Bacteriology Lab Final Flashcards
Name the dye present in MacConkey Agar that is responsible for staining microbes that ferment lactose
neutral red
The catalase test detects the enzyme catalase, which is responsible for converting ____________ to _____________
The catalase test detects the enzyme catalase, which is responsible for converting hydrogen peroxide to water and oxygen
Is Staphylococcus aureus catalase positive or catalase negative
Staphylococcus aureus is catalase positive
Is Streptococcus equi catalase positive or catalase negative?
Streptococcus equi is catalase negative
The oxidase test depends on the presence of _____________ in a bacterial cell
Cytochrome C Oxidase
Are most Staphylococcus spp. oxidase positive or oxidase negative?
Most Staphylococcus spp. are oxidase negative
(the negative test is the cue-tip marked ‘B’)
In the motility test, tetrazolium salts are added to help detect motility. When the bacterium grows, the dye from the salts is incorporated into the bacterial cells, where it is reduced to an insoluble red pigment.
What is the name of that red pigment?
formazan
What is the pH indicator utilized in the urease test?
phenol red
What does the Methyl Red (MR) test test for?
Low MW acids like lactic, formic, & acetic acids
The citrate test tests for ________________________
What is the indicator used?
ability to use citrate as sole carbon source
Indicator used: Bromothymol blue
Does Proteus mirabilis produce a positive or negative motility test?
positive
What color will a positive urease test produce?
bright pink
Which amino acid is involved in the indole test?
Tryptophan
Is Pseudomonas aeruginosa oxidase positive or oxidase negative?
Pseudomonas aeruginosa is oxidase positive
Rappaport-Vassiliades Broth is used mainly for which bacterial species?
*Salmonella *spp.
Identify these Gram{+] cocci in clusters
Staphylococcus spp
Identify these Gram[+] cocci in chains
Streptococcus spp.
(just remember, “strepto” means chain in Greek)
Identify these Gram[+], gamma-hemolytic cocci in pairs or short chains
Enterococcus spp.
Identify these large aerobic or facultative anaerobic Gram[+] rods that form endospores
Bacillus spp.
True or False:
Candida spp. can all produce pseudohyphae
True
If you see pseudohyphae, it’s more than likely Candida spp.
Identify these Gram[+] short rods:
Arcanobacterium spp.
T/F: MacConkey agar is designed to grow Gram-positive bacteria and differentiate lactose fermenters from non-fermenters
False.
MacConkey agar is designed to grow Gram-negative bacteria and differentiate lactose fermenters from non-fermenters
______________ is a differential, selective medium for the isolation of Shigella and Salmonella species from enteric pathological specimens. It contains lactose, sucrose and salicin.
Hektoen enteric agar
Between Microsporum spp. and Trichophyton spp., which one is known to have numerous microconidia?
Trichophyton spp.
Found in concentrated pigeon droppings due to their hig content of creatinine.
Identify.
Cryptococcus neoformans
Which one of these is Aspergillus spp?
That one.
Blood Agar is a general purpose enriched medium that is used to differentiate bacteria based on which properties?
hemolytic properties
Lactose-positive organisms display what color on MacConkey agar?
red/pink
lactose fermenters produce acid and lower the pH of the medium, producing red/pink colonies
Hektoen enteric agar contains indicators of lactose fermentation and H2S production. What are those indicators?
thiosulfate and ferric ammonium citrate
What are the components of Hektoen enteric agar that inhibit growth of Gram-positive organisms?
bile salts and bromothymol blue
What is the primary stain used in Gram-staining?
crystal violet
List the four basic steps in the Gram stain
- Primary staining (crystal violet)
- Add a mordant (Gram’s iodine)
- Decolorization (alcohol or acetone)
- Counterstaining (safranin or fuschin)
Gram-positive or Gram-negative?
Gram-positive
Gram-positive or Gram-negative?
Gram-negative
The image shows Staphylococcus aureus colonies surrounded by a zone of complete hemoylsis. Which toxin causes this type of hemoylsis?
alpha-toxin
Which one represents a positive catalase test?
What is the indicator used in the Indole test?
Kovac’s Reagent
IMViC is a group of individual tests used in differentiating which family?
Enterbacteriaceae
Identify.
Staphylococcus spp.
Identify.
Streptococcus spp.
Identify.
Enterococcus spp.
Name the three antimicrobial susceptibility tests we discussed in lab:
- Kirby Bauer
- E-Test
- Broth Microdilution
Regarding the Kirby Bauer test, does a larger diameter indicate greater antibiotic resistance or less antibiotic resistance?
Larger diameter = less antibiotic resistance/greater susceptibility
If the zone of inhibition is greater, that indicates that the bacteria is susceptible to the antibiotic, not resistant to it
Which type of agar plate is used in the **Kirby Bauer **test?
Mueller Hinton agar
The lowest concentration of antimicrobial agent that inhibits bacterial growth/multiplication is known as:
Minimal Inhibitory Concentration (MIC)
The lowest concentration of antimicrobial agent that allows less than 0.1% of the original inoculum to survive is known as:
Minimal Bactericidal Concentration (MBC) or Minimal Lethal Concentration (MLC)
T/F: The E-Test is a quantitative assay for determining MLC
False.
The E-Test is a quantitative assay for determining MIC (Minimal Inhibitory Concentration), NOT MLC (Minimal Lethal Concentration)
T/F regarding MIC:
The lower the MIC, the more susceptible the bacteria is to the antibacterial agent
True
What does ELISA stand for?
Enzyme Linked Immunosorbent Assay
Regarding Sandwich ELISA, are we testing a sample containing antigens or antibodies?
Antigen
For a Sandwich ELISA, the test kit comes coated with antibody. What we’re putting on as the analyte is the antigen
__________ are dyes that have the ability to absorb the short wavelength UV radiation and emit light of longer wavelength fluorescence
Fluorochromes are dyes that have the ability to absorb the short wavelength UV radiation and emit light of longer wavelength fluorescence
Which of the following does not involve specific antigen-antibody complexes?
- PCR
- IFA
- ELISA
- Agglutination
PCR
What is the 3rd reagent in the Gram stain?
alcohol or acetone
The 3rd stage is the decolorization stage
Does Klebsiella pneumoniae have a positive or negative Motility test?
negative
What bacteria is metallic green on Eosin-Methylene Blue agar?
E. coli
T/F: the Kirby-Bauer test is a quantitative assay for determining MIC
FALSE
The E-test is a quantitative assay for determining MIC. The Kirby-Bauer test measures zone of inhibition, but is not a quantitative determinant for MIC
What would be the test of choice to differentiate between Pseudomonas and Enterobacteria?
Oxidase test
Pseudomonas is oxidase-positive
T/F: PCR tests for Antibody interactions
False.
PCR tests DNA/RNA sequences
Which PCR detects product formation throughout the PCR reaction?
Real-time PCR
Which PCR only measures product after the PCR reaction is complete?
End-point PCR
Which PCR utilizes agarose gel electrophoresis?
End-point PCR
XLD agar is selective and differential for:
Gram-negative enteric bacteria, specifically Shigella and Salmonella
- Salmonella* will produce red colonies with black centers
- Shigella* will just produce red colonies
You see these colonies on XLD agar. What is your diagnosis?
- Salmonella*
- Salmonella* will first ferment the xylose creating a temporary acid reaction but this is reversed by the subsequent decarboxylation of lysine with alkaline metabolic products. Superimposed on the red (alkaline) colonies is the production of hydrogen sulfide, so most Salmonella have red colonies with a black center.
