Impact of ampicillin and cefuroxime on bacterial colonization and infection in patients on a neonatal intensive care unit.

The impact of ampicillin and cefuroxime on the bacterial flora of neonates was examined in a neonatal intensive care unit (NICU). For the first period of study (January-September 1989), ampicillin plus gentamicin were used as empirical therapy of infection. During this time, 92.6% of all Gram-negative bacilli (GNB) were resistant to ampicillin and 56.6% to cefuroxime. These percentages decreased significantly (P < 0.05) to 60.0% and 16.2% respectively, over the next period of study (October 1989-October 1990) when cefuroxime+gentamicin were used. A decrease in the number of cases of GNB from bacteraemia and meningitis was also significant (from 21.2% to 11.2%), and this correlated with a decline in the occurrence of Klebsiella pneumoniae. However, the number of enterococcal isolates and cases of enterococcal bacteraemia increased. These observations underline the important effect of ampicillin and cefuroxime in modulating the bacterial flora and its antibiotic resistance in patients on a NICU.