Semiquantitative cultures and routine tip cultures on umbilical catheters.

One hundred and fourteen umbilical catheters (79 arterial and 35 venous) were cultured with a semiquantitative technique. Twelve cultures were SQC positive with greater than or equal to 15 colonies, and all but two of these had greater than or equal to 100 colonies. Organisms usually considered to be pathogens were associated with SQC positive catheters, whereas organisms generally considered nonpathogens were associated with less than 15 colonies on SQC. Therefore SQC may help to differentiate between contamination and infection related to umbilical catheters. The one case with purulence at the cord base grew 100 colonies of Staphylococcus epidermidis on SQC. S. epidermidis showed a bimodal distribution in colony count and should be considered as a pathogen when high colony counts are present. Duration of catheterization was longer in SQC positive catheters. Empiric antibiotic use was associated with negative SQC. Further study is indicated in a newborn population with a lower rate to antibiotic use for correlation of SQC results with catheter-induced bacteremia and sepsis.