Study guide
16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections
ABIM Critical Care Medicine Study Guide Exam
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1 Chapter 1: Exam Orientation: Format, Blueprint & Study Strategy
1.1 ABIM Critical Care Medicine Exam: Format, Blueprint & Study Strategy
2 Chapter 2: Acute Respiratory Failure & ARDS
2.1 ARDS Definition, Pathophysiology & Phenotypes 2.2 Lung-Protective Mechanical Ventilation 2.3 Refractory ARDS: Prone Positioning, Neuromuscular Blockade & VV-ECMO
3 Chapter 3: Obstructive Airways, Pulmonary Vascular & Pleural Emergencies
3.1 Severe Asthma & COPD Exacerbations in the ICU 3.2 Massive & Submassive Pulmonary Embolism 3.3 Pulmonary Hypertension & Right Ventricular Failure in the ICU 3.4 Massive Hemoptysis, Complex Pleural Effusions & Thoracic Drainage
4 Chapter 4: Airway, Parenchymal & Nonthrombotic Pulmonary Emergencies
4.1 Airway Management, Upper-Airway Obstruction & Artificial-Airway Complications 4.2 Diffuse Alveolar Hemorrhage, Interstitial Lung Disease, Pulmonary Vasculitis & Noncardiogenic Edema 4.3 Severe Community-Acquired & Viral Pneumonia 4.4 Nonthrombotic Embolism (Air, Fat, Amniotic Fluid, Tumor, Septic) & Acute Chest Syndrome
5 Chapter 5: Mechanical Ventilation Modes, Dyssynchrony & Liberation
5.1 Mechanical Ventilator Modes & Advanced Breath Delivery 5.2 Patient-Ventilator Dyssynchrony & Waveform Analysis 5.3 Ventilator Liberation, Spontaneous Breathing Trials & Post-Extubation Support
6 Chapter 6: Shock Syndromes & Hemodynamic Principles
6.1 Shock Classification, Cellular Pathophysiology & Biomarkers 6.2 Hemodynamic Monitoring: Arterial Lines, CVP & Pulmonary Artery Catheter 6.3 Dynamic Assessment of Fluid Responsiveness & Resuscitation Targets
7 Chapter 7: Vasoactive Therapies & Mechanical Circulatory Support
7.1 Vasopressors & Inotropes: Pharmacology & Clinical Titration 7.2 Temporary Mechanical Circulatory Support: IABP, Impella & TandemHeart 7.3 Venoarterial ECMO (VA-ECMO) & Differential Hypoxemia 7.4 Post-Cardiac Arrest Care, Targeted Temperature Management & Neuroprognostication
8 Chapter 8: Acute Kidney Injury & Renal Replacement Therapy
8.1 KDIGO AKI Classification, Etiologies & Diagnostic Evaluation 8.2 Continuous Renal Replacement Therapy (CRRT) vs Intermittent Hemodialysis 8.3 Indications & Timing for RRT in Critical Illness: AKIKI & STARRT-AKI
9 Chapter 9: Electrolyte, Acid-Base & Endocrine Emergencies
9.1 Severe Dysnatremias: Hyponatremia, Hypernatremia & Osmotic Demyelination 9.2 Potassium, Calcium, Magnesium & Phosphate Disorders 9.3 Complex & Mixed Acid-Base Disorders: Boston vs Copenhagen vs Stewart 9.4 Endocrine Crises: DKA, HHS, Thyroid Storm, Myxedema Coma & Adrenal Crisis
10 Chapter 10: Glycemic Control, Hyperammonemia, Pituitary & Adrenal Disorders
10.1 ICU Glycemic Control & Severe Hypoglycemia 10.2 Non-Hepatic Hyperammonemia & Metabolic Encephalopathy 10.3 Pituitary Emergencies, Adrenal Excess & Critical Illness-Related Corticosteroid Insufficiency
11 Chapter 11: Acute Coronary Syndromes & Cardiac Arrhythmias
11.1 Acute Coronary Syndromes & Mechanical Complications of Myocardial Infarction 11.2 Critical Tachyarrhythmias: Atrial Fibrillation with RVR, VT & VF 11.3 Critical Bradyarrhythmias, Conduction Blocks & Temporary Cardiac Pacing
12 Chapter 12: Acute Heart Failure, Valvular & Pericardial Emergencies
12.1 Acute Decompensated Heart Failure & Cardiogenic Pulmonary Edema 12.2 Acute Valvular Regurgitation & Prosthetic Valve Emergencies 12.3 Pericardial Tamponade & Acute Aortic Syndromes
13 Chapter 13: Myocardial Disease, Hypertensive & Cardiac Device Emergencies
13.1 Fulminant Myocarditis, Stress & Peripartum Cardiomyopathy, and Hypertrophic Cardiomyopathy 13.2 Hypertensive Emergencies & Ruptured Abdominal Aortic Aneurysm 13.3 Implanted Cardiac Devices, LVAD Emergencies & Electrical Storm
14 Chapter 14: Sepsis & Systemic Infectious Diseases
14.1 Sepsis-3 Definitions & Surviving Sepsis Campaign 2026 Guidelines 14.2 Refractory Septic Shock & Adjunctive Therapies 14.3 Multidrug-Resistant Pathogens & Antimicrobial Stewardship in the ICU
15 Chapter 15: ICU-Acquired & Severe Focal Infections
15.1 Hospital-Acquired & Ventilator-Associated Pneumonia 15.2 Central Line-Associated Bloodstream Infections & Catheter-Associated UTIs 15.3 Intra-Abdominal Sepsis, Necrotizing Soft Tissue Infections & CNS Infections
16 Chapter 16: Focal, Special-Host & Systemic Infections
16.1 CNS Infections Beyond Bacterial Meningitis: Encephalitis, Brain Abscess & Epidural Abscess 16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections 16.3 Infective Endocarditis, Device Infections & Other Focal Cardiovascular Infections 16.4 Antimicrobial Pharmacokinetics, Allergy, Toxicity & Infection Prevention 16.5 Gastrointestinal & Hepatobiliary Infections: Fulminant C. difficile, Typhlitis, CMV Colitis & Abscesses
17 Chapter 17: Neurocritical Care & Coma
17.1 Coma, Altered Mental Status & Acute Delirium in the ICU 17.2 Status Epilepticus & Non-Convulsive Status Epilepticus 17.3 Acute Ischemic Stroke & Intracranial Hemorrhage
18 Chapter 18: Cerebrovascular Syndromes, Encephalopathy & Withdrawal States
18.1 Cerebral Venous Sinus Thrombosis, PRES & Reversible Cerebral Vasoconstriction Syndrome 18.2 Alcohol & Sedative Withdrawal, Wernicke Encephalopathy & Drug-Induced Encephalopathy
19 Chapter 19: Intracranial Hypertension & Neuromuscular Weakness
19.1 Intracranial Pressure Monitoring, Cerebral Perfusion & Tiered ICP Management 19.2 Acute Neuromuscular Respiratory Failure, ICU-Acquired Weakness & Brain Death Determination
20 Chapter 20: Traumatic Brain Injury, Spinal Cord Injury & Toxin-Mediated Paralysis
20.1 Traumatic Brain Injury Management & Paroxysmal Sympathetic Hyperactivity 20.2 Acute Spinal Cord Injury, Neurogenic Shock & Autonomic Dysreflexia 20.3 Toxin-Mediated Paralysis & Neuromuscular Crises: Botulism, Tetanus, Tick Paralysis & Myasthenic Crisis
21 Chapter 21: Gastrointestinal, Hepatic & Abdominal Emergencies
21.1 Acute Upper & Lower Gastrointestinal Bleeding in the ICU 21.2 Acute Liver Failure & Severe Acute Pancreatitis 21.3 Abdominal Compartment Syndrome & Acute Mesenteric Ischemia
22 Chapter 22: Luminal GI Emergencies & Complications of Cirrhosis
22.1 Esophageal, Gastric & Bowel Emergencies: Perforation, Obstruction, Ogilvie Syndrome & Colonic Ischemia 22.2 Complications of Cirrhosis: Alcohol-Associated Hepatitis, Hepatorenal Syndrome & Pulmonary Vascular Syndromes
23 Chapter 23: Trauma, Burns & Perioperative Critical Care
23.1 Polytrauma Resuscitation, Damage Control & Massive Transfusion 23.2 Severe Burn Injury, Inhalation Injury & Environmental Emergencies 23.3 Perioperative Critical Care for High-Risk Surgical Patients
24 Chapter 24: Thoracic Trauma, Environmental Injury & Obstetric Critical Care
24.1 Thoracic Trauma: Flail Chest, Pulmonary Contusion, Great Vessel & Tracheobronchial Injury 24.2 Environmental Injury: Drowning, Diving, Altitude, Heat, Cold, Electrical & Radiation 24.3 Obstetric & Genitourinary Emergencies and the Physiology of Pregnancy
25 Chapter 25: Transplantation, Donor Management & Post-Cardiac Surgery Care
25.1 Solid Organ Transplant Recipients & Deceased Donor Management 25.2 Post-Cardiac Surgery Critical Care: Bleeding, Tamponade, Low Output & Vasoplegia
26 Chapter 26: Hematologic Emergencies, Toxicology, Critical Ultrasound & ICU Liberation
26.1 Hematologic Emergencies in the ICU: HIT, DIC, TMA & Anticoagulant Reversal 26.2 Critical Care Toxicology, Toxidromes & Specific Antidotes 26.3 Critical Care Point-of-Care Ultrasound (POCUS) 26.4 ICU Liberation, Analgosedation, Goals of Care & Critical Care Ethics
27 Chapter 27: Transfusion Medicine, Hematologic & Oncologic Disorders
27.1 Transfusion Medicine: Products, Thresholds, Reactions & Apheresis 27.2 Red and White Cell Disorders, Hemoglobinopathies, Factor Deficiencies & Hypercoagulable States 27.3 Oncologic Emergencies, Hematopoietic Cell Transplant Complications & Cellular Therapy Toxicity
28 Chapter 28: Clinical Pharmacology, Adverse Drug Reactions & Specific Poisonings
28.1 Pharmacokinetic Principles, Dose Adjustment & Drug Interactions in Critical Illness 28.2 Adverse Drug Reactions: Anaphylaxis, Severe Cutaneous Reactions & Hyperthermic Syndromes 28.3 Specific Poisonings: Sodium-Channel Blockers, Lithium, Valproate, Theophylline, Iron, Sulfonylureas & Methemoglobinemia
29 Chapter 29: Ethics, Research Methods, Administration & Abdominal Ultrasound
29.1 Advance Care Planning, Nonbeneficial Treatment, Informed Consent & Confidentiality 29.2 Critical Care Research Methods, Statistics, IRB Oversight & Quality Improvement 29.3 Abdominal, Vascular & Procedural Point-of-Care Ultrasound
16.2 Infections in the Immunocompromised Host, Tropical & Bioterror Infections
Key Takeaways Explain This Topic AI
Neutropenic fever is treated within 1 hour with an antipseudomonal beta-lactam; vancomycin is added only for specific indications such as suspected catheter infection, skin or soft tissue infection, pneumonia, or hemodynamic instability.
Severe falciparum malaria is treated with intravenous artesunate, which reduced mortality compared with quinine; delayed hemolysis can occur 1 to 3 weeks later.
Strongyloides hyperinfection and dissemination are classically triggered by corticosteroids and present with gram-negative bacteremia and alveolar hemorrhage; treat with ivermectin.
Early cytomegalovirus disease after transplantation presents with fever, cytopenias, pneumonitis, or colitis, and is treated with intravenous ganciclovir.
Inhalational anthrax causes a widened mediastinum with hemorrhagic mediastinitis and pleural effusions, and is treated with a fluoroquinolone-based combination plus an antitoxin.
Last updated: October 2026
Febrile Neutropenia
Definition : a single temperature of 38.3 °C or more, or 38.0 °C sustained for an hour, with an absolute neutrophil count below 500/µL or expected to fall below it.
Act within 1 hour : draw blood cultures from a peripheral site and each catheter lumen, then start an antipseudomonal beta-lactam (piperacillin-tazobactam, cefepime, meropenem, or imipenem).
Add vancomycin only for an indication :
Suspected catheter-related infection.
Skin or soft tissue infection.
Pneumonia.
Hemodynamic instability.
Known colonization with resistant gram-positive organisms.
Severe mucositis in a patient on fluoroquinolone prophylaxis.
Add antifungal therapy for persistent fever after about 4 to 7 days, or for a suggestive CT (nodules with halo signs), with an echinocandin or a mold-active azole.
Think beyond bacteria : typhlitis (neutropenic enterocolitis), perirectal infection (avoid digital rectal examination and rectal thermometers), Clostridioides difficile , and viral reactivation.
G-CSF is not routinely added to treat established fever, but is used in high-risk settings.
Do not wait for neutrophil recovery before escalating in deteriorating patients; the inflammatory response is blunted, so physical findings are muted.
Transplant Recipients: Timeline Thinking
Time since transplant Typical infections
Under 1 month Surgical and nosocomial: wound, pneumonia, catheter and urinary infections, C. difficile , donor-derived infection, reactivated Candida , and HSV
1 to 6 months Opportunistic: cytomegalovirus , Pneumocystis , Aspergillus , Nocardia , Toxoplasma , Listeria , BK virus, EBV-driven post-transplant lymphoproliferative disease, reactivated tuberculosis, hepatitis B and C
Beyond 6 months Community-acquired pneumonia and urinary infections, late CMV, chronic viral disease, and endemic fungi
Cytomegalovirus disease presents with fever, leukopenia and thrombocytopenia, pneumonitis, hepatitis, or colitis; diagnose by quantitative PCR with tissue biopsy for organ disease, and treat with IV ganciclovir (valganciclovir for less severe disease). Resistance is managed with foscarnet, cidofovir, or maribavir.
Pneumocystis pneumonia presents with dry cough, progressive hypoxemia, and a markedly elevated LDH, with diffuse ground-glass opacity on CT. Treat with high-dose trimethoprim-sulfamethoxazole plus corticosteroids when PaO2 is below 70 mmHg or the alveolar-arterial gradient is above 35 mmHg.
Invasive aspergillosis : nodules with halo and later air-crescent signs, serum and BAL galactomannan; treat with voriconazole or isavuconazole.
Mucormycosis : diabetes with ketoacidosis, deferoxamine, or hematologic malignancy; rhino-orbital-cerebral or pulmonary disease with tissue necrosis. Treatment requires surgical debridement plus liposomal amphotericin B ; mucorales are resistant to voriconazole.
Asplenia : fulminant sepsis from encapsulated organisms ( S. pneumoniae , H. influenzae , N. meningitidis ), Capnocytophaga after dog bites, and severe babesiosis. Treat early and aggressively; vaccinate and educate.
HIV with advanced immunosuppression : consider Pneumocystis , tuberculosis, cryptococcosis, toxoplasmosis, disseminated Mycobacterium avium complex, and CMV retinitis, as well as the usual bacterial pathogens.
- Malaria, Babesiosis and Other Parasitic Emergencies
- Severe Falciparum Malaria
Criteria : impaired consciousness or coma, severe anemia, acidosis, hypoglycemia, kidney injury, pulmonary edema, shock, bleeding, parasitemia above about 10%, or jaundice with other organ dysfunction.
Treatment : intravenous artesunate , which reduced mortality compared with quinine in large trials. Follow with a full oral course (artemether-lumefantrine). Watch for delayed post-artesunate hemolysis at 1 to 3 weeks, and check a hemoglobin weekly for a month.
Supportive care : avoid overhydration (pulmonary edema is common), treat hypoglycemia, use kidney replacement therapy for acidosis and kidney failure, and transfuse for severe anemia. Exchange transfusion is no longer routinely recommended.
Avoid corticosteroids in cerebral malaria.
Babesiosis
Northeastern and upper midwestern United States; Ixodes ticks, which also transmit Lyme disease and anaplasmosis.
Severe disease occurs with asplenia , age over 50, HIV, and immunosuppression: hemolytic anemia, jaundice, ARDS, and disseminated intravascular coagulation.
Diagnosis : thin smear ring forms and "Maltese cross" tetrads, plus PCR.
Treatment : azithromycin plus atovaquone for mild disease; clindamycin plus quinine with exchange transfusion for high parasitemia (above about 10%), severe hemolysis, or organ failure.
Strongyloides Hyperinfection
Chronic autoinfection can persist for decades after exposure in endemic regions.
Corticosteroids (and HTLV-1 infection) convert it to hyperinfection and dissemination: diffuse alveolar hemorrhage, ileus, and recurrent gram-negative bacteremia and meningitis from enteric organisms carried by migrating larvae.
Diagnosis : larvae in stool, sputum, or BAL; serology before immunosuppression in at-risk patients.
Treatment : ivermectin (parenteral or rectal routes are used when ileus prevents absorption), plus antibiotics for the bacteremia. Screen and treat before starting steroids in at-risk patients.
Other Travel-Related Causes
Dengue : biphasic fever, severe myalgia, thrombocytopenia, plasma leakage with shock; supportive care with careful fluid titration.
Typhoid : fever, abdominal pain, relative bradycardia; treat with ceftriaxone or azithromycin.
Leptospirosis : freshwater exposure, conjunctival suffusion, jaundice with kidney failure (Weil disease), and pulmonary hemorrhage; treat with penicillin or ceftriaxone.
Rickettsial disease : Rocky Mountain spotted fever with a centripetal rash, hyponatremia, and thrombocytopenia; doxycycline empirically, because delay is fatal. Scrub typhus and murine typhus follow the same rule.
Bioterrorism Agents
Agent Presentation Treatment and prophylaxis
Anthrax ( Bacillus anthracis ) Inhalational: flu-like prodrome, then fulminant mediastinitis with a widened mediastinum and hemorrhagic pleural effusions; hemorrhagic meningitis in a third. Cutaneous: painless black eschar Combination therapy with a fluoroquinolone (plus a protein-synthesis inhibitor such as linezolid or clindamycin when meningitis is possible) and an antitoxin (raxibacumab or obiltoxaximab); drain effusions. Post-exposure prophylaxis is ciprofloxacin or doxycycline for 60 days plus vaccination
Plague ( Yersinia pestis ) Pneumonic: fulminant pneumonia with hemoptysis, person-to-person spread; bubonic: tender adenopathy Aminoglycoside (gentamicin or streptomycin), fluoroquinolone, or doxycycline; droplet precautions; prophylaxis for contacts
Tularemia ( Francisella tularensis ) Pneumonic or typhoidal illness after aerosol exposure; highly infectious in the laboratory Aminoglycoside, or fluoroquinolone or doxycycline; alert the laboratory
Smallpox (variola) Centrifugal, synchronous vesicopustular rash including the palms and soles, with a severe prodrome Isolation, vaccination of contacts, tecovirimat; airborne precautions
Botulinum toxin Descending flaccid paralysis with bulbar onset and clear sensorium Antitoxin plus mechanical ventilation (see the neuromuscular section)
Viral hemorrhagic fevers Fever, bleeding, shock Strict isolation, supportive care, agent-specific therapy where it exists
Varicella can mimic smallpox, but its lesions are asynchronous, centripetal, and spare the palms and soles . Notify public health authorities immediately for any suspected agent of bioterrorism.