staph, strep, gram pos rods, and gram neg diplos Flashcards
what is the media used that is selective and differential for staph spp.? What does it contain that makes it this way?
mannitol salt agar: high salt concentration
which coagulase tests is the bound coagulase, and free coagulase
slide coagulase = bound coagulase (also called “clumping factor”)
tube = free coagulase (that forms a complex with coagulase reacting factor in the plasma)
after catalase pos and coagulase neg tests, what differs S. saprophyticus from other coag neg staph? (and the results)
novobiacibn resistant while other staph are susceptible
micrococcus is a what color usually? What is the catalase and oxidase result, and what is the gram stain?
lemon-yellow colonies
catalase AND oxidase pos
gram pos cocci in tetrads
what are two disk tests to differ micrococcus and staph spp.?
furazolidone disk
- staph susceptible
- micrococcus resistant
bacitracin
- staph resistant
- micrococcus susceptible
what diseases can GAS cause?
pharyngitis, strep throat, scarlet fever, erysipelas, TSS, rheumatic fever and acute glomerulonephritis
what are the two toxins GAS makes?
streptolysin O and S
- O is oxygen liable
- S is oxygen stable
GAS are almost always ______ to bacitracin “A” disk?
S. pyogenes is susceptible to bacitracin
what are the two microbial agents in an SXT disk, and how does this disk show if strep is group A, B, C, F, G?
has trimethoprim and sulfamethoxazole
GAS and GBS are both RESISTANT
groups C, F, and G are all SUSCEPTIBLE
GBS causes what two things? Why do we test pregnant women for this?
neonatal sepsis and meningitis
pregnant women can pass it to their baby during birth since S. agalactiae is normal female urogenital flora (but can cause UTIs too)
what is one test done one blood plates to ID GBS?
CAMP test: streak vertical line of S. aureus down plate and horizontal (but not touching) of suspected GBS to it, and an arrow of hemolysis is made when “beta-lysin” from S. aureus meets the “CAMP factor” from GBS
What four organisms are hippurate pos?
GBS, listeria spp., garderella vaginalis, and some Campy spp.
GDS hemolysis looks like what on a blood plate?
What’s one test where both enterococci AND nonetnerococcci are both positive? What is the test that differentiates the two?
GDS: alpha or gamma hemolysis
All GDS: pos for bile esculin (black precipitate)
6.5% salt tolerance:
- enterococci pos
- nonenterococci neg
what test separates S. viridians from other GDS?
most GDS are pos for bile esculin while S. viridians is not
what is the gram stain of S. pneumoniae (“pneumococcus”) that makes it different from other strep? Where is normal flora in the body?
Gram pos diplococci
normal flora in the upper respiratory tract
what are the two morphologies on media that S. pneumo exhibit?
mucoid colonies, or umbilicated (doughnut shaped). The umbilictaed ones are autolysins
both kinds are alpha hemolytic
what test is used to identify S. pneumoniae?
S. pneumoniae is optochin “P” disk SUSCEPTIBLE
What is the other test to ID S. pneumoniae other than the optochin disk test?
bile solubility: either broth or plate methods
- sodium deoxycholate and sodium taurocholate speed up the autolysing behavior of S. pneumoniae
what is the test to distinguish the 80 types of pneumococci?
quelling reaction: the pneumococci types have different polysaccharide capsules, so by antigen-antibody reaction, the capsules begin to swell (if there’s a match between the pneumococci and the antibody they’re mixed with)
what are satelliting strep? Do they usually grow on BAP or chocolate?
nutrient deficient, nutritionally variant, strep that depend on
- thiol
- pyridoxal
- vitamin B
they do not usually grow on BAP or chocolate
what is the BAP hemolysis pattern of enterococcus, and how to ID?
usually show (alpha or) gamma hemolysis, but NOT beta
pos for:
- bile esculin
- 6.5% salt
- PYR disk POSITIVE (pink)
what is a common bacteria that pose a risk for infection in people who have indexing medical devices (cathaters/heart valves/ect)?
coag neg staph
(what is the gram stain for bacillus spp.? And how to tell B. anthracis from B. cerus?)
they’re all large, boxy gram pos rods with endospores
B. anthracis: non-hemolytic, nonmotile (and oxidase and catalase pos)
B. cerus: beta hemolytic and motile
(Bacillus grow well on BAP)
Corynebacterium spp. gram stain and what do this spp show when stained with methylene blue?
gram pos rods in clubs, V-L formation, palisades
they will show metachromatic granules after methylene blue treatment
what is a media that is selective and differential for Corynebacterium?
Telluride medium / tinsdale agar (many normal flora are inhibited by tellurite, while Coryne is not. Make grey-black colonies)
catalase, motility, and hemolysis for Coryne?
cat pos
nonmotile
non-beta hemolytic
- most Coryne are non hemolytic
how to tell C. diphtheriae from normal Coryne?
Has toxin. do an ELEK test
- filter paper with diptheriae antitoxin interacts with diphtheria toxin and creates a precipitate, showing positivity for the test
what is the disease caused Listeria monocytogenes
listeriosis (in neonates, pregnant women, and elderly/immunocompromised people)
can cause spontaneous abortions
listeria exhibits what on a wet prep and motility media?
tumbling motility on wet prep
umbrella motility on motility media
listeria is positive for five tests. what are they? which of them differentiate listeria from GBS?
catalase, CAMP, hippurate, bile esculin, and motile at 25ºC
GBS is neg for catalase, motility, and bile esculin
(also GBS is gram pos cocci while listeria is GPB)
what gram stain and hemolysis pattern does listeria usually have?
gram pos bacilli
small gray colonies with small zone of beta hemolysis
what does Erysipelothrix rheusiopathae cause? How to ID it?
causes erysipeloid “red skin lesions”
ID:
- gram pos pleomorphic non-sporeforming rods
- cat neg
(- alpha or gamma hemolysis)
- nonmotile
- and H2S pos
name the pinpoint colony that is normal flora in the female genital area. What is the gram stain, and how to differ it from G. vaginalis?
Lactobacillus is gram pos chains of rods, while G. vaginalis is short gram pos rods not in chains
what is the gram stain for Nocardia spp.? What is the most common type of Nocardia? What does this spp. cause in humans?
gram positive bacilli that are beaded/branching
N. asteroides most common type
they cause mycetomas (chronic tissue and bone disease)
True or false: Nocardia are partially acid fast (with Kunyon stain)
true: reddish-purple filaments mean a positive result (while blue means negative)
what spp. is small gram bacilli/rods that are beta hemolytic, catalase neg, nonmotile, cause pharyngitis, and identified by the reverse CAMP test?
Aracanobacterium haemolyticum
what species are positive for hippurate?
GBS, Campy, Gardenella vaginalis, Listeria
where can you find Listeria (in the environment)?
soil and water
what two media are made for G. vaginalis? What is the hemolysis for G. vaginalis that helps differ it from Lactobacillus
HBT medium and vaginalis “V” agar
they are beta hemolytic (while lactobacillus is alpha or gamma hemolytic)
what is the gram stain for Neisseria spp?
gram neg diplococci
what media is made for N. gonorrhoeae? Why? What diseases does this bacteria cause?
Modified Thayer Martin (or Martin-Lewis) because they have the nutrients this fastidious organism needs, as well as having antimicrobial agents for pretty much every other bacteria
causes gonorrhea (STD)
in women: cervicitis, PID, salpingus, endometritis, and peritonitis
in men: acute urethritis, prostatitis, and epididymitis
in neonates: conjunctivitis
what are the CTA sugar test results for N. gonorrhoeae, N. meningitidis, and N. lactamica? What do neg and pos results look like?
N. gonorrhoeae: glucose only
N. meningitidis: glucose and mactose
N. lactamica: glucose, maltose, and lactose
neg: red (no color change)
pos: yellow from acid formation
True or false: Neisseria meningitidis is part of the normal flora of the upper respiratory tract
true
what is the disease caused by N. meningitidis? What about the severe form?
meningitis: bacteria from URT get into bloodstream and spread to the meninges (the proactive layers surrounding the brain and CNS)\
severe meningococcemia: waterhouse-friderichsen syndrome
all Neisseria are both catalase and oxidase _____
positive :)
Just like Neisseria spp, M. catarrhalis is oxidase positive, catalase positive, gram neg diplococci.
Other than the Thayer Martin agar, how can you differentiate the two?
M. catarrhalis is both butyrate esterase test and DNAse test POSITIVE, while Neisseria is neg for both
