The presence of bacterial communities (microbiota) in the urinary bladder of adults is now well known and associations between bladder microbiota profiles and lower urinary tract symptoms (LUTS) have also been demonstrated. To date, it has not been established when the bladder microbiota becomes established and if such a microbiome exists in children. The purpose of this study was three-fold: 1) determine if a pediatric bladder microbiota exists, 2) compare the pediatric microbiota profiles of several urogenital sites, and 3) determine if differences exist in the urinary microbiota of children depending on voiding symptoms. We hypothesized that children do possess bladder microbiota, that bladder microbiota share some similarities with the microbiota of other urogenital sites, and that differences in  the bladder microbiota occurs based upon the presence or absence of voiding symptoms.

With IRB approval (201608793 (University of Iowa), 15-16363 (University of California, San Francisco)), 31 children were recruited. A validated voiding symptom questionnaire was completed and the following samples were collected: transurethral catheter catheterized urine (TCCU), perineal skin swab (PSS), urethral skin swab (USS), vaginal skin swab (VSS), and foreskin swab (FS). Samples were shipped overnight on ice to Loyola University Chicago. The specimens were assessed using the expanded quantitative urine culture (EQUC) protocol which is designed to detect bacteria and yeast found in pelvic floor samples. Bacteria and yeast detected by EQUC were isolated and then identified using Matrix Assisted Laser Desorption/Ionization - Time of Flight Mass Spectrometry (MALDI-TOF MS). The microbiota from each participant and/or sample type were clustered using the Bray-Curtis dissimilarity index via silhouette using R studio.

The 31 participants included 21 males and 10 females. 11 of 21 (52%) TCCU samples from males and 5 of 10 (50%) TCCU samples from females were EQUC-positive. 19 of the 28 (68%) USS samples were EQUC-positive. 24 of 28 (86%) PSS samples were EQUC-positive. 6 of 7 (86%) FS samples were EQUC positive. 8 of 10 (80%) VSS samples were EQUC-positive. 
Of the 31 participants, we collected symptom questionnaires from 27 participants; of those 27, only 4 were without voiding dysfunction. Of these 4 participants, only one had a positive TCCU sample. Therefore, the current sample size is too small to identify associations between bladder microbiota and voiding symptoms.

In terms of colony forming units per ml, the bladder microbiota in the samples were low biomass (0- 2340 CFU/mL, median of all TCCU samples is 10 CFU/mL, median of positive TCCU samples only is 40 CFU/mL) and most were composed of one genus (56%); only 2 EQUC-positive samples were composed of more than 2 genera (12.5%). 
There does not appear to be a relationship between the presence of cultivated microbes and the age of the participant; there also does not appear to be a relationship between age and the microbial profile or microbial abundance (Figure 1).
After subsampling by sex, we clustered the samples using the Bray-Curtis dissimilarity index via silhouette. For females, microbiota profiles trended toward clustering by participant, meaning that different samples from one participant tended to cluster together. For males, the profiles trended toward clustering by site, meaning that samples from different sites between participants would cluster together.

Cultivatable microbes can be detected in the bladders of approximately 50% of children. The TCCU samples were often low biomass and often featured only one genus. In females, the microbiota of the different urogenital sites appeared to be similar within the individual; in males, the microbiota of the different urogenital sites appeared to be similar by sampled site. Ongoing investigation is required to determine a possible relationship between pediatric voiding symptoms and the bladder microbiota in children.