The Detection of Microbial DNA in the Blood

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Abstract
The purpose was to determine the sensitivity of detecting microbial DNA in the blood of surgical patients as a measure for diagnosing systemic infection and/or translocation from the gut. Microbial infections and translocation of intestinal bacteria are thought to contribute to multiple system organ failure, but bacterial cultures are often negative in patients with this complication. DNA was extracted from the blood of 40 surgical patients and 20 healthy controls. Polymerase chain reaction (PCR) techniques were used to amplify genes from Escherichia coli, Bacteroides fragilis, and a region of 16S ribosomal RNA found in many gram-positive and -negative bacteria. Bacterial DNA genes were not detected in healthy volunteers but were found in all patients with positive blood cultures. All eight transplant patients receiving OKT3 therapy had microbial DNA in their blood, possibly indicating translocation from the gut. Sixty-four percent of critically ill patients had microbial DNA detected in their blood, but only 3 (14%) had positive blood cultures. The PCR method is more sensitive than blood cultures for detecting bacterial components in the blood of critically ill surgical patients and may detect microbial translocation from the intestine.