DEHYDRATED CULTURE MEDIA 135 



Bismuth Sulfite Agar and enrichment in Bacto-Tetrathionate Broth Base or Bacto- 

 Selenite Broth. 



The search for the inciting agents in bacillary intestinal disorders is of vital 

 importance in the public health laboratory. The value of the detection of typhoid 

 bacilli in active cases of typhoid fever as well as from carriers has long been recog- 

 nized, and a number of media are being successfully used for these purposes. 

 Media suitable for the isolation of Salmonella typhosa have not always proved 

 entirely satisfactory for the detection of Shigella and other Salmonella organisms 

 due either to the overgrowth of coliform organisms, or the inability of the medium 

 itself to support the growth of some particularly fastidious strains. 



Bacto-S S Agar gives excellent growth from small inocula of the different 

 types of Shigella and Salmonella organisms as they occur in fresh fecal specimens. 

 Strains of Flexner, Newcastle, Schmitz, Shiga, Sonne and alkalescens, as well as 

 the Salmonella, grow unrestricted. All strains of S. typhosa that have been en- 

 countered show excellent growth on S S Agar. Coliform organisms are quite 

 generally inhibited even when heavy inocula are employed. 



Shigella, Salmonella and other organisms not fermenting lactose form opaque, 

 transparent or translucent uncolored colonies, which generally are smooth. The 

 few lactose fermenting organisms which may develop on the medium are readily 

 differentiated due to the formation of a red color in the colony. At times, isolated 

 coliform colonies may not show a definite red color, being pink or nearly colorless 

 with a pink center. Occasionally an aerogenes type will develop a characteristic 

 large, white or cream colored opaque and mucoid colony. Some Proteus and 

 Salmonella types may, under certain conditions, produce black centered colonies. 



Hormaeche and Surraco,^ Hardy and co-workers^ and Rose and Kolodny,^ have 

 reported S S Agar as superior to other media that have been recommended for 

 isolation of Shigella and Salmonella organisms. Mayfield and Goeber* compared 

 media for isolation of Shigella organisms and found Bacto-S S Agar to yield the 

 greatest number of positive isolations. Pots^ and Caudill^ have reported on the 

 satisfactory use of S S Agar in isolation of Shigella organisms. In their studies 

 of the acute diarrheal diseases, Mosher, Wheeler, Chant and Hardy'' first enriched 

 their specimens in Selenite Broth and then plated on Bismuth Sulfite Agar, 

 S S Agar, MacConkey Agar and Desoxycholate Agar, while Watt and Cummings* 

 plated directly upon S S Agar. Hormaeche and his co-workers^ used S S Agar 

 in conjunction with others for isolation of Shigella as the causative agent of 

 infantile summer diarrhea. Vacarro et al.^*^ employed S S Agar in conjunction 

 with other plating media in the isolation of Salmonella and Shigella from healthy 

 carriers, and Neter^^ used it similarly in his study of the Proteus and Paracolo- 

 bactrum (paracolon bacilli) in feces of healthy infants. McClure and Crossley,^- 

 using S S Agar and other media, isolated S. newport in an epidemic of food 

 poisoning, and Cordy and Davis^^ isolated S. morbificans from horses and mules 

 in an outbreak of salmonellosis. Watt, DeCapito and Morgan^* isolated S. texas 

 on S S Agar after enrichment in Tetrathionate Broth. For the isolation and typing 

 of Salmonella and Shigella, Borman, Wheeler and Mickle^^ and Nelson et al.^^ 

 indicate the desirability of plating specimens on S S Agar and other substrates 

 before and after enrichment. Neter and Clark^'' have reported on the effectiveness 

 of culture media in isolation of enteric organisms, the usefulness of S S Agar, 

 especially with other media, being clearly demonstrated by their results. 



Bacto-S S Agar is specified for use in "Standard Methods for the Examination, 

 of Dairy Products"^^ for the isolation of pathogenic bacteria from cheese and in 

 "Diagnostic Procedures and Reagents" ^^ for the examination of specimens for 

 evidence of infection with Salmonella and Shigella. 



A survey of the methods used in the collection and preservation of stool speci- 

 mens for the isolation and identification of Salmonella, Shigella and intestinal 



