Original Article Elmer ress J Clin Med Res • 2011;4(1):17-19 Association Between Appendectomy and Clostridium difficile Infection Rashida Merchanta, William R. Mowera, c, Ariel Ouriana, Fredrick M. Abrahamianb, Gregory J. Moranb, Anusha Krishnadasanb, David A. Talanb Abstract Background: Recent theory proposes that the appendix functions as a reservoir for commensal bacteria, and serves to re-inoculate the colon with normal flora in the event of pathogen exposure or purging of intestinal flora. If true, we reasoned that flora from a nor- mal appendix could provide protection against Clostridium difficile. We conducted this investigation to examine the protective effect of an intact appendix and test the hypothesis that prior appendectomy will be more common among patients with a positive test for C. dif- ficile as compared with patients who test negative. Methods: We contacted patients who had undergone C. difficile testing and asked them whether or not they had a prior appendec- tomy. Using their responses and results from Toxin A & B EIA tests, we calculated the difference in appendectomy rates between those who tested positive for C. difficile, and those who tested negative. We considered a positive 15% absolute difference to represent a significant increase in appendectomy rate. Results: We enrolled 257 patients. Among the 136 who tested posi- tive for C. difficile, 27 (19.9%) had prior appendectomies, while among 121 patients testing negative for C. difficile, 38 (31.4%) had Manuscript accepted for publication December 1, 2011 aThe UCLA Emergency Medicine Center, UCLA Geffen School of Medicine, Los Angeles, CA, USA bDepartment of Emergency Medicine, Olive View-UCLA Medical Center, Sylmar, CA, UCLA Geffen School of Medicine, Los Angeles, CA, USA cCorresponding author: William R. Mower, UCLA-Emergency Medicine Center, 924 Westwood Blvd, Los Angeles, CA 90024, USA. Email: wmower@ucla.edu doi:10.4021/jocmr770w prior appendectomies, yielding a difference in appendectomy rates of -11.6% (95% Confidence Interval: -21.6% to -0.9%). Conclusions: The rate of prior appendectomy was actually lower among patients with a positive C. difficile test as compared to those with a negative test. Conversely, patients who tested positive for C. difficile were more likely to have an intact appendix than those who tested negative. These results suggest that rather than being protec- tive, an intact appendix appears to promote C. difficile acquisition, carriage, and disease. Keywords: Clostridium difficile; Appendix; Appendectomy; Mi- crobial reservoir; Infection Introduction The vermiform appendix is theorized to serve as a microbial reservoir that facilitates re-inoculation of colonic bacteria after serious gut infections [1, 2]. The appendix can harbor both commensal and potentially pathogenic bacteria and al- low these organisms to live in a state of biofilm, with the various microbes existing in a symbiotic relationship [1]. Additionally, the location of the appendix may contribute to its function as a reservoir for normal colonic bacteria since it provides somewhat of a distance and barrier from feces and contamination from potential pathogenic organisms [1, 2]. The idea that the appendix has the ideal environment to house enteric bacteria in biofilms is plausible, and its role in immune protection may be based upon providing normal colonic flora in times of need [1, 2]. The bacterium C. difficile is the most common cause of nosocomial diarrhea, with rates of C. difficile associated disease (CDAD) increasing, particularly among the elderly, adults, and children [3-7]. The generally accepted theory for the pathogenesis of C. difficile involves the disruption of normal intestinal flora, typically in the setting of prior antibi- otic use, which allows C. difficile to proliferate [5]. If the concept that the appendix serves a protective func- tion as reservoir for normal colonic bacteria is true, then it seems plausible that the risk of infections with pathogenic Articles © The authors | Journal compilation © J Clin Med Res and Elmer Press™ | www.jocmr.org 17