chapter 25 - microbial infection and pathogenesis Flashcards
What is an infection?
microorganism is established in a host, whether or not a host is harmed
What is a disease?
actual damage or injury that impairs host functions
What are pathogens?
microbial parasites that cause disease or tissue damage in a host
What is pathogenicity?
ability of a parasite to inflict damage of host
What is the infection process?
- exposure to pathogens
- adherence
- invasion
- multiplication
What is adherence
the ability of microbes to attach to host tissues
Why is adherence necessary
- necessary but not sufficient to start a disease
- pathogens adhere to epithelial cells by interactions between molecules on pathogens and host tissues.
- pathogen can form biofilm
What are the ways of entry of pathogens?
- mucous membranes
- skin surface
- punctured wounds
What are adhesins?
receptors (made up of glycoproteins and lipoprotein) on pathogen surface
What are host receptors?
extracellular matrix
cell surface glycoproteins
membrane liquid
Why do capsules from thick coating outside plasma membrane and cell walls?
- sticky and contains specific receptors to facilitate attachment to host tissue
- can evade host defense system
What are the different types of adherence structures?
- Fimbriae: uniformly distributed structures on bacterial cell surface. (implicated in specific adherence in infections by enteric bacteria).
- Pili: involved in attachment to urogenital epithelia by Neisseria gonorrhoeae
- Flagella: facilitates adherence to host cells
What is colonization and when does it occur?
growth of microorganims after they have gained access to host tissues.
begins at birth, while exposed to harmless bacteria.
What is the colonization mechanism?
- tightly packed epithelial cells line surface of urogenital, respiratory and digestive tracts; secretes mucous.
- mucous retains moisture and naturally inhibits microbial attachment through physical process (sneezing, swallowing)
- some microbes/pathogens/nonpathogens adhere + colonize
What is mucous?
thick secretion of water-soluble glycoproteins
What is saliva?
contains acid glycoproteins that forms film on tooth surface providing attachment site
What are dental plaques made of?
thick biofilm caused by extensive bacterial growth. (high lactic acid decalifies tooth enamel, resulting in cavities)
What is invasion?
the ability of pathogen to grow in host tissue, spread and cause disease
What is bacteremia?
presence of bacteria in the bloodstream, asymptomatic because immune system will remove them
What is septicemia?
bacteria multiplying in bloodstream spread systematically from initial point producing toxin
(usually beginning in a specific organ (intestine, kidney, lung. May lead to massive inflammation, septic shock)