Growth of microorganisms in total parenteral nutrition mixtures and related clinical observations.

The effect of lipid addition to TPN (Total Parenteral Nutrition) solutions on microbial growth was investigated. Staphylococcus epidermidis, which failed to grow or grew poorly in the absence of lipid, reached greater than 10(4) cfu/ml (colony forming units per ml), from an initial inoculum of approximately 50 cfu/ml after 24 h when lipid was added. Candida albicans grew more slowly in the presence of lipid, but nevertheless reached 10(4) cfu/ml after 40 h incubation. Klebsiella aerogenes grew readily in all solutions, whereas Escherichia coli failed to grow in any solution. Growth of S. epidermidis and K. aerogenes was improved when the inoculum consisted of starved cells; however, growth of starved cells of C. albicans lagged behind that of unstarved cells. The ability of S. epidermidis to grow in lipid-containing TPN mixtures is particularly important, since this organism is frequently associated with sepsis. In an infant surgical unit, where TPN is under the care of a nutrition team, samples of TPN fluids and giving sets were examined for microbiological contamination at the end of the 24 h administration period. Contamination was found in eight of the 98 systems examined from eight patients. The organisms were identified as coagulase-negative staphylococci and diphtheroids.