MIDI bacteria identifications (includes Gram stain)

MIDI analyzes fatty acids that are extracted from the cell walls of bacterial cultures and methylated.

An additional Microbial Id's form is recommended when submitting samples for this study.

Study Outline

MIDI Fatty Acid Database:

The MIDI system relies on qualitative and quantitative analysis of the fatty acid composition of organisms. The fatty acid profile provides a fatty acid fingerprint of the organism. The organism to be identified is grown on controlled culture medium under controlled time and temperature of incubation before comparing the fatty acid compositions with standard libraries.

The fatty acid extraction is initiated by the saponification (rupture) of the bacterial cell membrane, thus exposing the phospholipid bilayer membrane. Following saponification, methylation is used to attach a methyl group to the sodium salt product of the saponification step. The methyl group acts as a recognition marker for the gas chromatograph. The third step uses hexane to "pull" the fatty acids out of the aqueous phase and into an organic phase. The molecular weight of the hexane and ether enables the fatty acids to remain above the aqueous solution. The final step results in a washed final product of ether and fatty acids. The base wash removes any residual traces of water and methanol.

Upon injection of the final product into the gas chromatograph, the MIDI system software is equipped to identify the bacteria based on a known fatty acid profile already found in a standard library of known bacteria. A standard calibration is the first sample ran and allows the gas chromatograph to have a template in which to compare all carbon chains.

The MIDI data assigns a probable identification. The data are evaluated using microscopic morphology, Gram stain reaction and colony morphology.

Sample Requirements

Minimum sample size: Organism in viable media culture.
(However, there is a minimum lab charge of $75.00. )

An additional Microbial Id's form is recommended when submitting samples for this study.

Nelson Experts:

• April Wanstrom 801-290-7694, 800-826-2088
• Jay Jevne 801-290-7723, 800-826-2088

Sample Requirements

Minimum sample size: Organism in viable media culture.
(However, there is a minimum lab charge of $75.00. )

An additional Microbial Id's form is recommended when submitting samples for this study.