98 



would indicate that the presence and growth of the Welchii group is detri- 

 mental to the successful isolation of Bact. coll. This work of Hall and 

 Ellefson has recently been confirmed by Wagner and Monfort. 



Ellms (1919) reports sporing lactose decomposing aerobes from the 

 water supply of Milwaukee, and the feces of children. These strains differ 

 from those of Meyers and Ewing in that they are Gram positive and are 

 acid to methyl red. The importance of these aerobic spore formers to 

 the bacteriologist and engineer is apparent. Being much more resistant 

 than the non-sporing colon group, they would naturally survive the ordinary 

 methods of water treatment, and as they are capable of growing aerobic- 

 ally, they may be mistaken for Bad. coli, Bact. aerogenes, etc., in the or- 

 dinary routine examination. Their presence in a water may conceivably 

 account for the apparently poor results sometimes obtained in purification 

 processes. 



Muer and Harris, of the Mount Prospect Laboratory, observed that in 

 lactose peptone bile a concentration of 1-700 to 1-1000 brilliant green would 

 not appreciably affect the volume of gas produced by Bact. coli in seven 

 days, whereas Cl. ivelchii would not produce gas until the brilliant green 

 was diluted to 1-50,000. This observation is quite remarkable for, as is 

 well known, brilliant green is frequently used to inhibit Bact. coli. The 

 writer has observed a dilution of even 1-2,000,000 has a marked inhibitory 

 effect on the rate of growth of Bact. coli in peptone water. Their results, 

 however, are very distinct and significant. Probably the bile reacts in 

 some way with brilliant green. It is well known, for example, that in eosin 

 brilliant green agar a much higher concentration of brilliant green can be 

 employed without affecting Bact. typhi than in the Andrade brilliant green 

 medium of Krumwiede. The following table shows very clearly the in- 

 hibitory action of brilliant green on the anaerobic spore formers. It ap- 

 pears also that the growth of the anaerobes interferes with the isolation 

 of Bact. coli. In 17 samples Bact. coli was isolated when brilliant green 

 lactose bile was employed but was missed when plain lactose peptone bile 

 was used. 



TABLE LV. COMPARISON OF 115 SAMPLES OF WATER PLANTED IN BOTH 



PLAIN LACTOSE PEPTONE BILE AND BRILLIANT-GREEN LACTOSE BILE. 



(After Muer and Harris 1920) 



The chief interest of the water bacteriologist in these spore formers 

 is that the anaerobes interfere and confuse the presumptive test rendering 

 confirmation necessary, while the aerobic forms complicate the confirmatory 

 test as well, making it essential to resort to more detailed identification tests 

 where there is reason to suspect this type present. 



