PA THOOENICIT Y 535 



developed with methyl red is usually faint. The Voges-Proskauer reaction is 

 negative. Nitrates are not reduced. Catalase is produced, and all the members 

 that have been tested give the oxidase reaction described by Gordon and M'Leod 

 (1928). 



Antigenic Structure. — Most attention has been concentrated on the meningo- 

 coccus and the gonococcus. The meningococcus has been divided into four anti- 

 genic types — Types I, II, III and IV (see pp. 538-9) ; but the results obtained 

 depend largely on the source from which the strains are obtained. In epidemic 

 times most of the cocci isolated can be readily typed, but strains isolated 

 from sporadic cases in non-epidemic times are frequently inagglutinable with 

 any of the type sera. The gonococcus is even more irregular ; clear types are 

 difficult to establish. The majority of the strains appear to be related anti- 

 genically, and to fall more or less into one or other of two groups (Atkin 1925) 

 (see pp. 545-7). Little work has been done on the other Gram-negative 

 cocci ; one of the chief reasons for this is that most of them are auto-agglutinable, 

 and homogeneous suspensions cannot be obtained. The complement-fixation test, 

 however, seems to show that there is a group relationship between N. catarrhalis, 

 N. pharyngis, the gonococcus and the meningococcus (see Oliver 1929, Price 1933). 



Studies on the chemical fractionation of these organisms are still in their infancy. 

 Boor and Miller (1934) and Miller and Boor (1934), amplifying the work of Zozaya 

 (1931) and Zozaya and Wood (1932) (see p. 539), have extracted " nucleoproteins " 

 and polysaccharides from various members of the group. By the precipitation 

 reaction it was found that the nucleoproteins from the meningococcus, the 

 gonococcus, and N. catarrhalis not only resembled each other closely, but also had 

 an affinity with nucleoproteins extracted from pneumococci. Polysaccharides 

 prepared from the meningococcus and the gonococcus reacted in high dilution with 

 Type III antipneumococcal serum, as well as with antimeningococcal and anti- 

 gonococcal serum. The polysaccharide extracted from N. catarrhalis reacted with 

 antigonococcal but not with antimeningococcal serum. 



Pathogenicity. — The meningococcus gives rise to rhinopharyngitis, to epidemic 

 cerebrospinal meningitis, and to post-basic meningitis in children ; by intraspinal 

 injection of monkeys it is possible to produce a meningitis with pure cultures of 

 the organism. The gonococcus gives rise in human beings to gonorrhoaa, with 

 all its complications, but it is impossible to reproduce this disease in animals. 



Towards laboratory animals all the Gram-negative cocci behave in much 

 the same way. Injected intraperitoneally in large doses into mice or guinea- 

 pigs, they cause death in 1 to 3 days. Post mortem, there is a small amount of 

 peritoneal exudate, and sometimes a little fibrin deposit on the organs ; the spleen 

 is slightly enlarged, and there is hypersemia and degeneration of the viscera. The 

 organisms can be cultivated from the peritoneal exudate, but rarely from the 

 heart's blood. There is little multiplication of organisms inside the body ; no 

 true infection is set up, and death occurs from toxaemia. A similar result follows 

 the injection of heat-killed organisms, though generally a rather larger dose is 

 needed than of living cocci. It seems probable that the toxicity is due to some 

 constituent of the nucleoprotein, since " nucleoprotein " extracted from meningo- 

 cocci and gonococci is almost as toxic to mice as are the dead organisms themselves 

 (Boor and Miller 1934). 



