Identification techniques Flashcards
5 classes of proteobacteria
Alpha-proteobacteria
Beta-proteobacteria
Gamma-proteobacteria
Delta-proteobacteria
Epsilon-proteobacteria
Enterobacteriales in what class?
Gamma-proteobacteria
Escherichia, Salmonella, and Klebsella all belong to which family?
Enterobacteriaceae
Examples of culture collections where strains are deposited
- American type culture collection
-National Collection of Type cultures
-Public Health England
-NCIMB
Is C. violaceum ATCC 12473 same as NCTC 9757? true or false
True
Do bacterial strains within a single species behave differently?
Yes
Classes 1-4
Class 1 - Non-pathogeneic e.g k12 E.coli
Class 2 - Potentially pathogenic e.g. K. pneumoniae
Class 3 - pathogenic e.g. legionella spp.
Class 4 - No known class 4 bacterium (most viruses)
Howare classical taxonomy and identification completed?
- Relies on phenotypic analyses
- Morphology (cell size, shape, flagella), O2 tolerance
- G+C content of DNA
- Physiology and metabolism e.g. nutrient sources, Relationship to pH, temperature, salinity, products formed, Prescence of enzymes
Cell morphology + Gram reaction
Differ in shape: Cocci or bacilli
Different in gram test - Gram-positive (Purplish blue) or Gram-negative (Pink)
Cocci types
Coccus
Diplococci
Streptococci
Sarcina
Tetrad
Staphylococci
Diplococci encapculated
Bacilli types
Coccobacillus
Bacillus
Palisades
Diplobacilli
Streptobacilli
Oxygen tolerance types
Obligate aerobe - requires oxygen to survive
Obligate anaerobe - Requires no oxygen to survive
Facilitative anaerobe - Can live in aerobic or anaerobic consitions
Aerotolerant anaerobe - Can tolerate low concentrations of oxygen
Microaerophile - Requires low levels of oxygen to grow
Endospores
- Survival forms produced under unfavorable conditions e.g. when nutrients run out
- Can survive 100s/1000s of years
- High resistance to heat, drying, radiation, chemicals
- Low water content
- Contain calcium diplocolinate
- Special proteins protect DNA
Catalase test
h2o2 -> h2o + 1/2O2
Important in detoxifyibg h2o2 produced during metabolismP#
Positive result - Bubbles
Negative - No bubbles
Oxidase activity
Detects the presence of cytochrome c and associated oxidase
Kovac’s reagent (N, N, N’, N’ - Tetramethyl-p-phenylenediamine dihydrochloride)
Colourless when reduced
Purple when oxidised
Do you need more or less energy to break the GC bonds
More
Growth on lactose test
Growth on lactose
- Production of acid (pH changes)
- pH indicator phenol red
- Red -> yellow
- production of gas
Test for H2S
- Hydrogen sulphide production
- Formation of ferrous sulphide
- Fe2+ + S2- —> FeS (insoluble)
Black - Positive result
Orange - negative result
What are API kits?
Media kits for isolate identification
MacConkey’s agar for enterobactericae
Bile salts inhibit gram negative
+ve - Lac+ - acid - red - E.coli, E. aerogenes
Lac- - NH3 - colourless - P. vulgaris, S. aureus
What grows on chocolate agar and how to distungish them
Haemophilus, Neisseria
Add antibiotic
How do differentiate between Haemophilus and Neisseria
Make medium more selective through adding antibiotics which kill Haemophilus, but don’t kill Neisseria
How to differentiate between coliforms and E. coli
Chromogenic
Coliforms - Pink
E. coli - Purple
Listeria selective agar
Non-pathogenic Listeria colony - no halo
Pathogenic Listeria - Halo present
Mannitol salt agar for coagulase positve Staphylococcus
Selects for GM +ve (high salt)
Mannitol fermentation - H+ - red to yellow
When using selective media ALWAYS include controls
positive control - Ferments mannitol produces H+
Negative control
What percentage of bacterial strains can be lab cultured?
3%
