GN BROTH, HAJNA

Hajna developed gram-negative broth as an enrichment medium for recovery of Salmonella and Shigella from clinical and non-clinical specimens such as urine, blood clots, throat swabs, swabs from eating and drinking utensils etc. GN Broth, Hajna is also recommended by APHA for the microbiological examination of foods. Croft and Miller isolated more strains of Shigella from rectal swabs using this medium. Taylor and Schelhart showed the superiority of GN Broth to selenite enrichment media for isolation of Shigella. Hajna also suggested the enrichment of organisms from rectal swabs in this medium 1-6 hours before plating on solid media.

GN Broth, Hajna should be inoculated directly with the specimen. In case of stool specimens, approximately 1 gram should be used for inoculation. Appropriate references for processing of clinical and food samples should be followed. After incubation of 6-8 hours and again after 24 hours, sub-culturing on selective agar media should be carried out. The medium contains tryptose, which provides amino acids and other nitrogenous substances to support bacterial growth. The combination of sodium citrate and sodium deoxycholate inhibit gram-positive and some gram-negative bacteria such as coliforms. Phosphates serve as a buffering system. Sodium chloride maintains osmotic equilibrium. The higher concentration of mannitol over dextrose limits the growth of Proteus and enhances growth of mannitol fermenting Salmonella and Shigella. This enrichment broth should be used in conjunction with selective and non-selective plating media to increase the probability of isolating pathogens.

for selective enrichment of gram-negative organisms of the enteric group