Tag Archives: C. diff. Research Community

Researchers Perform A Systematic Review and Meta-Analysis In Order to Summarize Data on Antimicrobial Resistance to C. difficile Derived from Humans

 

 

 

 

 

 

 

Mohammad Sholeh1Marcela Krutova2Mehdi Forouzesh3Sergey Mironov4Nourkhoda Sadeghifard5Leila Molaeipour6Abbas Maleki5Ebrahim Kouhsari789
  • PMID: 32977835
  • PMCID: PMC7517813
  • DOI: 10.1186/s13756-020-00815-5

Free PMC article

Abstract

Background: Clostridioides (Clostridium) difficile is an important pathogen of healthcare-associated diarrhea, however, an increase in the occurrence of C. difficile infection (CDI) outside hospital settings has been reported. The accumulation of antimicrobial resistance in C. difficile can increase the risk of CDI development and/or its spread. The limited number of antimicrobials for the treatment of CDI is a matter of some concern.

Objectives: In order to summarize the data on antimicrobial resistance to C. difficile derived from humans, a systematic review and meta-analysis were performed.

Methods: We searched five bibliographic databases: (MEDLINE [PubMed], Scopus, Embase, Cochrane Library, and Web of Science) for studies that focused on antimicrobial susceptibility testing in C. difficile and were published between 1992 and 2019. The weighted pooled resistance (WPR) for each antimicrobial agent was calculated using a random-effects model.

Results: A total of 111 studies were included. The WPR for metronidazole and vancomycin was 1.0% (95% CI 0-3%) and 1% (95% CI 0-2%) for the breakpoint > 2 mg/L and 0% (95% CI 0%) for breakpoint ≥32 μg/ml. Rifampin and tigecycline had a WPRs of 37.0% (95% CI 18-58%) and 1% (95% CI 0-3%), respectively. The WPRs for the other antimicrobials were as follows: ciprofloxacin 95% (95% CI 85-100%), moxifloxacin 32% (95% CI 25-40%), clindamycin 59% (95% CI 53-65%), amoxicillin/clavulanate 0% (0-0%), piperacillin/tazobactam 0% (0-0%) and ceftriaxone 47% (95% CI 29-65%). Tetracycline had a WPR 20% (95% CI 14-27%) and meropenem showed 0% (95% CI 0-1%); resistance to fidaxomicin was reported in one isolate (0.08%).

Conclusion: Resistance to metronidazole, vancomycin, fidaxomicin, meropenem, and piperacillin/tazobactam is reported rarely. From the alternative CDI drug treatments, tigecycline had a lower resistance rate than rifampin. The high-risk antimicrobials for CDI development showed a high level of resistance, the highest was seen in the second generation of fluoroquinolones and clindamycin; amoxicillin/clavulanate showed almost no resistance. Tetracycline resistance was present in one-fifth of human clinical C. difficile isolates.

Keywords: Antimicrobial resistance; Clostridioides difficile; Meta-analysis; Metronidazole; Vancomycin.

Conflict of interest statement

The authors report no conflicts of interest in this work.

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https://pubmed.ncbi.nlm.nih.gov/32977835/

Vanderbilt University Medical Center Scientists Demonstrated C. diff. Exposed To Heme Increases Expression of a Protein System Not Previously Studied

 

Vanderbilt University Medical Center scientists have identified a C. diff protein system that senses and captures heme (part of hemoglobin) to build a protective shield that fends off threats from our immune system and antibiotics. The findings, reported in the journal Cell Host & Microbe, reveal a unique mechanism for C. diff survival in the human gut and suggest novel strategies for weakening its defenses.

In a cruel twist, the bacterium Clostridioides difficile (C. diff) makes us bleed and then uses our blood to defend itself against us.

C. diff the most common cause of health care-associated infections (HAI’s) in the United States causes diarrhea and inflammation of the colon (colitis). Individuals taking antibiotics, which disturb the protective gut microbiota, have increased risk for acquiring a C. diff infection, and 20% of patients suffer recurrent C. diff infections despite treatment.

When C. diff colonizes the gut, it produces toxins that cause tissue damage and inflammation. Blood cells burst, releasing heme, the part of hemoglobin that binds iron and oxygen.

Eric Skaar, Ph.D., MPH, Ernest W. Goodpasture Professor of Pathology, Microbiology and Immunology, and colleagues have studied how bacteria respond to heme, which is both a source of the nutrient iron and a reactive, toxic compound.

“Organisms that experience large amounts of heme have to have ways to deal with heme toxicity,” said Skaar, director of the Vanderbilt Institute for Infection, Immunology and Inflammation (VI4). “We wanted to understand how C. diff deals with heme exposure.”

The investigators demonstrated that C. diff exposed to heme increases expression of a protein system that had not been previously studied. They named the system HsmRA (heme sensing membrane proteins R and A) and showed that HsmR senses heme and deploys HsmA to capture it. They also found that the HsmRA system is genetically conserved in many bacterial species.

The binding of heme in the bacterial membrane by HsmA serves a protective purpose first by simply reducing the concentration of free heme, Skaar explained. The researchers also discovered that HsmA uses heme binding to protect C. diff from oxidative stress, including that produced by neutrophils and macrophages from our immune system to kill bacteria.

“C. diff is using cofactors from our own cells as a shield to protect against our innate immune response,” Skaar said.

Oxidative stress also plays a role in antibiotic action.

“Antibiotics have different molecular targets—they may prevent cell wall synthesis; they may prevent protein translation—but the net result of that stress on the cell is often the massive accumulation of oxidative stress that many believe to be a major contributor to why antibiotics kill bacteria,” Skaar said.

The investigators studied whether the HsmRA system protected C. diff against antibiotics.

“We found a really impressive phenotype with vancomycin and metronidazole, two of the front-line antibiotics used to treat C. diff,” Skaar said. “C. diff that expresses HsmA, when HsmA is bound to heme, is much more resistant to vancomycin and metronidazole.”

They also showed that C. diff strains with inactivated HsmR or HsmA had reduced colonization in a mouse model of relapse C. diff infection.

Skaar said it has not been clear why C. diff produces toxins that cause so much tissue damage.

“It’s interesting to speculate that a benefit of toxin-related damage is that C. diff can capture liberated heme and use it as a shield to protect itself against various insults that cause oxidative stress—that would be immune cells, antibiotics and potentially other bacteria.”

The findings suggest that targeting the HsmA-heme shield might increase the sensitivity of C. diff to antibiotics such as vancomycin and metronidazole. It’s not clear that HsmA, a membrane protein, will be a druggable target, Skaar said.

It might be possible, however, to deprive C. diff of heme building blocks by reducing tissue damage or by administering proteins that bind heme, he said. The researchers will explore whether they can increase the sensitivity of C. diff to antibiotics by co-administering a heme-binding protein during infection in an animal model.

“We’re excited about this as a potentially powerful strategy for treating C. diff,” Skaar said.

In other studies, the researchers will explore if the HsmRA system that is genetically conserved in many different organisms has the same functional role to protect against reactive oxygen species. They are also trying to understand the exact mechanism that HsmA-heme uses to detoxify oxidative stress.

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https://phys.org/news/2020-06-clostridioides-difficile-captures-blood-cell.html

Biologists Develop Models to Aid Development of Novel Therapies to Fight Clostridioides difficile (C. diff.) Pathogen

The Clostridium difficile pathogen takes its name from the French word for “difficult.” A bacterium that is known to cause symptoms ranging from diarrhea to life-threatening colon damage,

 

 

 

C. difficile is part of a growing epidemic of concern for the elderly and patients on antibiotics.

Outbreaks of C. difficile-infected cases have progressively increased in Western countries, with 29,000 reported deaths per year in the United States alone.

Now, biologists at the University of California San Diego are drawing parallels from newly developed models of the common fruit fly to help lay the foundation for novel therapies to fight the pathogen’s spread. Their report is published in the journal iScience.

C. difficile infections pose a serious risk to hospitalized patients,” said Ethan Bier, a distinguished professor in the Division of Biological Sciences and science director of the UC San Diego unit of the Tata Institute for Genetics and Society (TIGS). “This research opens a new avenue for understanding how this pathogen gains an advantage over other beneficial bacteria in the human microbiome through its production of toxic factors. Such knowledge could aid in devising strategies to contain this pathogen and reduce the great suffering it causes.”

As with most bacterial pathogens, C. difficile secretes toxins that enter host cells, disrupt key signaling pathways and weaken the host’s normal defense mechanisms. The most potent strains of C. difficile unleash a two-component toxin that triggers a string of complex cellular responses, culminating in the formation of long membrane protrusions that allow the bacteria to attach more effectively to host cells.

UC San Diego scientists in Bier’s lab-created strains of fruit flies that are capable of expressing the active component of this toxin, known as “CDTa.” The strains allowed them to study the elaborate mechanisms underlying CDTa toxicity in a live model system focused on the gut, which is key since the digestive system of these small flies is surprisingly similar to that of humans.

“The fly gut provides a rapid and surprisingly accurate model for the human intestine, which is the site of infection by C. difficile,” said Bier. “The vast array of sophisticated genetic tools in flies can identify new mechanisms for how toxic factors produced by bacteria disrupt cellular processes and molecular pathways. Such discoveries, once validated in a mammalian system or human cells, can lead to novel treatments for preventing or reducing the severity of C. difficile infections.”

The fruit fly model gave the researchers a clear path to examine genetic interactions disrupted at the hands of CDTa. They ultimately found that the toxin induces a collapse of networks that are essential for nutrient absorption. As a result, the model flies’ body weight, fecal output and overall lifespan were severely reduced, mimicking symptoms in human C. difficile-infected patients.

In addition to Bier, study coauthors include first-author Ruth Schwartz, Annabel Guichard, Nathalie Franc, and Sitara Roy.

The National Institutes of Health (R01 AI110713) funded the research.


Story Source:

Materials provided by the University of California – San Diego. Original written by Mario Aguilera. Note: Content may be edited for style and length.


Journal Reference:

  1. Ruth Schwartz, Annabel Guichard, Nathalie C. Franc, Sitara Roy, Ethan Bier. A Drosophila Model for Clostridium difficile Toxin CDT Reveals Interactions with Multiple Effector Pathways. iScience, 2020; 100865 DOI: 10.1016/j.isci.2020.100865

Transgenic fruit flies help scientists trace the cascade of symptoms caused by toxic infection

Date: February 7, 2020

Source: University of California – San Diego
Summary: Clostridium difficile, a bacterium is known to cause symptoms from diarrhea to life-threatening colon damage, is part of a growing epidemic for the elderly and hospitalized patients. Biologists have now developed models of the common fruit fly to help develop novel therapies to fight the pathogen

Researchers Report Bezlotoxumab Treatment Reduced C. diff. Recurrence in Cancer Patients

Abstract

Background

The incidence of Clostridioides difficile infection (CDI) is reportedly higher and the cure rate lower in individuals with cancer versus those without cancer. An exploratory post-hoc analysis of the MODIFY I/II trials (NCT01241552/NCT01513239) investigated how bezlotoxumab affected the rate of CDI-related outcomes in participants with cancer.

Methods

Participants received a single infusion of bezlotoxumab (10 mg/kg) or placebo during anti-CDI antibacterial treatment. A post-hoc analysis of CDI-related outcomes was conducted in subgroups of MODIFY I/II participants with and without cancer.

Results

Of 1,554 participants in the modified intent-to-treat (mITT) population, 382 (24.6%) were diagnosed with cancer (bezlotoxumab 190, placebo 192). Of participants without cancer, 591 and 581 received bezlotoxumab and placebo, respectively. In the placebo group, initial clinical cure (ICC) was achieved by fewer cancer participants versus participants without cancer (71.9% versus 83.1%; absolute difference [95% CI]: -11.3% [-18.6, -4.5]), however, CDI recurrence (rCDI) rates were similar in cancer (30.4%) and non-cancer (34.0%) participants. In participants with cancer, bezlotoxumab treatment had no effect on ICC rate compared with placebo (76.8% versus 71.9%), but resulted in a statistically significant reduction in rCDI versus placebo (17.8% versus 30.4%; absolute difference [95% CI]: 12.6% [-22.5, -2.7]).

Conclusions

In this post-hoc analysis of participants with cancer enrolled in MODIFY I/II, the rate of rCDI in bezlotoxumab-treated participants was lower than in placebo-treated participants. Additional studies are needed to confirm these results.

Open Forum Infectious Diseases, ofaa038, https://doi.org/10.1093/ofid/ofaa038
Published:
31 January 2020

 

To access the article in its entirety please click on the following link:

https://academic.oup.com/ofid/advance-article/doi/10.1093/ofid/ofaa038/5718256

Researchers From North Carolina State University Find That Antibiotics Give C.diff. Nutrient-Rich Environment

Using a mouse model, researchers from North Carolina State University have found that antibiotic use creates a “banquet” for Clostridium difficile (C. diff), by altering the native gut bacteria that would normally compete with C. diff for nutrients. The findings could lead to the development of probiotics and other strategies for preventing C. diff infection.

C. diff is a harmful bacterium that can cause severe, recurrent and sometimes fatal infections in the gut. Although the bacteria are commonly found throughout our environment, C. diff infections primarily occur in patients who are taking, or who have recently finished taking, antibiotics.

“We know that antibiotics are major risk factors for C. diff infection because they alter the gut microbiota, or composition of bacteria in the gut, by eliminating the bacteria that are normally there,” says Casey Theriot, assistant professor of infectious disease at NC State and corresponding author of a paper describing the research. “Our latest work suggests that the microbiota may provide natural resistance to C. diff colonization by competing with C. diff for nutrients in that environment; specifically, for an amino acid called proline.”

Theriot and postdoctoral fellow Joshua Fletcher introduced C. diff to antibiotic-treated mice and monitored their gut environment at four intervals: 0, 12, 24, and 30 hours after introduction. They conducted metabolomic and RNA sequencing analysis of the gut contents and the C. diff at these time points to find out which nutrients the bacteria were “eating.” Metabolomics allowed the team to trace the abundance of the nutrients in the gut, and RNA analysis indicated which genes in the C. diff were active in metabolizing nutrients.

The researchers found that the amount of proline in the gut decreased as the population of C. diff increased. Additionally, the amount of a proline byproduct called 5-aminovalerate also increased, indicating that C. diff was metabolizing the proline. The RNA analysis further confirmed C. diff‘s use of proline, as genes related to proline metabolism in C. diff increased during the early stages of colonization, when proline was abundant.

“We’ve been able to show that in the absence of competition C. diff is metabolizing proline and other amino acids in the mouse model, using it as fuel to survive and thrive,” Theriot says. “Hopefully this information could lead to the development of better probiotics, or ‘good’ bacteria that can outcompete C. diff for nutrients in the gut. The ultimate goal is to control these bacteria in ways that don’t rely solely on antibiotics.”

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https://www.sciencedaily.com/releases/2018/03/180328204122.htm