Cat. no. C8030 CRITERION™ XLT-4 Agar Base 114gm
Cat. no. C8031 CRITERION™ XLT-4 Agar Base 500gm
Cat. no. C8032 CRITERION™ XLT-4 Agar Base 2kg
Cat. no. C8033 CRITERION™ XLT-4 Agar Base 10kg
Cat. no. C8034 CRITERION™ XLT-4 Agar Base 50kg


Hardy Diagnostics CRITERION™ XLT-4 Agar Base is a highly selective plating medium for the detection and isolation of non- typhi Salmonella species.

This dehydrated culture medium is a raw material intended to be used in the making of prepared media products, which will require further processing, additional ingredients, or supplements.


Numerous media have been developed for the isolation and differentiation of enteric bacteria, most designed to recover a broad spectrum of enteric pathogens. Subsequently, overgrowth of inconsequential bacteria can be a problem, when recovery of a specific species is desired. This is true of Salmonella isolation media where Proteus Providencia, and Pseudomonas can interfere with the desired results.

Xylose-Lysine-Desoxycholate (XLD) media was developed as a selective and differential media for the isolation of gram-negative enteric pathogens. The sodium deoxycholate found in the XLD media is replaced by Tergitol 4 in Xylose-Lysine-Tergitol 4 (XLT-4) Agar. This addition makes XLT-4 more highly selective for Salmonella than its predecessor.(1-3)

Proteose Peptone No.3 in XLT-4 Agar provides a source of complex nitrogen compounds. Yeast extract is added to supply vitamins and co-factors. Differentiation on this medium is based on xylose, lactose, sucrose, lysine decarboxylation, and hydrogen sulfide production. The pH shifts in the medium due to the fermentation and decarboxylation reactions are visualized by the addition of phenol red. The Tergitol 4 in the XLT-4 Agar inhibits all gram-positive bacteria and molds, and inhibits the growth of numerous gram-negative bacteria including Proteus, Providencia and Pseudomonas species.(1-3) This attribute makes XLT-4 Agar excellent for the isolation and detection of non- typhi Salmonella.


Gram weight per liter: 57.0gm/L
Lactose 7.5gm
Sucrose 7.5gm
Sodium Thiosulfate 6.8gm
Sodium Chloride 5.0gm
L-Lysine 5.0gm
Xylose 3.75gm
Yeast Extract 3.6gm
Proteose Peptone No. 3 1.6gm
Ferric Ammonium Citrate 0.8gm
Phenol Red 80.0mg
Agar 16.0gm

Final pH 7.4 +/- 0.2 at 25ºC.

* Adjusted and/or supplemented as required to meet performance criteria.


Store the sealed bottle(s) containing dehydrated culture medium at 2-30ºC. Dehydrated culture medium is very hygroscopic. Keep lid tightly sealed. Protect dehydrated culture media from moisture and light. The dehydrated culture media should be discarded if it is not free-flowing or if the color has changed from its original pink.

Store the prepared culture media at 2-8ºC.



1. Suspend 57.0gm of the dehydrated culture media in 1 liter of distilled or deionized water. Stir to mix thoroughly.

2. Add 4.6ml of XLT-4 Agar Supplement.

3. Heat to boiling to dissolve completely. Do Not Overheat.

4. Do not autoclave.

5. Cool to 45-50ºC. in a waterbath.


For information on procedures and interpretation of results, consult listed references or refer to the prepared media Instructions for Use (IFU) for Cat. No. G165.


Rare strains of Salmonella do not produce H2S and will not appear black on XLT-4 Agar. However, these colonies will be pink to pinkish yellow, which differentiates them from the bright yellow colonies of non- Salmonella species.

XLT-4 Agar is used to aid in the isolation and differentiation of Salmonella species. Additional biochemical and serological tests are required for complete identification. See listed references for more information.(1-4)

Some strains of Salmonella may fail to grow, or grow poorly on this medium due to nutritional variances.

Non-Salmonella strains that are not completely inhibited on XLT-4 Agar may be encountered, and must be differentiated from Salmonella. Consult listed references for more information.(1-4)


Standard microbiological supplies and equipment such as autoclaves, incinerators, and incubators, etc., are not provided.


Test Organisms Inoculation Method* Incubation Results
Time Temperature Atmosphere
Salmonella enterica
ATCC ® 14028**
A 18-24hr 35°C Aerobic Growth; yellow to red colonies with black centers
Escherichia coli
ATCC ® 25922**
B 18-24hr 35°C Aerobic Partial to complete inhibition; yellow colonies
Proteus mirabilis
ATCC ® 12453
B 18-24hr 35°C Aerobic Inhibited
Staphylococcus aureus
ATCC ® 25923**
B 18-24hr 35°C Aerobic Inhibited

** Recommended QC strains for User Quality Control according to the CLSI document M22 when applicable.

User Quality Control


CRITERION™ XLT-4 Agar Base powder should appear homogeneous, free-flowing, and pink in color. The prepared media should appear slightly opalescent, and red in color.


1. Koneman, E.W., et al. Color Atlas and Textbook of Diagnostic Microbiology, J.B. Lippincott Company, Philadelphia, PA.

2. Jorgensen., et al. Manual of Clinical Microbiology, American Society for Microbiology, Washington, D.C.

3. Miller, R.G., et al. 1992. Xylose-Lysine-Tergitol 4: An improved selective agar medium for the isolation of Salmonella. Poultry Science; 71:398.

4. Miller, R.G., et al. 1991. Xylose-Lysine-Tergitol 4: An improved selective agar medium for the isolation of Salmonella. Poultry Science; 70:2429-2432.

5. Andrews, W.H., et al. 1995. Salmonella. In Bacteriological Analytical Manual, 8th ed. AOAC International, Gaithersburg, MD.

6. Vanderzant, C. and D.F. Splittstoesser (ed.). 1992. Compendium of Methods for the Microbiological Examination of Foods, 3rd ed. American Public Health Association, Washington, D.C.

7. Quality Assurance for Commercially Prepared Microbiological Culture Media, M22. Clinical and Laboratory Standards Institute (CLSI - formerly NCCLS), Wayne, PA.

ATCC is a registered trademark of the American Type Culture Collection.