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HardyCHROM™ SS NoPRO Agar, (for Salmonella and Shigella), a chromogenic medium for stool pathogen screening without false positives from Proteus 15x100mm plate, order by the package of 10, by Hardy Diagnostics

HardyCHROM™ SS NoPRO Agar is a selective chromogenic medium recommended for use as a primary screening medium for the isolation and differentiation of Salmonella and Shigella spp. These can be easily distinguished from non-pathogenic enteric bacteria based on colony color.This unique formula is patented.

HardyCHROM™ SS NoPRO Agar now contains a proprietary antibiotic which eliminates the growth of Proteus spp.

Manufactured and sold in the US under license from Glycosynth Limited under U.S. Patent No.’s 7,323,488 B2, 7,384,763 B2, and 7,709,223 B2.


Many formulations of culture media (such as HE, and XLD) have been developed to isolate and differentiate Salmonella and Shigella spp. from non-pathogenic enteric bacteria. Most formulations incorporate common ingredients such as carbohydrates (especially lactose), pH indicators, and an indicator system for the detection of hydrogen sulfide. These media are made selective by the addition of bile salts and can also differentiate between Salmonella/Shigella and lactose-fermenting organisms. However, the problem has always been that colonies of non-lactose-fermenting organisms that are not pathogenic can appear similar in appearance to Salmonella and Shigella and must be subjected to further testing by using Triple Sugar Iron (TSI) Agar, Lysine Iron Agar (LIA), or Kligler Iron Agar (KIA). Screening of primary plates or secondary plating from enrichment broths often requires the inoculation of large numbers of secondary screening tubes and/or the use of costly automated identification systems in order to rule out false-positives.

The use of chromogenic substrates (chromogens) in media formulations has increased greatly in the last several years. Chromogens, when broken down by specific bacterial enzymes, will result in colored colonies. Previously, chromogenic formulations were available for Salmonella spp., but not for Shigella spp.

HardyCHROM™ SS NoPRO Agar allows for the selective isolation and differentiation of Salmonella and Shigella spp. from non-pathogenic enteric bacteria, based on colony. Differentiation of Salmonella and Shigella spp. from non-pathogenic bacteria is accomplished by three mechanisms: chromogenic reactions, carbohydrate fermentation, and hydrogen sulfide production. HardyCHROM™ SS Agar provides better differentiation of colonies obtained from clinical samples and enrichment procedures, resulting in less secondary screening of isolates and less false-positive results.

Bile salts and sodium deoxycholate allow for the selective nature of HardyCHROM™ SS NoPRO Agar by inhibiting gram-positive organisms. Additional selective agents are added to reduce the number of normal enteric bacteria. Fermentable carbohydrates aid in the differentiation of enteric pathogens from delayed lactose fermenters. This reaction is visually enhanced by a pH indicator. The addition of ferric ammonium citrate and sodium thiosulfate enable the detection of H2S, noted by the production of black centered colonies. Sodium thiosulfate serves as the sulfur source and ferric ammonium citrate is added as the indicator. Peptones in the medium supply the principle source of organic nitrogen in the form of amino acids and long-chained fatty acids. Patented chromogenic substrates are incorporated to enable the production of different colored compounds when degraded by specific bacterial enzymes.

  • Reduces costly false-positive work-ups, due to Proteus spp.!
  • Less colony picking, subculturing, and identifications
  • No need for TSI, LIA, KIA tubes
  • Reduces use of expensive ID cards
  • Reduces the number of plates for primary stool setup
  • Increased specificity

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Cat No. Description Price Curr UOM Qty  
HDx, 15x100mm plt 10/pk R
$25.00 USD PK10

Manufacturer Category Organism
Hardy Diagnostics: prepared media

Media, Prepared

Salmonella spp. and Shigella spp.

Instructions for Use Video SDS


Brochures and Studies BioSafety Level