ARS | Publication request: GENETIC DIVERSITY OF HUMAN PATHOGENIC MEMBERS OF THE FUSARIUM OXYSPORUM COMPLEX INFERRED FROM GENE GENALOGIES & AFLP ANALYSES: EVIDENCE FOR THE RECENT DISPERSION OF A GEOGRAPHICALLY WIDESPREAD CLONAL LINEAGE & NOSOCOMIAL ORIG

Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 14, 2004
Publication Date: November 1, 2004
Citation: O Donnell, K., Sutton, D.A., Rinaldi, M.G., Magnon, K.C., Cox, P.A., Revankar, S.G., Sanche, S., Geiser, D.M., Juba, J.H., Van Burik, J.H., Padhye, A., Robinson, J.S. 2004. Genetic diversity of human pathogenic members of the fusarium oxysporum complex inferred from gene genalogies & aflp analyses: evidence for the recent dispersion of a geographically widespread clonal lineage & nosocomial orig. Journal of Clinical Microbiology. 42(11):5109-5120.

Interpretive Summary: Members of the filamentous mold genus Fusarium are best known for the economically devastating plant diseases they cause and for the plethora of toxins they produce that negatively impact on animal health and food safety. Over the past two decades, however, fusaria have emerged as the second most important group of opportunistic fungal pathogens due to the dramatic rise in immunocompromised and artificially immunosuppresed patients. The present molecular epidemiological study was conducted to determine the genetic diversity and relatedness of clinical isolates of the F. oxysporum complex, focusing on isolates from a Texas hospital reporting a pseudoepidemic in 1997-1998 and on strains isolated from the water system of geographically distant hospitals in Texas, Maryland and Washington suspected as a reservoir of hospital-acquired fusariosis. Over 70% of the clinical isolates investigated, including all of those from the pseudoepidemic and the water system of 3 hospitals, were shown to be members of a highly related genetic clone. Moreover, strains of the clone recovered from patients were conclusively shown to genetically match those isolated from the hospital water system of three U.S. hospitals, providing support for the hypothesis that hospitals may serve as a reservoir for fusarial infections.

Technical Abstract: Fusarium oxysporum is a phylogenetically diverse monophyletic complex of filamentous ascomycetous fungi responsible for localized and systemic life-threatening opportunistic infections, respectively, in immunocompetent and severely neutropenic patients. Although members of this complex were isolated in a pseudoepidemic and the water system from separate Texas hospitals during the 1990s, nothing is known about their genetic relatedness and population structure. This study was conducted to investigate the genetic diversity and population biology of a comprehensive set of clinically important members of the F. oxysporum complex, focusing on the 33 isolates from the Texas hospital reporting the pseudoepidemic and on strains isolated in the United States from the water system of geographically distant hospitals in Texas, Maryland and Washington suspected as a reservoir of nocosomial fusariosis. In all, 18 environmental isolates and 88 isolates from humans spanning four continents were genotyped. The major finding of this study, based on concordant results from phylogenetic analyses of multilocus DNA sequence data and amplified fragment length polymorphisms, is a recently dispersed geographically widespread clone is responsible for over 70% of all clinical isolates investigated, including all of those associated with the pseudoepidemic in Texas. Moreover, stains of the clone recovered from patients were conclusively shown to genetically match those isolated from the hospital water system of three U.S. hospitals, providing support for the hypothesis that hospitals may serve as a reservoir for nosocomial fusarial infections, and that care should be taken to protect immunocompromised patients from these sources.