Sept. 1, 1932 Commercial Honey and Spread of American Foulbrood 277 



Of the 171 cultures made with seedings between 8,000,000 and 

 500,000 spores per seeding, 48, or 28.07 per cent, showed growth at 

 the end of 10 da>s' incubation, while 79, or 46.20 per cent, showed 

 growth after 30 days' incubation. The latter number is 37.44 per 

 cent of the 211 total cultures showing growth after 30 days' incubation. 



Of the 142 cultures made with seedings between 400,000 and 50,000' 

 spores per seeding, only 4, or 2.82 per cent, showed growth at the end 

 of 10 days' incubation, while 12, or 8.45 per cent, showed growth 

 after 30 days' incubation. The latter figure is 5.69 per cent of the 

 211 cultures showing growth after 30 days' incubation. 



Of the 123 cultures made with seedings of 40,000 or fewer spores. 

 per seeding, no growth was obtained after 30 days' incubation. 



Of the 556 cultures made with all seedings, 30.58 per cent showed 

 growth at the end of 10 days' incubation and 69.42 per cent showed 

 no growth. The 170 positive cultures after 10 days' incubation is- 

 80.57 per cent (not shown in Table 6) of the 211 total positive 

 cultures obtained. In the interval between the 10 and 30 day incuba- 

 tion periods, 19.43 per cent (not shown in Table 6) of the 211 total 

 positive cultures, or another 7.37 per cent of all cultures made, showed 

 growth, making a total of only 37.95 per cent of all cultures which 

 showed growth at the end of 30 days' incubation, with 62.05 per cent 

 still showing no growth. 



The initial growth phases as described by Buchanan (5; IS, Ch. V) 

 are clearly more marked with spores than with simple vegetative 

 organisms, since there is a varying length of time necessary for spores 

 to germinate and start growing after implantation in a suitable 

 medium. In the light of observations on other spore-forming 

 organisms, it is probable that this factor, which seems to cause varia- 

 tions in the germination time of Bacillus larvae even within a lot 

 from a single source, is what has been termed "dormancy." Burke 

 (5, p. 283) , working with Clostridium botulinum, foimd : 



The individual (unheated) spores in a given culture of CI. botuUnum vary greatlj' 

 in the time required for germination under optimum growth conditions. The 

 majority germinate relatively quickly, but a few lie dormant for a longer time. 

 One hundred and forty-four days is the maximum period of dormancy recorded 

 here * * *. 



Burke states : 



The primary factors which cause the spore to lie dormant for long periods of 

 time under optimum growth conditions are believed to be inherent in the spore 

 itself. It is thought that relative permeability of the spore wall is one of the 

 factors. Environmental conditions may secondarily modify the period of 

 dormancy. 



Burke, Sprague, and Barnes (6, p. 560) observed the same phe- 

 nomenon with such non spore-bearing bacteria as Bacillus coli 

 ( = Escherichia coli). They found that spores of B. subtilis remained 

 dormant 39 days and those of B. megatherium 90 days, although a 

 large majority developed in 4 or 5 days. They believe: 



Dormancy must be considered a factor in infection. It reduces the chances of 

 infection by reducing the number of organisms that would otherwise start to 

 grow at one time. Since the cells begin to multiply at different times, the body 

 has an opportunity to initiate defensive reactions before all the cells develop. 

 If dormant for a sufficient period, the organisms will be excluded from the body 

 before development takes place. 



