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
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
If youâ€™re looking for an expert on the â€œnotoriousâ€ bacterium Clostridium difficile, consider Emory microbiologist Shonna McBride.
C. difficile is a prominent threat to public health, causing potential fatal cases of diarrheal disease. C. difficile can take over in someoneâ€™s intestines after antibiotics clear away other bacteria, making it dangerous for vulnerable patients in health care facilities. Healthcare-associated infections caused by other types of bacteria such as MRSA have been declining, leaving C. difficile as the most common cause, according to recently released data from the CDC.
Shonna McBride, PhD
McBrideâ€™s work focuses on how C. difficile is able to resist antimicrobial peptides produced by our bodies that keep other varieties of bacteria in check.
A 2013 paper from her lab defines genes that control C. difficile’s process for sequestering these peptides. It appears that its ability to resist host antimicrobial peptides evolved out of a system for resisting weapons other bacteria use against each other.
Since C. difficile requires an oxygen-free environment to grow, studying it can be more difficult than other bacteria. The McBride lab has a recent â€œvideo articleâ€ in the Journal of Visualized Experiments explaining how to do so using specialized equipment.
McBride explains in a recent Microbe magazine cover article that C. difficileâ€™s ability to form spores is connected to the threat it poses:
Without the ability to form spores, the strict anaerobe C. diffÄ±cile would quickly die in the presence of atmospheric oxygen. However, the intrinsic resilience of these spores makes them diffÄ±cult to eradicate, facilitating the spread of this pathogen to new hosts, particularly in health care settings where they withstand many of the most potent disinfectants.
Yet the process of sporulation is markedly different in C. difficile compared with other kinds of bacteria, she says in the review.