Objective: To describe the incidence and clinical characteristics of mycobacterial infection in renal transplant recipients.
Methods: We retrospectively analyzed the cases of mycobacterial infection in a series of 1261 renal transplants carried out in our Unit of Renal Transplantation from 1980 to 2000. Demographic parameters and clinical antecedents such as age, cause of end-stage renal disease, time of follow-up of the graft, previous renal function and type of immunosuppression were considered. Moreover, the clinical onset, diagnostic tools, treatment policy and evolution were studied. The pathogenesis of the different types of mycobacteria isolated was also analyzed. Diagnosis was made with the Ziehl-Neelsen staining method. Culture was performed by the conventional Löwenstein-Jensen method and the Bactec-460 radiometric method.
Results: We found mycobacterial infection in 27 patients (2.1%), due to Mycobacterium tuberculosis in 20 cases, M. kansasii in five patients, and M. fortuitum in two patients. The mean elapsed time from the renal transplant was 20.5 months; the infection appeared in 18 patients during the first eight months after transplantation. The clinical onset was pulmonary infection in 17 cases (12 M. tuberculosis and five M. kansasii); five had urinary symptoms (three M. tuberculosis and two M. fortuitum); three cases of M. tuberculosis infection had abdominal symptoms; another one began with a perineal tuberculous abscess; the rest of the patients were asymptomatic. The types of specimen on which microbiological identification was carried out were, in decreasing order: sputum and/or bronchial washing/pleural aspiration, urine, feces, gastric and peritoneal fluids, bone marrow and blood. The first-line drug isoniazid had the highest resistance index in the susceptibility test. Clinical dissemination was observed in eight patients, four of whom died. Another three patients had a significant impairment in renal function, and in one of these patients an allograft nephrectomy was necessary due to a severe septic syndrome.
Conclusions: Mycobacterial infection, mainly by M. tuberculosis, has an important impact on kidney transplant recipients, particularly during the first year after surgery. Diagnosis often presents some difficulties, and a delay in treatment represents a determinant factor for the evolution, with a risk of death or permanent damage in renal function. Therefore, early diagnosis is mandatory. When the Mantoux reaction is positive, antituberculous prophylaxis seems advisable.