Gram Positive Algorithm Flashcards by Ann M

What are the Gram-positive cocci?

Streptococcus (and Enterococcus)

- Staphlycoccus

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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

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How to differentiate between Gram-positive cocci based on morphology?

Streptococci appear as chains (strips)

Staphylococci appear as clusters

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Streptococci are classified according to what ability?

Hemolysis

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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)

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What type of hemolysis partially lyses RBCs and leaves a greenish discoloration of blood agar?

Alpha hemolysis

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Beta hemolysis - define

Completely lyses RBCs, leaving a clear zone of hemolysis around the colony on blood agar

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What type of hemolysis completely lyses RBCs and leaving complete zone of clearance around colony?

Beta hemolysis

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Gamma hemolysis - define

No hemolysis occurs

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What type of hemolysis is non-hemolytic (unable to lyse RBCs)?

Gamma-hemolytic

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S. pneumoniae displays what type of hemolysis when grown on blood agar?

Partial hemolysis (alpha hemolytic)

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S. viridans displays what type of hemolysis when grown on blood agar?

Partial hemolysis (alpha hemolytic)

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What streptococci display beta hemolysis when grown on blood agar?

Group A Streptococci (S. pyogenes)

- Group B Streptococci (S. agalactiae)

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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)

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Group A strep (S. pyogenes) displays what kind of hemolysis when grown on blood agar?

Beta (complete) hemolysis

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S. pyogenes displays what kind of hemolysis when grown on blood agar?

Beta (complete) hemolysis

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Group B streptococci (S. agalactiae) display what type of hemolysis when grown on blood agar?

Beta hemolysis

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S. agalactiae displays what kind of hemolysis when grown on blood agar?

Beta hemolysis

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What streptococci are gamma-hemolytic?

Group D strep: Enterococci and Nonenterococci

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Group D streptococci display what type of hemolysis when grown on blood agar?

Gamma-hemolysis (non-hemolytic)

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What type of streptococci are non-hemolytic?

Group D strep:
Enterococcus (E. faecium, E. faecalis)

Nonenterococcus (S. bovis)

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Which two antibiotics can differentiate among species of streptococci?

Bacitracin and Optochin

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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 -

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The alpha-hemolytic streptococci are differentiated based on sensitivity to which antibiotic?

Optochin

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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