Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/14/2010
Publication Date: 1/27/2010
Citation: Migheli, Q., Balmas, V., Harak, H., Sanna, S., Scherm, B., Aoki, T., O Donnell, K. 2010. Molecular Phylogenetic Diversity of Dermatologic and Other Human Pathogenic Fusaria from Hospitals in Northern Italy. Journal of Clinical Microbiology. 48(4):1076-1084. Interpretive Summary: Although Fusarium is best known as the most important group of toxin-producing plant pathogens, over 60 species within this large group of filamentous moulds have been shown to cause localized or deeply invasive infections in humans and other animals. Fusarial infections in an immunosuppressed or immunocompromised host are typically fatal if the patient fails to regain normal immune function. Accurate identification of human pathogenic fusaria requires the use of DNA typing data to accurately report on the pathogen. In this study 58 fusaria isolated from 52 Italian patients between 2004 and 2007 were subject to multilocus DNA sequence typing to characterize the spectrum of species and circulating genotypes associated with dermatological infections and other fusarioses in Northern Italy. Results of the molecular typing revealed that the isolates were genetically diverse and that they were nearly evenly divided among three large species complexes. DNA typing also revealed that three patients had mixed infections caused by two genetically distinct fusaria. Moreover, one patient was infected with a heretofore novel fusarial pathogen, Fusarium guttiforme. Further characterization of the latter pathogen revealed that it was pathogenic to its only known host, pineapple. Importation of F. guttiforme-containing pineapple into non-indigenous areas where this crop is produced could have devastating results, given that pineapple fusariosis has become a major constraint to the production of this crop in certain regions of South America. Accurate reporting on the agents of human and plant disease is absolutely critical to disease control and prevention, and is essential for communication of their epidemiology and population biology within the public health and phytopathological communities. Results of the present study will be of interest to and benefit clinical microbiologists, epidemiologists and plant pathologists.
Technical Abstract: Fifty-eight fusaria isolated from 52 Italian patients between 2004 and 2007 were subject to multilocus DNA sequence typing to characterize the spectrum of species and circulating sequence types (STs) associated with dermatological infections, especially onychomycoses and paronychia, and other fusarioses in Northern Italy. Sequence typing revealed that the isolates were nearly evenly divided among the Fusarium solani (FSSC, N =18), the F. oxysporum (FOSC, N = 20) and Gibberella (Fusarium) fujikuroi (GFSC, N = 20) species complexes. The three-locus typing scheme used for members of the FSSC identified 18 novel STs distributed among six phylogenetically distinct species, yielding an index of discrimination of 1.0. Phylogenetic analysis of the FOSC two-locus dataset identified nine STs, including four which were novel, and nine isolates of ST 33, the previously described widespread clonal lineage. With the inclusion of eight epidemiologically unrelated ST 33 isolates, the FOSC typing scheme scored a discrimination index of 0.787. The two-locus GFSC typing scheme, which was designed primarily to identify species, received the lowest discrimination index with a score of 0.492. The GFSC scheme, however, was used to successfully identify 17 isolates as F. verticillioides, two as F. sacchari and one as F. guttiforme. Because the present study represents the first report of the latter species causing a human mycotic infection, detailed morphological analyses were conducted which supported the molecular identification. In addition, results of a pathogenicity experiment revealed that the human isolate of F. guttiforme was able to induce fusariosis of pineapple, heretofore it’s only known host.