Abnormal colonization of neonates in an ICU: conversion to normal colonization by pharyngeal implantation of alpha hemolytic streptococcus strain 215.

Normal bacterial flora provide a natural defense mechanism against infection. Our experience indicates that "normal" flora for the ICU neonate contains alpha hemolytic (alpha-) streptococci as the predominant organism. The purpose of the current investigation is to study the feasibility of implanting a carefully selected, naturally occurring strain of alpha-streptococcus in the nasopharynx of neonates considered to be at high risk of infection because of the abnormal colonization of their pharynx with potential pathogens. Twenty-two infants in the neonatal intensive care unit have received nasopharyngeal implantation with strain 215 alpha-streptococcus. In 16 infants, alpha-streptococci, including the implant strain in pure or mixed alpha-streptococcal populations, constituted the predominant pharyngeal flora within 48 to 72 hr of implantation. The implant strain was not recovered from the remaining six infants. The procedure was apparently innocuous in this small number of patients. We conclude that implantation of a streptococcus can be established in the pharynx of infants abnormally colonized with pathogenic organisms in high titer and that successful implantation of strain 215 can result in prompt development of normal pharyngeal flora, with alpha-streptococci predominant, within 48 hr. There has been no evidence of infection or other adverse reaction caused by the implant strain.