Lactate production by aerobic bacteria grown in cerebrospinal fluid

The source of the abnormally high concentration of lactate in the cerebrospinal fluid in patients with bacterial meningitis is not known. It may represent a bacterial metabolite. To determine whether cerebrospinal fluid possesses appropriate substrates to support the growth of pathogenic aerobic bacteria, three Gram-positive and nine Gram-negative bacteria were separately inoculated in pooled normal cerebrospinal fluid. After incubation for 24 h, all Gram-positive bacteria increased lactate, eight Gram-negative bacteria decreased lactate, and one Gram-negative bacteria failed to significantly change the lactate concentration. We conclude that lactate produced in cerebrospinal fluid in patients with aerobic bacterial meningitis is not necessarily a bacterial metabolite.