Discussion
Post-transplant UTIs in kidney transplant patients are important causes of acute graft dysfunction. Increased morbidity and hospitalization rates are further major consequences of UTIs in kidney transplant recipients. Therefore understanding and exploring the UTI details is very crucial in transplant practice. In our study we found that UTI incidence in the first year after transplantation was 20.5%. Although the incidence of UTI in kidney transplant recipients have been reported ranging between 7%-80% depending on the diagnostic criteria used, our UTI rate is relatively lower than reported in the other studies where the first year UTIs are evaluated [1, 4, 14, 15]. In our study a lower rate of asymptomatic bacteriuria was found. The explanation for lower rate of ABU may be that a regular screening program was not used and urine culture studies were only performed in patients with UTI symptoms or pyuria in urinalysis observed during regular visits. Most patients with UTI attack presented as LUTI. CUTI incidence was found to be 34.3%. Three attacks were progressed into bacteremia. The relatively mild course of UTI attacks might result from early detection and immediate antibiotic treatment in our cohort.
It has previously been reported that, early (<3 weeks after transplantation) ureteric stent removal is associated with a lower rate of UTIs [16,17]. In our center we have not been followed this approach. Even though, presence of longer duration of ureteral stent was found in our cohort, we did not find higher rate of UTIs. Other factors such as, age, a longer duration of indwelling urinary catheter and presence of urologic complications, stood out as important risk factors in our patients. Thus, we recommend that patients with risk factors should be carefully screened for LUTI, CUTI and ABU.
The rates of UTI caused by ESBL-producing organisms were high in our cohort. More than half of UTI patients were exposed to at least one episode of UTI with MDROs. According to a recently published study from Australia, the authors isolated an ESBL-producing organisms in only 3,9% of urine cultures [18]. Bodro et. al. demonstrated that 37% of bacteria considered as MDROs in kidney transplant recipients’ UTIs [10]. Nevertheless, there are some studies showing higher rates of UTI with MDROs in kidney transplant recipients similar to our findings [19,20]. This finding gave us the opportunity to explore our infection control methods and came to a conclusion that, prophylactic use of quinolones up to seven days postoperatively may be responsible from the high rate of UTIs with MDROs [11]. Changing our method of prophylaxis was the most important consequence of this study. We stopped prophylactic use of quinolones in our practice in line with study results.
There are many studies showing that urinary tract infections are more common in female recipients [1,4,5]. However, there are also some studies that did not find any difference with respect to gender [7, 22, 23]. Interestingly, in our study, we showed that recurrent urinary tract infections with resistant microorganisms are more common in male transplant recipients. Male recipients also presented more often with CUTI. Therefore, our data suggest, starting treatment with a wide-spectrum antibiotic may be warranted for UTI infections in male transplants since they tend to be caused by resistant microorganisms and have a tendency to recur. There are studies in both the general population and the transplant population to support these findings [24-27]. Urinary outflow obstruction, possible prostatitis, and inadequate response to antibiotics due to long uroepithelial tissue compared to women are the mechanisms that explain this situation.
It is important to emphasize that, a UTI caused by ESBL-producing microorganisms carries an almost three times greater risk of recurrence [6]. Brakemeir et al reported that recurrence rate of UTI with ESBL producing bacteria was found to be 54% [21]. Our findings were also consistent with this previously published data.
These results should be interpreted with caution due to the single center and retrospective nature of the study and the relatively small number of patients. The low number of events limits further statistical analysis for exploring exact effect of male gender on resistant and recurrent UTIs.
In conclusion, our results shed an interesting perspective on UTI in kidney transplant recipients. We strongly believe that each center should explore their own UTI risk factors and causative agents that will direct them to manage these patients correctly. This study also highlights the importance of monitoring causative agents of UTIs, especially in male gender, in order to improve empiric therapy in transplant practice.