Dip slide culture of intraoperative peritoneal irrigation fluid for prediction of septic complication in elective colorectal surgery.

A controlled prospective study of a simplified technique, the dip slide culture method, for assessment of bacterial concentration in peritoneal irrigation fluid at the end of an elective colorectal operation is presented. The prediction of postoperative surgical infection based on intraoperative culture was compared between this method and a standard streak-plate technique in 190 patients. One gram of metronidazole was given intravenously as prophylaxis on induction of anesthesia and 12 h postoperatively. Intraoperative growth of members of the family Enterobacteriaceae or Staphylococcus aureus was strongly correlated to infection (P less than 0.001). By using this finding as a single criterion for the prediction of sepsis, sensitivity and specificity for the dip slide method were 70.8 and 94.3%, respectively, compared with 79.2 and 94.6%, respectively, for the streak-plate method. Of the 24 infections, 20 (83.3%) were correctly predicted when a combination of the two methods was used. An increasing number of Enterobacteriaceae or S. aureus in the dip slide culture resulted in a steady rise in the rate of infections from 5.7% at 0 CFU to 57% at greater than or equal to 80 CFU compared with 4.1% at 0 CFU/ml and 45.4% at greater than or equal to 800 CFU/ml with the streak-plate method. The differences were statistically significant at the greater than or equal to 5 CFU level with regard to wound infection (P less than 0.001) and deep surgical infection (P less than 0.01). It is concluded that the dip slide is a simple, rapid, and reliable method for the routine assessment of bacterial contamination in colorectal operations.