A new bacteriophage (phage) treatment-based approach to fighting Clostridium difficile (C. difficile) colonization and infection may one day provide for effective treatment against this potentially lethal disease.
A new bacteriophage (phage) treatment-based approach to fighting Clostridium difficile (C. difficile) colonization and infection may one day provide for effective treatment against this potentially lethal disease, according to the results of a study published recently in Antimicrobial Agents and Chemotherapy.1
Almost 40% of antibiotic-associated diarrhea cases in North America, Europe, and Australia are attributable to C. difficile (Peptoclostridium difficile) infection (CDI), which results in death in 10% of these cases.2 Acute cases of CDI are typically treated with antibiotics; however, this therapeutic approach has at least two important drawbacks. Not only has it been associated with high rates of recurrence, but it also creates conditions that allow for the development of antibiotic resistance.3 Collectively, a high prevalence rate combined with a high cost of infection control and less-than adequate treatment options make CDI a significant and ongoing clinical and economic burden.4,5
The use of phage therapy, which has been embraced in parts of Eastern Europe and Western Asia, is under investigation in several clinical trials, and has demonstrated efficacy in the past by fighting chronic and antibiotic-resistant suppurative infections.6 However, phage therapy has not been applied to CDI for a variety of reasons associated with C. difficile biology. Although difficult to accomplish, this technique has enormous potential to relieve the burdens associated with CDI.
Senior author Martha Clokie, PhD, a Professor of Microbiology in the Department of Infection Immunity and Inflammation at the University of Leicester, told Contagion that, "We did this work as there is a clear need for alternative treatment options for Clostridium difficile." In order to address this pressing need, Dr. Clokie and her colleagues used a variety of in vitro and in vivo methodologies to identify and characterize phages capable of accessing the C. difficile lytic life cycle, as well as determine their anti- C. difficile activity individually and in combination against clinically relevant C. difficile ribotypes.
The study produced a large suite of results. Seven effective phages were isolated, one siphovirus and six myoviruses. Using in vitro techniques, the host ranges of the phages were determined using 80 strains representing 21 major epidemic and clinically severe ribotypes. The seven phages provided complementary coverage as single-phage treatments, as demonstrated by their ability to lyse 18 of the 21 (86%) ribotypes and 62 of the 80 (78%) strains. When used independently, the phages demonstrated mixed and variable lytic properties, but when used in various combinations, higher C. difficile clearance rates and lower levels of regrowth were observed.
The efficacy of the most effective four-phage cocktail was also assessed using an in vivo hamster model. In one set of experiments, the cocktail was administered as animals were infected and at regular intervals thereafter prior to gut colonization analysis. Animals not treated with the cocktail showed high levels of C. difficile colonization in the lumen of the cecum and colon at 36 hours postinfection, while treated animals had significantly lower levels of recovered C. difficile colony forming unit counts in these same tissues. Challenge experiments were also conducted in order to assess the efficacy of the cocktail on CDI symptoms. Following the same infection/treatment regimen, animals were monitored for a body temperature drop of 2°C to 35°C, a sign that the animal is unable to recover from the infection. Those animals that did not receive treatment with the cocktail reached this endpoint at approximately 55 hours, which was significantly faster than treated animals (approximately 88 hours; P = 0.0007).
In order to place her team's study results into context, Dr. Clokie told Contagion that, "Using bacteriophages is a logical option but it took a long time to identify phages that target the correct strains of this pathogen. In this work we show that our phages can kill most of the clinically relevant and prevalent strains and optimized combinations are effective in clearing the bacteria when tested in vitro and in vivo. Whilst there is still a lot of work to do before these phages can be used to treat patients, we are excited at how promising they look at this stage."
William Perlman, PhD, CMPP is a former research scientist currently working as a medical/scientific content development specialist. He earned his BA in Psychology from Johns Hopkins University, his PhD in Neuroscience at UCLA, and completed three years of postdoctoral fellowship in the Neuropathology Section of the Clinical Brain Disorders Branch of the National Institute of Mental Health.