(M) Lab: Biochemical Identification of Bacteria (Part 1) Flashcards
Biochemical Identification/Properties of Bacteria
- 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
Culture and Sensitivity
- 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
Colony (Growth)
Serves as the artificial environment
Culture medium
- Basis for the follow-up tests to be performed
- The colonies are inoculated based on the biochemical test required to perform
Gram-Staining Reaction
- 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
Gram-positive cocci and gram-negative bacilli
- 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
Carbohydrate Fermentation
T or F: When you have the fermentation process, sugar is involved.
T
Carbohydrate Fermentation
Most common indicator
Phenol red
Carbohydrate Fermentation
Indicated by a change in color reported as:
- Positive: Yellow
- Negative: Original color / Red
When done alone, it can still be confirmatory if G/S results is G(-) cocci.
Carbohydrate Fermentation
Study the procedures for carbohydrate fermentation.
Go bestie mwa
Results for Carbohydrate Fermentation
N. gonorrhea
Glucose (+)
Maltose, Sucrose, Lactose (-)
Results for Carbohydrate Fermentation
N. meningitidis
Glucose, Maltose (+)
Sucrose, Lactose (-)
Results for Carbohydrate Fermentation
N. lactamica
Glucose, Lactose (+)
Maltose, Sucrose (-)
Results for Carbohydrate Fermentation
N. secca
Glucose, Sucrose (+)
Maltose, Lactose (-)
Results for Carbohydrate Fermentation
Assacharolytic
Glucose, Maltose, Sucrose, Lactose (-)
Carbohydrate Fermentation
- Labeled as dextrose
- Very important in G(-) cocci
Glucose
- A medically important G(-) cocci genus, is automatically a glucose fermenter
Neisseria
- Also important as it identifies N. meningitidis which is a very important pathogen
Maltose
- A non-fermenter; characteristic of Moraxella catarrhalis
- Tests negative for all sugar panels, despite being a G(-) cocci
Assacharolytic
- 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
Hemolysis of RBCs
Hemolysis of RBCs
Means you are not sure, you just have an idea about the genus and species
Screening/presumptive
Hemolysin production is best demonstrated in?
Clue: A differential medium for hemolysis
BAP
Hemolysis of RBCs
T or F: The pattern should be enhanced especially for G(+) cocci.
T
Hemolysis of RBCs
It is highly presumptive for G(+) cocci
Hemolysis pattern
Study the procedure for hemolysis of RBCs.
Go on pls !!
Identify the pattern.
- Partial hemolysis (incomplete)
- Greenish halo around the colony
- S. pneumoniae, Viridans strep
Alpha-hemolytic pattern
Identify the pattern.
- Complete hemolysis
- Yellowish halo around colony
- (Bright → if enhanced)
- S. aureus, S.pyogenes, S. agalactiae
Beta-hemolytic pattern
Identify the pattern.
- No hemolysis (no hemolysin)
- White colony, plain growth w/o any halo
- Group D Enterococci
Gamma-hemolytic pattern
- 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
Starch Hydrolysis
Starch Hydrolysis
Hydrolyses starch producing maltose, a monosaccharide
Amylases
Starch Hydrolysis
Cell walls are highly permeable to this sugar, it can easily enter the cell wall
Maltose
Starch Hydrolysis
Lyses the cell wall
Increased amounts of maltose
Same genus and species that differ in biochemical properties
Biotypes
Biotypes of Corynebacterium diphtheria?
- Gravitis
- Mitis
- Intermedius
Starch Hydrolysis
Positive results?
Colorless halo around bacterial growth
Starch Hydrolysis
Negative results?
Original color: blue/purple with growth
- Detects whether bacteria produce gelatinase
- Differentiates some members of the Enterobacteriaceae
Gelatin Liquefaction
Liquefies the medium
Gelatinase
Gelatin Liquefaction
Positive Results?
Liquid medium (change in the consistency)
Gelatin Liquefaction
Negative results?
Solid gel (as is)
- Used to verify results that involve changes in consistency or physical properties
- Done by titling the tube to check for changes
Tilt Tube Method
- 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
Pigment Production
Pigment Production
Produces purple colonies that can be demonstrated even on a MacConkey agar
Chromobacterium violaceum
Study the procedure for pigment production.
GOOOOO
Identify the organism based on pigment production.
- Lipochrome → golden colonies
S. aureus
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)
P. aeruginosa
Identify the organism based on pigment production.
- Prodigiosin → red colonies; by G(-) bacilli: S. marcenscens; enhanced if incubated at room temperature
S. marcenscens
Identify the organism based on pigment production.
- Violacein → violet pigment that can be demonstrated on a MAC
Chromobacterium violaceum
