Host pathogens Flashcards
microbiota
the microorganisms that normally colonize various sites in/within the body without causing disease
resident microbiota
inhabit sites for extended periods
transient microbiota
inhibit temporarily for days, weeks, or months then disappear
colonization
ability of microbe to stay affixed to a body surface and replicate
what does our microbiota do
competitively exclude pathogens
- covering of binding sites prevents attachment
- consumption of available nutrients
- production of compounds toxic to other bacteria
how is microbiota acquired
humans are initially colonized by microorganisms at birth
what can perturb our microbiota
by age 3, a child’s microbiome looks a lot like an adult’s and it becomes much more stable
pathogen
any bacterium, virus, fungus, protozoan, or helminth that causes disease
pathogenicity
the ability of an organism to cause disease
true (primary) pathogens
can cause disease in a host regardless of the host’s resident microbiota or immune system
* are never part of the normal microbiota
opportunistic pathogens
cause disease only under opportunistic conditions
- changes in the composition of the normal microbiota
- can be members of normal microbiota or common in the environment
infection
successful colonization and multiplication of microorganism within a host with or without the manifestation of disease
infectious disease
illness caused by damage to host cells by an infectious agent or its products resulting in signs and symptoms
virulence
degree or severity of disease
lethal dose 50 (LD50)
the number of microbes that kills 50% of an experimental group of animal hosts
infectious dose 50 (ID50)
number of microbes that will cause infection in approximately 50% of an experimental group of hosts
stages of pathogenesis
exposure and entry
adhesion to skin or mucosa
invasion through epithelium and immune invasion
infection
toxins or host immune response
tissue damage, disease
fecal-oral portal of entry
through mucosal surfaces of gastrointestinal transportct
respiratory portal of entry
through musical surfaces of respiratory tract
transplacental portal of entry
through the placenta to infect a fetus
skin portal of entry
through epithelial surfaces
urogenital portal of entry
through mucosal surfaces of genital and urinary tracts
parenteral portal of entry
through injection into the bloodstream (for example, infect bites or needle sticks)
adhesion
fimbriae adhesions
cell wall adhesions
glycocalyzx (slime and capsular polysaccharides)