MICROBIOLOGY CSMLS EXAM PREP
QUESTIONS & WELL DETAILED
ANSWERS|| GRADED A+|| LATEST
UPDATE 2026
if there is no zone of inhibition, what do you record? -CORRECTANSWER 6mm
because that accounts for the disc
what causes sharp irregular zones around the sensitivity discs? -CORRECTANSWER
beta-lactam antibiotics
- indicates that beta-lactamase production by the bacteria and should be interpreted as
resistant
susceptible vs intermediate vs resistant -CORRECTANSWER - susceptible =
susceptible to action of the antimicrobials and is stopped or killed by it
- intermediate = used for certain drug combinations that are difficult to test or produce
results of certainty
- resistant = resistant to the action of antimicrobial and keeps growing in its presence
,QC for susceptibility tests -CORRECTANSWER - each time new discs or panels are
received
- each time tests are performed (once a week)
- organisms are staph aureus, E.coli, pseudo, enterococcus
how should antimicrobial discs be stored? -CORRECTANSWER - long term = frozen at
-20C
- working supply in 4C
MRSA conditions -CORRECTANSWER - addition of NaCl
- 30-35C (lower temp is better)
- displays trailing on disc diffusion methods
- healthcare workers are screened for it
- use oxacillin screen test
Haemophilus test medium (HTM) is supplemented with -CORRECTANSWER - bovine
hematin
- yeast extract
- NAD
- thymidine phosphorylase
E-test is beneficial for using it on -CORRECTANSWER - anaerobes
- fastidious bacteria
,E-test results interpretation: low MIC and high MIC -CORRECTANSWER low MIC -
sensitive
high MIC - resistant
Staphylococcus aureus characteristics -CORRECTANSWER - double zone of beta
hemolysis
- creamy yellow color from lipochrome @48H
- ferments mannitol (yellow)
- catalase positive
- nitrate positive
- slide or TUBE coagulase positive
MSA media (mannitol salt agar) -CORRECTANSWER - 7.5% NaCl
- differential = mannitol and phenol red
- if it ferments mannitol it will be yellow, if it does not then it will be red
- staph aureus ferments (yellow)
MRSA oxacillin screen test -CORRECTANSWER - 6ug oxacillin
- 4% NaCl
- any growth on plate = resistant
, slide coagulase vs tube coagulase -CORRECTANSWER - slide = bound coagulase
- tube = free coagulase
false negative coagulase tests are commonly from -CORRECTANSWER weak bacterial
suspensions
gold standard of staph aureus is -CORRECTANSWER positive tube coagulase
what is found on the cell wall of S. aureus but not other staph species? -
CORRECTANSWER Protein A and clumping factor = used in latex reagent methods
thermostable nuclease test is used for -CORRECTANSWER ID of staph aureus
- food microbiology investigations of food poisoning
staphylococcus saprophyticus ID -CORRECTANSWER - bright white opaque colonies
- catalase positive
- nitrate positive
- novobiocin resistant
- common UTI
QUESTIONS & WELL DETAILED
ANSWERS|| GRADED A+|| LATEST
UPDATE 2026
if there is no zone of inhibition, what do you record? -CORRECTANSWER 6mm
because that accounts for the disc
what causes sharp irregular zones around the sensitivity discs? -CORRECTANSWER
beta-lactam antibiotics
- indicates that beta-lactamase production by the bacteria and should be interpreted as
resistant
susceptible vs intermediate vs resistant -CORRECTANSWER - susceptible =
susceptible to action of the antimicrobials and is stopped or killed by it
- intermediate = used for certain drug combinations that are difficult to test or produce
results of certainty
- resistant = resistant to the action of antimicrobial and keeps growing in its presence
,QC for susceptibility tests -CORRECTANSWER - each time new discs or panels are
received
- each time tests are performed (once a week)
- organisms are staph aureus, E.coli, pseudo, enterococcus
how should antimicrobial discs be stored? -CORRECTANSWER - long term = frozen at
-20C
- working supply in 4C
MRSA conditions -CORRECTANSWER - addition of NaCl
- 30-35C (lower temp is better)
- displays trailing on disc diffusion methods
- healthcare workers are screened for it
- use oxacillin screen test
Haemophilus test medium (HTM) is supplemented with -CORRECTANSWER - bovine
hematin
- yeast extract
- NAD
- thymidine phosphorylase
E-test is beneficial for using it on -CORRECTANSWER - anaerobes
- fastidious bacteria
,E-test results interpretation: low MIC and high MIC -CORRECTANSWER low MIC -
sensitive
high MIC - resistant
Staphylococcus aureus characteristics -CORRECTANSWER - double zone of beta
hemolysis
- creamy yellow color from lipochrome @48H
- ferments mannitol (yellow)
- catalase positive
- nitrate positive
- slide or TUBE coagulase positive
MSA media (mannitol salt agar) -CORRECTANSWER - 7.5% NaCl
- differential = mannitol and phenol red
- if it ferments mannitol it will be yellow, if it does not then it will be red
- staph aureus ferments (yellow)
MRSA oxacillin screen test -CORRECTANSWER - 6ug oxacillin
- 4% NaCl
- any growth on plate = resistant
, slide coagulase vs tube coagulase -CORRECTANSWER - slide = bound coagulase
- tube = free coagulase
false negative coagulase tests are commonly from -CORRECTANSWER weak bacterial
suspensions
gold standard of staph aureus is -CORRECTANSWER positive tube coagulase
what is found on the cell wall of S. aureus but not other staph species? -
CORRECTANSWER Protein A and clumping factor = used in latex reagent methods
thermostable nuclease test is used for -CORRECTANSWER ID of staph aureus
- food microbiology investigations of food poisoning
staphylococcus saprophyticus ID -CORRECTANSWER - bright white opaque colonies
- catalase positive
- nitrate positive
- novobiocin resistant
- common UTI
