Pediatricians have always had a difficult time defining the neonatal period. Is it 7, 28, 30, or 60 days, or some other length? The dispute is not academic. As two reports in this issue highlight (see pp 1052 and 1055), there are features of certain diseases that are age dependent and for which different strategies apply. In the present instance, the issue is the selection of antibiotics with which to treat infants whose symptoms are suggestive of, or who have, bacterial meningitis.
At one time, it was simpler. Infants younger than 1 month of age had Escherichia coli and other Enterobacteriaceae as the predominant organisms, and those older than 1 month of age experienced infection with Hemophilus influenzae type b and Streptococcus pneumoniae most commonly, with Neisseria meningiditis a distant third. One could then design initial antimicrobial regimens based on these "facts" and be almost certain that one was using