Five years of cefotaxime use in a neonatal intensive care unit.

In 1983 our antibiotic regimen for suspected neonatal septicemia was changed from amoxicillin-gentamicin to cefotaxime-amoxicillin. During the subsequent 5-year period we studied the effect of this change in regimen on the bacterial flora of the infants in the unit and the occurrence of serious infections. This was done with bacteriologic surveillance and analysis of the positive blood cultures from 1978 through 1987. A change in the relative numbers of isolated pathogens was observed; Klebsiella sp. and Escherichia coli decreased whereas Enterobacter sp. increased. The susceptibility of the Enterobacter isolates to cefamandole decreased from 85.3% in 1982 to 52.9% in 1983. The susceptibility of these bacteria to cefotaxime was 55.2% in 1983 and 55.0% in 1987. No change in susceptibilities to cefotaxime, amoxicillin or gentamicin was found in other pathogens. Although colonization with Enterobacter strains has increased and the susceptibility of these bacteria to the cephalosporins has decreased, the incidence of serious infections with Gram-negative bacteria decreased.