Laboratory, Growth Chamber, and Greenhouse Microbial Safety: Plant Pathogens and Plant-Associated Microorganisms of Significance to Human Health

Abstract

This chapter focuses on risk characterization and mitigation of worker exposure during culturing, inoculation of plants, and diagnosis of plant pathogens known to affect human health. There are increasing numbers of plant-pathogenic microbial organisms associated with human diseases or maladies. By the standard that agents are not associated with disease in healthy adult humans, almost all the plant pathogens and plant-associated microorganisms are in NIH risk group 1, for which biosafety level 1 (BL1) is usually recommended. By-products of plant pathogens in food, such as mycotoxins, can also cause illness. Healthy adults are not normally at risk of being infected by plant-associated microorganisms, but allergic reactions may occur. Good laboratory practices and some specific suggestions for dealing with plant-associated microorganisms are found in the methods manuals previously cited and the NIH guidelines. Samples of plant material obtained for isolation of pathogens or biocontrol agents are protected from contamination by using aseptic techniques. In the laboratory or greenhouse, autoclaving cultures and pathogen-infected material, or otherwise rendering them biologically inactive, is routine. Chemicals are not available or cost-effective for controlling many plant pathogens, and biocontrol agents are few. Other management practices to decrease the inoculum, and thus decrease exposure, are crop rotation, planting of resistant varieties (where available), planting date, and plowing under infected or infested plant material. These practices decrease inoculum by the process of competition with other microorganisms in the soil, where many plant pathogens are poor survivors.