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Fundamentals of MLS > Introduction to Microbiology > Flashcards

Introduction to Microbiology Flashcards

1
Q

What is a microorganism?

A

Broad term that is applied to any organism that cannot be seen with the un-aided eye (<= 0.1mm) and is often unicellular.

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2
Q

What are the characteristics of Prokaryotic Cells “primitive nucleus”?

A
  1. No organized nucleus.
  2. Once circular chromosome.
  3. No nucleolus.
  4. No mitochondria
  5. No endoplasmic reticulum.
  6. No golgi apparatus.
  7. 70S ribosomes
  8. Simple differentiation.
  9. No meiosis or mitosis.
  10. Absorption or photosynthesis.
  11. Bacteria
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3
Q

What are the characteristics of Eukaryotic Cells?

A
  1. Membrane bound nucleus.
  2. Nucleolus
  3. More than one chromosome.
  4. Mitochondria
  5. Endoplasmic reticulum
  6. Golgi apparatus.
  7. 80S ribosomes
  8. Tissues and organs.
  9. Meiosis or mitosis.
  10. Phagocytosis and pinocytosis.
  11. Protozoa, fungi, algae plants, & animals.
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4
Q

Compare the range of sizes for prokaryotic cells to eukaryotic cells.

A

Prokaryotic Cells: 0.1 to 10 um

Eukaryotic Cells: 10 - 100 um

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5
Q

What are the four classes of microorganisms?

A
  1. Protozoa; eukaryotic, often unicellular, e.g. giardia lamblia
  2. Bacteria; prokaryotic, unicellular, e.g. Streptococcus pyogenes.
  3. Fungi: eukaryotic, unicellular or multi, e.g. candida albicans (thrust)
  4. Viruses; neither pro or euk, unicellular, e.g. covid-19/HIV.
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6
Q

What is a bacterium?

A

Simplest living form that contains all the mechanisms necessary for growth and self-replication.

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7
Q

What do bacteria have the ability to do to produce energy?

A

Take compounds from their environment & utilize them to produce energy within the cell.

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8
Q

Describe the characteristics of the cytoplasmic (or plasma membrane) of bacterium.

A

• Cytoplasmic or Plasma Membrane (CM)
○ Separates cytoplasm from the cell wall
○ Made of Lipoprotein and is the deepest layer of the cellular envelope
○ Functions to regulate osmotic pressure, passage of nutrients into cell by diffusion or active transport

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9
Q

What is the cell wall of bacterium like?

A

Rigid structure outside of the cell membrane

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10
Q

Describe the characteristics of a nucleoid of a bacterium.

A

• Nucleoid
○ Bacterial growth occurs via asexual reproduction 1 bacterium to 2 identical bacterium cells
○ Bacteria also contain plasmids that replicate independently from the chromosome and can be transferred to other bacteria and often carry genes for antimicrobial resistance

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11
Q

Describe the capsule characteristics that some bacterium have.

A

• Capsule
○ Located outside the murein layer of G+ bacteria and the outer memb of G-
○ Surrounds the cell of polysaccharides or polypeptides
○ Can be seen microscopically as a void of stain around the cells
○ Increases virulence by protecting bacteria from phagocytosis and forming of a biofilm

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12
Q

Describe what pili are for some bacterium.

A

Fimbriae (Pili)
○ Primarily G- organisms
○ Hair like projections help bacteria adhere to surfaces or gene exchange via sex pili

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13
Q

Describe the flagella that some bacterium’s have.

A

• Flagella
○ Embedded into the cell envelope – propeller to make bacteria mobile in search of nutrients.
○ G+ rarely motile (mostly are gram negs that have flagella)
○ Can have one or many, along with different arrangements like monotrichous (one flagellum at one end) or Peritrichous (Flagella distributed over entire cell surface)

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14
Q

What makes a bacteria gram positive or gram negative?

A

Gram positive organisms have thicker layer of peptidoglycan than G-. Cell Wall (CW) contains teichoic acid and lipoteichoic acid which is not present in G-.

Gram negative organisms have a cell wall composed of two layers: Inner thin peptidoglycan, outer membrane composed of proteins, lipo-polysaccharides and phospholipids, in between the space is periplasmic space.

Draw a diagram of the two showing the differences.

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15
Q

What are organic and inorganic factors important to bacteria for?

A

Organic factors are required for growth.

Inorganic factors are important for cell metabolism.

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16
Q

What chemical elements, if altered, may affect the growth of the bacteria?

A

Organic growth factors such as:
- Carbon, nitrogen, vitamins (co-enyzme), etc.

Inorganic growth factors such as:
- Potassium (acts as a catalyst), iron, sulphur (co-enzyme), etc.

Oxygen and hydrogen also affect growth.

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17
Q

What pH do most pathogenic bacteria that affect humans grow best in?

A

Most pathogenic bacteria (to humans) grow at a neutral pH of 7.0 to 7.5.

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18
Q

In terms of moisture or dryness, what kind of environment do bacteria that affect humans like?

A

They like a moist isotonic environment (i.e. one where they will not burst/lyse or shrink or crenate).

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19
Q

What temperatures do bacteria like?

A

Mesophiles 35 - 37C
Psychrophiles 10-19C
Thermophiles 50-60C

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20
Q

What atmosphere environment do bacteria like?

A

Various. Some like aerobic atmosphere and others like anaerobic, ie. with or without O2.

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21
Q

What are the main mechanisms of aerobic metabolism and final end product?

A
  1. Respiration or oxidation.
  2. Pentose Phosphate Shunt Pathway or Entner-Douderoff pathway
  3. Final END product: PYRUVATE.
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22
Q

What are the main mechanisms for anaerobic metabolism?

A
  1. Fermentation
  2. Embden-Meyerhof-Parnas (EMP) Pathway.
  3. Final END Product: Pyruvate
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23
Q

What do all three pathways produce? And by what cycle can the product be further broken down?

A
  1. All three produce: PYRUVATE.

2. Can be further broken down by: KREB’s CYCLE or carry on to mixed acids product of fermentation.

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24
Q

What are virulence factors?

A

Virulence factors are components that determine capacity to cause disease but do not affects its own ability to survive.

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25
Q

List some virulence factors.

A
  1. Colonize surface (pilli)
  2. Invasion of tissue (trauma, extracellular enzymes that can break past skin barrier & breach immune system….hydrolyze host proteins & destroy host tissue).
  3. Production of toxins (exotoxins versus endotoxins)
  4. Evasion of immune system response (i.e. capsules)
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26
Q

What are exotoxins?

A
  1. Toxic microbial proteins that are excreted by organisms by gram pos and neg bacteria.
  2. Antigenic
  3. Heat labile
  4. Systemic.
  5. Slow action (days, for symptoms in host to appear).
  6. Toxoids (ex. diphtheria)
27
Q

What are endotoxins?

A
  1. Toxin is a complex part of organism (lipopolysaccharide from cell wall) that is released when the cell lyses.
  2. Toxins are composed of protein, lipid, and polysaccharide.
  3. Only with gram neg bacteria.
  4. Heat stable.
  5. Cannot be made into a toxoid.
  6. Fast action (hours).
28
Q

What are three types of exotoxins?

A
  1. Endotoxin – produced in the intestinal tract (acute diarrhea) E.coli, Salmonella, Staph aureus
  2. Cytotoxins – disrupt the epithelial cells – Shigella dysenteriae, C. diff,
  3. Neurotoxins – Pre-formed toxins ingested and cause food poisoning S. aureus, C. botulinum
29
Q

How do you describe the taxonomy of a pathogen?

A 
Domain - Bacteria (Eubacteria)
Kingdom - Proteobacteria
Class - Zymobacteria
Order Family - Enterobacterales (former Enerobacteraceae)
Genus - Shigella
Species - dysenteriae
30
Q

In clinical lab what two taxonomy names are most organisms refer to as by?

A

Genus & species (in that order)
E.g. Staphylococcus aureus

This is called a binomial system of nomenclature.

Note: Always capitalize genus’ first letter. Species is in all lowercase. Genus may be abbreviated by using the 1st upper case letter followed by a period.

31
Q

What is a phenotype?

A

Phenotypic characteristics relate to readily observable traits such as:

  1. Morphology
  2. Growth characteristics
  3. Antigenic properties
  4. Antimicrobial resistance
32
Q

Name two different type of morphologies.

A
  1. Cellular morphology - examined with microscopy, i.e. size shape & staining reactions, etc.
  2. Colonial morphology - examined by observing microbial growth on culture media and determining size, pigment, texture, etc. of the colonies.
33
Q

What is genotype?

A

Genotypic characteristics relate to the genetic makeup and involve molecular methods (i.e. using nucleic acid-based identification).

Base composition studies.

34
Q

What are the four stages of bacterial growth?

A

Lag - cells become adjusted to their environment
Log - exponential growth phase
Stationary stage - no increase in growth
Death - cessation of growth

35
Q

When should most laboratory testing be performed?

A

During the “LOG” - exponential growth phase.

Clinical importance of understanding bacterial growth:
All ID tests and antimicrobial tests must be done in the LOG PHASE of growth
In vivo antimicrobials work on actively dividing cells - in vitro (in the lab) need to simulate same environment

36
Q

How fast does E.coli generate during the “log” phase?

A

Some bacteria multiply very quick:

E. coli has generation time (double in number) of 15-20 minutes

37
Q

What phase does bacteria have the most enzymatic activity?

A

The “Log” phase (or exponential growth phase).

38
Q

What are the two types of dyes?

A

Positively charged chromophores - Basic stain.

Negatively charged chromophores - Acidic stain.

The chromophore groups of the dye give it color. They bind with cells by ionic, covalent, or hydrophobic binding.

39
Q

How do basic stains work?

A

Bind to negatively charged particles such as nucleic acids and proteins.

Also called: Cationic stain or positive stain.

Example: Crystal violet and safranin.

40
Q

How do acid stains work?

A

Negatively charged chromophores
Acidic stain
**Bind to positively charged particles of cell
Anionic stain or negative stain

Example: India Ink or eosin

41
Q

Name an example of two basic stains.

A

Crystal violet and safranin.

42
Q

What are the steps in gram staining?

A

Four steps:

  1. Crystal violet - Primary stain
  2. Iodine - Mordant
  3. Acetone-alcohol - Decolorizer
  4. Safranin - Counterstain
43
Q

What does gram stain accomplish?

A

Gram stain is a differential stain divides bacteria into two major groups Gram positive and Gram negative.

  • Based on different composition of the cell wall
  • G+ have thick peptidoglycan layer
  • G- have thin layer and an outer membrane of lipopolysaccharide
  1. Crystal violet – primary stain and rinsed with water
  2. Iodine – mordant forms a complex with CV in the cells traps the CV to the peptidoglycan layer
  3. Acetone-alcohol – Solvent dissolves the LPS of G- allowing CV complex to be easily removed. Also a dehydrating agent it shrinks the pores of thick peptidoglycan layer of G+ making it difficult to remove the CV complex
  4. Safranin stain organisms that were previously decolorized – the G- (Gram Neg)

Draw the colours/figures on slide 25.

44
Q

What determines the morphology of cellular arrangements? Describe what Staph spp. and Strep do as two examples.

A
  • Cellular arrangements are determined by the way the organisms divide.
  • Ex: Staph spp. Divide along both horizontal and vertical axis – producing a packet (or cluster) of cells.
  • Strep’s on the other hand divide along the vertical axis only producing chains or pairs of cells
45
Q

What is required when reporting of a gram stain?

A 
G+ or G- 
Morphology (Cocci or bacilli)
- microscopic characteristics
- shape
- arrangements
- staining reactions

Note: Cellular arrangement is most important for G+, best from patient sample or broth cultures

46
Q

What are the different types of medium forms that bacteria can be cultured in and why?

A
  1. Solid: allows bacteria to grow, immobilized in a single isolated colony for characterization & identification.
  2. Liquid (broth): used to enhance growth of organisms and demonstrate typical microscopic morphology for most organisms (i.e. is growth seen as turbidity or cloudiness).
  3. Semi-solid: Allows degrees of O2 tension to allow growth of aerobic, anaerobic and microaerophilic organisms in different areas of the tube; can observe motile organisms.
47
Q

Give examples of each different type of medium forms for bacteria cultures.

A
  1. Solid: 1-2% agar
  2. Liquid (broth) - none given
  3. Semi-Solid broth made with 0.05-0.3% agar.
48
Q

What are the different media types for bacteria culture?

A
  1. Simple – basic media (Mueller Hinton)
  2. Enriched – basic media + extra nutrients (Blood Agar)
  3. Differential – basic media + differentiating substance such as a pH indicator (MacConkey Agar)
  4. Selective – basic media + selective substances such as increased salt content (Mannitol Salt Agar)
  5. Enrichment (different then enriched)- basic LIQUID media + additional substance specific for one organism (Selenite F Broth)

Once you know this then review the notes in more detail on Slide 28.

49
Q

What are some basic media ingredients?

A

Basic ingredients:
Carbon, hydrogen, and nitrogen
Minerals, sodium chloride, and water

50
Q

List some other media ingredients besides the basic elements that bacteria needs to be cultured.

A

Other components:

  1. Solidifying agents (ex. agar, gelatin, potatoe, agarose, polyacrylic gels))
  2. Growth factors (ex. blood or yeast)
  3. Hydrogen ion concentration (ex. chemical indicators such as neutral red)

Note:
• Carbon and Hydrogen from glucose or lactose
• Nitrogen from peptones or extracts

51
Q

What is required for media quality control?

A

Media should:

  1. Sterile (heat sterilize using autoclave - 121°C at 15 PSI)
  2. Stable
  3. have a reasonable shelf life
  4. be clear and/or of proper colour, 5. consistency, depth, no haemolysis and no bubbles
  5. support the growth of organisms likely to be in the specimens tested
52
Q

What two things should be required for quality control - if specified?

A

If specified:

  • inhibit the growth of commensal organisms
  • give a typical biochemical response
53
Q

What higher level requirements are there for media quality control?

A

Media/culture should be monitored and tested for reproducibility & accuracy, with results documented in a logbook.

54
Q

What other quality management strategies are there in a microbiology lab?

A

Other quality management strategies include:

  1. Specimen procurement and handling
  2. Laboratory equipment monitoring and maintenance
  3. Analytical techniques – continuing competency
  4. Proper use of biological safety cabinet
  5. Quality control on reagents and media
  6. Everything from sample collection to results

All these steps need documentation to show that they occurred.

Note: Once this is learned review detailed notes on Slide 31.

55
Q

What types of descriptions are given for colonial morphology?

A
  1. Relative size: Large, small, tiny
  2. Pigmentation (color): Grey, white, red
  3. Hemolytic reaction: (if applicable to organism, especially important for the Streptococcus spp.) Beta, alpha, and γ
  4. Texture (if applicable to organism): dry or mucoid or wet; Dry (Corynebacterium spp) or mucoid (Klebsiella spp. and Streptococcus pneumoniae)
56
Q

What is important for the quality of the colonial morphology descriptions?

A

Consistency in descriptions is important to inform other people they might need to see your work without seeing the colonies.

It is important to aid in determining subsequent tests to perform for identification.

57
Q

What are the timing requirements for macroscopic evaluation of culture plates?

A

Macroscopic evaluation of culture plates are performed after 24 hours of incubation and must be documented.

58
Q

What criteria for classification in the lab are there for macroscopic characteristics of morphology?

A

Macroscopic characteristics:

  • size
  • pigmentation
  • optical density
59
Q

What is required for sterilization by an autoclave?

A

Utilizes steam under pressure to kill microorganisms:

  1. Pressure = 15 psi
  2. Temperature = 121°C
  3. Time = 15-20 min for sterilizing media
    a) 1 hour for sterilization of contaminated material
  4. Contact
  5. Moisture content
60
Q

What is the process for sterilization in the autoclave?

A

Process:

  1. Load the chamber
  2. Chamber closed and steam under pressure fills the chamber
  3. Completely sealed and insulated so heat doesn’t escape
  4. Once 121°C is reached the timing cycle begins
  5. Large loads will need more time

Note: Load items into containers metal or heat resistant plastic and avoid stacking items or crowding times tightly into chamber
Must open or bags for autoclaving to ensure steam penetration, remove lids from containers

61
Q

How do you know the sterilization autoclave process worked - using chemical methods?

A

How do I know it worked?
Chemical
Tape – with every load – see what has been processed
Turns from regular looking tape to tape with black stripes (show air removed, not sensitive to time and exact temperature)
Paper Chemical strips – with every load
Initial colour to final colour (all conditions met)

62
Q

What are biological tests for checking if autoclave properly sterilized?

A

Biological
Spores – weekly or every run
Geobacillus stearothermophilus (vials)
Three strips of spores
Two strips placed in with routine load in the bottom center of chamber
One strip is a positive control and is not autoclaved
Strips are placed in broth medium and incubated
Control strip should grow and other two should not grow

63
Q

What are the advantages & disadvantages for the biological tests to know if the autoclave sterilization worked?

A

Advantage
Very specific to temp and time
Disadvantage
Must incubate for 24 – 48 hours before result is known
Have to store autoclaved load until results are known

Note: Biological – test system containing viable organisms providing defined resistance to a specified sterilization process. Refer to manufacture of autoclave
Geobacillus stearothermophilus for sterilizers that use steam, hydrogen peroxide gas, or immediate use steam sterilizers.
Bacillus atrophaerus spores for dry heat or ethylene oxide sterilizers

64
Q

What kind of items can be autoclaved? Name at least 4.

A 
What can be autoclaved?
Surgical instruments
Dental instruments
Dressings
Gowns
Sterile saline
Media (microbiology)
Biomedical waste prior to incineration
Be careful though
Many items can be destroyed by the heat
Plastic items and rubber tubing = bad

Fundamentals of MLS (18 decks)

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