Gram Positive Algorithm Flashcards
What are the Gram-positive cocci?
- Streptococcus (and Enterococcus)
- Staphlycoccus
What are 2 tests to differentiate between the Gram-positive cocci?
- Appearance on Gram stain:
Streptococci appear as chains(strips), and Staphylocci appear as clusters - Catalase:
Streptococci is catalase-negative, Staphyloccus is catalase-positive
How to differentiate between Gram-positive cocci based on morphology?
Streptococci appear as chains (strips)
Staphylococci appear as clusters
Streptococci are classified according to what ability?
Hemolysis
Alpha hemolytic - define
Partially lyse RBCs (on BA) leaving a greenish discoloration of the culture medium surrounding the colony (which contains unlysed RBCs and a green-colored metabolite of hemoglobin)
What type of hemolysis partially lyses RBCs and leaves a greenish discoloration of blood agar?
Alpha hemolysis
Beta hemolysis - define
Completely lyses RBCs, leaving a clear zone of hemolysis around the colony on blood agar
What type of hemolysis completely lyses RBCs and leaving complete zone of clearance around colony?
Beta hemolysis
Gamma hemolysis - define
No hemolysis occurs
What type of hemolysis is non-hemolytic (unable to lyse RBCs)?
Gamma-hemolytic
S. pneumoniae displays what type of hemolysis when grown on blood agar?
Partial hemolysis (alpha hemolytic)
S. viridans displays what type of hemolysis when grown on blood agar?
Partial hemolysis (alpha hemolytic)
What streptococci display beta hemolysis when grown on blood agar?
- Group A Streptococci (S. pyogenes)
- Group B Streptococci (S. agalactiae)
What streptococci display beta hemolysis when grown on blood agar? What Streptococci is CAMP +ve Hippurate hydrolysis +ve What Streptococci is PYR +ve
- Group A Streptococci (S. pyogenes)
- Group B Streptococci (S. agalactiae)
CAMP+ve and Hippurate hydrolysis +ve
- Group A Streptococci (S. pyogenes)
PYR +ve
- Group B Streptococci (S. agalactiae)
Group A strep (S. pyogenes) displays what kind of hemolysis when grown on blood agar?
Beta (complete) hemolysis
S. pyogenes displays what kind of hemolysis when grown on blood agar?
Beta (complete) hemolysis
Group B streptococci (S. agalactiae) display what type of hemolysis when grown on blood agar?
Beta hemolysis
S. agalactiae displays what kind of hemolysis when grown on blood agar?
Beta hemolysis
What streptococci are gamma-hemolytic?
Group D strep: Enterococci and Nonenterococci
Group D streptococci display what type of hemolysis when grown on blood agar?
Gamma-hemolysis (non-hemolytic)
What type of streptococci are non-hemolytic?
Group D strep:
Enterococcus (E. faecium, E. faecalis)
Nonenterococcus (S. bovis)
Which two antibiotics can differentiate among species of streptococci?
Bacitracin and Optochin
Optocochin is used to differentiate among which type of hemolytic streptococci?
Other way of differentiating optochin affected organisms?
Alpha-hemolytic organisms: Strep viridans (-) Strep pneumoniae (+)
Strep pneumoniae
Bile solubility +
Quellung rxn +
Strep viridans
Bile solubility -
The alpha-hemolytic streptococci are differentiated based on sensitivity to which antibiotic?
Optochin
Optochin is used to differentiate among which bacteria?
Streptococci alpha hemolytics: S.pneumoniae and S. viridans
S. viridans is resistant
S. pneumo is sensitive
“OVRPS” (overpass)
S. pneumoniae is (sensitive, resistant) to optochin
sensitive
“OVRPS”
Which alpha hemolytic streptococcus is optochin sensitive?
S. pneumoniae
“OVRPS”
Which alpha hemolytic streptococcus is optochin resistant?
S. viridans
“OVRPS”
S. viridans is (sensitive, resistant) to optochin.
resistant
The alpha hemolytic streptococci can be differentiated based on what 3 characteristics?
1) capsule (S. pneumo has capsule; S. viridans does not)
2) optochin (S. pneumo is sensitive; S. viridans is resistant)
3) bile (S. pneumo is lysed by (soluble in) bile; S. viridans is bile insoluble)
How can alpha hemolytic streptococci be differentiated based on presence or absence of a capsule?
S. pneumoniae has a capsule
S. viridans does not have a capsule
Bacitracin is used to differentiate among which type of hemolytic streptococci?
beta-hemolytic (complete hemolysis)
The beta-hemolytic streptococci are differentiated based on sensitivity to which antibiotic?
Bacitracin
Bacitracin - used to differentiate which bacteria?
Streptococci beta (complete) hemolytics:
S.pyogenes (Group A strep) and S.agalactiae (Group B strep)
Group B strep are resistant
Group A strep are sensitive
“B-BRAS”
Group A strep is bacitracin (sensitive, resistant)
Sensitive
B-BRAS
S. pyogenes (Group A) is bacitracin (sensitive, resistant)
Sensitive
S. pyogenes = Group A strep
B-BRAS
Group B strep is bacitracin (sensitive, resistant)
Resistant
S. agalactiae is bacitracin (sensitive, resistant)
resistant
S. agalactiae = Group B strep
“B-BRAS”
Which beta-hemolytic streptococcus is bacitracin sensitive?
Group A strep (S. pyogenes)
Which beta-hemolytic streptococcus is bacitracin resistant?
Group B strep (S. agalactiae)
The gamma-hemolytic streptococci can be differentiated based on growth in what media?
bile +/- NaCl
Group D enterococci grow in bile and 6.5% NaCl
Non-enterococci grow in bile, but not in 6.5% NaCl
The Group D streptococci can be differentiated based on growth in what media?
Bile +/- NaCl
Bile +/- 6.5% NaCl is used to differentiate among what type of bacteria?
Gamma(non)-hemolytic streptococci
Which gamma-hemolytic bacteria grow in bile and 6.5% NaCl?
E. faecalis can ferment MSA (T/F)
Group D strep (enterococci)
E. faecalis and E. faecium
True
Which gamma-hemolytic bacteria grow in bile but not 6.5% NaCl?
Group D strep - nonenterococci
S. bovis and S. equinus
Which bacteria are alpha-hemolytic?
- Streptococcus pneumoniae
- Streptococcus viridans
Which bacteria are beta-hemolytic?
- Staphylococcus aureus
- Group A strep (Streptococcus pyogenes)
- Group B strep (Streptococcus agalactiae)
- Listeria monocytogenes
Name the bacteria:
- blue on Gram stain
- cocci in chains
- catalase -ve
- forms green ring around colonies when grown on blood agar
- optochin sensitive
Streptococcus pneumoniae
Name the bacteria:
- blue Gram stain
- cocci arranged in chains
- catalase -ve
- forms green ring around colonies when grown on BA
- optochin resistant
Streptococcus viridans
Name the bacteria:
- blue Gram stain
- cocci arranged in chains
- catalase negative
- forms clear area around colonies when grown on BA
- bacitracin sensitive
Streptococcus pyogenes
Name the bacteria:
- blue Gram stain
- cocci arranged in chains
- catalase -ve
- forms clear area around colonies when grown on blood agar
- bacitracin resistant
Streptococcus agalactiae
Name the bacteria:
- blue Gram stain
- cocci arranged in clusters
- catalase positive
- forms clear area around colonies when grown on BA
- coagulase positive
- ferments mannitol on MSA, yellow halo seen
- DNase +ve
Staphylococcus aureus
Purpose of Coagulase test
Differentiate S. aureus from other Staphylococcus spp
Name the bacteria:
- blue gram stain
- cocci arranged in clusters
- catalase +ve
- coagulase -ve
- novobiocin sensitive
- No growth on MSA
Staphylococcus epidermidis
Name the bacteria:
- blue gram stain
- cocci arranged in clusters
- catalase +ve
- coagulase -ve
- novobiocin resistant
- No growth on MSA
Staphylococcus saprophyticus
Ways to differentiate S. aureus from other Staphylococci
- Coagulase test
- Growth on MSA (S. aureus grows, other Staph do not)
What are the gram positive bacilli?
Bacillus, Clostridium, Listeria, Corynebacterium
What are 2 tests to differentiate between the Gram-positive bacilli?
Spore forming
List spore forming gram +ve bacilli
Bacillus, Clostridium
List non spore forming gram +ve bacilli
Listeria, Corynebacterium
Ways to differentiate spore forming, gram +ve bacteria
- Catalase test
- Spore shapes
Differentiation of spore forming, gram +ve bacteria based on morphology
Clostridium - Bottle shaped endospores (spore wider than body)
Bacillus - Oblong endospores
Bottle shaped endospore
Clostridium
Oblong endospores
Bacillus
Differentiation of spore forming, gram +ve bacteria based on ability to utilize catalase
Clostridium : catalase -ve
Bacillus : catalase +ve
Catalase +ve, gram +ve Bacillus spp
Bacillus cereus
Bacillus anthracis
Ways to differentiate gram +ve Bacillus spp
- Beta Hemolysis
- Quellung rxn
- Penicillin sensitivity
- Motility
Beta hemolysis classification of gram +ve Bacillus spp
Bacillus anthracis (Gamma hemolytic) Bacillus cereus (Beta hemolytic)
Quellung rxn classification of gram +ve Bacillus spp
Bacillus anthracis (+ve Quellung rxn) Bacillus cereus (-ve Quellung rxn)
Penicillin susceptibility classification of gram +ve Bacillus spp
Bacillus anthracis (Penicillin resistant) Bacillus cereus (Penicillin sensitive)
Motility classification of gram +ve Bacillus spp
Bacillus anthracis (non motile) Bacillus cereus (motile)
Name the bacteria:
- Oblong endospore
- Gamma hemolytic
- +ve Quellung rxn
- Penicillin resistant
- Non motile
Bacillus anthracis
Name the bacteria:
- Oblong endospore
- Beta hemolytic
- -ve Quellung rxn
- Penicillin sensitive
- Motile
Bacillus cereus
General morphology classification of Clostridium
Bacilli/rod shaped
Medically important Clostridium spp
C. tetani
C. perfringes
C. botulinum
C. difficile
Differentiate Clostridium gram +ve bacteria based on hemolysis:
C. perfringes - Double zone of hemolysis (inner beta, outer alpha)
C. tetani - Thin film, no distinct colonies/hemolysis
C. botulinum - Beta hemolysis
C. difficile - Gamma hemolysis
Differentiate Clostridium gram +ve bacteria based on sugar fermentation
C. perfringes + sugar fermentation
C. tetani - sugar fermentation
C. botulinum (no testing for sugar fermentation)
C. difficile + sugar fermentation
Which gram +ve Clostridium spp are + for sugar fermentation
C. perfringes
C. difficile
Which gram +ve Clostridium spp are - for sugar fermentation
C. tetani
Differentiate Clostridium gram +ve bacteria based on lipase, indole rxns
C. perfringes: Lipase - Indole -
C. tetani: Lipase - Indole variable
C. botulinum: Lipase + Indole -
C. difficile: Lipase - Indole -
Which gram +ve Clostridium spp are Lipase +ve?
C. botulinum
Which gram +ve Clostridium spp are Lipase -ve?
C. perfringes
C. tetani
C. difficile
Differentiate Clostridium gram +ve bacteria based on urease, nitrate rxns
C. perfringes: Urease - Nitrate +
C. tetani: Urease - Nitrate -
C. botulinum: Urease - Nitrate N/A
C. difficile: Urease N/A Nitrate N/A
Differentiate Clostridium gram +ve bacteria based on lecithinase rxns
C. perfringes Lecithinase +
C. tetani Lecithinase -
C. botulinum Lecithinase variable
C. difficile Lecithinase -
Which gram +ve Clostridium spp are Lectinase +
C. perfringes
Which gram +ve Clostridium spp are Lectinase -
C. tetani
C. difficile
Which gram +ve Clostridium spp are Lectinase variable
C. botulinum
Differentiate Clostridium gram +ve bacteria based on spore arrangment
C. perfringes: Sub terminal end
C. tetani: Terminal
C. botulinum: Subterminal/middle
C. difficile: Terminal end
Which gram +ve Clostridium spp have terminal spores
C. tetani
C. difficile
Which gram +ve Clostridium spp have subterminal spores
C. perfringes
C. difficile
Differentiate Clostridium gram +ve bacteria based on motility
C. perfringes: non motile
C. tetani: highly motile
C. botulinum: motile
C. difficile: motile
Which of the gram +ve Clostridium spp is non motile?
C. perfringes
Which of the gram +ve Clostridium spp is highly motile?
C. tetani
Name the gram +ve bacterium
- Double zone of hemolysis (inner beta hemolysis, outer alpha hemolysis)
- (+) Reverse CAMP test (CAMP factor produced by S. agalactiae used for detection)
- Nagler rxn
- (+) Sugar fermentation
- (-) Lipase
- (-) Indole
- (-) Urease
- (+) Nitrate reduction
- (+) Lecithinase
- Sub-terminal spore
- Non-motile
C. perfringes
Definitive Test for C. perfringes
- Litmus milk test
Write the test results for C. perfringes Sugar fermentation Lipase Indole Urease Nitrate Lecithinase
Sugar fermentation + Lipase - Indole - Urease - Nitrate + Lecithinase + \+ - - - + +
Which of the gram +ve clostridium spp have a positive biochemical test for sugar fermentation, and are nitrate + and Lectinase +?
C. perfringes
Which gram positive bacilli has the definitive test as Litmus milk test?
C. perfringes
Name the bacteria:
- Fine film of growth on BA rather than disecrete colonies b/c of swarming due to vigorous motility
- Sugar fermentation -
- Indole variable
- Urease -
- Nitrate -
- Lecithinase -
- Terminal spore (drum stick)
- Highly motile
C. tetani
Write the test results for C. tetani Sugar fermentation Lipase Indole Urease Nitrate Lecithinase
Sugar fermentation - Lipase - Indole variable Urease - Nitrate - Lecithinase - - - variable - - -
Which of the gram +ve clostridium spp have solely a variable biochemical test for indole and all other tests are -ve?
C. tetani
Microscopy is not enough to diagnose C. tetani (T/F)
True
Name the bacteria:
- Gram variable
- Beta hemolysis (complete hemolysis characterized by clear zone around colonies)
- Sugar fermentation N/A
- Lipase +
- Indole -
- Urease -
- Nitrate N/A
- Lecithinase variable
- Motile
- Subterminal/middle spore
C. botulinum
Which of the gram +ve clostridium spp have a positive biochemical test for only Lipase + and are lectinase variable?
C. botulinum
Write the test results for C. botulinum Sugar fermentation Lipase Indole Urease Nitrate Lecithinase
Sugar fermentation N/A Lipase + Indole - Urease - Nitrate N/A Lecithinase variable N + - - N v
Name the bacteria:
- Gamma hemolysis
- Sugar fermentation +
- Lipase -
- Indole -
- Urease N/A
- Nitrate N/A
- Lecithinase -
- Motile
- Terminal spore
C. difficile
Write the test results for C. difficile Sugar fermentation Lipase Indole Urease Nitrate Lecithinase
Sugar fermentation + Lipase - Indole - Urease N/A Nitrate N/A Lecithinase - \+ - - N N -
Which of the gram +ve clostridium spp have a positive biochemical test for only sugar fermentation?
C. difficile
Agar for isolation of C. difficile from fecal specimens
Cycloserine cefoxitin fructose agar (CCFA) or
cycloserine cefoxitin egg yolk agar (CCEY).
Definitive testing for C. difficile
- GDH (Glutamate Dehydrogenase) screening
- Toxin A/B test by enzyme immunoassay
Name the bacterium Non spore forming Pairs/short chains CAMP test - Arrowhead shape of beta hemolysis (produced by group B Strep) Catalase + Bile esculin + Growth in 6.5% NaCl + Umbrella type motility (wide on top with long growth line in motility media) Tumbling motility in hanging drop prep Pleocytosis = early diagnosis Serology highly unreliable
Listeria monocytogenes
Name the bacteria Non spore forming Produce metachromatic granules which stain darker than organism Small zone of beta hemolysis Loeffler's slant (pleomorphism) Black halos on Serum Tellurite/Modified Tinsdale Glucose + Catalase + Urease - Non motile
Corynebacterium diptheriae
Corynebacterium subtypes
- Gravis
- Mitis
- Intermedius
- Belfanti
What is a way to differentiate Corynebacterium subtypes?
Growth on Hoyle’s Tellurite agar
Differentiate Corynebacterium subtypes based on growth on Hoyle’s Tellurite agar and hemolysis?
Gravis - Grey/black, opaque, matte, broken easily into segments when touched with wire
No hemolysis
Mitis - Grey/black, opaque, glossy, smooth, size variation common
Small zone of beta hemolysis
Intermedius - Grey/black, transluscent, shiny
Small zone of hemolysis
Belfanti - Grey/black, opaque, glossy, smooth, size variation common
Small zone of hemolysis
Differentiate Corynebacterium subtypes based on biochemical tests Gravis, mitis, intermius Nitrate Urease Catalse Belfanti Nitrate Urease Catalse
Gravis, mitis, intermius vs belfanti Gravis, mitis, intermius Nitrate + Urease - Catalse + Belfanti Nitrate - Urease - Catalse +
Name the bacteria Non spore forming Pleomorphic Non hemolytic Nitrate reduction - Urea - Sucrose - Glucose +
Corynebacterium jekeium
Name the bacteria Non spore forming Pleomorphic Club like ends Gamma hemolysis Sucrose + Nitrate + Urease -
Corynebacterium xerosis