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384 ENVIRONMENTAL CONTAMTNATTON of CONTINUOUS DRIP FEEDING SYSTEMS

Continuous gastric and transpyloric feeding techniques have been advocated for low birth weight infants, but bacterial surveillance studies of these systems have not been reported. A preliminary investigation in our nursery showed that 176/576(31%) of formula samples obtained from the drip chamber were contaminated. Using the same feeding system with a broth of E. coli simulating the infant's stomach, 0/151 specimens of formula were contaminated, thereby eliminating the ascending route as the bacterial source. No positive cultures were obtained from 40 randomly sampled bottles of formula which were opened and exposed to room air for 8 hours. A prospective study in 115 infants showed that 255/902 (28%) of cultures from formula drip chambers were positive, but the presence of a vacuum flutter valve in the reservoir and the number of times formula was added to the chamber did not significantly affect the incidence of positive cultures. Milk reservoirs changed every 24 hours did not have a significantly different contamination rate from those changed every 12 hours. When cultures of formula were obtained from the original mixing bottle after being discarded by the nurse, 50/64 (78%) powdered formulas and 94/339 (28%) liquid formulas were positive. This study demonstrates a very high rate of bacterial contamination of infant formulas administered by continuous drip, elucidates contributing environmental factors, and emphasizes the need for meticulous care in formula mixing techniques.