HiSitest Agar

Intended Use

Recommended for determination of antibiotic susceptibility of fastidious microorganisms.

Composition

Final pH (at 25°C): 7.4±0.2

**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 31.32 grams 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

Hi-Sensitivity™ Test Agar is developed for antimicrobial susceptibility tests It gives a reproducible, semi-defined medium in which the mineral contents have been stabilized. The thymine and thymidine content is very low thus making it most suitable for testing antimicrobial activity of sulphonamides. It supports the growth of majority of micro-organisms without further supplementation. Tryptone, peptone, dextrose, vitamins provide nitrogen, carbon compounds and other essential growth nutrients.

This medium has been designed to overcome the problems occurring in Mueller-Hinton media as (1-4,5,6,7).

1. Different M.I.C. values in the broth and agar versions of the medium.
2. Agar shows antagonistic effect towards tetracycline.
3. High levels of sulphonamide and trimethoprim antagonists.
4. Poor reproducibility with different manufacturers peptones.
5. Poor growth supporting ability for Streptococci and variable growth rates with Gram-positive organisms.

Some mutant strains which are totally dependent on thymine and thymidine for their growth, will not grow on Hi-Sensitivity™™ Test Agar due to very low levels of these compounds in this medium as they are the naturally occurring antagonist of Trimethoprim. Care must be taken to recognize these strains (8,9,10). Some pathogenic organisms are nutritionally dependent due to intrinsic demands for special growth factors. Supplemental nutrients can be added to Hi-Sensitivity™ Test Agar to improve the growth of these organisms (3). The following nutrients can be used.

Type of specimen

Isolated Microorganism from Clinical samples.

Specimen Collection and Handling

For clinical samples follow appropriate techniques for handling specimens as per established guidelines (11,12). After use, contaminated materials must be sterilized by autoclaving before discarding.

Warning and Precautions

In Vitro diagnostic Use only. For professional use only. 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 clinical specimens. Safety guidelines may be referred in individual safety data sheets.

Limitations

1. Some pathogenic organisms are nutritionally dependent due to intrinsic demands for special growth factors

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 coloured homogeneous free flowing powder

Gelling: Firm, comparable with 0.8% Agar gel.

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

Reaction: Reaction 3.13% w/v aqueous solution at 25°C. pH : 7.4±0.2

pH

7.20-7.60

Cultural Response

Cultural characteristics observed after an incubation at 35 - 37°C for 18 - 24 hours

Key: *Corresponding WDCM numbers.

**Formerly known as Bacillus subtilis subsp. spizizenii * Formerly known as Bacteroides vulgatus

Storage and Shelf Life

Store dehydrated 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 clinical sample must be decontaminated and disposed of in accordance with current laboratory techniques (11,12).

Reference

1. Bridson E.Y., 1976, Arztl. Lab. 22:373.
2. Duncan I.B.R., 1974, Antimicrobial agents & Chemotherapy, 5:9.
3. Ericsson H.M. and Sherris J.C., 1971, Acta. Pathol. Microbiol., Scand Suppl., 217:1.
4. Garrod L.P. and Waterworth P.M., 1971, J. Clin. Path., 24:779.
5. Neussil H., 1976, Chemotherapy, Vol. 2:33.
6. Reller L.B., Schoenknecbt F.D., Kenny M.A. and Sherris J.C., 1974, J. Infect. Dis., 130:454.
7. Yourassowsky E., Vanderlinden M.P. and Schoutens E., 1974, J. Clin. Path 27:897.
8. Barker J., Healing D. and Hutchinson J.G.P., 1972, J. Clin. Path., 25:1086.
9. Tanner E.I. and Bullin C.H., 1974, J. Clin. Path., 27:565.
10. Thomas M. and Bond L., 1973, Med. Lab. Technol., 30:277.
11. Isenberg, H.D. Clinical Microbiology Procedures Handbook. 2nd Edition.
12. 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.