Lab Midterm Flashcards
MSA selective ingredient
7.5% NaCl
MSA differential ingredient
mannitol
are GP or GN more sensitive to salt?
Gram negative
enzyme needed to ferment mannitol?
MOH
color of a mannitol fermenter?
yellow
key Man+ organism
S. aureus
is coagulase performed with serum or plasma?
why?
plasma
it contains clotting factors
molecule that forms a clot
fibrin
CNS besides S. epidermidis
S. haemolyticus
coagulase detects (bound/free) enzyme
bound
bile esculin selective ingredient
bile
bile esculin differential ingredient
esculin
sugar in esculin
glucose
what reacts with esculin to give brown-black color?
iron
special bile esculin condition for Bacteroides
anaerobic environment
organism that would grow on bile esculin
E. faecalis
type II cytotoxins cause —- hemolysis
beta
y-hemolysis organism
E. faecalis
green colored hemolysis
alpha
a-hemolysis organism
S. pneumoniae
a-hemolysis results from…
oxidation of hemoglobin by peroxide to methemoglobin
hemolysin expressing maximal activity under anaerobic conditions
streptolysin O (SLO)
optochin inhibits…
ATPase
zone required to indicate susceptibility to 5 μg optochin
≥ 14mm
organism indicated by optochin sensitivity
S. pneumoniae
bacitracin mode of action
inhibits cell wall synth
S. pyogenes – bacitracin
sensitive
Staphylococcus – bacitracin
resistant
Bacillus licheniformis – bacitracin
resistant
Micrococcus – bacitracin
sensitive
SXT mode of action
inhibits folic acid metabolism
Group A strep example
S. pyogenes
Group B strep example
S. agalactiae
which strep group grows in the presence of bacitracin?
Group B grows
Group A does not grow
what is on the Staphaurex beads?
antibody against S. aureus
DNase positive result
colorless halo around DNase positive colonies
Example of DNase pos organism
S. marscesens
CAMP positive
arrowhead zone
is CAMP factor higher closer or further from the arrowhead?
further
organism streaked on CAMP plate (not being tested)
S. aureus
example of pos CAMP organism
Streptococcus agalactiae
novobiocin mode of action
interferes with DNA replication by inhibiting DNA gyrase
resistant to novobiocin
Staphylococcus saprophyticus
steps of growth-dependent microbiology
enrichment (selective or differential media)
isolation (pure culture)
identification
reducing agent used for
anaerobes
swaps placed in transport tube with…
sterile saline
specificity
few false —–
ability of test to recognize a pathogen
few false positives
sensitivity
few false ——
smallest quantity of pathogen that can be detected
few false negatives
rare organism, few false positives
GNC
ex. N. gonorrhoeae
(males/females) give more cells
males
N. gonorrhoeae swabs are plated on —– agar
Thayer-Martin
—— used for further confirmation of N. gonorrhoeae
oxidase
selective media
contain poisons or inhibitors which prevent growth of specific competitors
differential media
indicators that change color
often a pH indicator for acid production
sensitivity for finding a cell from a spinal tap smear
10^5
—— often required for spinal taps
culturing
—— mL blood needed to inoculate “blood bottles”
10-20 mL
2 blood bottles
aerobic
anaerobic
can take 5 days to grow in blood bottles
anaerobes
can take 2 weeks to grow in blood bottles
TB
preferred media for IDing UTI organisms
MacConkey
EMB
—– and —– are very sensitive to acid buildup, so fecal samples must be handled rapidly
Salmonella
Shigella
—— parasites can be directly observed in fecal samples
Giardia
first step for bites/wounds
selective & differential media
if swap doesn’t work on bite/wound
syringe aspiration or surgical biopsy
chromagar
colorimetric substrate broken down to give distinct color
cause urethritis (4)
Chlamydia
Ureaplasma
Trichomonas
N. gonorrhoeae
in (males/females) organisms can be found in exudates by microscopy
males
media choices for N. gonorroeae
chocolate agar
modified TM agar with 4 antibiotics
NYC medium lacking blood, plasma and soluble hemoglobin instead
culturing N. gonorrhoeae requires what environment?
3-7% CO2 incubator
N. gonorrhoeae
oxidase?
gram?
arrangement/shape?
oxidase pos
G N
diplococci
