Lab 4

effect of UVR dose on bacterial growth

• inhibits bacterial growth

• damages DNA & RNA

method used to determine UVR effects

UVR result

UVR result

UVR result

UVR result

UVR result

Purpose of Kirby-Bauer method sensitivity test

what media is used with Kirby-Bauer test and explain steps of procedure

Mueller-Hinton agar

non-selective, selective, and differential media

• non-selective: support the growth of a wide variety of organisms

• selective: encourages the growth of particular microbes while inhibiting the growth of others

• differential: contain chemical indicators that allow you to distinguish between different types of microbes

Mannitol-salt agar test purpose & steps. What microbes is it selective for?

• selective media for bacteria in genus staphylococcus

• differential for species that can ferment mannitol

• yellow=mannitol fermentation (S. aureus)

• red= no fermentation (S. epidermis)

Mannitol-salt agar test steps

1. collect sample w/moistened swab

2. inoculate plate using zig-zag 3x

3. incubate

What media is used to evaluate a disinfectant using the filter paper disk method?

nutrient agar

test and result

• Mannitol salt agar

• positive

test and result

• Mannitol salt agar

• negative

Blood agar plate (BAP) & hemolysis purpose. What is it selective for?

• non-selective type of agar

• differential for hemolysin (endotoxin) production

Blood agar plate (BAP) & hemolysis steps

1. collect sample w/ saline moistened swab

2. inoculate blood agar w/standard streak plate method

3. first streak w/swab, rest w/loop

4. incubate

test and result

• Blood agar plate (BAP) & hemolysis

• positive for alpha hemolysis

• partial hemoglobin breakdown

test and result

• Blood agar plate (BAP) & hemolysis

• positive for beta hemolysis

• hemoglobin completely broken down

test and result

• Blood agar plate (BAP) & hemolysis

• positive for gamma hemolysis (negative)

• non-hemolysis

Mitis-Salivarius agar purpose. What microbes is it selective for?

• selective for streptococcus genus

• differential for S. mitis, and S. salivarius

Mitis-Salivarius steps

1. collect saliva sample

2. inoculate MS plate via loop using standard streak method

3. incubate

test and result

• Mitis-Salivarius agar

• positive for S. salivarius

test and result

• Mitis-Salivarius agar

• positive for S. mitis

Biggy’s agar purpose. What microbes is it selective for?

• Selective media for Candida yeast. Agar contains chemicals that inhibit bacteria and other fungi

• agar is differential for different species of Candida. Species are distinguishable based on colony color and morphology

Biggy’s agar steps

1. Collect a sample of saliva in a sterile container

2. Using a sterilized loop, inoculate a Biggy agar plate using a standard streak plate procedure

3. Incubate the plate at 37 °C for 24-48 h

test and result

• Biggy’s agar

• positive

test and result

• Biggy’s agar

• negative

Snyder test agar purpose. What microbes is it selective for?

• selective for bacteria found in the human mouth e.g. streptococcus & lactobacillus

• results indicate person’s relative susceptibility to dental caries

Snyder test steps

1. melt 1 tube of Snyder’s test via hot water bath

2. collect sample of saliva in a sterile container & transfer

3. roll tube to distribute saliva

4. incubate

test and result

• Snyder test agar

• positive

• 24h = high susceptibility

• 48h = moderate

• 72h = slight

• >72h = negative

test and result

• Snyder test agar

• negative

Coagulase test purpose. What microbes is it selective for?

• used on Gram + staphylococcus-like bacteria to see if coagulase is produced

• used to differentiate S. aureus from other staphylococcus bacteria

• S. aureus can produce coagulase

Coagulase test steps

1. performed on microscope slide, test kit reading card, or tube of plasma

2. agglutination = positive

test and result

• coagulase test

• positive

test and result

• coagulate test

• negative

Bile esculin hydrolysis purpose. What microbes is it selective for?

• presumptive test for group D streptococcus & enterococcus

• includes opportunistic pathogens

• Common characteristics: gram + coccus, often produce hemolysins, can breakdown esculin in presence of bile

Bile esculin hydrolysis steps

• inoculate bile esculin slant w/loop

• incubate for 72 h

• > 50% black= positive

test and result

• bile esculin hydrolysis

• positive

test and result

• bile esculin hydrolysis

• negative

MacConkey agar test purpose and procedure. What microbes is it selective for?

• purpose

test and result

• MacConkey agar

• positive

test and result

• MacConkey agar

• negative

Eosin methylene blue (EMB) agar purpose & steps. What microbes is it selective for?

• purpose

test and result

• Eosin methylene blue (EMB) agar

• positive

test and result

• Eosin methylene blue (EMB) agar

• negative

Salt tolerance (6.5% NaCl) test purpose. What microbes is it selective for?

• used to differentiate group D enterococci from group D streptococci bacteria

• group D enterococci can grow under the high salt conditions

test and result

• Salt tolerance (6.5% NaCl)

• positive

test and result

• Salt tolerance (6.5% NaCl)

• negative

urine sample bacterial concentration method and media type