Dietary metabolites and urine acidity may affect the growth of bacteria in the urinary tract, potentially opening new avenues for treating urinary tract infections, according to a new study published in The Journal of Biological Chemistry (2015; 290:15949-60).
To investigate the body’s natural defenses against UTI, researchers at Washington University in St. Louis cultured Escherichia coli bacteria in urine from healthy volunteers and compared how effectively the antimicrobial protein siderocalin (SCN) hampered bacterial growth in different samples. During UTIs, cells in the urinary tract secrete SCN to inhibit bacterial proliferation by interfering with uptake of iron that the bacteria need to grow. SCN activity varies widely from person to person.
The authors considered what characteristics in the urine of healthy volunteers might influence the antimicrobial effectiveness of SCN. They found that elevated urine pH and small molecules called aryl sulfates, produced when gut microbes metabolize food, exerted a strong effect on SCN’s antibacterial activity.
Changing pH by itself promoted or inhibited bacterial growth in urine, the study showed, which could affect therapy for UTI. Acid urine has long been thought to reduce bacterial growth, but surprisingly, less acidic urine, with a pH closer to neutral, had a stronger effect on SCN activity than more acidic samples.
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