COMMENTARY

C difficile: Why Good ID Advice Still Matters

Paul G. Auwaerter, MD

Disclosures

March 20, 2017

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Hello. This is Paul Auwaerter, speaking for Medscape Infectious Diseases from the Johns Hopkins University School of Medicine.

I just finished several weeks on the inpatient infectious diseases consultation service. No surprise—we were asked to assist in the management of patients with Clostridium difficile infection or suspected infection. I continue to be surprised at the different practice patterns and assumptions by house staff and others on how to best manage this infection. I thought I would spend a few minutes musing about a couple of these areas.

The first is about diagnostics. Many institutions have adopted molecular testing technologies for C difficile that are more sensitive when compared with toxin-based methods. However, I saw the [molecular] test being used on patients who had one or two loose bowel movements—clearly not C difficile. The pretest probability was low; it was probably antibiotic-associated or related to tube feedings.

Continued efforts to try and educate people on when to order a C difficile test are important. It will always remain within the realm of judgment, but typically, you would like to see many, progressive, loose bowel movements before considering testing.[1]

Oral vancomycin, according to several studies, has become the drug of choice for moderate and severe C difficile infection. Yet, I see oral or intravenous metronidazole still being used, even for potentially severe C difficile infection. A recent large Veterans Administration study[2] confirmed that vancomycin is superior for severe C difficile, with a 4% lower chance of 30-day mortality.

I see a few other things routinely that I am not sure have any real basis in patients with a functioning alimentary canal. I see intravenous metronidazole being combined with oral vancomycin, with the typical American medicine philosophy that more must be better, when that is clearly not the case. I see oral vancomycin 500 mg, four times daily, being routinely given to patients without an ileus. The idea that 500 mg must be better than the standard 125-mg dose has no good basis in fact. The intraluminal levels of vancomycin are sky high at 125 mg, with this nonabsorbable antibiotic.

I also see people adopting a vancomycin taper for almost all patients, even those who might be receiving antibiotics concomitantly or systemically. Of course, there is a wide practice pattern, but I don’t think that first-time C difficile patients truly require a vancomycin taper. It could have other detrimental effects on the microbiome.

Another issue is fecal microbiota transplantation (FMT). Many of us thought this was a godsend. Early studies showed very high success rates. Now, with more experience, we are seeing cases that are not improved by FMT. Indeed, a recent, small, open-label study by Hota and colleagues[3] was terminated early because recurrence rates with FMT were 56% compared with 41% for oral vancomycin with a 6-week taper. As we begin to expand the use of FMT, we are not sure who is the right population to target for FMT.

Another issue is fidaxomicin. We said that oral vancomycin is the drug of choice for severe C difficile infection, but fidaxomicin has been shown to result in a lower recurrence rate; instead of the 25%-30% range, it is more in the upper teens. Yet, the expense has been a barrier to widespread adoption.

A new drug was just approved and is now on the market—bezlotoxumab, a monoclonal antibody against toxin B.[4] [Editor's note: The author indicated approval for both toxins A and B originally, but bezlotoxumab is approved only for toxin B, so we have made the correction here.] This is exciting technology, which achieves about a 10% reduction in recurrence rates compared with customary treatment. It is unknown how this will fit in and whether costs will largely mimic the fidaxomicin story to date.

Finally, some of the best successes against C difficile have taken place through limiting antibiotic use. A recent study[5] from the United Kingdom showed the impact of limiting fluoroquinolones: a marked improvement in C difficile rates on a population basis.

There are many areas in which infectious diseases physicians can make an impact on patient care and antimicrobial stewardship. You may have your own thoughts or see some other practices that do not have a great basis or are based on misunderstandings. I would be happy to hear about those. Thanks very much for listening.

Editor's Note: We encourage you to use the comments section to point out any concerns in clinical practices in the care of patients with C difficile infection that you have seen as well.

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