444 MANUAL OF DETERMINATIVE BACTERIOLOGY 



Key to the tribes of family Enterobacteriaceae. 



I. Ferment lactose with the formation of acid and visible gas within 24 hours at 

 37°C or within 48 hours at 25° to 30°C. Some transitional forms produce acid 

 and gas from lactose slowly. 



Tribe I. Eschericheae, p. 444. 

 II. Plant parasites. Ferment lactose with formation of acid, or acid and visible gas. 

 Usually attack middle lamellar substance in plant tissues, causing soft rots. 



Tribe II. Erwineae, p. 463. 



III. Ordinarily chromogenic producing a pink, red or orange-red pigment. Occa- 



sionall}^ non-pigmented. Ferment glucose and lactose with formation of 

 acid, or acid and visible gas. 



Tribe III. Serrateae, p. 479. 



IV. Lactose not fermented within 30 days either at 37°C or at 25° to 30°C. Urea 



decomposed within 48 hours. 



Tribe IV. Proteae, p. 486. 

 V. Lactose rarely fermented within 30 days either at 37°C or at 25° to 30°C. Urea 

 not decomposed within 48 hours. 



Tribe V. Salmonelleae, p. 492. 



TRIBE I. ESCHERICHEAE BERGEY, BREED AND MURRAY. 



(Preprint, Manual, 5th ed., October, 1938, vi.) 



Ferment glucose and lactose with the formation of acid and visible gas within 24 

 hours at 37°C, or within 48 hours at 25° to 30°C. Some forms produce acid and gas 

 from lactose slowly (occasionally not at all). Do not liquefy gelatin except slowly in 

 Aerobacter cloacae. 



Key to the genera of tribe Eschericheae.* 



I. Acetylmethylcarbinol not produced. Methyl red test positive. Salts of citric 

 acid may or may not be used as a sole source of carbon. 



Genus I. Escherichia, p. 444. 

 II. Acetylmethylcarbinol produced. Methyl red test negative. Salts of citric 

 acid used as sole source of carbon. 



Genus II. Aerobacter, p. 453. 

 III. Acetylmethylcarbinol may or may not be produced. Methyl red test variable. 

 Salts of citric acid may or may not be used as sole source of carbon. Gas not 

 as abundant as in previous genera. Capsulated forms from respiratory, intes- 

 tinal and genito-urinary regions. 



Genus III. Klebsiella, p. 457. 



Genus I . Escherichia Castellani and Chalmers\ . 



(Castellani and Chalmers, Manual Trop. Med., 3rd ed., 1919, 941; Colibacterium 

 Orla-Jensen, Jour. Bact., 6, 1921, 272; Colobactrum (in part) Borman, Stuart and 



* Levine (Jour. Bact., /, 1916. 153) was the first to show the inverse correlation be- 

 tween the methyl red and Voges-Proskauer tests and used these characters for the 

 primary separation of the Escherichia coli section and the Aerobacter aerogenes section 

 (Amer. Jour. Public Health, 7, 1917, 784). 



t Completely revised by Prof. M. W. Yale, New York State Experiment Station, 

 Geneva, New York, Nov., 1938; further revision, July, 1943. 



