Division of Infectious Diseases
The MUSC Infection Prevention Laboratory (MUSCIPL) is centered on evaluating the hypothesis that healthcare facilities are the primary incubators of human C. difficile infections, even for infections that occur in the community without apparent connections to hospital care. My current K23 award involves a comprehensive study of C. difficile epidemiology in a cohort of solid organ and bone marrow transplant patients, a group in whom asymptomatic carriage is presumed to be exceptionally prevalent. I have also previously conducted cross-sectional prevalence studies of C. difficile carriage in healthy, ambulatory adults, and this cohort continues to expand as more such colonized individuals are identified in the course of screening fecal transplant donors in the context of my clinical work with this treatment modality for recurrent C. difficile infections. My existing studies are centered on evaluation of the transmission patterns among asymptomatic carriers of C. difficile within inpatient and outpatient care settings.
My principal contribution to C. difficile microbiology and epidemiology has been to further establish the role that asymptomatic carriers play in the transmission of C. difficile to new patients. Based on several hospital cohort studies from the 1980s, asymptomatic carriers were known to outnumber symptomatic patients within hospitals, but the limited genotyping tools of the 1980s did not allow for direct evidence that asymptomatic carriers of C. difficile were the sources for disease transmission. Indirect evidence of such transmission at a ward level was possible using restriction endonuclease typing by the early 1990s (Clabots CR et al. J Infect Dis. 1992 Sep; 166(3):561-7), but my 2013 Clinical Infectious Diseases study was the first to document by multilocus variable number of tandem repeats analysis (MLVA), a highly discriminatory genotyping tool, that asymptomatic patients colonized with C. difficile regularly contaminate their hospital environments and regularly transmit their C. difficile to other patients both directly and via inadequately disinfected hospital rooms. The proportion of new C. difficile patients in the study with evidence of asymptomatic carriers as their transmission source was at least as great as that with C. difficile transmitted from symptomatic patients. My subsequent 2014 Journal of Clinical Microbiology study of healthy, non-hospitalized adults showed that 7/106 ambulatory asymptomatic adults are colonized with C. difficile. This suggests that asymptomatic carriers may be a source of continuous flow of new C. difficile into hospitals.