The bacterial flora of neonates in intensive care-monitoring and manipulation.

Unlike healthy babies, newborns hospitalized in the neonatal intensive care unit (NICU) are colonized with bacterial flora that reflects their exposure to pathogens in the NICU, not bacterial acquired from mother in the perinatal period. For example, nosocomial Gram-negative bacilli, such as klebsiella, enterobacter, and citrobacter but not Escherichia coli tend to colonize the gastrointestinal tract. Colonization with Gram-negative bacilli generally is a prerequisite for nosocomial infection with these pathogens, but surveillance cultures may not be a cost effective approach to predicting which babies will ultimately become ill. However, screening cultures to detect the emergence of antibiotic-resistant Gram-negative bacilli facilitate containment and guide empiric antibiotic therapy, and surveillance cultures are necessary to detect colonized babies when nosocomial Gram-negative bacilli become epidemic in the NICU. Such cultures are inexpensive and easy to perform if appropriate selective media are used. Surveillance cultures to detect coagulase-negative staphylococci, which numerous investigators claim are increasingly important NICU pathogens, are of little value since colonization is virtually universal in the first week of life. Documentation of colonization with group B streptococci or Staphylococcus aureus also cannot be justified on a routine basis. Screening for methicillin-resistant S. aureus, however, may be indicated since early detection of these strains can limit dissemination in the NICU. Research aimed at restoring colonization resistance with elements of normal bacterial flora or preventing colonization by nosocomial pathogens is in its infancy.