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If you’ve been following the news about antibiotic resistant bacteria, you may have heard about a particularly alarming plasmid: MCR-1. A plasmid is a circle of DNA that is relatively small and mobile – an easy way for genetic information to spread between bacteria. MCR-1 raises concern because it provides bacteria resistance against the last-resort antibiotic colistin. The CDC reports MCR-1 was found in both patients and livestock in the United States this summer.
David Weiss, director of Emory’s Antibiotic Resistance Center, and colleagues have a short letter in The Lancet Infectious Diseases showing that MCR-1 also confers resistance to an antimicrobial enzyme produced by our bodies called lysozyme. MCR-1-containing strains were 5 to 20 times less susceptible to lysozyme, they report.
This suggests that the pressure of fighting the host immune system may select for MCR-1 to stick around, even in the absence of colistin use, the authors say.
While the findings are straightforward in bacterial culture, Weiss cautions that there is not yet evidence showing that this mechanism occurs in live hosts. For those that really want to get alarmed, he also calls attention to a recent Nature Microbiology paper describing a hybrid plasmid with both MCR-1 and resistance to carbapenem, another antibiotic.
Posted on October 18, 2016 by
Lots of people in the United States consume a diet that is high in sugar and fat, and many develop non-alcoholic fatty liver disease, a relatively innocuous condition. NASH (non-alcoholic steatohepatitis) is the more unruly version, linked to elevated risk of cardiovascular and metabolic diseases, and can progress to cirrhosis. NASH is expected to become the leading indication for liver transplant. But only a fraction of people with non-alcoholic fatty liver disease go on to develop NASH.
Thus, many researchers are trying to solve this equation:
High-sugar, high-fat diet plus X results in NASH.
Emory hepatologist Frank Anania and colleagues make the case in a recent Gastroenterology paper that a “leaky gut”, allowing intestinal microbes to promote liver inflammation, could be a missing X factor.
Anania’s lab started off with mice fed a diet high in saturated fat, fructose and cholesterol (in the figure, HFCD). This combination gives the mice moderate fatty liver disease and metabolic syndrome (see this 2015 paper, and we can expect to hear more about this model soon from Saul Karpen). Leaky gut, brought about by removing a junction protein from intestinal cells, sped up and intensified the development of NASH.
The authors say that this model could be useful for the study of NASH, which has been difficult to reproduce in mice.
The researchers could attenuate liver disease in the mice by treatment with antibiotics or sevelamer, a phosphate binding polymer that soaks up inflammatory toxins from bacteria. Sevelamer is now used to treat excess phosphate in patients with chronic kidney disease, and is being studied clinically in connection with insulin resistance.
Posted on August 29, 2016 by
Congratulations to Alejandra Valdivia, PhD, winner of the Best Image contest held as part of the Emory Postdoctoral Research Symposium, which takes place next week (Thursday, May 19). She is in Alejandra San Martin’s lab, studying NADPH oxidase enzymes and how they regulate cell migration.
Valdivia submitted this image of mouse embryonic fibroblasts forming focal adhesions, points of contact of the cell with the extracellular matrix. Focal adhesions allow the cells to adhere and migrate.
Explanation: Red is for paxillin, a protein concentrated in focal adhesions. Green is phalloidin, a toxin from mushrooms that binds one type of the cytoskeletal protein actin, seen here as stress fibers. Blue is DNA, showing the cells’ nuclei.
Posted on May 9, 2016 by
Patients with heart failure who received an experimental stem cell therapy experienced a reduced rate of death, hospitalization and unplanned clinic visits over the next year compared to a placebo group, according to results presented Monday at the American College of Cardiology meeting in Chicago.
The results of the ixCELL-DCM study were published online Monday by The Lancet. It was reportedly the largest cell therapy study done in patients with heart failure so far (58 treated vs 51 placebo).
Emory University School of Medicine investigators led by Arshed Quyyumi, MD, and their patients participated in the study, and Emory was one of the largest enrolling sites. Lead authors were Timothy Henry, MD of Cedars-Sinai Heart Institute in Los Angeles and Amit Patel, MD of the University of Utah.
â€œFor the first time, a clinical trial has shown that administration of a cellular therapeutic results in an improvement in cardiac outcomes based on a prespecified analysis,â€ an editorial accompanying the paper in The Lancet says.
Posted on April 5, 2016 by
Some people with heart disease experience a restriction of blood flow to the heart in response to psychological stress. Usually silent (not painful), the temporary restriction in blood flow, called ischemia, is an indicator of greater mortality risk.
Cardiologists at Emory University School of Medicine have discovered that people in this group tend to have higher levels of troponin — a protein whose increased presence in the blood that is a sign of recent damage or stress to the heart muscle– all the time, independently of whether they are experiencing stress or chest pain at that moment.
The results were presented Sunday by cardiology research fellow Muhammad Hammadah, MD at the American College of Cardiology meeting in Chicago, as part of the Young Investigator Awards competition. Hammadah works with Arshed Quyyumi, MD, and Viola Vaccarino, MD, PhD, and colleagues at the Emory Clinical Cardiovascular Research Institute.
â€œElevated troponin levels in patients with coronary artery disease may be a sign that they are experiencing repeated ischemic events in everyday life, with either psychological or physical triggers,â€ Hammadah says.
Doctors test for troponin in the blood to tell whether someone has recently had a heart attack. But the levels seen in this study were lower than those used to diagnose a heart attack: less than a standard cutoff of 26 picograms per milliliter, in a range that only a high-sensitivity test for troponin could detect.
In a separate study, Emory investigators have shown that elevated troponin levels (especially: more than 10 pg/mL)Â predict mortality risk over the next few years in patients undergoing cardiac catheterization, even in those without apparent coronary artery disease.
There is already a lot of information available for doctors about the significance of elevated troponin. It has even been detected at elevated levels after strenuous exercise in healthy individuals. One recent study suggested that low levels of troponin could be used to rule out heart attack for patients in the emergency department.
More information about the mental stress ischemia study: Read more
Posted on April 5, 2016 by
How should doctors measure how messed up someoneâ€™s intestinal microbiome is?
This is the topic of a recent paper in American Journal of Infection Control from Colleen Kraft and colleagues from Emory and the Centers for Disease Control and Prevention. The corresponding author is epidemiologist Alison Laufer Halpin at the CDC.
A â€œmicrobiome disruption indexâ€ could inform decisions on antibiotic stewardship, where a patient should be treated or interventions such as fecal microbial transplant (link to 2014 Emory Medicine article) or oral probiotic capsules.
What the authors are moving towards is similar to Shannonâ€™s index, which ecologists use to measure diversity of species. Another way to think about it is like the Gini coefficient, a measure of economic inequality in a country. If there are many kinds of bacteria living in someoneâ€™s body, the disruption index should be low. If there is just one dominant type of bacteria, the disruption index should be high.
In the paper, the authors examined samples from eight patients in a long-term acute care hospital (Wesley Woods) who had recently developed diarrhea. Using DNA sequencing, they determined what types of bacteria were present in patients’ stool. The patientsâ€™ samples were compared with those from two fecal microbial transplant donors. Read more
Posted on March 21, 2016 by
Bacterial spores in capsules taken by mouth can prevent recurrent C. difficile infection, results from a preliminary study suggest.
Clostridium difficile is the most common hospital-acquired infection in the United States and can cause persistent, sometimes life-threatening diarrhea. Fecal microbiota transplant has shown promise in many clinical studies as a treatment for C. difficile, but uncertainty has surrounded how such transplants should be regulated and standardized. Also, the still-investigational procedure is oftenÂ performed byÂ colonoscopy, which may be difficult forÂ some patients to tolerate.
The capsule study, published Monday in Journal of Infectious Diseases, represents an important step in moving away from fecal microbiota transplant as a treatment for C. difficile, says Colleen Kraft, MD, assistant professor of pathology and laboratory medicine and medicine (infectious diseases) at Emory University School of Medicine.
Kraft and Tanvi Dhere, MD, assistant professor of medicine (digestive diseases) have led development of the fecal microbiota transplant program at Emory. They are authors on the capsule study, along with investigators from Mayo Clinic, Massachusetts General Hospital, Miriam Hospital (Rhode Island), and Seres Therapeutics, the study sponsor.
While this study involving 30 patients did not include a control group, the reported effectiveness of 96.7 percent compares favorably to published results on antibiotic treatment of C. difficile infection or fecal microbial transplant. Read more
Posted on February 12, 2016 by
This recent paper in Circulation, from Arshed Quyyumi and colleagues at the Emory Clinical Cardiovascular Research Institute, can be seen as a culmination of, even vindication for, Â Dean Jones’ ideasÂ about redox biology.
Let’s back up a bit.Â Fruit juices, herbal teas, yogurts, even cookies are advertised as containing antioxidants, whichÂ could potentiallyÂ fight aging. This goes back to Denham Harman and the free radical theory of aging.Â [I attemptedÂ to explain this several years ago in Emory Medicine.]
We now know that free radicals, in the form of reactive oxygen species, can sometimes be good, even essential for life. So antioxidants that soak up free radicals to relieve you of oxidative stress: that doesn’t seem to work.
Dean Jones, who is director of Emory’s Clinical Biomarkers laboratory,Â has been an advocate for a different way of looking at oxidative stress. That is, instead of seeing cells asÂ big bags of redox-sensitive chemicals, look at cellular compartments. Look at particular antioxidant proteins and sulfur-containing antioxidant molecules such asÂ glutathione and cysteine.
That’s what theÂ Circulation paper does. Mining the Emory Cardiovascular Biobank, Quyyumi’s team shows that patients with coronary artery disease have a risk of mortality that is connected to the ratio of glutathione to cystine (the oxidized form of the amino acid cysteine).
How this ratio might fit in with other biomarkers of cardiovascular risk (such as CRP, suPAR, PCSK9,Â more complicated combinationsÂ and gene expression profiles, even more links here) and be implemented clinically areÂ still unfolding.
Posted on February 5, 2016 by