Lab Quiz 2 (Lab 7 -> Lab 10)

Alpha hemolysis

• partial hemolysis

• hydrogen peroxide produced oxidizes hemoglobin causing that greenish grayish color

Beta hemolysis

• complete hemolysis

• streptolysin enzyme causes complete lysis of red blood cell

Blood Agar plate

used to determine hemolytic pattern of bacteria

Antiseptic

• product which destroys or inhibits growth of microorganisms in or on living tissue

  • ex: iodine, silver nitrate, triclosan, ethanol

Disinfectant

• product which destroys or inhibits growth of microorganisms on surfaces

  • ex: cresols (Lysol), bleach

When should I use Soap and Water

• Before, during, and after preparing food

• Before eating food

• Before and after caring for someone who is sick

• Before and after treating a cut or wound

• After using the bathroom, changing diapers, or cleaning up a child who has used the bathroom

• After blowing your nose, coughing, or sneezing

• After touching an animal, animal food, or treats, animal cages, or animal waste

• After touching garbage

• If your hands are visibly dry or greasy

When should I use Alcohol-Based Hand Sanitizer

• Before and after visiting a friend or a loved one in a hospital or nursing home, unless the person is sick with Clostridium difficile (if so, use soap and water to wash hands)

• If soap and water are not available, use an alcohol-based sanitizer that contains at least 60% alcohol, and wash with soap and water as soon as you can

• DO NOT USE hand sanitizer if your hands are visibly dirty or greasy: for example, after gardening, playing outdoors, or after fishing or camping (unless a handwashing station is not available). Wash your hands with soap and water instead

How should I use Soap and Water?

• Wet your hands with clean running water (warm or cold) and apply soap

• Lather your hands by rubbing them together with the soap

• Scrub all surfaces of your hands, including the palms, backs, fingers, between your fingers, and under your nails. Keep scrubbing for 20 seconds. Need a timer? Hum the “Happy Birthday” song twice

• Rinse your hands under clean, running water

• Dry your hands using a clean towel or air dry them

How should I use Alcohol-Based Hand Sanitizer

Use an alcohol-based hand sanitizer that contains at least 60% alcohol. Supervise young children when they use sanitizer to prevent swallowing alcohol, especially in schools and childcare facilities

• Apply. Put enough product on hands to cover all surfaces

• Rub hands together, until hands feel dry. This should take around 20 seconds

NOTE: Do not rinse or wipe off the hand sanitizer before it’s dry; it may not work as well against germs

How many colonies do countable plates have?

30-300 colonies

Dilution formula

D = ( volume added / total volume) (previous dilution)

Dilution Factor formula

DF = dilution^-1

Strict Aerobe

• can only respire O₂

• Will die without oxygen

• Brewer’s agar plate:

  • growth only on aerobic plate

• FTG tube:

  • growth in aerobic zone only

Facultative Anaerobe

• Can respire O₂

• If O₂ is not present will use alternate electron acceptors (or ferment)

• Prefers with oxygen bc more energy is produced

• Brewer’s agar plate:

  • Growth on both plates

  • Better growth on aerobic plate

• FTG tube:

  • Growth throughout tube, but more dense at top

Aerotolerant Anaerobe

• Does not use O₂ for respiration but tolerates it.

• Uses alternate electron acceptors or ferments

• O₂ is not toxic to them

• Brewer’s agar plate:

  • Growth on both plates

  • Equal growth on both plates

• FTG Tube:

  • Even growth throughout tube

Strict Anaerobe

• Does not use O₂ for respiration

• Uses alternate electron acceptors or ferments

• O₂ is toxic to them

• Brewer’s agar plate:

  • Growth only on anaerobic plate

• FTG tube:

  • Growth in anaerobic zone only

Media to Test Oxygen Requirements

• Fluid thioglycollate (FTG) tubes

• Brewer agar plates

Fluid thioglycollate (FTG) tubes

• Oxygen indicator: resazurin (red when oxygen is present)

• Reducing agent: thioglycollate

  • reduces any O₂ to water to keep media anaerobic

• Autoclaved prior to use to purge of any oxygen

Brewer agar plates

• Oxygen indicator: resazurin

• Reducing agent: thioglycollate

• One will be placed in anaerobic jar while one plate will be left under aerobic conditions

How to tell if the inside of an anaerobic jar is anaerobic

• Methylene blue strip is white

• Condensation

Parts of an Anaerobic Jar

• Screw clamp

• Gasket

• Palladium catalyst and holder

• Hydrogen GasPak generator

• Inverted inoculated plates

• Anaerobic indicator strip (methylene blue)

Pour plate quantification technique

• allows us to estimate the number of viable cells in our original bacterial stock culture

Hemolytic patterns

• alpha-hemolytic

• beta-hemolytic

• non-hemolytic

Catalase Test

• Catalase breaks down hydrogen peroxide to water and oxygen gas

• Procedure:

  • Add few drops of H₂O₂ to small test tube

  • Pick colony with stick, place in H₂O₂

  • Check immediately for bubbling

• Positive test result

  • Oxygen production (bubbling)

Oxidase Test

• Cytochrome oxidase is an enzyme in the electron transport chain of some aerobic organisms

• Procedure

  • Smear colony of filter paper

  • Add drop of oxidase reagent

• Positive test result

  • Pink color

UV Light

• can be used to control microbial growth

• creates thymine dimers that lead to kinks in bacterial DNA

Factors that limit usefulness of UV light for decontamination

• Cannot penetrate surfaces

• More effective at killing some organisms than others (bacterial spores can be more resistant)

Bacteriophage replication

• The ability of a virus to replicate depends on whether it can a suitable host to infect

• The phage needs to be virulent

• Ex: T4 phage specifically infects E. coli (host specificity)

Lytic Cycle

1. Adsorption

2. Penetration

3. Bacterial chromosome degraded

4. Replication

5. Maturation

6. Release

Cultivation of Bacteriophages

• To propagate phages, they must be cultured with their appropriate host strain

• No host = no phage replication

Coagulase Test

• way to differentiate S. aureus from S. epidermidis

• Coagulase is an enzyme that clots plasma

  • S. aureus has it (+)

    • tube becomes solid

  • S. epidermidis does not have it (-)

    • tube remains liquid