Culture & Colonies

Culture Media

any medium that contains all what is needed to support bacterial growth

Culture

growth of organism in culture media

Pure Culture

• 1 spp. only

• best way to obtain:

  • Streak Plate method

Mixed Culture

• more than 1 spp.

Stock Culture

• used in QC procedures

• used in research

• i.e. ATCC - American Type Culture Collection

Types of Culture Media: Apparatus

1. Tubed

2. Plated

Tubed

1. Weigh

2. Dissolve w/ H2O or deionized H2O

3. Dispense

4. Sterilize

Plated

1. Weigh

2. Dissolve w/ H2O or deionized H2O

3. Sterilize

4. Dispense

Inoculation

placing an organism on media

Incubation

• allows bacteria to grow

• usually at 35-37 degrees Celsius for 18-24 hrs

Types of Culture Media: Physical State

1. Liquid

2. Semi-solid

3. Solid

4. Bipahsic

Liquid

• in a tube

• deep or broth

• no solidifying agent

• 0% agar

• Growth:

  • turbidity

Liquid Examples

• Trypticase Soy Broth

• Brain Heart Infusion

• Alkaline Peptone Water

Semi-solid

• in a tube to produce slant/deep/butt manner

• 0.5-1% agar

• i.e.

  • Sulfide Indole Motility (SIM)

Solid

• petri dish; or

• tube

• Growth:

  • Colonies

Solid: Liquefiable

• initially liquid

• will solidify

• can be liquid again by heating

Solid: liquefiable examples

• Eosin Methylene Blue (EMB

• MacConkey

• Mannitol Salt Agar (MSA)

Solid: Non-liquefiable

• will no longer liquefy

• i.e.

  • Rice Medium

Biphasic

• solid and liquid

Biphasic example

• Castaneda’s (growing Brucella)

• Human Blood Bilayer Tween (HBT) (Gardnerella vaginalis)

Types of Culture Media: Use/Purpose

1. General purpose/isolation Media

2. Enrichment Media

3. Enriched Media

4. Selective Media

5. Differential Media

6. Selective and Differential Media

7. Transport Media

8. Antibiotic Susceptibility testing

General purpose/isolation Media

• contains only the necessary nutrition to support material growth

• for routine cultivation of bacteria

• for non-fastidious

General purpose/isolation Media Example

Nutrient Agar

Nutrient Broth

Enrichment Media

• Used to enhance bacterial growth or bacterial yield

• Usually contains added supplements or vitamins

Enrichment Media Examples

1. Selenite broth

   • Salmonella & Shigella

2. Tetrathionate Broth

   • Salmonella & Proteus

Enriched Media

• support growth of fastidious organisms

• usually contains blood

Enriched Media Example

• Sheep Blood Agar

  • Streptococci

• Horse Blood Agar

  • Haemophilus

• Human Blood Agar (HBA)

  • Garnerella Vaginalis

• Chocolate Agar Plate (CAP)

  • heating blood agar

  • for Neisseria

Selective Media

• Promotes the growth of the desired organism.

• Inhibits the growth of other organisms

• Contains inhibitors

Selective Media Example

• Cystine tellurite Blood agar

• Lowenstein Jensen Media

• Thayer Martin media

• MacConkey agar

• Cystine tellurite Blood agar

• C. diphtheriae

• Inhibitor:

  • Potassium tellurite

• Lowenstein Jensen Media

• M. tubersulosis

• Inhibitor:

  • Malachite green

• Thayer Martin media

• Neisseria

• Inhibitor:

  • antibiotics

• MacConkey agar

• gm(-) bacilli

• Inhibitor:

  • Crystal Violet

Differential Media

differentiate organisms growing together

Selective and Differential Media

• EMB

• MacConkey

• TCBS

Transport Media

• Maintain viability of organisms.

• Keep the specimens alive during specimen transport.

Biochemical test media

Used for biochemical testing, which aids in bacterial identification.

Biochemical test media examples.

• LIA

• TSI

• Urea Agar

• SIM

• MRVP Broth

Polypeptide-D-Glutamic acid

Bacillus anthracis

P. aeruginosa

fruity

overripe grape-like

corn taco

corn tortilla-like

S. aureus

on MSA

colonies w/ odor similar to an old sock

Nocardia spp.

freshly plowed field

CoNS

Coagulase (-)

Staphylococci = whit colony

C. difficile

w/ Horse stable or Back yard odor

Haemophilus spp.

Mousy odor

Neisseria spp.

yellow or off-white

some spp. = sticky

S. aureus

Yellow

creamy/butyrous

“butter-like”

Serratia marcesecens

red pigmet at Room temp.

Chromobacterium violaceum

violet

Klyvera spp.

blue pigment

Prevotella melaninogenica

brown-black

Y. enterocolitica & Aeromonas spp.

Bull’s eye colonies

M. Tuberculosis

Cauli flower-like growth

Proteus

Swarming

BAP

B. pertussis

mercury droplets

shiny half pearls

M. bovis

water droplets

M. xenopi

bird’s nest appearing colonies