HiCrome™ Serratia Agar

Intended use

Recommended for the chromogenic differentiation of Serratia from food samples.

Composition**

Final pH (at 25°C): 7.2±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 39.57 gram in 1000 ml purified/distilled water. Heat to boiling to dissolve the medium completely. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Cool to 45-50°C. Mix well and pour into sterile Petri plates.

Principle And Interpretation

Serratia are opportunistic gram-negative bacteria classified in the tribe Klebsiellae and the large family Enterobacteriaceae. Serratia marcescens strains are resistant to several antibiotics and are involved in nosocomial infections, particularly urinary tract infections and wound infections. Non pigmented strains are generally more resistant as they usually harbor resistance plasmids (1,2). It is the most common clinical isolate and the most important human pathogen. The conventional media like MacConkey Agar has very poor specificity and may result in false positives. The chromogenic media selectively differentiates Serratia spp giving bluish purple colour from other Enterobacteriaceae. Peptone special provides all the nitrogenous compounds and vitamins required for the growth of organisms. The chromogenic substrate is specifically cleaved by Serratia giving bluish purple coloured colonies. Selective mix inhibits other Enterobacteriaceae and other interfering bacterias.

Type of specimen

Food samples

Specimen Collection and Handling

For food samples follow appropriate techniques for handling specimens as per established guidelines (3). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

Read the label before opening the container. Wear protective gloves/protective clothing/eye protection/face protection. Follow good microbiological lab practices while handling specimens and culture. Standard precautions as per established guidelines should be followed while handling specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. Since it is an enzyme-substrate based reaction, the intensity of colour may vary with isolates.
2. Some strains may show poor growth due to nutritional variations.
3. Further biochemical characterization is required for confirmation.

Performance and Evaluation

Performance of the medium is expected when used as per the direction on the label within the expiry period when stored at recommended temperature.

Quality Control

Appearance: Cream to yellow homogeneous free flowing powder

Gelling: Firm, comparable with 1.5% Agar gel

Colour and Clarity of prepared medium: Light amber coloured, clear to slightly opalescent gel forms in Petri plates

Reaction: Reaction of 3.95% w/v aqueous solution at 25°C. pH : 7.2±0.2

pH: 7.00-7.40

Cultural Response

Cultural characteristics observed after an incubation at 35-37°C for 24 hours.

Key : (*) Corresponding WDCM numbers, (#) Formerly known as Enterobacter aerogenes

Storage and Shelf Life

Store between 15-25°C in a tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label. On opening, product should be properly stored dry, after tightly capping the bottle in order to prevent lump formation due to the hygroscopic nature of the product. Improper storage of the product may lead to lump formation. Store in dry ventilated area protected from extremes of temperature and sources of ignition Seal the container tightly after use. Product performance is best if used within stated expiry period.

Disposal

User must ensure safe disposal by autoclaving and/or incineration of used or unusable preparations of this product. Follow established laboratory procedures in disposing of infectious materials and material that comes into contact with sample must be decontaminated and disposed of in accordance with current laboratory techniques (4,5).

Reference

1. Grimont P. A. D., Jackson T. A., Ageron E. and Noonan M. J., 1988, Int. J. Syst. Bacteriol., 38:1-6.
2. S. Cooney, S Fanning, in Encyclopedia of Food Safety, 2014.
3. Salfinger Y., and Tortorello M.L., 2015, Compendium of Methods for the Microbiological Examination of Foods, 5th Ed., American Public Health Association, Washington, D.C.
4. Isenberg, H.D.Clinical Microbiology Procedures Handbook 2nd Edition.
5. Jorgensen, J.H., Pfaller, M.A., Carroll, K.C., Funke, G., Landry, M.L., Richter, S.S and Warnock., D.W. (2015) Manual of Clinical Microbiology, 11th Edition. Vol. 1.