Infectious Disease
Core concepts
Sepsis recognition and source control, meningitis, endocarditis, pneumonia, tuberculosis, HIV, Clostridioides difficile, and skin and soft tissue infection dominate. Sepsis care begins with cultures and broad-spectrum antibiotics within the first hour for septic shock, plus fluids and lactate. Bacterial meningitis shows neutrophilic pleocytosis, low glucose, and high protein; give dexamethasone with or before the first antibiotic dose in suspected pneumococcal disease. Infective endocarditis uses modified Duke criteria and blood cultures before antibiotics when the patient is stable.
Traps
- Delaying antibiotics to obtain cultures in unstable sepsis.
- Withholding dexamethasone until after antibiotics in suspected pneumococcal meningitis.
- Treating C. difficile with antimotility agents or continuing the offending antibiotic unnecessarily.
- Missing that a new murmur plus fever demands echocardiography.
- Starting ART in cryptococcal meningitis too early.
- Ignoring tuberculosis isolation and contact tracing.
Worked example
CSF in a 45-year-old with fever, neck stiffness, and confusion: opening pressure elevated, 2,400 white cells with 88% neutrophils, glucose 28 mg/dL (serum 110), protein 180 mg/dL. This is bacterial meningitis. Start empiric vancomycin plus ceftriaxone, add dexamethasone before or with the first dose, and do not wait for culture. Rule of thumb: in meningitis, the LP result guides refinement, but the first antibiotic is chosen by age and risk factors.