Fungi associated with drug recalls and rare disease outbreaks

Donald G Ahearn, R Doyle Stulting

Fungi rarely cause disease outbreaks associated with use of microbe-contaminated drugs. These rare episodes typically involve a restricted spectrum of common environmental species with relatively low virulence, rather than classical pathogens. Review of data involving over-the-counter contact lens solutions and prescription drug-related recalls revealed six episodes during the past decade with significant adverse health and financial impact (including loss of vision and death). Contaminations involved fungi mostly identified with the genera Aspergillus, Exserohilum, Fusarium, Paecilomyces, and Rhizopus. These organisms are noted for their capacity to produce resistant morphotypes (chlamydoconidia, ascospores) under various adverse conditions, generally with temperature survival/tolerances markedly in excess of maximal growth temperatures. High constituent levels of melanin, trehalose and heat-shock proteins facilitate differential survival of morphotypes following exposures to toxic chemicals and temperatures above 80 °C. Adverse environmental factors that induce resistant morphotypes are suggested to occur more readily in situ than during in vitro testing. Rare unexplained, sporadic drug contamination episodes with select thermotolerant fungi may relate, in part, to resistant dormant stages.