K490 ONPG

K1490 WEE-TAB ONPG</P>

PRINCIPLE/DISCUSSION:

Fermentation of lactose depends on the presence of two enzymes: permease, which allows the lactose to enter the bacterial cell, and beta-galactosidase, which splits lactose into glucose and galactose, which are subsequently metabolized. ONPG tests can be used to differentiate slow lactose fermenters, which are thought to be deficient in permease, and non-fermenters. It is also useful to dif-ferentiate Pseudomonas cepacia and Pseudomonas maltophilia, which are positive, from other pseudomonads, which are negative. The demonstration of beta-galactosidase is accomplished by the hydrolization of ortho-nitro-phenol-beta-D-galacto- pyranoside liber-ating ortho-nitrophenol with its characteristic yellow color.

ACTIVE INGREDIENTS:

Each tablet contains 0.2 mg. of O-nitrophenyl-beta-D-galacto- pyranoside

MATERIAL SAFETY DATA:

This product does not contain any materials known at this time to be hazardous.

STORAGE:

Store tightly covered in a dry place at room temperature.

MATERIALS REQUIRED:

ONPG tablets require fresh 24 hour growth on culture media. Consult the Manual of Clinical Microbiology for recommended media for the specimen. The following items are required but not provided:

Small test tubes (e.g. 12 X 75) (provided with WEE-TAB single test)

Inoculating loop

Distilled water, pH 7.0-7.2

PROCEDURE:

(1) Dissolve one ONPG tablet in 1 ml. of distilled water in a small test tube. For WEE-TABS use 0.5 ml or to bottom of label.

(2) Inoculate heavily. A loopful of organism from a culture plate or slant should be sufficient.

(3) Incubate at 37C for up to 6 hours or until the yellow color of a positive test appears. WEE-TABS are finished at 2 hours.

INTERPRETATION

The appearance of a yellow color at any time during the 6 hours is a positive result. A positive ONPG test shows that the organism being tested contains the enzymes necessary for the fermentation of lactose and therefore may be classified as a lactose fermenter.

QUALITY CONTROL:

A known positive and negative test organism should be run with each batch. Dispose of all used material in a manner appropriate for biohazardous material.

CHARACTERISTIC REACTIONS

E. coli +

Enterobacter +

Citrobacter +

Klebsiella +

S. arizona +

Proteus -

Salmonella -

Pseudomonas (most) -

P. cepacia +

P. maltophilia +

Shigella var.

See the Manual of Clinical Microbiology for a more complete listing.

REFERENCES:

(1) Manual of Clinical Microbiology, Fifth Edition, Chapter 36, "Enterobacteriaceae"