Factors of bacteriuria in children and young adults following hematopoietic stem cell transplantation

Presence of bacteriuria and urinary microbiota composition is an important index of immunocompromised conditions. These parameters are scarcely studied in patients undergoing hematopoietic stem cell transplantation (HSCT). The aim of this work was to evaluate detection rates of cultured aerobic microbiota from urine samples taken by clinical indications before HSCT and within 4 months after the treatment. The study was approved by the Independent Ethics Committee and the Scientific Council of the I.P. Pavlov First Saint Petersburg State Medical University. We evaluated results of bacterial cultures from 734 urine specimens taken in 50 patients with oncohematological and inborn diseases at the age ranging from 1 to 21 years who were subjected to allogeneic HSCT. The analysis was performed for 3 age groups: 1–5, 6–14, and 15–21 years old. The bacterial cultures proved to be positive with 37.6% of urine samples. The following microbes were revealed at highest rates: K. pneumoniae, 95/734 (12.9%); E. faecalis, 90/734 (12.3%); E. coli, 65/734 (8.9%); E. faecium, 50/734 (6.8%). The bacteriuria rates have shown distinct time dependence, with significantly decreased K. pneumoniae and E. coli detection at earliest terms (1st month) after myeloablative conditioning, which could be explained by effective antibacterial prophylaxis over the time of conditioning and in early posttransplant period. We have shown that the frequency of positive tests for K. pneumoniae и E. coli in these samples were different for distinct age groups, i.e., the positivity rates were significantly higher in youngest children (up to 5 years old) as compared with older age groups, being sufficiently increased 2–3 months after HSCT which may be an index of antibiotic resistance as well as a risk factor for infectious complications of other organs. We have also shown a highly significant increase in K. pneumoniae и E. coli positivity rates when using myeloablative conditioning regimen before HSCT. The immunotoxic effects of cytostatic therapy in HSCT deserve further studies, including biodiversity analysis of urinary microbiota by means of new-generation DNA sequencing. These results may serve as a basis for rational antibacterial therapy in HSCT.