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1-Scientific & lab basis of microbiology > Basic identification of bacteria > Flashcards

Basic identification of bacteria Flashcards

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1
Q

List genera of aerobic Gram-negative bacilli that are oxidase-negative.

(8)

A

OX- GNB:

  • Acinetobacter (2xCB)
  • Morganella
  • Proteus
  • Providencia
  • Salmonella
  • Shigella
  • Stenotrophomonas (lab grown green, ox “yellow”)
  • Yersinia
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2
Q

List genera of aerobic Gram-negative bacilli that are oxidase-positive.

(5)

A

OX+ GNB:

  • Aeromonas
  • Pasteurella (safety pin)
  • Plesiomonas
  • Pseudomonas
  • Vibrio (vibroid)
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3
Q

What are two types of alpha-hemolytic streptococci,
and what biochemical can you use to differentiate them?

A

S.pneumo

  • capsule -> optichin-R

Viridans Group streptococci (VGS) (S.mitis/S.mutans)

  • no capsule = opt-S
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4
Q

What are two types of beta-hemolytic streptococci,
and what biochemicals can you use to differentiate them?

A

GAS (bacitracin-s, PYR+)

GBS (bacitrcin-R, PYR-, CAMP+)

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5
Q

What are two types of gamma-hemolytic streptococci,
and what biochemical can you use to differentiate them?

A

GDS (e.g. S.bovis)

Enterococcus (g. in 6.5% NaCl)

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6
Q

When is bacitracin used in the lab?

A

a.k.a. TaxoA

Differentiates GAS vs GBS

  • GAS = bac-S
  • GBS = bac-R
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7
Q

Catalase positive organisms

A
  • Nocardia
  • Pseudomonas
  • Listeria
  • Aspergillus
  • Candida
  • E. coli
  • Staphylococci
  • Serratia
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8
Q

What test can you use to detect DNase activity?

A

Toluidine Blue O

E.g. for Elizabethkingea meningoseptica

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9
Q

What test can you use to detect DNase activity?

A

Toluidine Blue O

E.g. for Elizabethkingea meningoseptica

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10
Q

Genera of lactose-fermenting gut microbiota

A
  • Citrobacter
  • Escherichia
  • Enterobacter
  • Klebsiella
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11
Q

When is optichin used in the lab?

A

a.k.a. TaxoP

Differentiates S.pneumo vs. VGS

  • S.pneumo = opti-s
  • VGS = opti-R
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12
Q

Bacteria that are oxidase-positive:

(Genera)

A
  • Neisseria
  • Pseudomonas
  • Burkholderia
  • Brucella
  • Legionella
  • Vibrio
  • Campylobacter
  • Helicobacter
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13
Q

What are the general traits of Pseudomonas spp.?

  • Gram stain
  • Motility
  • Oxygen requirements
  • Oxidase
  • Catalase
  • Indole
  • Sugar fermentation & TSI reaction
  • Nitrate reduction
  • Citrate
  • Lipase
A
  • GS: GNB thin
  • motile by polar flagellum (<=1)
  • Facultative anaerobe
  • OX +
  • CAT +
  • Indole -
  • Non-lactose fermenter (TSI K/K)
  • Nitrate reduction +
  • Citrate +
  • Lipase +
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14
Q

What are three biochemical tests you can use to distinguish S.pneumoniae from VGS?

A
  • Optichin/TxP (S.pneumo = S)
  • Bile solubility (S.pneumo = +)
  • Inulin fermentation (S.pneumo = +)
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15
Q

Urease Positive Organisms

A
  • Cryptococcus
  • H. pylori
  • Proteus
  • Ureaplasma
  • Nocardia
  • Klebsiella
  • S. epidermidis
  • S. Saprophyticus
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16
Q

Bacillus

A

O2: O2 (obl/facan)

CAT+

Gram: GP bacilli. Oval endospores, central to subterminal.

ANTHRACIS:

  • GV, Long chains.
  • BAP colonies ground glass, beaten egg.

CEREUS:

  • Pallisades (not long chains)
  • BAP colonies ~green, larger than anthracis.
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17
Q

Corynebacterium

A

O2: O2 (obl/facan) CAT+ GS: GP bacilli Club/diphtheroid shape Form V’s, palisades, or Chinese letters

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18
Q

Erysipelothrix

A

O2: O2 (obl/facan) CAT- GS: Weak GP bacilli

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19
Q

Gardnerella

A

O2: FACAN CAT- GS: GV coccobacilli.

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20
Q

GI commensals (MGIF)

A

OX- L(N)F GNB Enterococcus ANA’s

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21
Q

GP branching filaments

A

AEROBIC: Nocardia (weakly acid-fast) ANO2: Actinomyces (not AF)

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22
Q

You see Gram-negative bacilli on your slide from a culture grown aerobically.

What genera could they be?

A

Coliforms:

  • Escherichia
  • Klebsiella (encapsulated)
  • Enterobacter
  • Serratia
  • Citrobacter
  • Shigella
  • Salmonella
  • & other Enterobacterales

Non-fermenters:

  • Pseudomonas
  • Acinetobacter

Pasteurella

HACEK organisms:

  • Haemophilus (can be coccobacilli)
  • Aggregatibacter
  • Cardiobacter
  • Eikenella
  • Kingella

Bacillus*

*Bacillus & related genera can easily over-decolourize on Gram stains.

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23
Q

You see Gram-negative cocci on your slide from a culture grown aerobically.

What genera could they be?

A
  • Neisseria (coffee-bean shape)
  • Moraxella (coffee-bean shape)
  • Haemophilus/HACEK (coccobacilli)
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24
Q

You see Gram-positive bacilli on your slide from a culture grown aerobically.

What genera could they be?

A
  • Corynebacterium
  • Bacillus
  • Listeria
  • Erysipelothrix
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25
Q

You see Gram-positive cocci on your slide from a culture grown aerobically.

What genera could they be?

A
  • Staphylococcus
  • Streptococcus
  • Enterococcus
  • “Nutritionally variant streptococci” (Granulicatella, Abiotrophia)
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26
Q

You see Gram-negative bacilli on your slide from a culture grown ANaerobically.

What genera could they be?

A
  • Bacteroides
  • Fusobacterium
  • Prevotella
  • Prophyromonas
  • Leptotrichia
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27
Q

You see Gram-negative cocci on your slide from a culture grown ANaerobically.

What genera could they be?

A
  • Veillonella*

* Veillonella is phylogenetically Gram-positive, within the Negativicute**s group, so stains Gram-negative.

28
Q

You see Gram-positive bacilli on your slide from a culture grown ANaerobically.

What genera could they be?

A
  • Clostridium
  • Actinomyces
  • Cutibacterium & Propionibacterium
  • Eggerthella
  • Eubacterium
29
Q

You see Gram-positive cocci on your slide from a culture grown ANaerobically.

What genera could they be?

A
  • Peptostreptococcus
  • Parvimonas
  • Finegoldia
  • Staphylococcus saccharolyticus
30
Q

You see Gram-negative bacilli on your slide. They appear curved.

What genera could they be?

A
  • Vibrio (comma-shaped)
  • Campylobacter (gull-winged)
  • Helicobacter
  • Anaerobiospirillum
  • Arcobacter
31
Q

You see Gram-negative bacilli on your slide. They appear fusiform.

What genera could they be?

A
  • Fusobacterium
  • Leptotrichia
  • Capnocytophaga
32
Q

You see Gram-negative coccobacilli on your slide.

What genera could they be?

A
  • Haemophilus*
  • Acinetobacter*
  • Aggregatibacter*
  • Moraxella*
  • Pasteurella*
  • Bacteroides*
  • Brucella* (RG3!)
  • Francisella* (RG3!)
33
Q

You see Gram-variable bacilli on your slide.

What genera could they be?

A
  • Bacillus (Paenibacillus, Lysinibacillus)
  • Clostridium
  • Gardnerella
  • Leptotrichia
34
Q

What bacterial are obligate intracellular bacteria?

(genera)

A
  • Chlamydia/Chlamydophila
  • Coxiella
  • Rickettsia
  • Orientia
  • Ehrlichia
  • Anaplasma
35
Q

What bacterial are spirochetes?

(genera)

A
  • Borrelia/Borreliella
  • Leptospira
  • Treponema
36
Q

You see TINY Gram-negative bacilli on your slide.

What genera could they be?

A
  • Brucella (RG3!)
  • Francisella (RG3!)
37
Q

How can we determine the serotype of an H.influenzae isolate?

A

Latex agglutination

(unless non-mucoid strain, a.k.a. non-typeable)

38
Q

How can we determine the serotype of an H.influenzae isolate?

A

Latex agglutination

(unless non-mucoid strain, a.k.a. non-typeable)

39
Q

Lactobacillus

A

O2: FACAN. (Grows better ANO2) CAT- GS: GP bacilli Colonies: Look like VGS (but different GS) ID with growth on LBS

40
Q

Listeria

A

O2: FACAN CAT- GS: GPB (can be coccobacilli). Single or short chains. - GS of CSF or old cultures look GV coccoid, very similar to S.pneumo!

41
Q

What organisms can grow on B.cepacia selective agar?

A
  • B.cepacia complex
  • Ralstonia spp.
42
Q

What organisms can grow on B.cepacia selective agar?

A
  • B.cepacia complex
  • Ralstonia spp.
43
Q

What’s in Chocolate agar that allows it to support Haemophilus influenzae growth?

A
  • NAD (Factor V)
  • Hemin (Factor X)
44
Q

What genus is Lowenstein-Jensen agar used to culture?

A

Mycobacterium spp., including M.tuberculosis

45
Q

What organisms grow on MacConkey agar?

A

Enteric Gram-negative organisms.

Fermentation of lactose in the medium turns colonies pink.

46
Q

What organisms grow on Sabouraud agar?

A

Fungi

47
Q

What is in Thayer-Martin agar that allows it to select for Neisseria gonorrhoeae and N. meningitidis?

A
  • Vancomycin
  • Trimethoprim
  • Colistin
  • Nystatin
48
Q

How can we determine the serogroup of an N.meningitidis isolate?

A

PCR assay with two targets:

  • ctrA = N.meningitidis capsular transport gene (confirms spp. ID & encapsulated).
  • said = serogroup-specific poly-sialyltransferase gene.

NB: Serotyping done @NML for surveillance.

49
Q

How can we determine the serogroup of an N.meningitidis isolate?

A

PCR assay with two targets:

  • ctrA = N.meningitidis capsular transport gene (confirms spp. ID & encapsulated).
  • said = serogroup-specific poly-sialyltransferase gene.

NB: Serotyping done @NML for surveillance.

50
Q

Nocardia

A

O2: STRICT aerobe CAT+ GS: GP bacilli, weakGPB - Long, thin, delicate,branching chains/filaments. - Filaments can break apart from culture

51
Q

Obligate intracellular bacteria

A
  • Chlamydia
  • Coxiella
  • Ehrlichia
  • Rickettsia
52
Q

Oral cavity commensals (MOF)

A

CoNS Dips NP Neisseria VGS ANA GPC + Lactobacillus

53
Q

How do we determine S.pneumoniae serotypes?

A

Done by Quellung reaction

54
Q

How do we determine S.pneumoniae serotypes?

A

Done by Quellung reaction

55
Q

Skin commensals (MSF)

A

CoNS Dips NP Neisseria VGS ANA GPC + Propioni

56
Q

What is the Trichrome stain used for?

A

To detect intestinal protozoa/spx

57
Q

What is the Trichrome stain used for?

A

To detect intestinal protozoa/spx

58
Q

Which bacteria stain acid-fast:

(genera)

A
  • Mycobacterium spp.
  • Actinomycetes (e.g. Nocardia, Rhodococcus).
  • Legionella micdadei
59
Q

What organisms would you want to use a Fite stain to see?

A
  • Mycobacterium leprae
    • Often decolourizes with ZN/Kinyoun stains

NB: Nocardia will also stain Fite+, so non-specific.

60
Q

What organisms would only stain weakly with Gram stain, so a Giemsa stain would be preferred?

(genera)

A
  • Borrelia/Borreliella
  • Ehrlichia
  • Anaplasma
  • Rickettsia
  • Helicobacter
61
Q

What organisms would you want to use a GMS stain to see?

(GMS = Gomori methenamine silver)

A

Fungi

  • Used broadly as a fungal screen in histology
  • Including Pneumocystis jiroveci

(Histoplasma granuloma shown with question)

62
Q

What organisms would you want to use an India ink stain to see?

A

Cryptococcus spp.

63
Q

What organisms would you want to use a Mucicarmine stain to see?

A
  • Cryptococcus spp.
64
Q

What organisms would you want to use PAS (Period acid-Schiff) stain to see?

A

Tropheryma whipplei in tissue

(PAS+ macrophages in the lamina propria are pathognomonic for Whipple’s disease)

65
Q

What organisms would you want to use a Warthin-Starry stain to see?

A
  • Spirochetes:
    • Treponema (e.g. syphilis)
    • Borrelia/Borreliella
    • Leptospira
  • Helicobacter pylori
  • Bartonella henselae (bacillary angiomatosis)
66
Q

What organisms would you want to use a Ziehl-Neelsen stain to see?

A
  • Acid fast bacteria:
    • Mycobacterium spp.
    • Actinomycetes (e.g. Nocardia, Tsukamurella, Gordonia)
    • Legionella micdadei
  • Coccidian parasites, e.g. Cryptosporidium
67
Q

Strictly aerobic GN bacilli

A

Pseudomonas

1-Scientific & lab basis of microbiology (9 decks)

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