PMID:4869617

Citation	King, S and Metzger, WI (1968) A new plating medium for the isolation of enteric pathogens. I. hektoen enteric agar.Appl Microbiol 16:577-8
Abstract	A new agar plating medium for the isolation of enteric pathogens is described. This medium contains greater quantities of peptone to offset the inhibitory effects of bile salts. Additional carbohydrates and larger quantities of those previously used have also been incorporated into the medium to differentiate pathogens from some of the slow lactose fermenters. The use of an indicator system never used before in a differential plating medium opens new possibilities for improvement over traditional and newer selective media. Known strains from the various genera of Enterobacteriaceae have been tested for colonial differentiation as well as for possible inhibitory effects. The results show the medium to be highly selective for the shigellae as well as for other enteric pathogens.
Links	PubMed
Keywords	Agar; Bile Acids and Salts; Enterobacter; Enterobacteriaceae; Escherichia coli; Indicators and Reagents; Proteus; Salmonella; Shigella
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Main Points of the Paper

• Describes the development of Hektoen Agar (HE)
  • selective for Shigella as well as other pathogens while inhibiting normal intestinal flora
  • contains several indicators which allow for colonies to be specifically identified, increasing the confidence of the identification

Materials and Methods Used

• Medium contains:
  • Lactose
  • Sucrose
  • Salicin
  • Bile salts
  • Sodium chloride
  • Proteose peptone
  • Beef extract
  • Agar
  • Bromothymol blue
  • Andrades' indicator

• Post-Boiling Additives
  • Sodium thiosulfate
  • Ferric ammonium citrate
  • Sodium deoxycholate
  • H₂S indicator

• Strains
  • Escherichia coli
  • Citrobacter
  • Proteus mirabilis
  • Paracolobactrum arizonae
  • Salmonella
  • Shigella
  • Pseudomonas
  • Providencia

Phenotype Annotations

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Species	Taxon ID	Strain	Gene (if known)	OMP	Phenotype	Details	Evidence	Notes
Escherichia coli	NCBI:562			Absent growth on Hektoen agar	Growth	No growth on Hektoen Agar	Plating Assay	Table 1- non-pathogenic enteric bacteria
Citrobacter	NCBI:544			Decreased growth rate on Hektoen Agar	Growth	Non-pathogenic enteric bacteria exhibits slow growth on Hektoen Agar	Plating Assay	Table 1
Proteus mirabilis	NCBI:584			Absent growth on Hektoen agar	Growth	on Hektoen Agar	Plating Assay	Table 1- non-pathogenic enteric bacteria
Paracolobactrum arizonae	NCBI:59203			Absent growth on Hektoen agar	Growth	on Hektoen Agar	Plating Assay	Table 1
Salmonella	NCBI:590			Absent growth on Hektoen agar	Growth	on Hektoen Agar	Plating Assay	Table 1
Shigella	NCBI:620			Absent growth on Hektoen agar	Growth	on Hektoen Agar	Plating Assay	Table 1
Shigella	NCBI:620			Green colonies on Hektoen agar Absent utilization of carbon source (lactose, etc.) Absent cellular carbohydrate metabolic process	Staining Results	growth on Hektoen agar	Plating Assay	Table 2-strain doesn't utilize any of the sugars present in the media.
Shigella	NCBI:620			Raised colony morphology on Hektoen agar	Morphology	growth on Hektoen agar	Plating Assay	Table 2
Shigella	NCBI:620			Moist colony appearance on Hektoen agar	Morphology	growth on Hektoen agar	Plating Assay	Table 2
Salmonella	NCBI:590			Blue-green to blue colonies with black centers on Hektoen Agar Growth on Hektoen Agar Absent cellular carbohydrate metabolic process	Growth	Blue-green to blue colonies with black centers on Hektoen Agar	Plating Assay	Table 2- strain unable to utilize sugars present in the media
Salmonella	NCBI:590			Blue-green to blue colonies with black centers on Hektoen agar Absent cellular carbohydrate metabolic process Absent utilization of carbon source (lactose, etc.)	Growth	tested on Hektoen Agar	Plating Assay	Table 2- strain unable to utilize sugars present in the media
Pseudomonas	NCBI:286			Green colonies on Hektoen agar Absent cellular carbohydrate metabolic process Absent utilization of carbon source (lactose, etc.)	Staining Results	on Hektoen Agar	Plating Assay	Table 2- strain cannot utilize sugars present in the medium
Pseudomonas	NCBI:286			Brown colonies on Hektoen agar*Absent *Absent utilization of carbon source (lactose, etc.) Absent cellular carbohydrate metabolic process	Staining Results	on Hektoen Agar	Plating Assay	Table 2- strain cannot utilize sugars present in the medium
Pseudomonas	NCBI:286			Flat colonies on Hektoen agar Absent utilization of carbon source (lactose, etc.) Absent cellular carbohydrate metabolic process	Morphology	on Hektoen Agar	Plating Assay	Table 2- strain cannot utilize sugars present in the medium
Pseudomonas	NCBI:286			Irregular colonies on Hektoen agar Absent utilization of carbon source (lactose, etc.) Absent cellular carbohydrate metabolic process	Morphology	on Hektoen Agar	Plating Assay	Table 2- strain cannot utilize sugars present in the medium
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Notes

• Visit the Hektoen Agar Method Page for more information
• For additional information, read Part II

References

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