Expert: John Locke - 5/12/2010

Question
So we are required to make our own flow chart of a Gram - and gram + bacteria. We were given 11 bacteria and we were suppostu do a flow chart of them to specify our unknow for our unknow project. the bacteria we were given were:
Gram +
M.luteus
B.cereus
S.aureus
S.lactis
C.xerosis
S.epidermidis
Gram -
E.coli
P.aeruginosa
P.vulgaris
A.faecalis
So we are suppostu make two flow charts one of gram - and one of gram positive.
The requirements are For each organism we are to have these tests:
1. Carbohydrate fermentation
2. Oxygen requirement
3. Selective media which confirms Gram stain status (choose one)

Also we are required to complete at least two of these per organism:
mannitol salt agar, starch agar, gelatin, IMVic, hydrogen sulfide test, urease test, nitrate reduction test, catalase test, and oxidase test.

We are not allowed to do:
Blood agar, Casein or hydrolysis tests!!!!

Can you please help me put my flow charts together. I started my gram + chart with a methyl red test then for organisms with neg. results i did a MSA test. for the positive result i did a voges-proskauer test, and thats were i got stuck for the gram + flow chart.
For gram - chart i had a harder time and im really confused on this one.....
Is there any way you can help me finish my flow charts with the requirement from the teacher. You see once we started doing our unknow project we cant ask teacher any question or else she will take point of our grade with every question we ask so i got to use the book or the internet. Was hopping you can help me.

Thank you
sunshine

Answer
Thanks for using AllExperts. This is a fairly involved question, and I cannot provide a complete answer; the easiest solution would be to catalog all of the characteristics of these organisms first, if you haven't done so already. A comprehensive microbiology review text--Lippincott's Illustrated Review of Microbiology, for instance--would include all the laboratory features of these organisms. From there you would need to walk through the test results individually to determine which tests would be most appropriate. I'll make a few suggestions, but I will admit up front that this will not solve the problem for you. Part of the difficulty is that not all the of requirement for this project are needed to differentiate between these organisms; that is, you don't necessarily need all the tests included here to determine what the unknown is, particularly given how few choices there are to start with.

For the Gram positives, you obviously will want to divide the bacilli from the cocci. For the cocci, you may wish to split off the Staph organisms immediately by the catalase test, then differentiate between the remaining organisms via the coagulase test. Novobiocin susceptibility and oxygen requirement would differentiate Micrococcus from the coagulase-negative Staph, since Micrococcus is also catalase-positive. Bacillus cereus can be identified on the basis of morphology, the catalase test (positive), oxygen requirement, and the oxidase test.

For the Gram negatives, I would suggest first using the oxidase test. Proteus is urease positive, so be sure to include that test for the organism; it is also a glucose fermenter but not a mannitol fermenter, and it tests positive for mixed acid fermentation. Use nitrate, oxidase, and citrate to identify Alcaligenes. E. coli can be identified by the combination of methyl red, citrate, nitrate reduction, and mannitol. Pseudomonas should be indole negative, methyl red negative, Voges–Proskauer test negative, and citrate positive.

Use this for what it's worth, and good luck.