Stachybotrys chartarum (chartarum = atra = alternans) and other problems caused by allergenic fungi

Abstract

Stachybotrys chartarum is a cellulose-decaying fungus with worldwide distribution. It grows well at room temperature and with humidity above 93%. S. chatarum requires special media high in cellulose and low in sugar and nitrogen to compete with Penicillium and Aspergillus. Ninety percent of field-collected spores are not culturable. S. chartarum can produce macrocyclic trichothecenes but is highly dependent on strain and environmental conditions. In strains implicated in mycotoxicosis, not all produce detectable trichothecenes. Therefore, the presence of S. chartarum is not proof of toxin presence. Trichothecenes are potent inhibitors of protein and DNA synthesis. By the inhalation route, occupational stachybotrytoxicosis causes chest and upper airway symptoms, fever, leucopenia, dermatitis; starts in 2-3 days of exposure; and lasts 3 weeks. Investigation of the environment of the cluster of pulmonary hemorrhage in 10 infants in Cleveland, Ohio, and similar cases elsewhere are presented. The Centers for Disease Control and Prevention considers S. chartarum a serious health threat. However, even though there are now techniques of measuring S. chartarum conidia and estimating trichothecene mycotoxin in indoor air samples, no standards exist that relate to health effects. Those standards available are numerical or comparison of indoor/outdoor counts or both. Upper limit of noncontaminated indoor environment is 100-1000 colony-forming units (CFU) m3. There is no compelling evidence that exposures expected in most mold-contaminated indoor environments are likely to result in measurable health effects. However, when the health care worker suspects a problem in the home environment, a questionnaire and home visit may be helpful. High indoor exposures are associated with infrequent ventilation or vacuuming, pets, visible mold, and old carpets. To screen the indoor air, an experienced pollen and mold counter could use a Burkard personal air sampler. Health-based exposure standards for molds and mycotoxins do not exist. When available data indicate extremely high mold levels, cleanup consisting of removal of all contaminated material, cleaning accessible heating, ventilation, and airconditioning parts and filters, and preventive maintenance are indicated. There is a brief summary of the diseases of plants, animals, and humans caused by several common allergenic fungi and the mycotoxins they produce.