Method This is an experimental prospective study carried out on 3-month to 12-year-old children. The data were collected by observing patients diagnosed with bacterial meningitis, hospitalised and treated, in a hospital paediatrics ward from March 2001 to March 2003. The subjects were selected by convenient sampling. There were two groups, with group A including 20 meningitis patients taking oral antibiotics such as amoxicillin, ampicillin, erythromycin over 24 h before referral to hospital and group B including 20 meningitis patients not taking any antibiotics. Just after hospitalisation the first lumbar puncture (LP) was done.

Results The findings showed CSF culture negative in all 25 samples in group A, whereas there were biochemical changes suggesting bacterial meningitis in CSF of the subjects, but in group B in which all samples had not taken antibiotics there were 13 cases (60%) of positive CSF culture regarding microorganisms such as Meningococcus, Streptococcus and Escherichia coli. The number of cells in the first group taking antibiotics was between 120 and 3170, with mononuclear domination, while that was in the second group, not taking any antibiotics, as 220 to 3910 with polymorph nucleon domination. Regarding sugar and protein in CSF, there was no change in both groups. So, taking antibiotics before LP can affect meningitis microorganism and make LP culture negative. According to the findings, oral antibiotics can possibly have no serious effect on CSF cells except for leucocytes.