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Study finds greater risk of meningitis if antibiotics prescribed in the preceding year

The risk of viral or bacterial meningitis was doubled following prescription of antibiotics in the previous 12 months, according to a new study published in the British Journal of General Practice.

There was a dose-response, with patients who had four or more antibiotic prescriptions in the previous 12 months having a stronger association with meningitis, particularly bacterial meningitis.

The authors, from King’s College London, caution that because this is an observational study they cannot be certain if this relationship is causal, as an underlying factor may explain the results. For example, the link between antibiotics and meningitis could reflect an ongoing susceptibility to infections, which led to patients going to the GP and being prescribed antimicrobials for a variety of infections, including meningitis.

The study analysed electronic health records from 685 UK general practices for patients of all ages and found 7,346 people who developed meningitis between 1992 and 2014. These cases were compared to 29,384 people who did not develop meningitis and were matched for factors such as age.

Professor David Armstrong, lead author of the study from the King’s Division of Health and Social Care Research, said: “Meningitis was more common following antibiotic prescription, which could be the result of antibiotics lowering the threshold for later infections. This could be through disturbance of the patient’s nasal microbiome or through other mechanisms. These findings may be another reason for caution in prescribing antibiotics.”

The researchers hypothesised that the antibiotics may have affected the body's natural defences by changing the pattern of commensal bacterial growth in the upper air passages.

Meningitis is an infection of the protective membranes that surround the brain and spinal cord, which can have bacterial or viral causes. A common bacterial cause of meningitis is meningococcal bacteria, such as Neisseria meningitides, which are carried by many people in their nasal passages.

 ‘The relationship between prior antimicrobial prescription and meningitis: a case-control study’ by Armstrong et al is published in British Journal of General Practice and can be accessed here.