PHS Lab 3 quiz Flashcards
(43 cards)
the coagulase is what kind of test
biochemical
the agglutination test is what kind of test
serological
purpose of the coagulase test
distinguish between staph aureus (pathogenic) and staph epi (not pathogenic)
true or false
coagulase negative means it’s staph epidermidis
true
explain the principle of the coagulase test
coagulase convers fibrinogen into fibrin when incubated with bacteria.
thus, bacteria that produce coagulase (staph aureus) will precipitate rabbit plasma. it will be GELLED, while the coagulase negative will be liquid
name 3 things that need to be done in order for the coagulase test to be accurate
-use same amount of inoculum
-if you dont add enough bacterial colonies — false negatives will occur
-refrigerate the rabbit plasma!! it can degrade if not refrigerated
explain what a coagulase negative vs positive test tube will look like in our lab
positive - the liquid will NOT FLOW and will be a thick opaque clot
negative - the liquid will be free flowing
true or false
an infection always causes a disease
FALSE
true or false
in order for there to be a disease, the host must be infected by a microorganism
TRUE
but, infection does NOT always cause disease
define pathogenicity
the ability of an organism to cause disease
define virulence
the degree of pathogenicity within a group/species of microorganisms
how are some bacteria HIGHLY VIRULENT?
bc they have virulence factors that decrease the host defenses and assist the survival and growth of the bacteria – increase tissue damage and their ability to invade
what are “strict pathogens”
name 2
ALWAYS associated with pathogenicity
mycobacterium TB, Nessieria gonorrhea
define opportunistic pathogens
they take advantage of the environment and the compromised host to cause an infection
give 2 examples of opportunistic pathogens and explain how they are opportunistic
staph epi – normally on the skin and commensal, but can cause UTI
pseudomonas - causes resp tract infections in immunocomp and hospitalized ppl
define commensals and give an example
they colonize the normal flora of the host and are often beneficial to the host
e. coli – live in large intestine because of the rich nutrients there. they synthesize vitamin K!
the severity and occurrence of infectious disease depends on….. (4 things)
patient factors (bb or imm. comp)
size of the inoculum of bacteria
the site of infection
virulence factors
in order for ____ infection to occur, the bacterial inoculum usually must be large
salmonella
a low microbial count _______ (where) may signify a SERIOUS infection
in a normally sterile environemnt
like blood, CSF, pleural fluid, and urine in the bladder and kidneys
name 3 bacteria that cause UTI even tho they are part of the normal flora
name the flora they are part of
staph epi - skin throat, eye, reproductive system
e. coli - small and large intestine, reproductive system
pseudomonas - small and large intestine
name 2 kinds of virulence factors
give specific example of each
enzymes and toxins
enzyme - coagulase produced by staph aureus protects the bacteria from being phagocytised!!
toxins - e coli, staph, and salmonella have enterotoxins that cause gastroenteritis
serological tests like agglutination are designed to do what?
detect the presence of antibodies in serum to a specific antigen(s)
3 broad types of bacterial antigens and where they are derived from
O, H, and K antigens
O - derived from cell wall of gram (-) bacteria
H - derived from flagella of motile enteric bacilii
K - a surface antigen part of the polysaccharide capsule. secreted by the organism
virulent strains are named based on the presence of antigens
E. coli O157:H7 causes…….
Salmonella O group D9-12 causes…..
severe gastroenteritis
typhoid fever
