PHS Lab 3 quiz Flashcards
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
the agglutination test is a ___-___ test performed where?
what will occur if the bacteria is mixed with its corresponding antibody??
antigen-antibody
in a slide or in a tube
there will be macroscopic clumping bc an antibody-antigen complex will be formed
the ____ test is useful to detect ____ carriers who harbor the bacteria but are asymptomatic
aggulutination
salmonella
salmonella antigen is mixed with the individual’s serum
the sera (pale yellow) and the antigen solutions for the agglutination test must be kept in what conditions?
on ice
explain what a negative vs positive agglutination test will look like
positive - will show clumped areas and clear areas
negative - the suspension will be homogenously cloudy/opaque
name the classification, shape, and if they are lactose fermenters:
pseudmonas
e. coli
salmonella
pseudomonas and salmonella:
gram negative bacilli (rod shaped), do NOT ferment lactose
e. coli - gram negative bacilli (rod) and DO ferment lactose
compare and contrast staph aureus and epi
both are gram positive cocci that grow in clusters and are high in salt
staph aureus ferments mannitol and staph epi does NOT
gram positive cocci that grow in chains
name 2 possible bacteria
strep pyogenes
strep agalactiae
gram positive bacilli (rods)
name 1
cornebacterium
diptheriae
what color do gram positive vs gram negative appear
gram positive - blue
gram negative - pink
acid fast bacteria stain what color?
name 1
mycobacterium tubercuolosis
RED
which bacteria (plural) grow on nutrient agar media
anything, just not fastidious (have specific growth requirement)
it’s a nonselective basal media
which type of bacteria grow on mannitol salt agar and why
gram positive bacteria like staph aureus
high salt concentration inhibits the growth of gram (-)
which bacteria grows on macConkey agar and why
gram (-)
crystal violet and bile salts inhibit the growth of gram (+)
differentiate between prophylactic, empiric, and definitive antimicrobial therapy
prophylactic - prevent a disease from occuring
empiric - initiating treatment before a firm diagnosis and the specific microorganism is not known. – cover the pathogens that are known to be associated with specific sites of infection
definitive - therapy based on lab results – antibiotic sensitivity
when treating infections, the peak concentraiton of antibiotic in the infected tissue must have what relationship to MIC?
be equal to or greater then
prophylactic therapy is used to prevent post op infections such as…
endocarditis
chemoprophylaxis is used to prevent..
development of disease when travelling to endemic areas (malaria)
the USP criteria for antimicrobial effectiveness depends on
the product category
