MOLECULAR EPIDEMIOLOGY OF GASTRIC COLONIZATION BY ENTEROCOCCUS-FAECALIS IN A SURGICAL INTENSIVE-CARE UNIT

We applied restriction endonuclease analysis of genomic DNA using puls ed field gel electrophoresis (PFGE) to study gastric colonization with Enterococcus faecalis among patients hospitalized in the surgical int ensive care unit (SICU). Isolates were obtained by culturing prospecti vely the gastric contents of 140 patients in the SICU. In addition, cu ltures of respiratory specimens were obtained daily and cultures of bl ood, nor normally sterile body fluids, wounds, and urine were obtained when indicated clinically. A total of 177 isolates were obtained from 45 patients. Concentrations of E. faecalis in gastric fluid ranged fr om 1 x 10(2) colony forming units (CFU)/ml to greater than 5 x 10(7) C FU/ml (mean 8.0 x 10(6) CFU/ml). Overall, 33 different DNA types were identified by PFGE. In examining strain variation among isolates obtai ned from multiple anatomic sites over time, we found that the same DNA type was recovered from gastric aspirates, sputum, and wounds in a gi ven patient and that these strains were carried over time. In general, given individuals were colonized with their own unique DNA type; howe ver, one DNA type (type C) was shared by 11 different patients, and se ven DNA types were shared by two individuals each. These results demon strate the potential importance of gastric colonization as a reservoir for nosocomial strains of E. faecalis in an SICU setting.