The Kaiser Permanente early onset sepsis calculator gives a great insight into this problem ... http://www.dor.kaiser.org/external/DORExternal/research/InfectionProbabilityCalculator.aspx
Anyway from the data provided the EOS risk is very low and observation is all that is needed unless clinical features of sepsis appear.
By the way, why wait to stop antibiotics at 48 hours? EOS cultures are almost always positive by 24 hours or not at all.