Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Bacteria that cause urinary tract infections invade bladder cells

19.12.2007
Scientists at Washington University School of Medicine in St. Louis have found definitive proof that some of the bacteria that plague women with urinary tract infections (UTIs) are entrenched inside human bladder cells.

The finding confirms a controversial revision of scientists' model of how bacteria cause UTIs. Previously, most researchers assumed that the bacteria responsible for infections get into the bladder but do not invade the individual cells that line the interior of the bladder.

"Our animal model of UTIs has allowed us to make a number of predictions about human UTIs, but at the end of the day, we felt it was critical to show this in humans, and now we've done just that," says senior author Scott J. Hultgren, Ph.D., the Helen L. Stoever Professor of Molecular Microbiology at the School of Medicine.

The results appear in the December issue of Public Library of Science Medicine.

Fully understanding what bacteria do in the bladder is critical to developing better diagnoses and treatments for UTIs, Hultgren says. The bacterium Escherchia coli is thought to be responsible for 80 percent to 90 percent of UTIs, which occur mainly in women and are one of the most common bacterial infections in the United States. Scientists estimate that more than half of all women will experience a UTI in their lifetimes, and recurrent UTIs will affect 20 percent to 40 percent of those patients.

"Recurrence is one of the biggest problems of UTIs," says Hultgren. "Even though we have treatments that eliminate the acute symptoms, the fact that the disease keeps recurring in so many women tells me that we need to develop better treatments."

Prior to the work of Hultgren and his colleagues, most microbiologists and urologists believed for a variety of reasons that E. coli wasn't getting into bladder cells.

"For example, there is a barrier in the bladder that prevents toxins and other things in your urine from leaking back into the body," notes David Rosen, an M.D./Ph.D. student at the School of Medicine and lead author of the paper. "And it was thought that bacteria could not penetrate that barrier."

A biopsy could reveal the presence of bacteria in bladder cells, but taking a tissue sample in an infected bladder incurs an unacceptable risk of allowing bacteria to spread into the bloodstream, a dangerous condition called sepsis.

Scientists also thought that if the bacteria were getting into bladder cells, they would replicate and spread rapidly, sometimes leading to sepsis. But after Hultgren first discovered that bacteria are able to invade bladder cells in 1998, he later found evidence in his animal model that bacteria could establish residence inside those cells. He showed that this process involved several behavioral changes that allow the bacteria to form cooperative communities known as biofilms. By working together, bacteria in biofilms build themselves into structures that are more firmly anchored in infected cells and are more resistant to immune system assaults and antibiotic treatments.

To prove that the model correlates with human infections, Rosen led an analysis of human urine samples sent from a clinic at the University of Washington in Seattle. The 100 patients who gave samples were either suffering from an active, symptomatic infection or had previously suffered infections. Researchers analyzing the specimens were not told which group of patients individual specimens had come from.

Using light and electron microscopy and immunofluoresence, scientists found signs of bladder cell infection in a significant portion of the samples from patients with active UTIs. These included cells enlarged by bacterial infection and shed from the lining of the bladder.

In addition, Hultgren's experiments had previously suggested that some bacteria progress to a filament-like shape when exiting out of the biofilm. Rosen was able to identify bacteria with this filamentous morphology in 41 percent of samples from patients with symptomatic UTIs.

Neither indicator was detected in urine from women who did not have active infections. This was anticipated: Hultgren's animal model work suggests that when women are between episodes of symptomatic infection, intracellular E. coli may be in dormant phases where there would be little cause for bacteria or the cells they infect to be shed into the urine.

Further research is needed to determine if the infection indicators Rosen detected in urine samples from symptomatic women are signs of increased risk of recurrent infection. But looking for those signs using immunofluorescent staining and a variety of microscopy methods is unlikely to be practical on a widespread clinical basis. So to follow up, Hultgren plans a search for biochemical indicators linked to higher risk of recurrent UTIs and of infection spreading to a patient's kidneys. His lab also continues to be involved in many different efforts to develop new vaccines and treatments.

"What we're learning about how bacteria behave in the bladder may also have application to other chronic, treatment-resistant infections such as sinus infections and ear infections," he says. "We're increasingly starting to realize that biofilm formation is generally an important strategy bacteria use to evade host responses and antibiotic therapies. Attacking biofilms is going to be a really important approach as we enter a new era of fighting infectious diseases."

Michael C. Purdy | EurekAlert!
Further information:
http://www.wustl.edu

More articles from Health and Medicine:

nachricht New malaria analysis method reveals disease severity in minutes
14.08.2017 | University of British Columbia

nachricht New type of blood cells work as indicators of autoimmunity
14.08.2017 | Instituto de Medicina Molecular

All articles from Health and Medicine >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

Climate change: In their old age, trees still accumulate large quantities of carbon

17.08.2017 | Earth Sciences

Modern genetic sequencing tools give clearer picture of how corals are related

17.08.2017 | Life Sciences

Superconductivity research reveals potential new state of matter

17.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>