Isolation ofShigella sonneiby fluid media

Abstract

SUMMARYSelenite F broth prepared in the laboratory from single ingredients was found to be significantly more efficient than nutrient broth in the isolation ofShigella sonneifrom human faeces. It was more efficient than direct plating on deoxycholate citrate agar for diagnosing Sonne dysentery in a local outbreak. The difference was significant. There was, however, no significant advantage for enrichment over direct plating when stools posted from Bristol to Cardiff were examined.Laboratory prepared selenite F broth was preferable to the same medium purchased commercially from two different firms. The product of one firm was significantly better than that of the other.Two methods of sterilization of laboratory prepared selenite F broth were studied. Seitz filtered selenite was less inhibitory to the growth of small numbers ofShigella sonnei. Sterilization by heating in free steam for periods of 15 mm and over impaired the ability of selenite F broth to allow multiplication of small numbers ofShigella sonnei.