124 DIFCO MANUAL 



BACTO 



DEXTROSE STARCH AGAR (B66) 



DEHYDRATED 



Proteose Peptone No. 3, Difco 15 g 



Bacto-Dextrose 2 g 



Soluble Starch, Difco 10 g 



Sodium Chloride 5 g 



Disodium Phosphate 3 g. 



Bacto-Gelatin 20 g 



Bacto-Agar 10 g 



Bacto-Dextrose Starch Agar is recommended as a complete solid medium for 

 the propagation of pure cultures of Neisseria gonorrhoeae. This highly nutritious 

 medium without any additions will also support excellent growth of a large 

 number of pathogenic organisms such as the meningococcus, streptococcus and 

 pneumococcus. This medium is far superior to the ordinary infusion media for 

 the cultivation of these discriminating bacteria. Bacto-Dextrose Starch Agar, in 

 half concentration, is recommended as a Stock Culture Agar for the maintenance 

 of cultures of gonococcus, meningococcus and others not capable of splitting 

 starch. 



In the development of a simple medium for the cultural detection of the 

 gonococcus, it was considered that luxuriant growth of all strains of N. gonor- 

 rhoeae was a requisite. Bacto-Dextrose Starch Agar, a nutritious medium with- 

 out enrichment, fulfilled this requirement satisfactorily, giving luxuriant growth 

 of freshly isolated fastidious strains of the gonococcus. It was soon shown, how- 

 ever, on this highly nutritious medium that in mixed cultures, as were en- 

 countered especially in chronic cases of gonorrhoea, extraneous forms developed 

 too rapidly and overgrew the gonococcus. For this reason, an enriched Chocolate 

 Agar prepared with Bacto-Proteose No. 3 Agar as discussed on page 116 or 

 Bacto-G C Medium Base, page 122, is recommended for the isolation of the 

 gonococcus. 



For the cultivation of the gonococcus, it is imperative to have the incubation 

 atmosphere saturated with moisture. Satisfactory conditions can be obtained 

 if the plates of Dextrose Starch Agar are incubated in a closed container, which 

 contains cotton, a towel or a sponge saturated with water. A can with a suitable 

 cover, Novy jar, desiccator or any other convenient sized container capable of 

 retaining the moisture is entirely satisfactory. About 200 ml. of water added in 

 this manner is ample for a container of one or two gallons capacity. Plates in- 

 cubated under these conditions will give a luxuriant growth of many gonococci 

 when identically inoculated plates incubated in the ordinary manner in the 

 incubator show no growth. If the culture requires carbon dioxide for growth 

 this may be supplied as indicated under Bacto-Proteose No. 3 Agar, page 118. 

 Carbon dioxide is recommended for isolation, but is not generally necessary, 

 in the presence of abundant moisture, for growth of isolated strains. 



Swancara^ described a method of obtaining partial carbon dioxide tension in 

 individual tubes by placing a cotton plug just over the medium following inocu- 

 lation. The percussion tip from a match is removed and the match broken and 

 placed on this plug. The tube is then sealed with a rubber stopper or screw cap. 

 The match head is then ignited by applying heat to the outside of the tube. 



Nutritional factors so conducive to the growth of the gonococcus proved 

 equally satisfactory for many other pathogenic bacteria, making Bacto-Dextrose 

 Starch Agar, without added enrichment, a most excellent medium for the propa- 

 gation of streptococci, pneumococci, meningococci and others. For mass growth 

 of these organisms Bacto-Dextrose Starch Agar is recommended as being superior 



