Molecular taxonomy of theAlternariaandUlocladiumspecies from humans and their identification in the routine laboratory

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Abstract
Summary. TheAlternariaandUlocladiumspecies reported from humans are studied taxonomically using rDNA internal transcribed spacer (ITS) sequence data. The ITS variability within the genus is relatively limited. The two most important, longicatenate species,Alternaria alternataandA. infectoria, clearly differ in their ITS domains, due to a 26‐bp insert in ITS1 of the latter species. A number of taxa inhabiting particular plant species, such asA. longipeson tobacco andA. malion apple, but also the common saprobic speciesA. tenuissimacannot reliably be distinguished fromA. alternatausing this method. The large number of described noncatenate, obligatory plant pathogens are extremely rare as agents of human disease; clinical routine identification does not need to include these taxa. The predictivity of a simplified polymerase chain reaction–restriction fragment length polymorphism procedure of rDNA for the recognition of the relevant species or species aggregates is established in a randomized test. The method was found to be rapid and cost‐effective. Its efficacy extended to the identification of sterile and meristematicAlternariastrains, some of them previously classified in genera such asChmeliaandBotryomyces. Microscopic morphology and some additional tests remain necessary to allow identification of the aggregates of potential etiological agents of human disease. About 14% of the sequences deposited in GenBank were found to be misidentified.Alternaria infectoriais one of the most common clinicalAlternariaspecies, despite its low degree of melanization. The lack of pigmentation has frequently led to misidentification of such isolates.