It is well-established that fidaxomicin reduces the recurrence rate of C. difficile infection (CDI), but this study from my old research group at GSTT / KCL is the first to evaluate the impact of treatment with fidaxomicin on environmental contamination. The bottom line is that patients treated with fidaxomicin had less C. difficile contamination than patients treated with vancomycin / metronidazole.

In total, the rooms of 38 / 66 (57.6%) patients treated with metronidazole / vancomycin had one or more positive environmental cultures compared with 25 / 68 (36.8%) patients treated with fidaxomicin (P = 0.02). Similarly, when considering all of the sampled environmental sites (four per room), 68 / 264 (25.8%) were positive in patients treated with metronidazole / vancomycin compared with 47 / 272 (17.3%) in patients treated with fidaxomicin (P = 0.02) (see Figure below).

Figure: Environmental contamination with C. difficile in the rooms of patients treated with fidaxomicin vs. vancomycin / metronidazole.

There are two plausible mechanisms by which treatment with fidaxomicin would result in reduced environmental contamination. One is through a shorter duration of symptoms. Another is through reduced shedding of spores during symptoms. There was no difference in the PCR Ct value between the two groups, suggesting that the bacterial load was not massively different, at least at the time the sample was taken. So, it seems most likely that a shorter duration of symptoms explains the reduced level of environmental contamination. Whilst shorter duration of symptoms for patients on fidaxomicin has been reported previously, it was not measured in this study.

The study was not randomised; instead, it was performed either side of a switch of front-line treatment for CDI from vancomycin / metronidazole to fidaxomicin. Thus, there could have been other changes that explained the difference in contamination. But it’s important to note that no changes to the cleaning / disinfection policy were made during this period, so this seems unlikely.

Curiously, 20-25% of the C. difficile isolated in the patient’s room did not match the ribotype of the current room occupant. It’s tempting to say that this is leftover from the previous room occupant, but the hospital uses hydrogen peroxide vapour (HPV) for terminal disinfection, so this seems unlikely. Perhaps these patients are infected with more than one ribotype? Or it’s imported into the room by healthcare workers? But the most likely source is from prior occupants who were not recognised to be infected or colonised with C. difficile, and whose rooms were not therefore decontaminated with HPV.

Another curiosity is the finding that patients treated with fidaxomicin stayed in the hospital around twice as long as those treated with vancomycin / metronidazole (median 26 v 12 days, p=0.01). Could it be that patients treated with vancomycin / metronidazole died more quickly / often? This seems unlikely since there was no difference in all-cause 30-day mortality. So this remains a mystery!

So patients treated with fidaxomicin have less C. difficile environmental contamination. Since admission to a room previously occupied by a patient with CDI is a risk factor for acquisition in the incoming occupant, it seems likely that a higher level of contamination would increase this risk further (for hospitals that are not using HPV). But a higher level of C. difficile environmental contamination is also important during the patient’s stay, since it likely increases the chances of contaminating staff hands and equipment.

Fidaxomicin is a lot more expensive than vancomycin / metronidazole, but this study (along with those showing less recurrence and shorter duration of symptoms) suggest that it is money well spent.