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Principles > Systematic bacteriorology 1 > Flashcards

Systematic bacteriorology 1 Flashcards

Revision

1
Q

How do you classify microorganisms?

A
  1. Appearance/ Structural features (microscopic analysis)
    - Shape
    - Size
    - Arrangement
    - Cell Wall i.e. Gram positive/Gram negative
  2. Growth Requirements;
    - Aerobic/Anaerobic (e.g. strict anaerobes)
    - Requirement for blood products (e.g. serum proteins)
    - Sensitivity to inhibitory agents (e.g. NaCl, Bile, K tellurite)
  3. Enzyme/metabolic tets;
    - Coagulase test, Catalase test.
    - Haemolysis (streptococci ONLY),
    - Biochemical profiling (e.g. carbohydrates metabolised)
  4. Molecular tests;
    - Immunological tests, e.g. cell surface antigens
    - DNA sequencing e.g. qPCR or 16sRNA
    - Protein profilin e.g. Mass-spec analysis
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2
Q

How do you identify microorganisms?

A

Microscopy (single colony or pus sample)

  • Pure culture or polymorph
  • Shape, size, grouping
  • Structures (capsules, flagella, spores)
  • Staining (Gram, Ziehl Neelson, Fluorochroms)
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3
Q

What are the common shapes of bacteria?

A

Common Shapes:

  • Cocci - spheres
  • Baccilli (rods)
  • Spiral-shaped
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4
Q

What are Coccus and what is an example of a coccus?

A

Division in one plane to produce two cocci:

e.g. Diplococcus

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5
Q

What are Cocci and what are some examples?

A

Division in one plane to produce chains 4-20 cocci: e.g. streptococcus
Division in three planes to produce clumps: e.g. Staphylococcus

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6
Q

What are Bacillus/Bacilli and do they exist individually or as multiples?

A

Rod-shaped bacteria

Chains of bacilli, tend to see chaining more in gram +ve bacteria than gram -ve bacteria.

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7
Q

What is a curved rod?

A

Slightly curved rod: vibrio
Gm -ve
34 recognised species vibrio cholerae

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8
Q

Why are some bacterium spiral shaped hat name is given to describe the different types of spiral bacteria?

A

Rigid spiral bacterium: spirillum
Flexible spiral bacterium;
Spirochaete
(In very viscus solution things like senum or aliva, its dynamically more efficient to move as a spiral)

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9
Q

What role do fusiform play in sore throats and tumours?

A

Fus bacteria are the second most likely cause of a sore throat.
The cause of about 10% of colon tumours

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10
Q

What different structures can bacteria have?

A

Flagella, Pili and capsules can characterise species and strains.
(Bipolar flagella tufts spirillum volutans)
(Capsule k.pneum)
Spores; inert structures, resistant to physical and chemical challenge e.g. C.difficile.
Binary fission
Sporulation
Prespore
Endospore
Cell Lysis
Spore Germination

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11
Q

What affects the gram stain of a bacteria?

A 
Retention of crystal violet/iodine complex by gram - positive bacteria.
Simple method that distinguishes 2 major classes of bacteria according to cell wall structure.
Gram -ve
Lipopolysaccharide
Outer membrane
Peptidoglycan
ytoplasmic membrane
Gram +ve
Multi-layered peptidoglycan
Secondary Polymer
Cytoplasmic membrane
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12
Q

What are the limitations of gram stain?

A

Gram variable bacteria and microbes that do not stain with crystal violet/iodine complex exist
Not all organsims stain well with Gram stain e.g.
Mycobacterium tuberculosis
- The organism that causes TB
- Has a lipid rich/ waxy cell wall that does not take up th stain
Treponema Pallidum
- A spirochaete organism that causes syphilis, a sexually transmitted infection/ disease.
Other staining methods or diagnostic tests must be used for these infections

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13
Q

What are the different types of Aerobic and Anaerobic bacteria?

A

Bacteria are also classified by their ability to use (or tolerate) oxygen
Aerobic (grow in oxygen/ air)
Obligate Aerobes (require oxygen)
Obligate Anaerobes (killed by oxygen)
- Respiration uses electron acceptor other than oxygen
- Smaller reduction potential than O2
- Less proton motive force across membrane (ATP synthase)
- Less energy released per molecule oxidised.
Facultative Anaerobes (tolerate oxygen)
Capnophillic (prefer high Co2 levels).

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14
Q

What is Selective Media and what are some examples of Selective Media?

A

A media that selects for the growth of specific prokaryotes.

  • Presence of specific substances permits the growth of one organisn over another
  • Mannitol Salt agar (MSS)
  • (7.5% salt allows preferential isolation of sta[hylococci)
  • Salmonella-Shigela (SS)
  • bile salts inhibit coliforms
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15
Q

What is Differential Media and what do MacConkay Agar and Eosin and Methylene Blue (EMB) consist of?

A

Incorporation of chemicals produces visible changes in colonies that facilitate identification (differentiation)
MacConkay Agar
- bile salts and crystal violet
- Lactose only C source and neutral red indicates fermentation.
- Facilitate identification of Enetrobacteriaceae.
Eosin and Metylene Blue (EMB)
- lactoe salts and two dyes
- allows identification of lactose fermenters e.eg. E.coli

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16
Q

How do you identify Streptococcus spp.?

A

Haemolysis or Hemolysis
alpha - greening of the colonies
beta - Lancefield grouping A, B, C, F, G - Colony soze Large (pyrogenic) o Small (S.milleri). Group A streptococci.
gamma - no heamolysis

17
Q

What is the process of Serological tests and what can they be used for?

A

Host immune response to Ag by the raising of Abs.
Ab specific to microbe/ virus (polyclonal) or single componenet monoclonal).
Detect presence of specific IgM Ab to virus/ microbe.
Demonstrate in vitro by agglutination (aggregation) reation.
Rapid detection of viruses (24 hours), even possible to identify the stages of infection using 2 different tests.
Can identify specific serotypes of bacteria.

18
Q

What is the process of Agglutination?

A

Slide agglutination use Ag/Ab specificity.
Antibodies are attached to a latex bead (or red blood cell). If they attach to the antigen, they mix and agglutination is detected.
If they do not attach to the antigen, they mix and Ab remains in suspention.

19
Q

What can DNA technology tell us?

A 
Genome sequencing
- Bacterial
- Archaea
- Eukaryota
- Phage
- Viruses
Specific Primers amplify specific piece of DNA.
Successful amplification of DNA target may indicate the presence of an organism or even specific virulenxe factor.
Real time of qPCR (Virology)
DNA sequenceing of product may allow
 Precise identification. Ribotyping 16S RNA
Spa Typing S. aureus
20
Q

What is 16sRNA?

A

RNA component Holoenzyme in a ribosome.

21
Q

What does Multi locus sequence Yping (MLST) allow us to do?

A

Increasing resolution

  • 16sRNA, spa, etc.
  • MSLT
  • Entire genome sequencing
22
Q

What is MALDI-TOF (Matrix Assisted Laser Desorption Ionization Time-Of-Flight) and what are the benefits and what is it not so good at?

A

Ion Source
- Ionize and transfer analyte ions into gas phase
Generates a series of ions from a sample dependent on its conctituents
Separates the ions according to mass and charge
Detectts the spectrum of protins released from a sample.
Results in characteristic signature
Not so good for Strptococci and Staphylococci
Powerful (99% correct)
Rapid (colony tested in 6 minutes)
Precise (Species, subspecies, sometimes strain level)
Cost-effective (17-32% cost of conventional techniques)

23
Q

How do you carry out a gram stain?

A
  1. Prepare a heat-fixed film of bacteria on a glass slide.
  2. Stain with crystal violet for 1 min and rinse with water.
  3. Treat with Gram’s iodine for 1 min and rinse with water.
  4. Briefly decolourize with acetone or ethanol (a few seconds depending on thickness of film)
  5. Counter stain with basic fuchsin or safranin (pink dye) for 1 min and rinse with water.
  6. Blot dry and view under oil immersion.
24
Q

What are the 3 groups that colony characteristics are categorised into and what are the options in each category?

A 
Form
- Punctiform
- Circular
- Filamentous
- Irregular
- Rhizoid
- Spindle
Elevation
- Flat
- Raised
- Convex
- Pulvinate
- Umbonate
Margin
- Entire
- Undulate
- Lobate
- Erose
- Filamentous
- Curled
25
Q

How do you biochemically characterise bacteria?

A 
Through Metabolic profiling
- Utilisation of Carbon sources;
- Utilisation of amino acids;
and also through Exo-enzyme production
- Catalase (2H2O2 to 2H2) & O2)
- Coagulase (clot plasma)
- Hydrolysis of lipid
- Urease (urea converted to ammonia and CO2)
26
Q

What process is now common in chemical profiling?

A

Automated Biochemical profiling is now common.

Inoculate/Resuspend Single Colony. Transfer 100µls.

27
Q

What is the Linnaean classification of bacteria?

A 
Kingdom - Bacteria
Phylum - Firmicutes
Class - Bacilli
Order - Bacillales
Family - Bacillaceace
Genus - Bacillus
Species - Subtilis
and strain, resistance, toxin information etc.
28
Q

What are some examples of specific microbiology tests?

A 
Blood culture.
Urine culture.
Faeces culture.
Swab of pus.
Specimens for polymerase chain reaction (PCR tests).
Blood for serology
- Antibodies/antigen
- etc.
29
Q

What 4 different ways can you classify microorganisms and what different categories come under each one?

A
  1. Appearance/Structural feautres (microscopic analysis)
    - Shape
    - Size
    - Arrangement
    - Cell Wall; i.e. Gram positive/Gram negative
  2. Growth Requirements;
    - Aerobic/Anaerobic (e.g. strict anaerobes)
    - Requirement for blood products (e.g. serum proteins)
    - Sensitivity to inhibitor y agents (e.g. NaCl, Bile, K tellurite)
  3. Enzyme/metabolic tests;
    - Coagulase test, Catalase test.
    - Haemolysis (Streptoccocci ONLY),
    - Biochemical profiling (e.g. carbohydrate metabolised)
  4. Molecular tests;
    - Immunological tests, e.g. cell surface antigens
    - DNA sequencing e.g. qPCR or 16sRNA
    - Protein profiling e.g. Mass-spec analysis.

Principles (57 decks)

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