Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
if there is no zone of inhibition, what do you record? 6mm because that accounts for the disc
beta-lactam antibiotics
what causes sharp irregular zones around the sensitivity
discs? - indicates that beta-lactamase production by the bacteria
and should be interpreted as resistant
- susceptible = susceptible to action of the antimicrobials
and is stopped or killed by it
- intermediate = used for certain drug combinations that
susceptible vs intermediate vs resistant
are difficult to test or produce results of certainty
- resistant = resistant to the action of antimicrobial and
keeps growing in its presence
- each time new discs or panels are received
- each time tests are performed (once a week)
QC for susceptibility tests
- organisms are staph aureus, E.coli, pseudo, enterococ-
cus
- long term = frozen at -20C
how should antimicrobial discs be stored?
- working supply in 4C
- addition of NaCl
- 30-35C (lower temp is better)
MRSA conditions - displays trailing on disc diffusion methods
- healthcare workers are screened for it
- use oxacillin screen test
- bovine hematin
- yeast extract
Haemophilus test medium (HTM) is supplemented with
- NAD
- thymidine phosphorylase
- anaerobes
E-test is beneficial for using it on
- fastidious bacteria
, Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
low MIC - sensitive
E-test results interpretation: low MIC and high MIC
high MIC - resistant
- double zone of beta hemolysis
- creamy yellow color from lipochrome @48H
- ferments mannitol (yellow)
Staphylococcus aureus characteristics
- catalase positive
- nitrate positive
- slide or TUBE coagulase positive
- 7.5% NaCl
- differential = mannitol and phenol red
MSA media (mannitol salt agar) - if it ferments mannitol it will be yellow, if it does not then
it will be red
- staph aureus ferments (yellow)
- 6ug oxacillin
MRSA oxacillin screen test - 4% NaCl
- any growth on plate = resistant
- slide = bound coagulase
slide coagulase vs tube coagulase
- tube = free coagulase
false negative coagulase tests are commonly from weak bacterial suspensions
gold standard of staph aureus is positive tube coagulase
what is found on the cell wall of S. aureus but not other Protein A and clumping factor = used in latex reagent
staph species? methods
ID of staph aureus
thermostable nuclease test is used for
- food microbiology investigations of food poisoning
- bright white opaque colonies
staphylococcus saprophyticus ID - catalase positive
- nitrate positive
, Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
- novobiocin resistant
- common UTI
- leucocidin
- hyaluronidase
what virulence factors does staphylococcus aureus have?
- staphylokinase (clots)
- hemolysins
_______ is the most common cause of skin, soft tissue
S. aureus
and post traumatic infections
1) food poisoning - heat stable enterotoxin (fast)
three diseases caused by S. aureus exotoxins 2) toxic shock syndrome - tampons
3) scalded skin syndrome - rash & desquamation of skin
- penicillin G
what antibiotics can staphylococcus have?
- beta-lactamase (oxacillin and methicillin)
drug of choice for MRSA vancomycin
- 3% hydrogen peroxide
- detects catalase enzyme by breaking the hydrogen per-
oxide down into water and oxygen
catalase test: reagent and purpose
- differentiates staph from strep
- also shows/IDs anaerobes
- light and heat
what can cause breakdown of catalase reagent (hydrogen
peroxide)? - store in amber bottle in fridge
- QC done daily
- platinum wires
false positives for catalase
- picking up some of the BAP agar
- older colonies
false negatives for catalase
- breakdown of hydrogen peroxide
QC organisms for catalase
, Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
- positive = staph
- negative = strep
- durham tube collects gas (positive)
- reagents A and B are added, if red = positive
nitrate reduction test - zinc dust is added and if colourless = positive
- used as the staph genus test
Reagent A - sulfanilic acid in acetic acid
what are reagents A and B in nitrate test?
Reagent B - alpha naphthylamine in acetic acid
reagent for coagulase is rabbit plasma
- citrate anticoagulant = false clotting
false positive coagulase tests - autoagglutination
-
- weak bacterial suspension
- incubation over 35C
false negative coagulase tests
- frequent and excess agitation
- if serum is used = no fibrinogen = no clot
positive = staph aureus
QC organisms for coagulase test
negative = staph epidermidis
- purpose is to detect enzyme that depolymerizes (un-
winds) DNA and convert it into oligonucleotides
DNase test: purpose and positive organisms - staph aureus
- Moraxella
- serratia
- xanthomonas maltophilia
- hydrochloric acid (clearing = positive, cloudy = negative)
Study online at https://quizlet.com/_hlgs66
if there is no zone of inhibition, what do you record? 6mm because that accounts for the disc
beta-lactam antibiotics
what causes sharp irregular zones around the sensitivity
discs? - indicates that beta-lactamase production by the bacteria
and should be interpreted as resistant
- susceptible = susceptible to action of the antimicrobials
and is stopped or killed by it
- intermediate = used for certain drug combinations that
susceptible vs intermediate vs resistant
are difficult to test or produce results of certainty
- resistant = resistant to the action of antimicrobial and
keeps growing in its presence
- each time new discs or panels are received
- each time tests are performed (once a week)
QC for susceptibility tests
- organisms are staph aureus, E.coli, pseudo, enterococ-
cus
- long term = frozen at -20C
how should antimicrobial discs be stored?
- working supply in 4C
- addition of NaCl
- 30-35C (lower temp is better)
MRSA conditions - displays trailing on disc diffusion methods
- healthcare workers are screened for it
- use oxacillin screen test
- bovine hematin
- yeast extract
Haemophilus test medium (HTM) is supplemented with
- NAD
- thymidine phosphorylase
- anaerobes
E-test is beneficial for using it on
- fastidious bacteria
, Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
low MIC - sensitive
E-test results interpretation: low MIC and high MIC
high MIC - resistant
- double zone of beta hemolysis
- creamy yellow color from lipochrome @48H
- ferments mannitol (yellow)
Staphylococcus aureus characteristics
- catalase positive
- nitrate positive
- slide or TUBE coagulase positive
- 7.5% NaCl
- differential = mannitol and phenol red
MSA media (mannitol salt agar) - if it ferments mannitol it will be yellow, if it does not then
it will be red
- staph aureus ferments (yellow)
- 6ug oxacillin
MRSA oxacillin screen test - 4% NaCl
- any growth on plate = resistant
- slide = bound coagulase
slide coagulase vs tube coagulase
- tube = free coagulase
false negative coagulase tests are commonly from weak bacterial suspensions
gold standard of staph aureus is positive tube coagulase
what is found on the cell wall of S. aureus but not other Protein A and clumping factor = used in latex reagent
staph species? methods
ID of staph aureus
thermostable nuclease test is used for
- food microbiology investigations of food poisoning
- bright white opaque colonies
staphylococcus saprophyticus ID - catalase positive
- nitrate positive
, Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
- novobiocin resistant
- common UTI
- leucocidin
- hyaluronidase
what virulence factors does staphylococcus aureus have?
- staphylokinase (clots)
- hemolysins
_______ is the most common cause of skin, soft tissue
S. aureus
and post traumatic infections
1) food poisoning - heat stable enterotoxin (fast)
three diseases caused by S. aureus exotoxins 2) toxic shock syndrome - tampons
3) scalded skin syndrome - rash & desquamation of skin
- penicillin G
what antibiotics can staphylococcus have?
- beta-lactamase (oxacillin and methicillin)
drug of choice for MRSA vancomycin
- 3% hydrogen peroxide
- detects catalase enzyme by breaking the hydrogen per-
oxide down into water and oxygen
catalase test: reagent and purpose
- differentiates staph from strep
- also shows/IDs anaerobes
- light and heat
what can cause breakdown of catalase reagent (hydrogen
peroxide)? - store in amber bottle in fridge
- QC done daily
- platinum wires
false positives for catalase
- picking up some of the BAP agar
- older colonies
false negatives for catalase
- breakdown of hydrogen peroxide
QC organisms for catalase
, Microbiology CSMLS Exam prep
Study online at https://quizlet.com/_hlgs66
- positive = staph
- negative = strep
- durham tube collects gas (positive)
- reagents A and B are added, if red = positive
nitrate reduction test - zinc dust is added and if colourless = positive
- used as the staph genus test
Reagent A - sulfanilic acid in acetic acid
what are reagents A and B in nitrate test?
Reagent B - alpha naphthylamine in acetic acid
reagent for coagulase is rabbit plasma
- citrate anticoagulant = false clotting
false positive coagulase tests - autoagglutination
-
- weak bacterial suspension
- incubation over 35C
false negative coagulase tests
- frequent and excess agitation
- if serum is used = no fibrinogen = no clot
positive = staph aureus
QC organisms for coagulase test
negative = staph epidermidis
- purpose is to detect enzyme that depolymerizes (un-
winds) DNA and convert it into oligonucleotides
DNase test: purpose and positive organisms - staph aureus
- Moraxella
- serratia
- xanthomonas maltophilia
- hydrochloric acid (clearing = positive, cloudy = negative)
