(M) Lab: Biochemical Identification of Bacteria (Part 1)

Question 1

• One important request from doctors that we received in the laboratory
• Done to specifically identify the genus and species of the pathogen that causes the infection or disease of the patient

Answer 1

Culture and Sensitivity

Question 2

• Growing a specific bacteria
• Demonstrated by the presence of colonies on the culture medium
• Where you will get a new sample for follow-up biochemical identification

Answer 2

Colony (Growth)

Question 3

Serves as the artificial environment

Answer 3

Culture medium

Question 4

• Basis for the follow-up tests to be performed
• The colonies are inoculated based on the biochemical test required to perform

Answer 4

Gram-Staining Reaction

Question 5

• These two groups are the most common pathogens we observe in the laboratory
• Two groups of bacterium cover the majority of the isolates recovered in the laboratory
• Also causative agents of infections
• The common workflow for the different biochemical tests focuses on these two groups

Answer 5

Gram-positive cocci and gram-negative bacilli

Question 6

• Observe and check for the fermentation process in a sample or colony
• Can the bacteria ferment a carbohydrate, specifically sugar
• The end product is acid formation or production
• Identifies genus and species of G(-) cocci
• Only for screening or it is only presumptive

Answer 6

Carbohydrate Fermentation

Question 7

T or F: When you have the fermentation process, sugar is involved.

Answer 7

T

Question 8

Carbohydrate Fermentation

Most common indicator

Answer 8

Phenol red

Question 9

Carbohydrate Fermentation

Indicated by a change in color reported as:

Answer 9

• Positive: Yellow
• Negative: Original color / Red

Question 10

When done alone, it can still be confirmatory if G/S results is G(-) cocci.

Answer 10

Carbohydrate Fermentation

Question 11

Study the procedures for carbohydrate fermentation.

Answer 11

Go bestie mwa

Question 12

Results for Carbohydrate Fermentation

N. gonorrhea

Answer 12

Glucose (+)
Maltose, Sucrose, Lactose (-)

Question 13

Results for Carbohydrate Fermentation

N. meningitidis

Answer 13

Glucose, Maltose (+)
Sucrose, Lactose (-)

Question 14

Results for Carbohydrate Fermentation

N. lactamica

Answer 14

Glucose, Lactose (+)
Maltose, Sucrose (-)

Question 15

Results for Carbohydrate Fermentation

N. secca

Answer 15

Glucose, Sucrose (+)
Maltose, Lactose (-)

Question 16

Results for Carbohydrate Fermentation

Assacharolytic

Answer 16

Glucose, Maltose, Sucrose, Lactose (-)

Question 17

Carbohydrate Fermentation

• Labeled as dextrose
• Very important in G(-) cocci

Answer 17

Glucose

Question 18

• A medically important G(-) cocci genus, is automatically a glucose fermenter

Answer 18

Neisseria

Question 19

• Also important as it identifies N. meningitidis which is a very important pathogen

Answer 19

Maltose

Question 20

• A non-fermenter; characteristic of Moraxella catarrhalis
• Tests negative for all sugar panels, despite being a G(-) cocci

Answer 20

Assacharolytic

Question 21

• Is also important for the screening/presumptive ID of the groups of different bacteria
• Basis for specific follow-up tests
• Because of the enzyme hemolysin that causes RBC lysis

Answer 21

Hemolysis of RBCs

Question 22

Hemolysis of RBCs

Means you are not sure, you just have an idea about the genus and species

Answer 22

Screening/presumptive

Question 23

Hemolysin production is best demonstrated in?

Clue: A differential medium for hemolysis

Answer 23

BAP

Question 24

Hemolysis of RBCs

T or F: The pattern should be enhanced especially for G(+) cocci.

Answer 24

T

Question 25

# Hemolysis of RBCs It is highly presumptive for G(+) cocci

Answer 25

Hemolysis pattern

Question 26

Study the procedure for hemolysis of RBCs.

Answer 26

Go on pls !!

Question 27

# Identify the pattern. * Partial hemolysis (incomplete) * Greenish halo around the colony * S. pneumoniae, Viridans strep

Answer 27

Alpha-hemolytic pattern

Question 28

# Identify the pattern. * Complete hemolysis * Yellowish halo around colony * (Bright → if enhanced) * S. aureus, S.pyogenes, S. agalactiae

Answer 28

Beta-hemolytic pattern

Question 29

# Identify the pattern. * No hemolysis (no hemolysin) * White colony, plain growth w/o any halo * Group D Enterococci

Answer 29

Gamma-hemolytic pattern

Question 30

* Based on this biochemical test, we look at whether the bacterium produces an amylase enzyme * Differentiates for G(+) bacilli, specifically the biotypes of **Corynebacterium diphtheria**

Answer 30

Starch Hydrolysis

Question 31

# Starch Hydrolysis Hydrolyses starch producing maltose, a monosaccharide

Answer 31

Amylases

Question 32

# Starch Hydrolysis Cell walls are highly permeable to this sugar, it can easily enter the cell wall

Answer 32

Maltose

Question 33

# Starch Hydrolysis Lyses the cell wall

Answer 33

Increased amounts of maltose

Question 34

Same genus and species that differ in biochemical properties

Answer 34

Biotypes

Question 35

Biotypes of Corynebacterium diphtheria?

Answer 35

* Gravitis * Mitis * Intermedius

Question 36

# Starch Hydrolysis Positive results?

Answer 36

Colorless halo around bacterial growth

Question 37

# Starch Hydrolysis Negative results?

Answer 37

Original color: blue/purple with growth

Question 38

* Detects whether bacteria produce gelatinase * Differentiates some members of the Enterobacteriaceae

Answer 38

Gelatin Liquefaction

Question 39

Liquefies the medium

Answer 39

Gelatinase

Question 40

# Gelatin Liquefaction Positive Results?

Answer 40

Liquid medium (change in the consistency)

Question 41

# Gelatin Liquefaction Negative results?

Answer 41

Solid gel (as is)

Question 42

* Used to verify results that involve changes in consistency or physical properties * Done by titling the tube to check for changes

Answer 42

Tilt Tube Method

Question 43

* Whether bacterium releases a specific pigment, therefore producing specific-colored colonies * Very helpful for the presumptive identification of genus and species * Confirmatory for Chromobacterium violaceum

Answer 43

Pigment Production

Question 44

# Pigment Production Produces purple colonies that can be demonstrated even on a MacConkey agar

Answer 44

Chromobacterium violaceum

Question 45

Study the procedure for pigment production.

Answer 45

GOOOOO

Question 46

# Identify the organism based on pigment production. * **Lipochrome** → golden colonies

Answer 46

S. aureus

Question 47

# Identify the organism based on pigment production. * **Pyoverdin** → green colonies; the most common pigment by aeruginosa; usually in MHA * **Pyocyanin** → blue or blue green colonies * **Pyorubin** → red colony (rare) * **Pyomelanin** → brown colonies (rare)

Answer 47

P. aeruginosa

Question 48

# Identify the organism based on pigment production. * **Prodigiosin** → red colonies; by G(-) bacilli: S. marcenscens; enhanced if incubated at room temperature

Answer 48

S. marcenscens

Question 49

# Identify the organism based on pigment production. * **Violacein** → violet pigment that can be demonstrated on a MAC

Answer 49

Chromobacterium violaceum