646 PROTEUS 



products which are characteristic of ordinary cadaveric decomposition." Amongst these 

 decomposition products they consider mercaptan and the oxy-acids to be of particular 

 significance ; indole, skatole, and HgS are less characteristic. According to this definition 

 the Proteus group would be classed amongst the, non- putrefactive bacteria. The connota- 

 tion that Rettger and Newell attach to the term putrefaction is that it is essentially 

 an anaerobic process ; it is dependent therefore on the anaerobic growth of bacteria. 

 Proteus bacilli, when grown under anaerobic conditions, do not digest proteins, and therefore 

 cannot be regarded as capable of causing true putrefaction. They are, however, frequently 

 associated with the anaerobes in putrefying organic material, and no doubt assist these 

 greatly by using up oxygen and rendering the conditions suitable for their growth. It 

 may be noted that this definition would not meet with universal acceptance. 



Biochemical Reactions. — Acid and gas are formed from glucose, sucrose, 

 glycerol, xylose, and almost always from salicin. Mannitol, lactose, dulcitol, starch, 

 dextrin, sorbitol, and raffinose are never fermented. The action on maltose is 

 variable and is of value in classification. Moltke (1927), who examined 194 strains, 

 found that 37 fermented maltose, and 157 did not. The maltose-positive strains 

 fermented sucrose and salicin within 24 hours, while the maltose-negative strains 

 took 3-15 days to ferment sucrose and 10-21 days to ferment salicin. All but one 

 of the maltose-positive strains produced indole, while the maltose-negative strains 

 uniformly failed to do so. A negative correlation was observed between the fer- 

 mentation of maltose and the ability to digest coagulated horse serum. In the 

 definition of the group by Winslow and his colleagues (1920) it is stated that 

 the gas produced from glucose and sucrose consists entirely of COg. Mendel (1911), 

 however, gives the gas ratio as Hj : CO2 = 6-8 : 1, while Yacob (1932) gives it as 

 3-4 : 1. These latter figures agree with our own findings. The fermentative activity 

 of Proteus is fairly constant, but occasional strains are anaerogenic on isolation 

 (Edwards 1942), and others lose their power to attack certain sugars on prolonged 

 cultivation. Proteus morgani is restricted in its fermentative power from the 

 start. The action on litmus milk is subject to some variation. Usually a true 

 rennet clot is produced, which retracts and squeezes out whey. Digestion of the 

 clot sets in and is accompanied by progressive alkalinization of the medium. The 

 litmus is reduced. The clot is often digested completely within a week, and the 

 reaction is strongly alkaline. Slight initial acidity is sometimes observed, and 

 not infrequently proteolysis may overshadow coagulation, so that there is not 

 time for a definite clot to form. Most strains attack milk rapidly, imparting to 

 it a yellow colour, a bitter soapy flavour and a foul odour, but some strains have 

 little or no coagulative or proteolytic effect (Plahn 1937). The reaction to the 

 methyl-red and Voges-Proskauer tests varies with different strains. Nitrates are 

 reduced to nitrites. Methylene blue is decolorized slowly in broth cultures. Urea 

 is decomposed with the production of ammonia — a reaction that may be used 

 in the differentiation of Protects from Salmonella (Ferguson and Hook 1943). 

 Phenylalanine is broken down with the formation of phenylpyruvic acid (Henriksen 

 and Closs 1938). 



Antigenic Structure. — Our knowledge is both deficient and conflicting. Most 

 workers (Cantu 1911, Wenner and Rettger 1919, Taylor 1928) who have prepared 

 immune sera against different strains have found that a given serum may agglutinate 

 either the homologous strain only or a number of heterologous strains as well. 

 Any simple subdivision by agglutination or absorption of agglutinins has proved 

 impossible. Moltke (1927), who paid special attention to the H and antigens, 



