BACTERIOLOGY OF MEAT AND MEAT PRODUCTS 135 



green broth tubes. After 12 iShrs. incubation the latter, after 

 dilution, is brushed over a few additional L.B.A. plates. This 

 broth medium favours the growth of Gaertner group bacilli over 

 the other intestinal bacteria. The composition of these media 

 is given in the appendix. 



All the white colonies (at least on the primary plates) must 

 be subcultivated and investigated. The labour is much dimin- 

 ished, without risk of overlooking true Gaertner bacilli, if to 

 the L.B.A. salicin and saccharose (J- p.c.) are added as well as 

 lactose. Many para-Gaertner bacilli are in this way eliminated, 

 as if they ferment salicin and saccharose they will form red 

 colonies. 



All the white colonies are subcultivated into double tubes of 

 litmus broth containing salicin, saccharose and lactose. The 

 tubes, which after two days incubation show neither acid nor 

 gas, are further culturally examined The colonies which possess 

 the cultural characters of the Gaertner group must be fully in- 

 vestigated, including agglutination and virulence tests. 



The agglutination tests must be carried out with anti-sera 

 from both of the food poisoning strains, i.e. B. enteritidis and 

 B. suipestifer. They should also include the immunization of a 

 rabbit and testing the agglutination properties of its serum upon 

 known members of the Gaertner group. 



The presence of B. coli group organisms in the food can be 

 judged from the number of red colonies on the L.B.A. plates. 



If it is wished to ascertain if bacilli of the Proteus group are 

 present this can be done by inoculating 5 per cent, nutrient 

 gelatine plates with the material and investigating Proteus-like 

 colonies. This is an unsatisfactory method and a useful medium 

 for the isolation of this group of organisms is greatly needed. 



Anaerobic cultures can be made by the inoculation of glucose 

 broth and glucose agar plates, incubating all under anaerobic 

 conditions at suitable temperatures. The different kinds of 

 organisms present must be carefully examined and investigated. 



It is also advisable to cut sections and otherwise micro- 

 scopically examine the meat to see if the bacilli are chiefly on 

 the surface and also if the meat fibres are from apparently 

 healthy animals. 



