C. diff: Attacking an Epidemic
Since 2001, the rate of Clostridium difficile infection — which devastates the colon — has increased dramatically in the United States. C. difficile causes about 500,000 infections each year (Centers for Disease Control and Prevention, 2011).
Why did the annual number of C. diff infections grow by nearly 43 percent from 2001 to 2012, and the incidence of recurrent C. diff jump 189 percent during the same period?
According to the literature, a mutation occurred in C. difficile in 2001, causing it to become far more virulent and harder to control, says Drexel gastroenterologist Neilanjan Nandi, MD, assistant professor of medicine. "C. diff infection existed before 2001, but we didn't recognize it as the epidemic it is today," Nandi says. "Before C. diff mutated, it produced two toxins — A and B — that attacked the lining of the intestine. When it mutated, the new strain, known as NAP1 RT027, started producing a binary toxin, a combination of A and B that produces a greater volume of toxin, which is also more virulent." A similar strain that produces binary toxin, RT078, has been found in livestock, placing animal-based foods as potential infectious reservoirs.
Another factor contributing to the C. diff epidemic is overuse of antibiotics. The intestines contain about 100 trillion bacterial cells and up to 2,000 different kinds of bacteria. Many help protect the body from infection. "Broad spectrum antibiotics kill everything, which means they kill the good gut flora as well as the bad," explains Nandi. "However, antibiotics don't kill the C. diff spores because they are impervious. Without the healthy bacteria needed to prevent those spores from regerminating and excreting tons of toxin, C. diff infection can recur."
Other factors may have helped select for this mutant strain, Nandi says. Recent studies suggest that trehalose, a naturally occurring sugar (e.g., in mushrooms, honey) used as an ingredient/preservative in processed foods, may have contributed. Pre-2001 C. diff strains utilized trehalose inefficiently. However, both RT027 and RT078 possess mutations that enable enhanced growth on trehalose. "Enough basic science research has been done to substantiate this," Nandi says. Natural trehalose was expensive to isolate, but manufacturing breakthroughs enabled mass production in the year 2000, followed by the notable introduction of trehalose into human foods (e.g., pasta, ice cream). Nandi points out that the decade and a half since trehalose introduction is the same time frame in which the dramatic increase in C. diff infection occurred.
The standard testing protocol for C. diff can yield false positives for individuals who are colonized with inactive bacteria and not infected. Because of this, C. diff infection is over-diagnosed, leading clinicians to prescribe unnecessary antibiotics. A study to better diagnose active C. diff infection was led by Barbara Fry-Arrighy, BS, MT(ASCP)SM, director of Infection Control & Prevention at Hahnemann University Hospital, with a multidisciplinary team including Nandi, internist Kevin D'Mello, MD, assistant professor of medicine, and Michele Kutzler, PhD, associate professor of medicine.
"Hahnemann now has the lowest C. diff rate in Pennsylvania," notes Nandi.
The team amended the existing hospital policy for early detection of C. diff infection by adding symptom assessment guidelines for nurses and clinicians. These include review of recent laxative or stool softener administration to rule that out as a possible cause of diarrhea symptoms. "In the majority of cases studied, patients who were on laxatives or stool softeners experienced diarrhea," says Fry-Arrighy. "Our guideline now states that only patients who have watery diarrhea three times in a 24-hour period without the aid of a laxative or stool softener are tested for C. diff." In addition, clinicians were educated about limiting the use of antibiotics, particularly levofloxacin.
After implementation of the guidelines and related education, the use of levofloxacin decreased by 44 percent. The rate of health-care associated C. diff infection decreased dramatically — by 85 percent.
"Hahnemann now has the lowest C. diff rate in Pennsylvania," notes Nandi. "Our team received the 2017 Hospital Health System Association of Pennsylvania 'In Safe Hands' award for our achievements.
"What causes the C. diff infection?
"Fecal matter is everywhere," Nandi says. "That's why the safest and most effective way to prevent C. diff is hand washing in a sink with soap and running water for at least 20 seconds..."
The most common way to get C. diff is by fecal oral transmission. "Fecal matter is everywhere," Nandi says. "That's why the safest and most effective way to prevent C. diff is hand washing in a sink with soap and running water for at least 20 seconds," he says. "Alcohol-based hand sanitizers don't kill C. diff." Some people are at greater risk for infection than others. "It's clear that people who are taking antibiotics, frequently visiting hospitals, and being exposed to bacterial spores that may be present on surfaces in health care facilities are at greater risk," says Kutzler, who also has an appointment in microbiology and immunology. "Just being exposed doesn't mean that you're going to get an infection."
Kutzler's lab is collaborating with Pfizer, Inc., and Drs. Seth Welles and Neal Goldstein, faculty in Drexel's Dornsife School of Public Health, to study underlying patient risk factors that may contribute to the acquisition of C. diff infection. "Our primary goal is to understand why some patients develop C. diff infection and others don't, even if they are colonized. We will use that to build a clinical prediction tool for C. diff infection, disease severity and recurrence in patients upon admission to the hospital. This research will also help us to design C. diff vaccines and clinical trials."
In a related study, Kutzler, Nandi, D'Mello, and faculty in the School of Public Health are analyzing the microbiome of patients with recurrent C. diff. Since 2014, a team has been screening and recruiting hospital patients to donate stool and serum for a biorepository to be used in the study. "It's clear that disturbances in the gut microbiota caused by prior use of antibiotics play a central role in C. difficile," says Kutzler. "Having a diverse microbiome is very important in protecting against these infections."
After one episode of C. diff infection, a person has a 10 to 20 percent chance of recurrence. After a second episode, this rises to 40 to 65 percent. After a third episode, the rate is 80 percent.
The most therapeutic and cost-effective treatment to date for recurrent C. diff is fecal microbiota transplantation (FMT). Nandi has been performing this procedure since 2009, and at Drexel since 2014, as an investigational therapy under IRB approval. Drexel College of Medicine was the first academic medical center in the Philadelphia region to offer FMT. "In FMT, we lavage the colon to get rid of as many C. diff spores as possible. Then we flood the colon with stool from a healthy donor," Nandi explains. "One FMT can result in a 91 percent remission rate. A second FMT can result in a 97 percent remission rate."
Looking to the future, Kutzler is developing a DNA-based vaccine that neutralizes the toxins created by the C. diff bacteria. Drexel has patented the vaccine and licensed it to Inovio Pharmaceuticals. It is in the preclinical testing phase.
Kutzler's lab is also collaborating with Pfizer to test its C. diff vaccine, which is in Phase 3 clinical trials. Drexel is the only site in Philadelphia that is testing this vaccine.
Nandi is pleased with their efforts. "C. diff is a devastating infection. It can cause dehydration, which may lead to kidney damage, and toxic megacolon, all of which can lead to death," he explains. "We are excited about the work we're doing to control this epidemic."
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