Bacterial colonization and infection in the neonate.

The vast majority of healthy term neonates tolerate their abrupt introduction to the bacterial world with little risk of infection. However, infants who require a longer hospital stay are at greater risk of having an infection, particularly when intensive care is needed. In one study, 15.3 percent of the infants in an intensive care unit acquired a nosocomial infection. Gram-negative bacilli have emerged as the principle cause of nosocomial infection. Nosocomial infection due to gram-negative bacilli usually occurs in neonates already colonized with gram-negative bacilli in the pharynx or intestine, and the risk of colonization with hospital strains of gram-negative bacilli (which are often resistant to multiple antibiotics) increases dramatically the longer a baby stays in intensive care. The factors which predispose individual neonates to colonization and infection with gram-negative bacilli require further study, but gram-negative bacilli are most often transmitted among neonates on the hands of personnel. Neonates in whom intestinal colonization with gram-negative bacilli develops are a particularly important reservoir of gram-negative bacilli in the nursery; once colonized, infants may harbour antibiotic-resistant hospital strains of gram-negative bacilli in their stool for more than a year. Pharyngeal colonization with alpha streptococci appears to protect neonates from pharyngeal colonization with gram-negative bacilli, and bacterial interference may play an important role in regulating intestinal colonization as well. Investigation of the mechanisms of bacterial interference may lead to better understanding of the colonization process and development of alternatives to classic infection control methods.