Pathogen Health Dictionary

This term means disease-producing, and is a term applied, for example, to bacteria capable of causing disease.... pathogenic

The ways in which a disease or disorder starts and develops. The term applies in particular to the physiological and cellular activities that are involved in the mode of origin and development of the condition.... pathogenesis

Ability to cause disease.... pathogenicity

Micro-organisms that cause diseases, parasitising plants, animals and humans (see PARASITE). Some organisms are frequently PATHOGENIC, whereas others rarely cause disease. Opportunistic pathogens are those which rarely cause serious infection in healthy people but can do so in patients with weakened immune systems (immunocompromised – see IMMUNITY). Pathogens include BACTERIA, viruses (see VIRUS), prions (see PRION), fungi (see FUNGUS), PROTOZOA and metazoa (multicellular microorganisms called HELMINTHS or worms). The pathogenicity of an organism is called its virulence, which is measured by the number of organisms required to cause disease. The 50 per cent of lethal dose (LD50) is the quantity of a particular pathogen needed to cause infection in half of the hosts invaded.... pathogens

The atypical mycobacteria. The commonest PPEM to cause human disease is the Mycobacterium avium-intracellulare complex. PPEM differ from M. tuberculosis in their source (environmental or zoonotic), rate of growth, temperature of growth and ability to produce pigment on culture. Mostly infect immunologically compromised humans and the disease caused by some species may be clinicallyindistinguishable from true human tuberculosis.... potentially pathogenic environmental mycobacteria (ppem)