Enterococcus species are the most frequent cause in the first six months; then it is Escherichia coli.
WASHINGTON, D.C.—Researchers who studied symptomatic UTIs in renal transplant recipients found that Enterococcus species are the most common causative pathogens within the first six months following renal transplantation. After six months, Escherichia coli emerges as the most common UTI-causing organism.
“What is interesting in this study is that the microbiology suggests that the bacteria change with time,”said lead study investigator Jose Raygada, MD, an infectious diseases fellow at Wayne State University in Detroit. He reported study findings here at a joint meeting of the Interscience Conference on Antimicrobial Agents and Chemotherapy and the Infectious Diseases Society of America.
One reason Enterococcus species are the most common pathogens in the first six months following transplantation is that patients are in the hospital, where Enterococcus species are frequent nosocomial pathogens, Dr. Raygada said. Another reason is that patients often receive prophylaxis with trimethoprim/sulfamethoxazole (TMP/SMX), which covers gram-negative bacteria, not gram-positive bacteria such as Enterococcus.
Dr. Raygada and his colleagues reviewed the medical records of 284 adults who received a kidney transplant between July 2001 and December 2007. The mean post-transplant follow-up was 1,506 days (range 240-2,456 days). All recipients were given TMP/SMX prophylaxis for six months. Of the 284 patients, 70 (mean age 50.6 years) had a total of 165 UTIs and 214 (mean age 46.6 years) did not have UTIs. Eighteen patients (mean age 51.4 years; 78% female) had recurrent UTIs (mean age 51.4 years).
Overall, the most common pathogens among the 70 UTI patients were E. coli (36%), Enterococcus (19%), and Klebsiella (15%). During the first six months after transplantation, however, Enterococcus species caused 35% of UTIs and E. coli caused 14%. After six months, E. coli caused 46% of the UTIs.
Twelve percent of the UTIs occurred within four weeks of transplantation; 18% occurred between one and six months and 70% occurred more than six months after transplantation. Compared with patients who did not experience UTIs, those who did were more likely to be female (61% vs. 31%) and more likely to have diabetes (43% vs. 26%). Donor source, retransplants, delayed graft function, presence of ureteral stents, and steroid use were similar in both groups.
“UTIs are common in kidney transplant patients, and we need to continue to give prophylaxis; during the first six months, you should never [assume] the problem is related to the common organism E. coli,” Dr. Raygada said.