Diagnostic of Medically important Gram Negative Bacteria

Representative Gram Negative Bacteria Gram-negative Cocci –Neisseria gonorrhoea –Neisseria meningitis Gram-negative rods –Enterobacteriaceae family Escherichia, Enterobacter, Salmonella, Shigella, Klebsiella, Proteus, Morganella –Pseudomonaceae family Pseudomonas

Identification Oxydase Pseudomonaceae Neisseriaceae Fermentation of glucose NeisseriaceaePseudomonaceae Enterobacteriaceae Fermentation of lactose McConkey Enterobacter Escherichia Klebsiella Serratia Proteus Salmonella Shigella Morganella + — + + — —

Identification of Oxidase Negative Gram Negative Rods MacConkey –Selective and differential medium –Prevents growth of Gram + –Lactose fermentation Pink colonies

IMViC Tests Indole, Methyl Red, Voges-Prosakaur, Citrate (IMViC) : –These four tests include an important series of determinations which are collectively called the IMViC reaction series –The IMViC reaction series allows the discrimination of bacteria of the Enterobacteriaceae family.

IMViC: Indole Test Principal –Some microorganisms can metabolize tryptophane by the tryptophanase Tryptophane Tryptophanase Indole + acide Pyurvic + NH 3 Kovac’s reagent Red color

IMViC Test Methyl Red-Voges Proskauer Methyl Red Test : –Fermentation with accumulation of acids: Glucose  pyruvate  lactic and/or acetic acid + CO 2 Voges Proskauer Test –Fermentation with accumulation of butanediol –Glucose  pyruvate  acetoine  2 butanediol + CO

IMViC Test : Citrate Utilization Unique carbon source –Citrate Indicator –Bromthymol blue Citrate utilization generates alkaline end products –Changes from green to blue Positive Klebsiella, Enterobacter Negative E. coli

TSI — Three Sugars and Iron Three sugars –Glucose (limiting) –Sucrose –Lactose Proteins –Cysteine Indicator –Phenol red

SIM — H 2 S, Indole and Motility Semi-solid medium –Allows to visualize motility Cystein metabolism Cysteine  H 2 S; H 2 S+ FeSO 4  Black precipitate Tryptophan metabolism (A) Tryptophan  Indole + NH 4 + Pyruvate (B) Indole + Kovac reagent  Red

Non inoculated Non-motile H 2 S and motile Indole + -

Multi Test: Enteropluri-test Strips of multiple metabolic tests –Use of a constant inoculum –Quick –Reading can be automated –Preparations and inconsistencies are normalized