Describe the purpose of the key ingredients found in the media for the Indole test
A 1% tryptone broth is the medium used for the test. Detecting indole requires the addition of the Kovac's reagent to the broth. The key chemical in Kovac's is para-dimthylaminobenzaldehyde which reacts with indole resulting in a red layer that floats on
Describe the purpose of the key ingredients found in the media for the Methyl Red test
Some bacteria utilize the "mixed acid fermentation" pathway producing strong acidic end products and acetyl methyl carbinol. Detecting mixed acid fermentation involves using a pH indicator called methyl red. If a solution's pH is 4.4 or below, the additio
Describe the purpose of the key ingredients found in the media for the Voges-Proskauer test
Detecting butanediol fermentation involves adding two reagents, Barritt's A (alpha-naphthol) and Barritt's B (potassium hydroxide), both detects acetyl methyl carbinol. Butanediol fermentation produces neutral products that are difficult to detect and ace
Describe the purpose of the key ingredients found in the media for the Simmons Citrate
The Simmons Citrate Agar contains citrate as the only food source. Another key ingredient is the pH indicator brom thymol blue. At pH above 7.6, this indicator turns a blue color. Below pH 7.6 the indicator is green. As the bacteria utilize the citrate, t
Define the term "fermenter
All enterobacteriaceae ferment glucose. A fermenter breaks down glucose for energy producing acidic products and gas.
List the characteristics of the family Enterobacteriaceae
Enterobacteriaceae commonly called "Enterics" are aerobic or facultative anaerobic Gram negative rods that ferment glucose.
Evaluate results of the IMVic testing
Indole(+)= red layer, Indole(-)= no red color. MR(+)= red color, MR(-)= yellow/orange. VP(+)= pink/orange/red, VP(-)= no pink/orange/red. Citrate(+)= blue, Citrate(-)= green, no blue.
Discuss the importance of the duration time for incubation for the Indole test
After inoculation of the broth, it incubates for no more than 4 or 5 days. Some bacteria can break down indole, a longer incubation may result in false negative result.
Discuss the importance of the duration time for incubation for the Methyl Red test
Requires an incubation time of two to five days. The bacteria require time to conduct the fermentation pathway.
Discuss the importance of the duration time for the incubation for the Voges-Proskauer test
Requires at least 48 hours incubation. After the addition of the Barritt's reagents, an incubation time of 30 minutes must occur. Evaluating before 30 minutes will result in a false negative conclusion.
The results of tests on E. coli
Indole(+), MR(+), VP(-), Citrate(-)
The results of tests on E. aerogenes
Indole(-), MR(-), VP(+), Citrate(+)
Compare the Embden-Meyerhof-Parnas (EMP) pathway to the Entner-Douderoff (ED) pathway.
In the EMP pathway is a fermentation pathway and the pyruvic acid is the final acceptor resulting in the formation of strong acid products. It does not require the presence of oxygen, anaerobes utilize this pathway. The ED pathway depends on oxygen as the
List the TRIBES of Enterobacteriaceae and give examples of the genera in each tribe.
ESCHERICHIEAE-Escherichia, Shigella.
EDWARDSIELLEAE-Edwardsiella.
SALMONELLEAE-Salmonella.
CITROBACTERIACEAE-Citrobacter.
KLEBSIELLEAE-Klebsiella, Enterobacter, Serratia.
PROTEAE-Proteus, Morganella, Providencia.
YERSINIEAE-Yersinia.
Discuss the purpose of the KIA test
Lactose and glucose are sources of energy in KIA, phenol red is the pH indicator, and ferric ammonium citrate and sodium thiosulfate help detect hydrogen sulfide gas production. Lactose fermenters produce yellow slants and butts because enough acid is pro
Discuss the purpose of the urease test
The urea agar contains urea and phenol red. ID the presence of urease by detecting the production of ammonia. The media is a salmon color and with the production of ammonia, the media turns bright fuscia pink.
Given various KIA results, determine whether the organism is a fermenter of glucose and lactose, and whether the organism produces gas and hydrogen sulfide.
Lactose and glucose fermenter A/A.
Lactose non-fermenter and gluose fermenter K/A.
Glucose and lactose non-fermenter K/K.
Any blackening of the medium indicates hydrogen sulfide production. Gas production is indicated by bubbles, splitting of the medium,
Describe the positive and negative result for the urease tests.
Urease(+)= hot pink. Urease(-)= original color, not hot pink.
Result of tests on E.coli
A/A, gas(+), hydrogen sulfide(-), urease(-)
Result of tests on Prot. mirabilis
K/A, gas(-), hydrogen sulfide(+), urease(+)
Result of tests on P. aeruginosa
K/K, gas(-), hydrogen sulfide(-). It is a gram(-) that does not ferment glucose, not enterobacteriae.