Bacterial colonization of neonates admitted to an intensive care environment

In order to elucidate some of the factors responsible for the high rate of nosocomial infection associated with neonatal intensive care, we studied bacterial colonization in 63 infants admitted to a neonatal intensive care unit. In a six-month period, cultures of nose, throat, umbilicus, and stool were obtained on admission and every three days from all infants staying in the NICU greater than or equal to 3 days. Study infants did not develop "normal" aerobic flora. Forty-eight percent of infants grew Escherichia coli from stool, but 52% had stool colonization with Klebsiella, Enterobacter, or Citrobacter, the only other Enterobacteriaceae encountered. KEC were also isolated from throat, nose, and umbilicus in 22%, 22%, and 24% of patients, respectively. The risk of stool colonization with KEC increased with duration of hospitalization: 2% of infants were colonized on admission, 60% after 15 days, and 91% after 30 days. Stool colonization with E. coli seemed to protect infants from colonization with other gram-negative bacilli. Thirteen of 20 infants, however, developed pharyngeal GNB colonization in spite of pre-existing abundant growth of alpha streptococci. Antibiotic therapy for greater than 3 days was associated with the isolation of KEC in stool and GNB in the throat, but birth weight less than 2,500 gm and lack of breast milk feedings were not.