Hester F. Vismer

Production of fumonisin analogs by Fusarium species.

The fumonisins, a family of food-borne carcinogenic mycotoxins, were first isolated in 1988 (21) from cultures of Fusarium verticillioides (Sacc.) Nirenberg (previously known as Fusarium moniliforme Sheldon). During the same year, the structures of the fumonisins were elucidated (6) and fumonisin B1 was shown to cause equine leukoencephalomalacia (34). There have been numerous publications dealing with this group of novel, carcinogenic mycotoxins, and comprehensive reviews of different aspects of the fumonisins are available (20, 22, 23, 24, 35, 36, 37, 41, 43, 46, 52, 55, 60, 61, 66). Due to the widespread occurrence of the fumonisins in maize, a dietary staple in many countries, the carcinogenic risk of fumonisins to humans was evaluated by the International Agency for Research on Cancer in 1993, and the toxins produced by F. moniliforme were evaluated as “Group 2B carcinogens,” i.e., probably carcinogenic to humans (24). This review focuses on the Fusarium species that produce fumonisins and the fumonisin analogs produced by each of these species.

Phylogeny of the Ophiostoma stenoceras-Sporothrix schenckii complex

Ophiostoma stenoceras is a well-known sapwood-colonizing fungus occurring on some coniferous and hardwood hosts in the Northern Hemisphere. In the Southern Hemisphere, the fungus has been reported only from New Zealand. The human pathogen, Sporothrix schenckii, has been suggested to be the anamorph of O. stenoceras. The aim of this study was to gain a better understanding of the phylogenetic relationship between these two species. The study also provided the opportunity to confirm the identity of some Sporothrix and O. stenoceras-like isolates recently collected from wood and soil around the world. For this purpose, the DNA sequence of internal transcribed spacer (ITS) regions of the ribosomal RNA operon was determined. Isolates of O. nigrocarpum, O. albidum, O. abietinum, O. narcissi and O. ponderosae, all morphologically similar to O. stenoceras, were included in the study. From phylogenetic analyses of the sequence data, four main clades were observed. These represented O. stenoceras, O. nigrocarpum and two separate groups containing isolates of S. schenckii. Our results confirm earlier suggestions that S. schenckii should be classified within the teleomorph genus Ophiostoma but support studies separating O. stenoceras and S. schenckii. Ophiostoma albidum and O. ponderosae should be considered synonyms of O. stenoceras. The status of O. narcissi and O. abietinum needs further clarification. The two groups within S. schenckii might represent two species, but this needs to be confirmed. This study represents the first reports of O. stenoceras from Colombia, Kenya, Uruguay and South Africa.

Taxonomy and phylogeny of new wood- and soil-inhabiting Sporothrix species in the Ophiostoma stenoceras-Sporothrix schenckii complex

Sporothrix, one of the anamorph genera of Ophiostoma, includes the important human pathogen S. schenckii and various fungi associated with insects and sap stain of wood. A survey of fungi from wood utility poles in South Africa yielded two distinct groups of Sporothrix isolates from different geographical areas. DNA sequence and morphological data derived in this study showed that isolates in these groups represent two novel species in the S. schenckii-O. stenoceras species complex. A new species isolated from pine poles and rosebush wood and phylogenetically closely related to S. pallida is described here as Sporothrix stylites. Phylogenetic analyses also confirmed the synonymy of S. albicans and S. nivea with S. pallida. Sporothrix stylites and S. pallida also are related closely to the isolates from soil, previously treated as “environmental” isolates of S. schenckii. Soil isolates are clearly distinct from human isolates of S. schenckii. We describe the former here as Sporothrix humicola. The isolates from eucalypt poles group peripheral to most other species in the S. schenckii-O. stenoceras complex and are newly described as Sporothrix lignivora. Phylogenetic analyses of sequences of isolates from soil and wood together with those of clinical isolates showed that the human-pathogenic strains form an aggregate of several cryptic species.

A dimorphic fungus causing disseminated infection in South Africa.

BACKGROUND The genus emmonsia contains three species that are associated with human disease. Emmonsia crescens and Emmonsia parva are the agents that cause adiaspiromycosis, and one human case of Emmonsia pasteuriana infection has been described. We report a fungal pathogen within the genus emmonsia that is most closely related to E. pasteuriana in human immunodeficiency virus (HIV)-infected adults in South Africa. METHODS Between July 2008 and July 2011, we conducted enhanced surveillance to identify the cause of systemic, dimorphic fungal infections in patients presenting to Groote Schuur Hospital and other hospitals affiliated with the University of Cape Town, Cape Town, South Africa. DNA sequencing was used to identify pathogenic fungi. RESULTS A total of 24 cases of dimorphic fungal infection were diagnosed, 13 of which were caused by an emmonsia species. All 13 patients were HIV-infected, with a median CD4+ T-cell count of 16 cells per cubic millimeter (interquartile range, 10 to 44), and all had evidence of disseminated fungal disease. Three patients died soon after presentation, but the others had a good response to a variety of antifungal agents and antiretroviral therapy. Phylogenetic analysis of five genes (LSU, ITS1-2, and the genes encoding actin, β-tubulin, and intein PRP8) revealed that this fungus belongs in the genus emmonsia and is most closely related to E. pasteuriana. CONCLUSIONS The findings suggest that these isolates of an emmonsia species represent a new species of dimorphic fungus that is pathogenic to humans. The species appears to be an important cause of infections in Cape Town.

Reduction of patulin in apple juice samples — influence of initial processing

Abstract Patulin is a secondary metabolite produced by a wide range of fungi including Penicillium expansum, a common contaminant of apples. Patulin is reputed to be a mutagen and recommendations have been made that levels should not exceed 50 ng g in apple juice intended for human consumption. The production of apple juice requires the use of ripe fruit, which may be pre-disposed to fungal contamination with P. expansum and concurrent contamination with patulin. During a study using selected over-ripe fruit, triplicate samples of apples were withdrawn at several points prior to maceration. The mean patulin level in the non-processed fruit was found to be 920 ng g , but this level dropped to 190 ng g following an initial water treatment step. Analyses of the wash water showed that appreciable levels had been transferred from the solid to the aqueous phase. Additional removal, by hand, of rotten and damaged fruit prior to further processing, significantly reduced the mean patulin level in the juice to 55 ng g . High patulin levels were recorded in the rotten fractions ( mean = 2335 ng g ). Mycological analyses tended to support the chemical data, in that removal of the rotten fruit significantly reduced the total fungal counts in the juice samples.

Prevalence, epidemiology and geographical distribution of Sporothrix schenckii infections in Gauteng, South Africa.

Sporotrichosis is a subcutaneous fungal infection caused by the traumatic implantation of the dimorphic, pathogenic fungus, Sporothrix schenkii. It constitutes the most common subcutaneous fungal infection in the general population in South Africa. Sporotrichosis in South Africa dates back to 1914, when the disease was first diagnosed in the gold mines. Occupational and recreational circumstances of infection are well established, and the environmental requirements for contracting the disease are better understood. Sporotrichosis cases were recorded from 42 suburbs in the greater Pretoria area as well as from 23 towns outside the Pretoria municipal boundary. It occurred in 154 patients with ages ranging from less than 1 year to 90 years old, with males predominating. Females in the area seemed to be at lesser risk, mainly becoming infected through gardening injuries, insect bites or other minor injuries due to outdoor activities. Exposure to possible sources of the fungus, either from recreational or occupational activities in males, was the main determining factor in acquiring the disease. The lymphocutaneous and localized forms of the disease were most often recorded. Our study indicates that, while there is no pronounced seasonal variation, the onset of the disease seemed to be mainly in the cooler and dryer months of the year.

Cancer patterns in four districts of the Transkei region — 1991 - 1995

BACKGROUND Oesophageal cancer (OC) is an important public health problem among the Xhosa-speaking people of the Transkei region in the Eastern Cape Province, South Africa, with incidence rates for males among the highest in the world. OBJECTIVES To record the occurrence of cancer among men and women of all ages in four districts in the Transkei during the period 1991-1995, to identify common cancers and to compare the variations in cancer incidences in this region with incidences in Africa and the rest of the world. DESIGN Cancer registration of cases reported from all clinics and hospitals was conducted in the four selected districts. SETTING The districts included Centane (Kentani), Butterworth, Bizana and Lusikisiki in the Transkei region. METHODS Active and passive methods were used to collect data, which were analysed using the Statistical Analyses Systems (SAS) package. RESULTS The mean annual number of all cancer cases reported was 310, with age-standardised incidence rates (ASIRs, world standard) of 98.2/100,000 and 74.3/100,000 for males and females, respectively. The most frequently reported cancer was OC, with mean annual ASIRs of 76.6/100,000 and 36.5/100,000 for males and females, respectively, with a male/female ratio of 2:1. CONCLUSION The present data confirm previous reports that OC rates in Centane have consistently remained very high, whereas time-dependent changes in the incidence of OC have occurred in Butterworth, Bizana and Lusikisiki suggesting changes in the risk determinants in these districts.

Fumonisin production by Fusarium species isolated from freshly harvested corn in Iran.

Fifty-one strains of Fusarium verticillioides and F. proliferatum isolated from corn collected from four different geographic areas in Iran, namely Fars, Khuzestan, Kermanshah and Mazandaran (an endemic oesophageal cancer (OC) area) were evaluated for their ability to produce fumonisins B1 (FB1), B2 (FB2) and B3 (FB3) in corn culture. Fumonisin levels were determined by high-performance liquid chromatography. All tested strains of F. verticillioides and F. proliferatumproduced fumonisins within a wide range of concentrations, 197–9661 μg/g, 18–1974 μg/g, and 21–1725 μg/g for FB1, FB2, and FB3, respectively. The highest mean concentrations of FB1, FB2, and FB3 were 3897, 806 and 827 μg/g, respectively. Overall, 61% of the F. verticillioides and F. proliferatum strains produced higher levels of FB3 than FB2. The mean ratios of FB1:FB2, FB1:FB3 and FB1:total fumonisins were 8, 7 and 0.7 for F. verticillioides and 5.7, 10.7 and 0.7 for F. proliferatum, respectively. Significant differences in some of the meteorological data (rainfall, relative humidity and minimum temperature) from the four provinces were observed. Fumonisin levels produced by F. verticillioides strains isolated from Khuzestan province (tropical zone) were significantly (P < 0.01) higher than the other three provinces. This is the first report of the fumonisin-producing ability of F.verticillioides and F. proliferatum strains isolated from corn harvested from different geographic areas in Iran.

Production of Fumonisins by Fusarium Verticillioides Strains on Solid and in a Defined Liquid Medium — Effects of L-Methionine and Inoculum

In order to evaluate the toxicological and carcinogenic effects of fumonisins, large amounts of fumonisins need to be purified, which requires optimal conditions for production in culture. Five strains of F. verticillioides were compared for their ability to produce fumonisins in solid and liquid media with and without the addition of methionine, a fumonisin precursor. Inoculations were made either with lyophilized cultures or a concentrated inoculum. Growth in liquid medium, measured by biomass, was directly correlated to total fumonisin production when a lyophilized inoculum was used. Fumonisin production was stimulated by the addition of0.2% L-methionine to solid media for most strains. Levels ranged from 1500–3900 mg/kg in rice, and 2900–12500 mg/kg in maize cultures inoculated with lyophilized cultures; 200–4800 mg/kgin rice, and 1500–4200 mg/kg in maize cultures inoculated with concentrated inoculum. Strains that produced relatively high levels of fumonisins in solid media did not necessarily do so in liquid medium and vice versa. Total fumonisin levels in liquid medium ranged from 40–590 mg/l inoculated with lyophilized cultures and < 1–110 mg/l inoculated with concentrated inoculum, without adding the precursor. F. verticillioides strains therefore varied in their ability to produce fumonisins, and conditions for production need to be optimized individually for each strain.

Molecular Characterization of Fusarium globosum Strains from South African Maize and Japanese Wheat

The fungus Fusarium globosum was first isolated from maize in South Africa and subsequently from wheat in Japan. Here, multiple analyses revealed that, despite morphological similarities, South African maize and Japanese wheat isolates of the fungus exhibit multiple differences. An amplified fragment length polymorphism-based similarity index for the two groups of isolates was only 45%. Most maize isolates produced relatively high levels of fumonisins, whereas wheat isolates produced little or no fumonisins. The fumonisin biosynthetic gene FUM1 was detected in maize isolates by Southern blot analysis but not in the wheat isolates. In addition, most of the maize isolates produced sclerotia, and all of them produced large orange to dark purple sporodochia in carrot agar culture, whereas wheat isolates did not produce either structure. In contrast, individual isolates from both maize and wheat carried markers for both mating type idiomorphs, which indicates that the fungus may be homothallic. However, a sexual stage of F. globosum was not formed under standard self-fertilization conditions developed for other homothallic species of Fusarium. The inability to produce the sexual stage is consistent with the high similarity of 87–100% and GST index of 1.72 for the maize isolates, which suggests that these isolates are undergoing asexual but not sexual reproduction. Together, the results suggest that the South African maize and Japanese wheat isolates of F. globosum are distinct populations and could be different species.