A/ACit+

Acid/Acid Citrate Positive Group
The organisms in this group are Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, Klebsiella oxytoca, Klebsiella pneumonia, and Serratia marcescens. These organisms require a large variety of tests, and most of them hinge on a single test, so great care should be taken in performing them. One of which, Motility, can be hard to read in the best of times. Try to find some tubes to compare with yours to help. Remember that Thiogel and the Decarboxylase tests takes several days to take full effect. Furthermore the Decarb tests must be checked at 24 hours as well as at 96.

Tests
Essential: SIM, Thiogel, DNase, PR Lactose, MR-VP (MR is the only relevant one at this point)

Helpful: Decarboxylase Arginine (sometimes), Lysine, and Ornithine

Key
1-A: Methyl Red positive, Decarb Lysine positive after 96 hours other decarb negative Citrobacter fruendii

1-B: Methyl Red negative GO TO 2

2-A: Thiogel positive DC arg variable GO TO 3

2-B: Thiogel negative DC arg - GO TO 4

3-A: DNase positive, Lactose negative may have red/pink pigment, DC Lys/Orn +, Arg - Serratia marcescens

3-B: DNase negative, slow Lactose positive (may take two days), DC Arg/Orn weak+, Lys- Enterobacter cloacae

4-A: Indole positive Klebsiella oxytoca

4-B: Indole negative GO TO 5

5-A: Non-motile,  DC Lys +, Lys/Orn - Klebsiella pneumonia

5-B: Motile, DC Orn +, Arg/Lys - Enterobacter aerogenes