Infectious Diseases and Clinical Microbiology
Sepsis
Recognise sepsis early, take cultures, measure lactate and give broad-spectrum antibiotics within one hour, with 30 mL/kg crystalloid for hypotension or high lactate, and vasopressors to keep mean arterial pressure at 65 mmHg or above.
Central nervous system infection
Do not delay antibiotics for lumbar puncture when there are signs of raised intracranial pressure or focal neurology - image first, and give dexamethasone with or just before the first antibiotic dose in suspected bacterial meningitis.
Endocarditis, HIV and tropical infection
Endocarditis is diagnosed using the Duke criteria, with three sets of blood cultures before antibiotics and echocardiography (transoesophageal if transthoracic is negative but suspicion remains). In HIV, a CD4 count below 200 cells/µL prompts prophylaxis against Pneumocystis jirovecii. Falciparum malaria with severe features is treated with intravenous artesunate.
Antibiotics and stewardship
Stop unnecessary antibiotics, review at 48 hours and narrow according to culture. Clostridioides difficile colitis follows antibiotic use; stop the culprit drug and give oral vancomycin or fidaxomicin. Distinguish true IgE-mediated allergy from gastrointestinal intolerance, which is often mislabelled.
Worked example: CSF with 2000 white cells (90% neutrophils), protein 2.5 g/L, glucose 1.0 mmol/L against serum glucose 6.0 mmol/L (ratio 0.17) and lactate 6 mmol/L indicates bacterial meningitis - start empirical cephalosporin plus dexamethasone now; do not wait for culture.
Trap: assuming a normal CSF glucose excludes meningitis, and forgetting that partially treated meningitis gives a lymphocyte-predominant picture.