|Short, Dylan P|
Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/23/2011
Publication Date: 12/1/2011
Citation: Short, D.G., O'Donnell, K., Zhang, N., Juba, J.H., Geiser, D.M. 2011. Widespread occurrence of diverse human pathogenic types of the fungus Fusarium detected in plumbing drains. Journal of Clinical Microbiology. 49(12):4264-4272. Interpretive Summary: The number of deeply invasive infections of humans caused by member of the filamentous fungus Fusarium has increased significantly over the past couple of decades. This increase is attributed primarily to the expanding number of immunocompromised and immunosupressed patients. Because fusarial infections in patients who are persistently and profoundly immunologically impaired are often fatal, it has become a significant public health concern. The present study was conducted to test the hypothesis that plumbing systems might serve as a significant environmental reservoir of human pathogenic isolates. At least one Fusarium culture was recovered from 80% of buildings (N = 131) and 66% of sinks (N = 471) sampled. DNA typing of the 297 Fusarium isolates collected revealed that the six most common types in sinks were identical to the six most common types associated with human infections. This result strongly supports an epidemiological link between Fusarium infections and plumbing systems and suggests that the drain inhabiting types may be well adapted to forming and growing in biofilms. The results of this study should be of interest to and benefit: 1) epidemiologists who are charged with identifying and protecting patients at risk from this environmental reservoir, 2) infectious disease specialists in diagnosing and treating fungal infections, and 3) clinical microbiologist’s efforts to elucidate the genetic diversity of these pathogens. Moreover, knowledge of this reservoir, and the proclivity of the most common fusaria to form and grow in biofilms, provides disease control specialists with knowledge critical to reducing the exposure of patients at risk to these opportunistic pathogens.
Technical Abstract: It has been proposed that plumbing systems might serve as a significant environmental reservoir of human pathogenic isolates of Fusarium. We tested this hypothesis by performing the first extensive multilocus sequence typing (MLST) survey of plumbing drain-associated Fusarium isolates, and comparing the diversity observed to the known diversity of clinical Fusarium isolates. We sampled 471 drains, mostly in bathroom sinks, from 131 buildings in the United States using a swabbing method. We found that 66% of sinks and 80% of buildings surveyed yielded at least one Fusarium culture. The 297 isolates of Fusarium collected were subjected to MLST to identify the phylogenetic species and sequence types (STs) of these isolates. Our survey revealed that the six most common STs in sinks were identical to those most frequently associated with human infections. These results have important implications for human health in that they support the hypothesized epidemiological link between Fusarium infections and plumbing systems, and indicate a very high potential for exposure to these pathogens. The relative rarity of Fusarium infections, however, indicates that routine exposure does not present an increased risk except to the growing population of persistently neutropenic individuals. We speculate that the most prevalent STs, by virtue of their ability to form and grow in biofilms, are well adapted to plumbing systems.