Epidemiology and clinical consequences of vancomycin-resistant enterococci in liver transplant patients

BACKGROUND

Vancomycin-resistant enterococci (VRE) are increasingly important as pathogens in liver transplant patients. To guide control efforts, we conducted an epidemiological study of the frequency, source, and modes of transmission of VRE at our center.

METHODS

During September 1998 through August 1999, we obtained weekly surveillance cultures from consenting liver transplant patients and surfaces in their rooms. Pooled handwash specimens from personnel also were obtained. Specimens were processed on selective media to detect VRE, and isolates were typed by pulsed field gel electrophoresis. Information was collected from patient records concerning in-hospital treatment and clinical course.

RESULTS

Serial cultures were obtained during 33 admissions of 29 patients. VRE were detected in initial specimens from 6 admissions, and nosocomial acquisition of VRE occurred in 12 (44%) of the remaining 27 admissions. Seven different strain types of VRE were detected. The initial site of acquisition was stool in all cases; bile became culture-positive in only two patients. Overall, 16 (55%) of the 29 patients became colonized, usually after transplantation. VRE were detected in environmental cultures during 10 admissions and in 2 of 21 pooled handwashes. No statistically significant differences in clinical status or treatment were found when colonized patients were compared to noncolonized controls. The only VRE infection resulted from a choledochojejunostomy anastomotic leak.

CONCLUSION

Alimentary tract colonization by VRE occurred commonly in liver transplant patients, probably by cross-transmission. The clinical consequences were modest in the patients studied, but colonized transplant patients provide a substantial reservoir for continued VRE transmission in hospitals.

Endemic contamination of clinical specimens by Mycobacterium gordonae

Contamination of clinical specimens by Mycobacterium gordonae is a significant endemic problem in many laboratories. To investigate this problem, 84 cases at 1 hospital were retrospectively identified during 20 months. The overall rate of specimen contamination was 2. 4%, and 72 of the contaminated specimens were respiratory. A case-control comparison showed that the risk of respiratory specimen contamination was significantly increased if the specimen was expectorated (odds ratio [OR], 3.62; 95% confidence interval [CI], 1. 36-9.50) or if the patient consumed fluids within 2 days before specimen collection (OR, 8.92; 95% CI, 1.40-71.20). Cultures of tap water, ice, and iced drinking water all yielded M. gordonae at 10(-2)-10(0) cfu/mL. A culture survey of consenting patients showed contamination of 8 (24%) of 34 sputum specimens collected immediately after a tap water mouth rinse. These findings demonstrate that endemic specimen contamination arises from mycobacteria in hospital tap water and provide a foundation for control efforts.

An outbreak of bloodstream infections arising from hemodialysis equipment

An outbreak of 29 cases of bloodstream infection by 16 pathogens occurred during 8 months at two chronic hemodialysis centers. Consequences included 21 hospital admissions and removal of 23 dialysis catheters. An epidemiologic investigation comparing case-patients with uninfected controls showed that risk was significantly (P < .05) associated with having a catheter for vascular access; receiving treatment on a Monday, Wednesday, Friday schedule; and receiving treatment on one heavily contaminated dialysis machine. Culture studies and mock trials showed that bloodstream pathogens were present in a recently installed, commercially marketed attachment for disposal of spent priming saline and could enter blood line tubing directly or indirectly during dialyzer priming and tubing assembly. The outbreak was halted by measures directed at the attachment. Investigation of this problem demonstrated that microbial overgrowth in the attachment caused bloodstream infections and underscores the importance of microbiologic considerations in the design and use of hemodialysis equipment.

Pathogenesis of early operative site infections after orthotopic liver transplantation

BACKGROUND

We hypothesized that operative site infections after orthotopic liver transplantation arise from bacteria in bile or jejunum.

METHODS

To ascertain the validity of this hypothesis and to assess the effect of systemic antibiotic prophylaxis, we obtained intraoperative cultures of peritoneum, fascia, explant and donor liver bile, and jejunal lumen in 77 liver transplantations, and we monitored outcome.

RESULTS

Pathogens were recovered from peritoneum, fascia, or bile in 11 cases. By univariate analysis, a positive culture was significantly associated with choledochojejunostomy (P=0.0002), previous liver transplantation (P=0.0002), and previous hepatobiliary surgery (P=0.002). Operative site infections during the first 2 weeks after transplantation occurred only in cases with positive intraoperative cultures, and three of the four infections were caused by the same bacteria detected intraoperatively. Antibiotic susceptibility of intraoperative isolates was tested in nine cases; infection occurred in two of three cases in which the isolates were resistant to the systemic antibiotic prophylaxis and in none of six cases with susceptible isolates.

CONCLUSIONS

Our findings suggest that systemic antibiotic prophylaxis for more than 2 days may be beneficial in cases with bacterial contamination of the operative site but may not be necessary in other cases.