Gram-negative diplococci in CSF and an open-bench centrifuge
On a Monday morning, a 19-year-old student is brought to the emergency department with fever 39.2°C, severe headache, neck stiffness and a non-blanching petechial rash. A lumbar puncture is performed after a CT scan shows no mass lesion. CSF appearance is turbid; cell count 1,800/µL with 85% neutrophils, protein 2.1 g/L, glucose 0.9 mmol/L (serum glucose 6.2 mmol/L). Gram stain shows numerous Gram-negative diplococci. The laboratory technician is working alone in a small room with a class II biological safety cabinet, but the centrifuge is outside the cabinet. The clinician asks for preliminary results immediately and wants to know whether to start ceftriaxone and dexamethasone. The hospital has no infectious diseases physician on call. What should the technician report and do, and what biosafety and public health actions follow?
1. Interpret the CSF findings. What is the most likely diagnosis, and what should be reported as a preliminary result and how urgently?
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Interpretation. Turbid CSF with 1,800/µL, 85% neutrophils, protein 2.1 g/L and CSF glucose 0.9 mmol/L (ratio 0.15) is a bacterial meningitis pattern. Gram-negative diplococci make Neisseria meningitidis the leading cause. This is a critical result and must be phoned immediately, with read-back and documentation.
Clinical advice. Do not wait for culture. The clinician should start ceftriaxone immediately and give dexamethasone before or with the first antibiotic dose if there is no contraindication. Place the patient under droplet precautions for at least 24 hours after effective therapy. Collect blood cultures before antibiotics if this does not delay treatment, and send CSF for culture and, where available, PCR. The laboratory should report the Gram stain as a preliminary finding and state that confirmation is pending.
2. The centrifuge is outside the biosafety cabinet and the technician must perform a Gram stain and culture. What biosafety practices are required, and what should be done if a tube breaks during centrifugation?
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Biosafety. Neisseria meningitidis is a BSL-2 organism with a low infectious dose and risk of aerosol transmission. Gram stain and culture manipulations should be done in the class II biological safety cabinet, with gloves, gown and eye protection. Centrifugation must use sealed safety cups or rotors; if the centrifuge is outside the cabinet, load and unload it inside the cabinet or use a sealed cup, and wait 30 minutes before opening after a spill.
Breakage. If a tube breaks, do not open the centrifuge immediately. Wait, then wear full PPE, use a spill kit, absorb and disinfect with an appropriate disinfectant, discard sharps safely, and report the incident. Seek medical advice and document exposure. Review the SOP and consider moving the centrifuge or using a sealed rotor.
3. By 16:00 the hospital has three more suspected cases among students who share a dormitory. What public health and laboratory actions are indicated, and what specimens should be collected from close contacts?
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Public health. Notify the public health authority immediately; four cases in a dormitory suggest an outbreak. Identify close contacts (household or dormitory roommates, kissing contacts, and anyone exposed to oral secretions) and arrange chemoprophylaxis within 24 hours, for example a single dose of ciprofloxacin 500 mg, or rifampicin or ceftriaxone according to national guidance. Advise contacts to seek care urgently if fever or rash develops. Do not close the whole school unless public health advises.
Laboratory. Send the isolate to the reference laboratory for serogrouping and antimicrobial susceptibility. Collect blood cultures and CSF from new cases; nasopharyngeal swabs may be used for carriage studies but are not needed to decide prophylaxis. Keep a line list and monitor for new cases.