PHS Lab 3 quiz

Question 1

the coagulase is what kind of test

Answer 1

biochemical

Question 2

the agglutination test is what kind of test

Answer 2

serological

Question 3

purpose of the coagulase test

Answer 3

distinguish between staph aureus (pathogenic) and staph epi (not pathogenic)

Question 4

true or false

coagulase negative means it’s staph epidermidis

Answer 4

true

Question 5

explain the principle of the coagulase test

Answer 5

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

Question 6

name 3 things that need to be done in order for the coagulase test to be accurate

Answer 6

-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

Question 7

explain what a coagulase negative vs positive test tube will look like in our lab

Answer 7

positive - the liquid will NOT FLOW and will be a thick opaque clot

negative - the liquid will be free flowing

Question 8

true or false

an infection always causes a disease

Answer 8

FALSE

Question 9

true or false

in order for there to be a disease, the host must be infected by a microorganism

Answer 9

TRUE

but, infection does NOT always cause disease

Question 10

define pathogenicity

Answer 10

the ability of an organism to cause disease

Question 11

define virulence

Answer 11

the degree of pathogenicity within a group/species of microorganisms

Question 12

how are some bacteria HIGHLY VIRULENT?

Answer 12

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

Question 13

what are “strict pathogens”

name 2

Answer 13

ALWAYS associated with pathogenicity

mycobacterium TB, Nessieria gonorrhea

Question 14

define opportunistic pathogens

Answer 14

they take advantage of the environment and the compromised host to cause an infection

Question 15

give 2 examples of opportunistic pathogens and explain how they are opportunistic

Answer 15

staph epi – normally on the skin and commensal, but can cause UTI

pseudomonas - causes resp tract infections in immunocomp and hospitalized ppl

Question 16

define commensals and give an example

Answer 16

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!

Question 17

the severity and occurrence of infectious disease depends on….. (4 things)

Answer 17

patient factors (bb or imm. comp)
size of the inoculum of bacteria
the site of infection
virulence factors

Question 18

in order for ____ infection to occur, the bacterial inoculum usually must be large

Answer 18

salmonella

Question 19

a low microbial count _______ (where) may signify a SERIOUS infection

Answer 19

in a normally sterile environemnt

like blood, CSF, pleural fluid, and urine in the bladder and kidneys

Question 20

name 3 bacteria that cause UTI even tho they are part of the normal flora

name the flora they are part of

Answer 20

staph epi - skin throat, eye, reproductive system

e. coli - small and large intestine, reproductive system

pseudomonas - small and large intestine

Question 21

name 2 kinds of virulence factors

give specific example of each

Answer 21

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

Question 22

serological tests like agglutination are designed to do what?

Answer 22

detect the presence of antibodies in serum to a specific antigen(s)

Question 23

3 broad types of bacterial antigens and where they are derived from

Answer 23

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

Question 24

virulent strains are named based on the presence of antigens

E. coli O157:H7 causes…….

Salmonella O group D9-12 causes…..

Answer 24

severe gastroenteritis

typhoid fever

Question 25

the agglutination test is a ___-___ test performed where?

what will occur if the bacteria is mixed with its corresponding antibody??

Answer 25

antigen-antibody

in a slide or in a tube

there will be macroscopic clumping bc an antibody-antigen complex will be formed

Question 26

the ____ test is useful to detect ____ carriers who harbor the bacteria but are asymptomatic

Answer 26

aggulutination

salmonella

salmonella antigen is mixed with the individual’s serum

Question 27

the sera (pale yellow) and the antigen solutions for the agglutination test must be kept in what conditions?

Answer 27

on ice

Question 28

explain what a negative vs positive agglutination test will look like

Answer 28

positive - will show clumped areas and clear areas

negative - the suspension will be homogenously cloudy/opaque

Question 29

name the classification, shape, and if they are lactose fermenters:

pseudmonas
e. coli
salmonella

Answer 29

pseudomonas and salmonella:
gram negative bacilli (rod shaped), do NOT ferment lactose

e. coli - gram negative bacilli (rod) and DO ferment lactose

Question 30

compare and contrast staph aureus and epi

Answer 30

both are gram positive cocci that grow in clusters and are high in salt

staph aureus ferments mannitol and staph epi does NOT

Question 31

gram positive cocci that grow in chains

name 2 possible bacteria

Answer 31

strep pyogenes
strep agalactiae

Question 32

gram positive bacilli (rods)

name 1

Answer 32

cornebacterium
diptheriae

Question 33

what color do gram positive vs gram negative appear

Answer 33

gram positive - blue

gram negative - pink

Question 34

acid fast bacteria stain what color?
name 1

Answer 34

mycobacterium tubercuolosis

RED

Question 35

which bacteria (plural) grow on nutrient agar media

Answer 35

anything, just not fastidious (have specific growth requirement)

it’s a nonselective basal media

Question 36

which type of bacteria grow on mannitol salt agar and why

Answer 36

gram positive bacteria like staph aureus

high salt concentration inhibits the growth of gram (-)

Question 37

which bacteria grows on macConkey agar and why

Answer 37

gram (-)

crystal violet and bile salts inhibit the growth of gram (+)

Question 38

differentiate between prophylactic, empiric, and definitive antimicrobial therapy

Answer 38

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

Question 39

when treating infections, the peak concentraiton of antibiotic in the infected tissue must have what relationship to MIC?

Answer 39

be equal to or greater then

Question 40

prophylactic therapy is used to prevent post op infections such as…

Answer 40

endocarditis

Question 41

chemoprophylaxis is used to prevent..

Answer 41

development of disease when travelling to endemic areas (malaria)

Question 42

the USP criteria for antimicrobial effectiveness depends on

Answer 42

the product category