Is “community-acquired” CDI real?

A recent high profile US study delved into apparent community-associated CDI cases to evaluate healthcare exposures. The study was large, evaluating almost 1000 cases of community-associated CDI from 8 US states. Only 177 (18%) of the 984 cases had no recent healthcare exposure (Figure 1). Furthermore, healthcare exposure was only evaluated for the 12 weeks prior to the positive specimen, so I would wager that a portion of this 18% acquired their infecting C. difficile in a healthcare facility.  CA-CDIFigure 1. Data demonstrating that most MRSA and CDI presenting on admission to hospital are likely to have been acquired in a healthcare facility.  

So, it seems that the majority of these cases are more likely to be community-onset, healthcare-acquired CDI, rather than community-acquired CDI. I feel like we’ve been here before. In the 1990s before the emergence of distinct strains of CA-MRSA, MRSA presenting at hospital admission was commonly termed ‘community-associated’ or, worse, ‘community-acquired’ when really it was MRSA that had been acquired in hospital during a previous stay (Figure 1). The situation has now changed since distinct MRSA clones have emerged that have the capacity to cause infection outside the healthcare environment.

Turning our attention to the UK, the mandatory report scheme classifies cases of CDI as ‘Trust-apportioned’ if the specimens is collected from patients who have been in hospital for four or more days (Figure 2). It is tempting to speculate that the cases of CDI that are non Trust-apportioned are CA-CDI. However, the definition for ‘Trust-apportioned’ does not account for previous healthcare contact, and the rate of Trust-apportioned and non-Trust-apportioned cases tracks so closely that, once again, these are likely to be healthcare-acquired CDI presenting on admission.

Slide1Figure 2. Number of cases of CDI in England through the mandatory reporting scheme, 2004-2013.

The epidemiology of C. difficile is fundamentally different to MRSA, in that healthy neonates typically have a high rate of C. difficile colonization. Thus, there is a ready reservoir for a low rate of genuinely community-acquired CDI. However, it seems to me that most “CA-CDI” reported thus are likely to be acquired in a healthcare facility and I have not seen any data to convince me that community-acquired CDI is increasing.

Article citation: Chitnis et al. Epidemiology of Community-Associated Clostridium difficile Infection, 2009 Through 2011. JAMA Intern Med 2013;173:1359-67.

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