Plant and Human Pathogenic Bacteria Exchanging their Primary Host Environments

Adaptation of plant and human pathogenic bacteria to niches of existence differing from their original ones is a sophisticated mechanism for survival. Research indicates that certain plant bacterial pathogens are capable of causing disease in humans, and some human bacterial pathogens can inhabit the plant environment and cause disease in plants. The infection of humans by plant bacteria may occur at direct physical contact with diseased plants and/or via the respiratory tract in mainly immunocompromised or otherwise stressed individuals. Indirect transmitters of plant and human microbes can be wind, rain, dust, insects, and animals. Human pathogenic bacteria may contaminate the soil and irrigation water, colonize the rhizosphere, more rarely also the phyllosphere, and can survive as epiphytes. Thus, the plant environment may become a reservoir of human pathogens. A source of foodborne human pathogenic bacteria can be unprocessed or unwashed fruits and vegetables. Especially during the last decade, the processes underlying the cross-kingdom performance of pathogenic bacteria are intensively researched. However, in reality, the risk for human health at infections by plant bacteria and by human bacterial pathogens surviving in the plant environment is still underestimated. The goal of the current review is to increase the interest in these issues in agricultural and general environments. Some basic strategies for infection and symptoms of diseases caused by the microorganisms under consideration are described. The potency of certain plant bacterial pathogens to surpass barriers towards humans and the interaction of human bacterial pathogens with the plant environment are addressed and the existing information is critically discussed.