chapter 5 microbiology Flashcards
whats a pathogen?
microorganism capable of causing disease
what does opportunistic mean?
cause disease only in compormised individuals
LD 50
“lethal dose” number of organisms needed to kill half the hosts cells
ID 50
Infectious dose, number of organisms needed to infect half the hosts
Communicable disease
spread from host to host. When a disease is highly communicable it is considered contagious
Endemic
constanly present at a low level in a specific population
Epidemic
occurs more frequently than usual
pandemic
worldwide distribution
stages of infectious diseases are….
incubation period, prodomal period, acute specific illness, recovery period.
incubation period
time between acquisition of organism or toxin and the commencement of symptoms
prodomal period
non specific symptoms like fever and malaise, loss of appetite
acute specific illness
specific symptoms start occurring
recovery period
illness stops and returns to normal
what are the determinates of pathogenicity?
transmission, adherence, invasiveness and toxigenicity
How are pathogens transmitted?
inhalation, ingestion, inoculation
name the 4 important portals of entry for pathogens
skin, respiratory tract, gastrointestinal tract, genitourinary tract
what are biofilms?
aggregates of interactive bacteria attached to a solid surface( including prosthesis). Up to 65% of human infections are associated with biofilms
what is a quorum in biofilms?
sensing molecules- biofilms secrete this which tend to repulse incoming bacteria or activate the communal bacteria to seek new bodies
sessile organisms in biofilms
harder to eradicate when sessile
planktonic biofilm organisms
easier to eradicate
what does collagenase and hyaluronidase to for bacteria
degrade intercellular substances allowing easy spread of bacteria through tissue
what does coagulase do for bacteria?
accelerates formation of fibrin clot which helps protect the organisms from phagocytes
what does immunoglobulin A protease do for bacteria?
kills IgA on mucosal layers
leukocidins role for bacteria is …
kills neutrophilic leukocytes and macrophages