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  • Writer's pictureP.K. Peterson

What Everyone Needs to Know about Urinary Tract Infections

“A wise man proportions his belief to the evidence.”

David Hume, Scottish philosopher and historian


“Welcome to the Great UTI Scandal, a story of unnecessary suffering for millions, needless hospital admissions, antibiotic resistance, sepsis-related deaths and basic ignorance of the science around female bodies.”

Kate Muir, Scottish writer and documentary maker (The Guardian, December 17, 2023)


The first documented description of urinary tract infections (UTIs) appeared in 1550 BCE in the Ebers Papyrus, an Egyptian medical papyrus of herbal knowledge. Despite their ancient history, their massive importance (about 150 million people develop a UTI each year), and solid evidence to inform treatment, UTIs are often mismanaged. The goal of this Germ Gems post is to clarify who does and who doesn’t need treatment for a UTI and to suggest why the management of this infection may be improving.

What is a UTI? In the 1950s, Dr. Edward Kass, a renown infectious diseases physician, and his colleagues at Boston City Hospital and Harvard Medical School established the definition of what constitutes a UTI. Through their groundbreaking studies, they determined that cultures of properly collected urine samples from healthy people contain less than 100,000 organisms (called colony forming units [CFU]) per ml of urine. It therefore followed that urine cultures containing equal to or greater than 100,000 CFU/ml, represent an infection. This became and remains the definition of a UTI to this day.

A UTI is an infection in any part of the urinary system, including the kidneys, ureters, bladder, and urethra. Most infections involve the lower urinary tract, the bladder (cystitis) or the urethra (urethritis). Lower UTIs are by far the most common, but infections involving the upper tract, that is kidneys (pyelonephritis), are the most serious, precipitating hospitalizations and sometimes death. (UTIs killed an estimated 196,500 people in 2015).

Most UTIs are caused by gram-negative bacteria, most commonly E. coli. (Gram-negative bacteria are becoming increasingly resistant to antibiotics.) Some UTIs, however, are caused by the yeast Candida. (Candida is usually a pathogen in the lower urinary tract [bladder].)

Symptoms and signs of UTIs. The most common symptoms of lower UTI (bladder infection or cystitis) are burning with urination, needing to urinate frequently, and pain above the pubic bone or in the back. People with pyelonephritis are considerably sicker and, in addition to the above symptoms, may experience flank pain, fever, nausea and vomiting, and blood-tinged urine.

Most people with UTIs, however, have no symptoms at all. Some studies indicate that more than 30% of women and 10% of men over the age of 65 years have asymptomatic UTIs. This entity—asymptomatic bacteriuria—is the cause of most mismanagement of the infection.

Treatment of UTIs. Symptomatic UTIs are treated with antibiotics (for bacterial infections) or antifungal drugs (for Candida infections). The choice of which agent to use is often guided by results of antibacterial susceptibility tests. Your primary care provider (with input from an infectious diseases specialist in complicated cases) will make recommendations regarding dosage and route of administration of antibiotics, as well as duration of therapy.

With one important exception—pregnant women—asymptomatic bacteriuria should not be treated. Dr. Lindsay Nicolle, professor of medicine and medical microbiology at the University of Manitoba, and her colleagues provided the basis for this recommendation in their landmark studies.

Over the past several decades, they demonstrated unequivocally that treatment of asymptomatic bacteriuria offers no clinical benefits. They also showed that such treatment can and frequently does result in serious side effects like Clostridioides immitis colitis, and less commonly, but very seriously, development of Achilles tendon rupture related to fluoroquinolones, like ciprofloxacin and levofloxacin.

Equally important, treatment of asymptomatic bacteriuria also fuels the emergence of antibiotic-resistant bacteria which is a huge global health threat.

Gender considerations. Of the 150 million people who develop UTIs annually, a large majority are women. In fact, UTIs are the single most common form of bacterial infection in women. Up to 10% of women have a UTI in a given year, and half of all women have had at least one UTI at some time in their lifetime.

Women get more UTIs than men because women have a shorter urethra. This means there is less distance for bacteria to travel to reach the bladder. UTIs in women occur most frequently between the ages of 16 and 35, coinciding with the age of increased sexual activity. “Honeymoon cystitis,” a UTI that can occur after a woman’s first sexual encounter or after a long period without sexual activity, can be especially troublesome. To my knowledge, no cases have ever been reported in men.


“Genitourinary Syndrome of Menopause” (GMS) is another genitourinary health problem that’s gender-related. It’s a relatively new term for a condition previously known as atrophic vaginitis or vulvovaginal atrophy. GMS is related to an antibiotic-associated disturbance of the vaginal microbiome. Older women bear the brunt of the disorder. The good news is that GMS responds to low dose vaginal estrogen (which can cut the incidence of associated UTIs by 50%).

Closing the gender gap. Anouk Petersen, a co-author of a McKinsey Health Institute (MHI) Report at the United Nations General Assembly said: “Women have been treated by the scientific and medical communities as though they are small men, when our entire biology is different …We must evolve our understanding of women’s health to look at the whole person in a much more specific way if we are going to close this gap.”


The prospects for closing the gender gap in health appear to be improving. The release of MHI’s report coincided with the launch of the Global Alliance for Women’s Health, a multisector global platform to improve investment in women’s health. At least 42 organizations have signed up to support the alliance, pledging $55 million. According to a report from the World Health Economic Forum appearing in The Guardian in January 2024, “[I]mproving women’s health ‘could add at least $1tn a year to global economy.’”


Improving the management of UTIs in women and related problems like GMS is one small step on the way to improving women’s health. But I’m sure the millions of women who suffer from UTIs or GMS would embrace it as a good place to start.


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Main Page images courtesy of Shuxian Hu, MD. Dr. Hu is a scientist in the Neuroimmunology Research Laboratory at the University of Minnesota.

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