Summary

A temporal lobe abscess was diagnosed in a 57-year-old man. A urethral catheter had been inserted 12 days earlier, just prior to clot evacuation of a subacute haematoma secondary to an arterio-venous malformation. Fever persisted despite debridement and treatment with meropenem and vancomycin. Gram stains of operative samples showed no bacteria. Extended cultures grew pinpoint colonies after 5 days. Meanwhile, sequencing of bacterial 16S rDNA from operative specimens had identified Mycoplasma hominis; the bacterial colonies were subsequently similarly identified. The patient responded promptly following addition of oral doxycycline 100 mg two times per day. There is a growing literature of similar cases. Transient bacteraemia, following urinary catheterisation, with seeding of existing sites of inflammation is the proposed explanation. Urethral carriage of M. hominis is 15% and catheterisation is a common procedure. Mycoplasma hominis maybe more common than appreciated, especially as the need for extended cultures makes a correct diagnosis less likely.