Cosmos Biomedical

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CHROMOSENSE URINARY TRACT AGAR

A chromogenic medium for the isolation, enumeration and direct identification of urinary tract pathogens such as E.coli, KES (Klebsiella - Serratia), Enterococci and Staphylococci.

Code: CB1/405

Typical formula g/l

Peptone mix 18.7

L-Tryptophan 2.0

Chromogenic mix
13.8

MUG 0.1

Agar
12.0

pH 6.8 +/- 0.2

Directions

Suspend 46.6g in 1000ml of cold distilled water. Bring to the boil to dissolve completely. Sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C and distribute into sterile petri dishes. Use within 48 hours from the preparation.

Description

Chromogenic Urinary tract Agar is a diagnostic medium useful for the isolation, enumeration and direct presumptive rapid identification of urinary tract pathogens: E. coli, Enterobacter- Klebsiella- Serratia (KES) , Proteus-Morganella-Providencia, Enterococci, Staphylococci. The differentiation between the different bacterial species or genus is achieved by:

a chromogenic substrate for beta-galactosidase (GAL) which is split with the liberation of an insoluble pink dye.

a chromogenic glucopyranoside derivative which is split by beta-glucosidase (GLU) with the formation of an insoluble blue-green dye.

MUG for the fluorogenic detection of beta-glucuronidase enzyme (GUR).

L-Tryptophan for the detection of tryptophan deaminase (TDA) of Proteus spp. Morganella spp., Providencia spp. and for indole test of E.coli colonies.

The opaque white background of the medium enhances the colour of the colonies.

Method

Chromogenic Urinary Tract Agar (CUTA) can be used according to the usual laboratory practices for urine bacterial count, by spreading the specimen on the agar surface and incubating at 37°C for 18-24 hours. The cultivated colonies can be identified with the following scheme:

Colonies

Enzyme

Additional characterisation

Enzyme

Results

on CUTA

activity

on CUTA

activity

Large pink colonies

GAL +

fluorescent under Wood lamp

GUR +

E.coli

indole positive

IND +

Pink colonies

GAL +

not fluorescent under Wood lamp

GUR -

supplementary identification needed

Small blue-green

GLU +

Enterococci

colonies

GAL -

St.agalactiae

Blue to purple

GLU +

Klebsiella, Enterobacter,

colonies

GAL +

Serratia

Brown colonies

TDA +

Proteus-Morganella-Providencia

with brown halo

GLU -

glucosidase negative strains

Blue colonies

TDA +

Proteus-Providencia

with brown halo

GLU +

glucosidase positive strains

Colourless

supplementary identification tests

Colonies

needed

Notes:

It is reported that some strains of the bacterial genus reported above have abnormal biochemical patterns.

Between the Proteus-Morganella-Providencia group, P.mirabilis is indole negative and can be easy recognised

Biochemical identification is needed for species identification within Klebsiella Enterobacter Serratia (KES) group

A Pyroglutamate (PYR) test might be necessary to differentiate enterococci from S.agalactiae

S.saprophyticus and S.xylosus produces small pink colonies and are MUG negative.

Biochemical tests are necessary for species identification of micro-organisms producing colourless colonies.

Gram staining is recommended to confirm any doubtful colour reactions.

User quality assurance (24 h-37°C)

Productivity control

E. coli ATCC 25922: growth, large pink colonies fluorescent under a Wood’s lamp

E. aerogenes ATCC 13048: growth, blue colonies not fluorescent under a Wood’s lamp

S. aureus ATCC 25923: growth, colourless colonies

Storage

Dehydrated medium: 2-8°C

User prepared plates: 24 hours at 2-8°C

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Peptone mix	18.7
L-Tryptophan	2.0
Chromogenic mix	13.8
MUG	0.1
Agar	12.0