632 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Isolation of Typhoid Bacilli.* — C. H. Browning W. Gilmour, and 

 T. J. Mackie describe a method for the isolation of typhoid bacilh from 

 faeces bj means of brilliant green in fluid medium. The diamidotri- 

 phenylmethane group of dyes, including malachite and brilliant green, 

 are fairly actively bactericidal to the typhoid-coli group as well as to 

 Grram-positive organisms, but brilliant green is markedly more active 

 than malachite green in its inhibitory effect upon the coli group. It is, 

 therefore, likely to prove useful in the detection of a small number of 

 typhoid bacilli in the presence of a large number of organisms of the 

 B. coli type. The method is as follows. A stock solution of Bayer's 

 brilliant green extra cryst. 1 p.c. is made up every few weeks. Before 

 use, a 1 : 10,000 dilution of the dye is prepared from this. Of this 

 dilution, varying quantities — * 04, • 08, ' 12, * 16, * 22, • b c.cm. — 

 are added to a series of peptone water tubes of weakly alkaline reaction. 

 A loopful of faeces is added to each tube. After 20-24 hours incubation 

 at 37° C, a loopful from each tube is stroked on a MacConkey plate 

 (two 10 cm. plates in all are quite sufficient to accommodate three strokes 

 from each dilution). These plates are incubated and examined in the 

 ordinary way. Comparison of results thus obtained with those of direct 

 platings of material upon MacConkey's medium, as well as experiments 

 with artificial mixtures of typhoid and colon l)acilli, indicate that this is 

 a selective medium of great value. The optimum concentration of 

 brilliant green for the growth of typhoid bacilli varies for different 

 strains, as the use of the range of dilutions shown above will indicate. 



Isolation of Typhoid Bacilli. f — T. Bongartz has made use of 

 Bitter's China-blue method in extensive investigations connected with 

 typhoid epidemics, and has found it of great service, giving more satis- 

 factory results than any other method tried. The method of preparing 

 the medium is given in abbreviated form ; 2 p.c. of lactose is added to 

 a neutral 2 or '4 p.c. meat-juice-peptone-salt-agar. After steaming, there 

 are added to each 100 c.cm. of the hot agar, firstly 9 drops of saturated 

 watery solution of china-blue, and secondly 2 5 c.cm. of a 0*1 p.c. 

 malachite green solution. This is sterilized for ten minutes and poured 

 in plates. Non-lactose fermenters appear on such plates after 16 to 24 

 hours incubation, and may be tested with a typhoid agglutinating serum. 

 In this way a positive result may be reported on the day after the 

 material is received. This medium is more easily prepared than that of 

 Conradi and Drigalski, and at a smaller cost. 



Bacteriological Examination of Soils. f— After a resume of the 

 various media used for these investigations, P. E. Brown points out that 

 soil itself is the most suitable medium for the purpose. Fresh soil gives 

 more constant results than sterilized or air-dried soils. For measuring 

 the ammonification due to soil bacteria, albumin solution or dried blood 

 may be added to the soil, but the most satisfactory results are obtained 

 by using casein. 10 c.cm. of 10 p.c. casein solution are added to each 

 100 gm. of fresh soil. The optimum incubation period at room temper- 

 ature is three days. 



* Journ. of Hygiene, xiii. (1913) pp. S-S-o 42. 



t Centralbl. Bakt., Ite Abt. Orig., Ixxi. (191.3) pp. 228-32. 



X Centralbl. Bakt., 2te Abt., xxxix. (1913) pp. 61-78. 



