapy, Dexamethasone, and LP Strategy

  Treat immediately: draw blood cultures, give dexamethasone and empiric antibiotics before/with first dose, and obtain CT only when indicated (focal deficit, immunocompromise, papilledema). Tailor regimen by age/risk (Listeria coverage if >50 or immunocompromised).
• Acute Pyelonephritis — Adult

  Acute pyelonephritis is infection of the renal parenchyma and upper urinary tract, usually presenting with fever, flank pain, costovertebral-angle tenderness, urinary symptoms, or systemic illness. Urine culture should be obtained before antibiotics when feasible because resistance is common and definitive therapy should be narrowed to susceptibility results. Imaging is selective in uncomplicated disease but urgent when obstruction, stones, abscess, emphysematous infection, severe sepsis, unusual anatomy, o
• Acute Pyelonephritis — Adult Management

  Fever, flank pain, and urinary symptoms; send cultures; start empiric antibiotics tailored to local resistance and risk factors; image when complicated or not improving.
• Adult Bacterial Meningitis — Empiric Antibiotics, Dexamethasone, and LP Strategy

  Give empiric antibiotics immediately after blood cultures; dexamethasone should precede or accompany first antibiotic dose in suspected pneumococcal meningitis. CT before LP if focal deficit, seizure, immunocompromise, or papilledema; otherwise proceed directly to LP.

B

• Bacterial Meningitis — Adult Empiric Therapy

  Suspect with fever, neck stiffness, and altered mental status; give empiric IV antibiotics and dexamethasone without delay, obtain blood cultures, and perform lumbar puncture when safe.
• Bacterial Meningitis — Adult Empiric Therapy & Dexamethasone

  Suspected acute bacterial meningitis is a medical emergency. Obtain blood cultures and perform lumbar puncture promptly when safe, but do not delay empiric IV antibiotics for CT imaging, lumbar puncture, or transfer when those steps would postpone treatment. Current WHO guidance recommends ceftriaxone or cefotaxime as first-line empiric therapy for community-acquired bacterial meningitis, with additional coverage tailored to age, immune status, resistance patterns, and local epidemiology. Dexamethasone shou

C

• Cellulitis and Abscess — ED Management

  Differentiate purulent abscess requiring incision and drainage from nonpurulent cellulitis; choose antibiotics based on severity and MRSA risk; ensure follow up.
• Cellulitis vs Abscess — Diagnosis & Treatment

  Cellulitis is a diffuse bacterial infection of the dermis and subcutaneous tissue, whereas a cutaneous abscess is a localized collection of pus. The distinction matters because uncomplicated nonpurulent cellulitis is treated primarily with antibiotics active against streptococci, while an abscess requires drainage and may not benefit from antibiotics unless systemic illness, extensive surrounding cellulitis, impaired host defenses, recurrent disease, or other risk features are present. Examination should al
• Clostridial Myonecrosis (Gas Gangrene) — Immediate Debridement and Antitoxin Strategy

  Fulminant myonecrosis with excruciating pain, systemic toxicity, crepitus, and skin discoloration; often after trauma or injection. Management is immediate wide surgical debridement, high‑dose IV penicillin plus clindamycin for toxin suppression, hemodynamic support, and consideration of hyperbaric oxygen as an adjunct.
• Clostridioides difficile — Fulminant Management

  Fulminant Clostridioides difficile infection is defined by hypotension or shock, ileus, or toxic megacolon. Treat immediately with high-dose oral or enteral vancomycin plus IV metronidazole, add rectal vancomycin when ileus limits drug delivery, stop unnecessary inciting antibiotics, and obtain early surgical consultation for worsening organ failure or megacolon.
• Clostridioides difficile Infection — Adult

  Clostridioides difficile infection is toxin-mediated colitis that occurs when toxigenic C. difficile proliferates after disruption of the intestinal microbiome, often following antibiotic exposure or health care contact. Diagnosis requires compatible diarrhea or ileus plus appropriate stool testing; testing formed stool or repeatedly testing asymptomatic patients creates false diagnoses. For an initial nonfulminant episode, fidaxomicin is preferred when available, with oral vancomycin an acceptable alternat
• Community Acquired Pneumonia — Adult Management

  Risk stratify for site of care, give guideline concordant antibiotics, and reassess early for response and complications.
• Community-Acquired Pneumonia — Adult

  Adult community-acquired pneumonia is an acute infection of the pulmonary parenchyma acquired outside the hospital. Diagnosis requires a compatible clinical syndrome plus radiographic evidence when feasible. Management depends on illness severity, comorbidities, local resistance, and risk factors for MRSA or Pseudomonas rather than the abandoned health care-associated pneumonia category.
• Community-Acquired Pneumonia (Adults) — Severity Scores, Empiric Antibiotics, and Disposition

  Fever, cough, pleuritic chest pain with infiltrate on imaging. Use PSI or CURB‑65 for disposition. Start guideline‑concordant empiric antibiotics and consider MRSA/Pseudomonas coverage based on risk factors; treat for atypicals as indicated and switch to oral therapy when stable.
• Community‑Acquired Pneumonia in Adults — Outpatient vs Inpatient

  Community-acquired pneumonia in adults is diagnosed by a compatible acute respiratory syndrome plus objective evidence of a pulmonary infiltrate, using chest radiography or, where expertise is established, lung ultrasound. A healthy outpatient without major comorbidity can usually receive amoxicillin or doxycycline, with macrolide monotherapy only where pneumococcal resistance is acceptably low.
• Cryptococcal Meningitis in HIV — Induction to Maintenance

  Treat with induction (amphotericin B + flucytosine), consolidation (high‑dose fluconazole), and maintenance; aggressively manage intracranial pressure; delay ART to reduce IRIS risk.

G

• Gonorrhea & Chlamydia — 2025 Treatment Guidance

  Gonorrhea and chlamydia are common bacterial sexually transmitted infections that are frequently asymptomatic. Current CDC treatment for uncomplicated gonorrhea is ceftriaxone 500 mg IM once for patients weighing less than 150 kg and 1 g IM once for those weighing at least 150 kg.

H

• Herpes Zoster — Antivirals & Postherpetic Neuralgia Prevention

  Herpes zoster is reactivation of varicella-zoster virus in a sensory ganglion, producing pain and a unilateral vesicular eruption in a dermatomal distribution. Treat uncomplicated zoster with oral valacyclovir, famciclovir, or acyclovir, plus multimodal pain control.
• Hospital- and Ventilator-Associated Pneumonia — Adult

  Hospital-acquired pneumonia develops 48 hours or more after admission and is not incubating at presentation; ventilator-associated pneumonia develops more than 48 hours after endotracheal intubation. Diagnosis is clinical, based on a new pulmonary infiltrate plus infectious respiratory features and deterioration, because no single biomarker or culture result is diagnostic. Initial antibiotics should be guided by local ICU or hospital antibiograms, severity, prior IV antibiotic exposure, and risk for MRSA or
• Hospital‑Acquired & Ventilator‑Associated Pneumonia — Empiric Therapy

  Hospital-acquired pneumonia occurs at least 48 hours after admission and was not incubating on arrival; ventilator-associated pneumonia occurs more than 48 hours after endotracheal intubation. Empiric HAP/VAP therapy should cover Staphylococcus aureus plus Pseudomonas and other gram-negative bacilli.

I

• Infective Endocarditis — Diagnosis and Treatment

  Infective endocarditis is infection of the endocardial surface, usually a heart valve or intracardiac device, producing bacteremia, valvular destruction, emboli, and immune phenomena. Diagnosis integrates multiple blood cultures, echocardiography, microbiology, and clinical criteria. Management requires prolonged pathogen-directed antimicrobial therapy and early involvement of an endocarditis team because heart failure, uncontrolled infection, abscess, prosthetic material, and recurrent embolization can req
• Infective Endocarditis — Duke Criteria, Empiric Therapy, and Surgical Indications

  Suspect with fever and new murmur, embolic phenomena, or positive blood cultures. Obtain 3 sets of blood cultures before antibiotics when feasible; use Duke criteria for diagnosis. Start empiric therapy based on native vs prosthetic valve and tailor to cultures; identify indications for surgery (heart failure, uncontrolled infection, embolic risk).
• Infective Endocarditis — Modified Duke Criteria, Empiric Therapy, and Surgical Indications

  Suspect IE with persistent bacteremia, new murmur, or emboli. Obtain three sets of blood cultures before antibiotics when possible, apply Modified Duke Criteria, start empiric IV therapy tailored to native vs prosthetic valve and MRSA risk, and evaluate for surgery when heart failure, uncontrolled infection, or embolic risk is present.
• Influenza in Adults — Testing & Antivirals

  Influenza can cause uncomplicated febrile respiratory illness, viral pneumonia, bacterial superinfection, myocarditis, encephalopathy, and decompensation of chronic cardiopulmonary disease. Oral or enteric oseltamivir is preferred for hospitalized influenza and for many severe/progressive cases.

L

• Lemierre Syndrome — Fusobacterium Septic Thrombophlebitis of the Internal Jugular

  Young, previously healthy patient with recent oropharyngeal infection develops fever, neck pain, and septic emboli. Suspect Lemierre syndrome—septic thrombophlebitis of the internal jugular vein—most often due to Fusobacterium necrophorum.
• Leptospirosis — Conjunctival Suffusion, AKI & Weil Disease

  Leptospirosis is a zoonotic spirochetal infection acquired through contact with water or soil contaminated by infected animal urine. It can cause fever, severe myalgias, conjunctival suffusion, aseptic meningitis, AKI, thrombocytopenia, jaundice, and pulmonary hemorrhage; antibiotics should be started promptly when clinical suspicion is high rather than delayed for confirmatory testing.

N

• Native Vertebral Osteomyelitis — Diagnosis & Treatment

  Suspect with back pain, fever, and elevated CRP/ESR. MRI is diagnostic; obtain blood cultures and biopsy if needed. Treat with 6 weeks of targeted antibiotics; surgery for instability, abscess, or neurologic deficits.
• Necrotizing Otitis Externa — Pseudomonas Coverage and Skull-Base Osteomyelitis

  Severe external otitis in diabetics/immunocompromised with granulation tissue and skull-base osteomyelitis risk. Obtain imaging for extent and initiate anti-pseudomonal therapy with close ENT follow-up.
• Necrotizing Soft Tissue Infection — Early Debridement, Broad Antibiotics, and Toxin Suppression

  NSTI is a surgical emergency. High suspicion with pain out of proportion, bullae, crepitus, or systemic toxicity mandates immediate broad-spectrum antibiotics and urgent operative debridement; repeat debridements are common. Add clindamycin for toxin suppression in suspected streptococcal/staphylococcal disease.
• Neutropenic Fever — Empiric Antibiotics

  Oncologic emergency: start broad spectrum antipseudomonal beta lactam within 60 minutes after cultures; risk stratify for outpatient vs inpatient management.
• Neutropenic Fever — Oncologic Emergency

  Start antipseudomonal IV antibiotics within 60 minutes; risk stratify for inpatient vs outpatient therapy; escalate for instability or persistent fever.

R

• Rabies Post Exposure Prophylaxis — Wounds and Vaccination

  Rabies postexposure prophylaxis is a prevention emergency because clinical rabies is almost uniformly fatal once symptoms begin. Management is based on exposure risk, immediate wound cleansing, prior vaccination status, human rabies immune globulin when indicated, and completion of the recommended vaccine schedule without unnecessary delay.

S

• Septic Arthritis (Native Joint) — Arthrocentesis, Empiric Coverage, and Washout

  Acute monoarthritis with fever and elevated inflammatory markers warrants urgent arthrocentesis. Start empiric IV antibiotics after cultures and arrange operative washout for large joints or if poor response to needle drainage.
• Spinal Epidural Abscess — MRI, Targeted IV Antibiotics, and Surgical Decompression

  Fever, back pain, and neurologic deficits constitute the classic triad but are often incomplete. Maintain high suspicion in IVDU, diabetes, or bacteremia. Obtain urgent MRI, start broad IV antibiotics, and coordinate early surgical decompression for neurologic deficits or failure of medical therapy.
• Spinal Epidural Abscess — Red Flags, MRI, and Early Decompression

  Back pain with fever and new focal neurologic deficits warrants urgent MRI for spinal epidural abscess; start empiric anti-staphylococcal therapy and obtain early neurosurgical consultation for decompression when deficits or instability are present.
• Spontaneous Bacterial Peritonitis — Empiric Therapy

  Perform diagnostic paracentesis in all hospitalized patients with cirrhosis and ascites; treat SBP with third generation cephalosporin and give albumin in select cases.
• Spontaneous Bacterial Peritonitis — Empiric Third-Gen Cephalosporin and Albumin

  Suspect SBP in cirrhosis with ascites and abdominal pain or encephalopathy. Diagnose via ascitic PMN ≥250/µL; start empiric third-generation cephalosporin and give albumin to reduce renal failure in high-risk cases.
• Staphylococcus aureus Bacteremia — Evaluation & Source Control

  SAB is never a contaminant until proven otherwise. Obtain repeat blood cultures, evaluate for endocarditis, source control, and treat with pathogen‑directed therapy for adequate duration.
• Strongyloides Hyperinfection — Steroid-Triggered Dissemination & Ivermectin

  Strongyloides stercoralis can persist for decades through autoinfection and become rapidly fatal when corticosteroids or other immunosuppression trigger hyperinfection. Respiratory and gastrointestinal deterioration, gram-negative bacteremia, or meningitis in an at-risk patient should prompt urgent ivermectin therapy and reduction of immunosuppression when possible.
• Syphilis — Staging, Testing, and Treatment

  Syphilis is a systemic infection caused by Treponema pallidum with primary, secondary, latent, and tertiary manifestations; neurologic, ocular, and otic disease can occur at any stage. Treat primary, secondary, and early latent syphilis with benzathine penicillin G 2.4 million units IM once.

T

• Tetanus Prophylaxis — Wound Management

  Tetanus prevention after a wound depends on wound classification and the patient's tetanus immunization history. Clean the wound, remove devitalized tissue and foreign material, give a tetanus toxoid-containing vaccine when indicated, and add tetanus immune globulin for contaminated or major wounds in patients without adequate prior immunization or with severe immunodeficiency.
• Toxoplasmosis in HIV — CNS Disease Management

  Empiric therapy for typical ring‑enhancing brain lesions in AIDS while confirming diagnosis; pyrimethamine + sulfadiazine + leucovorin is standard; treat acute phase ≥6 weeks, then chronic maintenance.

W

• Whipple Disease — Arthralgia, Malabsorption & PAS-Positive Macrophages

  Whipple disease is a rare systemic infection caused by Tropheryma whipplei, classically producing migratory arthralgias years before weight loss, diarrhea, abdominal pain, and malabsorption. Diagnosis relies on tissue-based demonstration of characteristic PAS-positive macrophages with organism-specific PCR, and prolonged antibiotic therapy must penetrate the CNS because neurologic relapse can occur.