Tag Archives: Clostridium difficile Research

Researchers Find Key Role of Excess Calcium In the Gut In C. difficile infections (CDI)

New research shows, it can’t make this last, crucial move without enough of a humble nutrient: calcium.

And that new knowledge about Clostridium difficile (a bacterium also known as “C. diff“) may lead to better treatment for the most vulnerable patients.

The discovery, made in research laboratories at the University of Michigan Medical School and the U.S. Food and Drug Administration, is published in the online journal PLoS Pathogens.

It helps solve a key mystery about C. diff: What triggers it to germinate, or break its dormancy, from its hard spore form when it reaches the gut.

Though the findings were made in mice, not humans, the researchers say the crucial role of calcium may help explain another mystery: Why some hospital patients and nursing home residents have a much higher risk of contracting C. diff infections and the resulting diarrhea that carries its spores out of the body.

That group includes people whose guts are flooded with extra calcium because they’re taking certain medications or supplements, have low levels of Vitamin D in their blood or have gut diseases that keep them from absorbing calcium.

The new discovery shows that C. diff can recognize this extra calcium, along with a substance called bile salt produced in the liver, to trigger its awakening and the breaking of its shell.

Previous research had suggested it couldn’t do this without another key component, an amino acid called glycine. But the new findings show calcium and the bile salt called taurochlorate alone are enough. Mouse gut contents that were depleted of gut calcium had a 90 percent lower rate of C. diff spore germination.

“These spores are like armored seeds, and they can pass through the gut’s acidic environment intact,” says Philip Hanna, Ph.D., senior author of the new paper and a professor of microbiology and immunology at U-M. “Much of the spore’s own weight is made of calcium, but we’ve shown that calcium from the gut can work with bile salts to trigger the enzyme needed to activate the spore and start the germination process.”

Ironically, the researchers say, one way to use this new knowledge in human patients might be to add even more calcium to the system.

That could awaken all the dormant C. diff spores in a patient’s gut at once, and make them vulnerable to antibiotics that can only kill the germinated form. That could also prevent the transmission of more spores through diarrhea to the patient’s room. That could slow or stop the cycle of transmission that could threaten them or other patients in the future.

Hanna’s graduate student, Travis Kochan, made a key observation that led to the discovery. He noted that the fluid “growth medium” that the researchers typically grow C. diff in for their studies had calcium in it. He realized this could artificially alter the results of their experiments about what caused C. diff spores to germinate.

So, he used a chemical to remove the calcium while leaving all the other nutrients that                  keep C. diff growing. The result: no new spore germination happened in the calcium-free growth medium.

FDA’s Center for Biologics Evaluation and Research conducted further research in laboratory dishes and in the guts of mice. FDA’s Paul Carlson, Ph.D., a former U-M research fellow, and fellow FDA scientists in his laboratory found that C. diff spores that were mutated so that glycine couldn’t act on them could still germinate and colonize mice. This suggested that calcium, and not glycine, was critical for this process.

Both mutant and regular forms of the bacteria could still activate an enzyme inside the C. diff spore that led the bacteria to start dissolving their hard shell. This released the store of calcium that the spore had been harboring inside itself, and increases the local level of the nutrient even further.

“These spores don’t want to germinate in the wrong place,” says Kochan, whose grandfather suffered from a severe C. diff infection which ultimately led to his death. “C. diff spores have specialized to germinate in the gut environment, especially in the environment of the small intestine, where calcium and the bile salt injection from the liver comes in.”

Hanna notes that the bile salt connection to C. diff spore germination was first discovered at U-M in 1982 by a team led by Ken Wilson, M.D.

Calcium and the gut

Certain ailments and treatments cause defects in calcium absorption, but are also risk factors for C. diff infections. For example, patients with vitamin D deficiency are five times more likely to get C. diff.

Medications aimed at calming acid reflux – such as proton pump inhibitors – and steroids can increase the amount of calcium in the gut. A Vitamin D deficiency can keep the body from reabsorbing calcium through the gut wall, allowing it to build up.

And people with inflammatory bowel diseases such as Crohn’s and colitis also have a harder time absorbing calcium from food through their gut walls.

Older adults are also often counseled to take calcium supplements to compensate for lower calcium levels and protect their bones from fracturing.

Hanna cautions that the new findings should not cause any patients to stop taking their medications or doctor-recommended supplements, or to start taking new ones. But he hopes to work with clinicians at U-M and beyond to test the new knowledge in a clinical setting. Meanwhile, he and Kochan and their FDA and U-M colleagues will continue to study C. diff germination in mice and look for ways to block the enzymes crucial to spore germination.

 

To read the article in its entirety – please click on the following link to be re-directed:

http://www.news-medical.net/news/20170713/Scientists-reveal-key-role-of-excess-gut-calcium-in-C-diffc2a0infections.aspx?utm_source=dlvr.it&utm_medium=twitter

Researchers Suggest a Portion Of C. diff. Cases In Europe Involve Infections Associated With Other Sources Outside of Healthcare-Associated Infections

As part of a multicenter study, investigators from the University of Oxford, the University of Leeds, Astellas Pharma Europe, and elsewhere used a combination of ribotyping, sequencing, phylogenetics, and geographic analyses to retrace the genetic diversity and potential sources of C. difficile isolates involved in infections in European hospitals.

Recent research suggests a proportion of Clostridium difficile cases in Europe involve not only hospital-acquired infections but also infections associated with other sources, such as food.

As stated in the article:

https://www.genomeweb.com/sequencing/clostridium-difficile-genetic-patterns-europe-point-possible-infection-sources-beyond?utm_source=Sailthru&utm_medium=email&utm_campaign=GWDN%20Mon%20PM%202017-04-24&utm_term=GW%20Daily%20News%20Bulletin

David Eyre, a clinical lecturer at the University of Oxford, was slated to present the work at the European Congress of Clinical Microbiology and Infectious Diseases annual 2017 meeting in Vienna this past weekend. The study was funded by Astellas Pharma’s Europe, Middle East, and Africa (EMEA) program.

“We don’t know much about how C. difficile might be spread in the food chain, but this research suggests it may be very widespread,” Eyre said in a statement. “If that turns out to be the case, then we need to focus on some new preventative strategies such as vaccination in humans once this is possible, or we might need to look at our use of animal fertilizers on crops.”

“This study doesn’t give us any definitive answers,” he explained, “but it does suggest other factors [than hospital infections] are at play in the spread of C. difficile and more research is urgently needed to pin them down.”

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Some of the strains clustered by locale, consistent with spread from one individual to the next, for example in a healthcare setting. But more unexpectedly, the team also saw strains smattered across seemingly unconnected sites. And because at least one of those strains had previously been linked to pig farming, the researchers speculated that some infections may have been transmitted through food sources.

 

To read the article in its entirety click on the following link:

https://www.genomeweb.com/sequencing/clostridium-difficile-genetic-patterns-europe-point-possible-infection-sources-beyond?utm_source=Sailthru&utm_medium=email&utm_campaign=GWDN%20Mon%20PM%202017-04-24&utm_term=GW%20Daily%20News%20Bulletin

Clostridium difficile Research Suggests That Positively Selected Sites In the Surface Layer Proteins May Play A Role In Driving the Emergence of Hyper-virulent Strains

  • Mark Lynch,
  • Thomas A. Walsh,
  • Izabela Marszalowska,
  • Andrew E. Webb,
  • Micheál MacAogain,
  • Thomas R. Rogers,
  • Henry Windle,
  • Dermot Kelleher,
  • Mary J. O’ConnellEmail author and
  • Christine E. Loscher

To Read Abstract/Article In Its Entirety Please Click On the Following Link:

https://bmcevolbiol.biomedcentral.com/articles/10.1186/s12862-017-0937-8

 

Abstract

Background

Clostridium difficile is a nosocomial pathogen prevalent in hospitals worldwide and increasingly common in the community.

Sequence differences have been shown to be present in the Surface Layer Proteins (SLPs) from different C. difficile ribotypes (RT) however whether these differences influence severity of infection is still not clear.

Results

We used a molecular evolutionary approach to analyse SLPs from twenty-six C. difficile RTs representing different slpA sequences. We demonstrate that SLPs from RT 027 and 078 exhibit evidence of positive selection (PS).

We compared the effect of these SLPs to those purified from RT 001 and 014, which did not exhibit PS, and demonstrate that the presence of sites under positive selection correlates with ability to activate macrophages.

SLPs from RTs 027 and 078 induced a more potent response in macrophages, with increased levels of IL-6, IL-12p40, IL-10, MIP-1α, MIP-2 production relative to RT 001 and 014. Furthermore, RTs 027 and 078 induced higher expression of CD40, CD80 and MHC II on macrophages with decreased ability to phagocytose relative to LPS.

Conclusions

These results tightly link sequence differences in C. difficile SLPs to disease susceptibility and severity, and suggest that positively selected sites in the SLPs may play a role in driving the emergence of hyper-virulent strains.