experiment 1 cultivation of bacteria

8/7/2019 experiment 1 cultivation of bacteria

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Diagnosis of Bacterial Infection

Bacterial Cultivation


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Outline

General procedure of bacteriological

Diagnosis

Culture medium

concept

categories

bacterial growth patterns

Inoculation and transfer techniques


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Specimens collection

General Procedure of Bacteriological Diagnosis

General rules

The specimens should be representative of the infectiousprocess;

Sufficient material;

Avoid the contamination of specimens;

Be sent to the lab immediately in an appropriate method and

examined ASAP.Be collected before using antimicrobial agents, e.g.

antibiotics.


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specimens

General Procedure of Bacteriological Diagnosis

Isolation, identification

Biochemical tests

EIA, ELISA, IF test, agglutination test

Antigen detection

Molecular Biological Diagnosis(hybridization, PCR, RT-PCR,etc)

Serological diagnosis (Ab titer)convalescent phase / acute phase4

Morphologic identification

microscopy & staining


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Culture medium

is the mixture of various nutrients that is

suitable for the growth of microorganisms.

ypes ofCulture Media

based on the function and chemical components

based on the physical state


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Based on the function and the chemical components:

Basic Medium

--contains thebasic nutrients for the most bacterial growth;

--thebase of other kind of media.

--e.g. broth.

Nutrient Medium/Enriched Medium

Additional or special nutrients (e.g., serum, growth

factors, trace elements) are added to support some

fastidious bacterial growth.e.g. blood agar.


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Selective Medium

the medium that canprevent the certain bacterialgrowth while permitting others.

e.g. SS agar

Differential MediumSome special substrates and indicators are added into the

media in order to produce a visual differentiation

when several bacteria grow on the same kind of medium.

e.g. EMB agar (Eosin-methylene blue agar).


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E.colion EMB S.dysenteriae on EMB


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Double sugar iron slant

Citrate slant


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Anaerobic Medium

a medium for the cultivation of certain anaerobes. The

medium contains reducing agent, such as non-saturation

fatty acid.


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Based on the physical state

Liquid medium:

Without agar.

for the proliferation of bacteria.

Solid medium:

1.5-2.5% agar. for the isolation and identification of bacteria

e.g., slant, Petri dishes/plates.

Semisolid medium:

0.3-0.5% agar.

for the observation of bacterial motility and preservation ofbacteria.


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Bacterial growth patterns

In liquid medium:

Superficial growth;

Turbidity/diffuse;

Precipitate growing;

(sediment)

In solid medium:

Confluent growth / Smear;

Colony:

a cluster of microorganisms growing

on a solid medium. It is directly visible

and arises from a single cell.


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In semi-solid medium: Only grow along the line of inoculation

Grow diffusely


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General procedure of bacteriological Diagnosis

Culture medium

concept

categories

bacterial growth patterns

Inoculation and transfer techniques


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Streak-plate technique

four-area streak plate technique

IV

III 1/5I

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Rotateplate 90r

Flame loop

Rotate 90r

Rotate 90rIII

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Flame loop


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Slant inoculation


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Liquid medium inoculation


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2 students/group

Inoculation method Culture media Bacterial strains

Streak plate 2 plates (1plate/student) A mixed liquid

ofS.aureus & E.coli

Slant inoculation 2 slants (1slant/student) 1 E. coli slant

Liquid medium 1 liquid medium 1 E. coli slant

inoculation 1 liquid medium 1 B. subtitis slant

Semisolid medium 1 semisolid medium 1 Proteus slant

inoculation (Stabbing) 1 semisolid medium 1 S.dysenteriae slant

Markyour freshly inoculated plate/tube;

Shake up the mixed liquid of bacterial strains before using it.

Prepare Gram Stain & Acid-fast Stain.

NOTE!!!

experiment 1 cultivation of bacteria

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