Examples of Bacterial Identification

Identification of bacteria

เอนก ภู่ทอง ภาควิชาเทคนิคการแพทย์ คณะสหเวชศาสตร์ มหาวิทยาลัยธรรมศาสตร์

Biochemical test for bacteria

เอกสารนี้  แสดงการอ่านและแปรผลการทดสอบเชื้อแบคทีเรีย  จัดทาขึ้นเพื่อเป็นบันทึกช่วยในการเรียนรู้ของนักศึกษาเทคนิค การแพทย์

Staining

Gram’s stain

Gram negative Gram positive appearance Purple Pink to red interpret Gram positive Gram negative

Appearance on bacteriological agar

Sheep blood plate

Alpha-hemolysis

Beta-hemolysis

Gamma-hemolysis

MacConkey agar

colony 1 2 3 4

appearance pink colony pink colony no growth colorless colony

interpret Lactose fermenter Lactose fermenter Non lactose fermenter

Shigella-Salmonella Agar (SS agar)

Pink colony

Colorless colony with black center colony 1 2 appearance pink colony Colorless colony

Colorless colony interpret Lactose fermenter Non Lactose fermenter

3

Colorless colony with black center

Non Lactose fermenter H2S producing colony

TCBS

Yellow colony

V.parahaemolyticus and V.cholera on TCBS
Green colony

colony
1 2

appearance
Green colony Yellow colony

interpret
Non sucrose fermenter Sucrose fermenter

biochemical test

Triple Sugar Iron Agar (TSI)

Non fermenter
No fermentation pH= 7.4 O2

K/N

Non lactose fermenter
Dextrose Mixed acid

O2

A/A
Initial reaction

Dextrose Mixed acid

O2

K/A
Delayed reaction

lactose fermenter
Dextrose + Lactose Mixed acid O2

A/A

Triple Sugar Iron Agar (TSI)

1

2

3

4

-Fermentation Yellow ~Acid (A) Red~Alkaline (K) No change ~Neutral (N) -Gas positive  G -H2S positive  +

tube appearance Slant Butt Gas H2S interpret
Slant/butt, gas, H2S

1 Yellow Yellow + A/AG

2 red yellow + K/AG

3 red yellow + K/A+

4 red neutral K/N

Lysine Iron Agar (LIA)

Slant  Lysine Deaminase (LDA) purple = negativenon LDA producer red=positive LDA producer Butt Lysine Decorboxylase (LDC) yellow =negative non LDC producer purple = positive LDA producer

tube appearance Slant Butt H2S interpret Slant/butt

control purple purple

1 purple yellow -/-

2 red yellow +/-

3 purple purple -/+

4 purple purple + -/+

SIM
1 2 3

tube sulfur indole motile Sulfur, indole, motile

1 -/-/-

2 + + -/+/+

3 + + + +/+/+

Simmon’s Citrate agar
- To tests the ability of organisms to utilize citrate as a carbon source - Sodium citrate is the sole source of carbon

1

2

tube appearance bacteria

1 No growth

2 growth

agar interpret

Not change -

Blue +

Tolerance testing

Bacitracin susceptibility test

Clear zone  susceptibility positive

No clear zone  resistance negative

1

2

6.5% NaCl

control appearance interpret clear -

1 clear Negative (-)

2 turbid Positive (+)

Immunological testing

Anti-serum agglutination test
1 2

1 appearance interpret Non agglutinate Negative (-)

2 agglutinated Positive (+)