Gut microbiota imbalance linked to higher UTI risks in women

A recent Nutrients journal study investigates the association between gut microbial dysbiosis and risk factors in women with a history of urinary tract infections (UTIs).

Study: Associations between Gut Microbiota Dysbiosis and Other Risk Factors in Women with a History of Urinary Tract Infections. Image Credit: mi_viri / Shutterstock.com

What causes UTIs?

UTIs are common bacterial infections that affect over 150 million people worldwide. Compared to men, UTIs are more prevalent among adult women, with 50-60% of women experiencing them at some point in their lifetime.

The frequent use of antibiotics to treat UTIs may lead to the emergence of antibiotic-resistant bacterial strains. Antibiotics also reduce the abundance of beneficial gut bacteria and increase pathogenic strains, which could cause UTI recurrences.

Several studies have indicated that gut microbial dysbiosis leads to kidney illnesses and UTIs through the intestine-kidney axis. Most UTIs are caused by uropathogenic Escherichia coli (UPEC), Klebsiella spp., Enterobacter spp., Staphylococcus spp., Proteus spp., and Enterococcus spp.

Patients infected with UPEC strains experience recurrent UTIs (rUTIs). Previous studies have shown that UPEC strains differ from commensal E. coli in terms of their genetic makeup, which encodes for toxins, flagella, surface polysaccharides, and iron acquisition factors.

E. coli residing in the intestine can reach the urinary tract through migration or contamination to ultimately cause UTIs. One previous study has shown that gut microbial dysbiosis exacerbates pathogenic bacterial growth that may reach the urinary tract and cause UTIs.

Strain analysis has revealed similar E. coli strains in the intestine and urinary tract, supporting the theory of the gut microbiota-UTI axis. Thus, it is important to understand whether gut microbial dysbiosis influences the repeated occurrence of UTIs.

About the study

Women between the ages of 18 and 45 years who were diagnosed with UTIs in the past five years were selected for the current study. Women with two or more episodes of symptomatic UTIs in the previous six months or more than three UTIs in the previous year were categorized under rUTIs.

Uropathogenic bacteria were isolated from participants’ urine samples. Another study group comprised women who had not contracted UTIs in the previous 12 months; however, these individuals had a history of sporadic UTIs, which is also known as non-recurrent UTIs (nUTIs).

Women with comorbidities such as renal lithiasis, immunosuppressive states, neurological conditions, surgical interventions of the urinary tract, constipation, and diabetes were excluded, as these conditions can influence the incidence of UTIs.

The selected participants underwent a fecal dysbiosis test at a specialized laboratory. Dysbiosis was present with a Flora index level of six or more.

Study participants also completed a questionnaire that provided information on their nutritional health, lifestyle, including smoking, drinking alcohol, and coffee consumption habits, and medical history, including information on antibiotic resistance due to repeated antibiotic treatments.

Study findings

The risk of intestinal mucosal hyperpermeability increases with the excessive intake of simple carbohydrates and fats, heavy metals in food and water, low fiber, a high concentration of pesticides and insecticides in food, chronic alcohol consumption, and unnecessary antibiotic treatments.

Consistent with findings reported in previous studies, gut microbial dysbiosis was found to promote the onset and progression of obesity. Lifestyle and dietary changes alter the bacterial composition and abundance in the intestine, which could trigger the incidence of UTI. Furthermore, frequent antibiotic use could lead to the emergence of multi-resistant microorganisms, which was validated by testing the sensitivity of bacteria to antibiotics.

Over 70% of women with intestinal dysbiosis develop rUTIs. According to a recent study, the human intestinal microbiota is sensitive to food preservatives and non-caloric sweeteners.

Mechanistically, food emulsifiers alter intestinal microbiota composition by inducing intestinal inflammation. The consumption of less than one liter of water each day, chronic alcohol use, and higher intake of processed meals that contain high calories, fats, salt, and added sugar can also lead to intestinal dysbiosis.

Dietary supplements can effectively maintain a healthy gut and reduce the abundance of pathogenic bacteria. For example, commercially available probiotic products containing cranberry extract and two strains of Lactobacillus have significantly reduced rUTI episodes in young premenopausal women.

Conclusions

Two key risk factors of rUTIs include microbial dysbiosis and multi-resistance to antibiotics. Increased consumption of energy drinks and carbonated water and a lower water intake can influence the incidence of rUTIs.

Prebiotics and probiotics can positively restore intestinal microbiota and subsequently prevent UTIs. A healthy lifestyle with limited antibiotic use may also protect women against rUTIs.

Taken together, the study findings highlight that antibiotic therapies significantly reduce beneficial bacteria from the gut, which ultimately promotes the uncontrolled proliferation of pathogenic E. coli strains.