Interstitial Cystitis/ Bladder Pain Syndrome (IC/BPS) is still incompletely understood. Recent work suggests that the urinary microbiome plays an important role. This biological data could have implications in the diagnosis and treatment of IC/BPS. During evaluation of urinary symptoms, a urine culture is collected to rule out a urinary tract infection. We propose that there may be a correlation between low level bacterial counts in urine cultures in IC/BPS in the absence of a clinical urinary tract infection, defined as >100,000 colony-forming units (CFU) of bacteria.  

The objective of this study is to examine the relationship between the findings of low colony-count cultures and patients with IC/BPS.

Patient charts were reviewed from February 2017 through July 2017. Patients with a diagnosis of IC/BPS based on
ICD−10 coding, over the age of 18 were included in our analysis. Urine samples were sent for culture at each visit.
These cultures were assessed for growth, CFU, and type of bacteria. Statistical analysis was used to compare
urine culture results.

Our cohort was comprised of 428 patients, with a total of 826 urine cultures.  Twenty-one of the patients were male (5%), providing 38 (5%) of the urine culture results. 

The most common culture result was no growth, 561 (67.9%), followed by 10,000-50,000 CFU, (112, 13.6%), and then >100,000 CFU (66, 8.0%) (Table 1). The most common types of bacteria found in positive cultures were Enterococcus 26%, E. Coli 15%, Group B Strep (GBS) 13.6%, and Klebsiella 10.6% (Table 2). 

We compared CFU of the four most common bacteria types, Enterococcus, E. Coli, Group Beta Strep, and Klebsiella with a significance value of p< 0.0083.  Enterococcus grew out at lower CFU levels, 10,000-50,000CFU more often than E. Coli (p=0.007). GBS more commonly grew at 100-1000CFU compared to E Coli (p<0.001) and Klebsiella (p=0.001) (Table 3). Males were more likely than females to have no growth and lower colony forming units. When bacteria did grow, excluding contaminated cultures, there was no difference between males and females for type of bacteria.

Our data show that in patients with IC/BPS, urine cultures were significantly more likely to grow bacteria with a
lower CFU, most commonly 10−50,000 CFU. Enterococcus was the most common bacteria. The findings may be
related to several factors including regional microbiome and requires further investigation.

The most common urinary bacteria cultured from patients with IC/BPS were Enterococcus, E. coli, group B Streptococcus (GBS), and Klebsiella. In patients with IC/BPS these bacteria tend to culture out at lower CFU than 100,000 CFU. Clinicians can consider treating patients with IC/BPS with urinary cultures positive for bacteria with less than 100,000 CFU at this time.

This study emphasizes the need for making the DNA sequencing tests more available and more research into the microbiome of healthy bladders compared to those with IC/BPS. This area is poorly understood and may cause unnecessary use of antibiotics in patients with IC/BPS symptoms and re-addresses the role of infection in IC/BPS. It is still unclear if we should be treating patients with IC/BPS who have bacterial cultures of <100,000 CFU. Although, the most common growth count in this study were <100,000 CFU, knowing the microbiome of the healthy bladder and in IC/BPS patients can help to answer that question.

Human Microbiome Project, C., Structure, function and diversity of the healthy human microbiome. Nature, 2012. 486(7402): p. 207-14
Brubaker, L. and A.J. Wolfe, The Female Urinary Microbiota/Microbiome: Clinical and Research Implications. Rambam Maimonides Med J, 2017. 8(2)
Brubaker, L. and A.J. Wolfe, The female urinary microbiota, urinary health and common urinary disorders. Ann Transl Med, 2017. 5(2): p. 34