Genetic Diversity of Human Pathogenic Members of the Fusarium oxysporum Complex Inferred from Multilocus DNA Sequence Data and Amplified Fragment Length Polymorphism Analyses: Evidence for the Recent Dispersion of a Geographically Widespread Clonal Lineage and Nosocomial Origin

Abstract

Fusarium oxysporum is a phylogenetically diverse monophyletic complex of filamentous ascomycetous fungi that are responsible for localized and disseminated life-threatening opportunistic infections in immunocompetent and severely neutropenic patients, respectively. Although members of this complex were isolated from patients during a pseudoepidemic in San Antonio, Tex., and from patients and the water system in a Houston, Tex., hospital during the 1990s, little is known about their genetic relatedness and population structure. This study was conducted to investigate the global genetic diversity and population biology of a comprehensive set of clinically important members of the F. oxysporum complex, focusing on the 33 isolates from patients at the San Antonio hospital and on strains isolated in the United States from the water systems of geographically distant hospitals in Texas, Maryland, and Washington, which were suspected as reservoirs of nosocomial fusariosis. In all, 18 environmental isolates and 88 isolates from patients 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 that a recently dispersed, geographically widespread clonal lineage is responsible for over 70% of all clinical isolates investigated, including all of those associated with the pseudoepidemic in San Antonio. Moreover, strains of the clonal lineage recovered from patients were conclusively shown to genetically match those isolated from the hospital water systems of three U.S. hospitals, providing support for the hypothesis that hospitals may serve as a reservoir for nosocomial fusarial infections. Members of the phylogenetically diverse monophyleticFusarium oxysporum complex (FOC) are best known as cosmopolitan soilborne plant pathogens that are responsible for economically devastating vascular wilts of an enormous range of agronomically important plant hosts (6). Members of the FOC are also frequently isolated from nonplant sources, particularly from the soil but also from air and animals. Over the past 2 decades, however, fusaria have emerged as opportunistic pathogens causing life-threatening disseminated infections in immunocompromised patients (3). In patients who are persistently neutropenic, deeply invasive fusarial infections cause 100% mortality (18). Most localized and disseminated cases of fusariosis are caused by members of the Fusarium solani species complex, followed by members of the FOC (1). Fortunately, the recent development of one strain of F. oxysporum as a model system will greatly facilitate the molecular genetic dissection of fungal virulence determinants during plant and animal pathogenesis (24).Although molecular epidemiological studies have been completed for nosocomial fusariosis (1, 25), most of the analyses were conducted on members of the F. solani species complex.

Fungal root endophytes of tomato from Kenya and their nematode biocontrol potential

“…Total DNA was extracted from 20 mg of lyophilized mycelia using the Wizard Magnetic DNA Purification System for Food (Promega, Mannheim, Germany) according to the manufacturer's instructions. The ITS region was amplified using ITS1-F (5′-TCCGTAG GTGAACCTGCGG-3′) and ITS4-R (5′-TCCTCCGC TTATTGATATGC-3′) primers (White et al 1990), while the tef1α was amplified using EF-1 (5′-ATGGGTAA GGARGACAAGAC-3′), EF-2 (5′-GGARGTACCA GTSATCATG-3′) primers (O'Donnell et al 2004) and EF1-728F(5′-CATCGAGAAGTTCGAGAAGG-3′), EF1-986R (5′-TACTTGAAGGAACCCTTACC-3′) primers for Trichoderma specific isolates (Carbone and Kohn 1999). The ß-tubulin region was amplified using Bt2a (5′-GGTAACCAAATCGGTGCTGCTTTC-3′) and Bt2b (5′-ACCCTCAGTGTAGTGACCCTTGGC-3′) primers (Glass and Donaldson 1995).…”

Polyphasic insights into the microbiomes of the Takamatsuzuka Tumulus and Kitora Tumulus

“…Recently, at least 300 phylogenetically distinct species were estimated (O'Donnell et al, 2015). O'Donnell et al (2004O'Donnell et al ( , 2007 and Zhang et al (2006) reported that fusaria pathogenic to humans and other animals belong to either the FSSC or FOSC clade. In light of the conclusion by Dupont et al (2007) regarding the Lascaux Cave, we suggested that most TT and KT fusaria in the FSSC clade 3 were also deeply involved in the deterioration of the murals .…”

EF-1α gene and IGS rDNA sequencing of Fusarium oxysporum f. sp. vasinfectum and F. oxysporum f. sp. phaseoli reveals polyphyletic origin of strains

“…Within formae speciales, subdivision into races has also been described based on the ability of distinct strains to infect different varieties of a plant host species (O'Donnell et al, 2009). Fusarium oxysporum strains that can cause infection in humans and animals have also been described which cause high mortality in immunodeprived patients (O'Donnell et al, 2004). Although morphological distinction of F. oxysporum from other species of the genus is attainable, infra-specific identification with such method is not feasible.…”