Daily and Weekly Urine Variations in Bacterial Growth Susceptibility in Postmenopausal Women With no History of Urinary Tract Infection: A Pilot Study.

Objective: To evaluate bacterial growth in the bladder as a major virulence factor during urinary tract infections (UTIs), we assessed the variability of uropathogenic bacterial growth in urine samples over multiple timepoints from 3 postmenopausal women with no history of UTI.

Methods: Following IRB approval, postmenopausal women who never had a UTI provided mid-stream urine samples 3 times daily (8 a.m., 12 p.m., and 4 p.m.), twice a week over 2 weeks, as well as dietary intake logs. Each sample was studied for pH and bacterial growth using 3 uropathogenic Escherichia coli (E.coli) strains (LRPF007, KE40, UTI89), 1 uropathogenic Enterococcus faecalis strain (HRH40), and 1 non-pathogenic E. coli strain (W3110).

Results: Similar mean growth yields were observed for the uropathogenic strains (mean ∆OD =0.1-0.13) with high variability (standard deviation [SD]= 0.12-0.28) and lower mean growth for the non-pathogenic strain (mean ∆OD =0.05). Urine from each individual at different collection times never had the same bacterial growth potential for any bacterial strain. There were significant associations between urine pH decrease with higher fat (P = .017), vitamin D (P = .02), magnesium (P = .049), fluid (P = .013), and ash (P = .01) intake.

Conclusion: Major variations were observed in the bacterial growth response in the urine of the same individuals. These variations imply a requirement for a normalization procedure, eg, growth in synthetic urine, for analysis of bacterial growth in urine. There were significant associations between decreased urine pH and several nutrients found in foods that are classified as highly acidic.