20 
1 organisms that have been millenia in the making. For 
2 instance, the meningococcus, which can produce meningitis 
3 and/or overwhelming sepsis, is far more commonly carried 
4 by a substantial fraction of the population as a harmless 
5 component of the throat flora in the winter months. More 
6 pertinently, virulent E. col i organisms, not even the 
7 weakened strains about which much debate has centered, 
8 are poor pathogens at best. And while certain bacterial 
9 products made by some strains are thought to augment their 
10 potential invasiveness, the vast majority of instances of 
11 serious E. col i disease occur in infants or in hosts with 
12 immunologic or anatomic predisposition. 
13 My second point is complementary to t- h e first: 
14 Even the most virulent of microorganisms has a dosage 
15 threshold below which its mechanism of pathogenesis fails. 
15 When persons are bitten by a demonstrably rabid wolf, less 
17 than half proceed to get rabies, and the presumed reason 
10 for the others' failure to become ill is a dosage effect. 
19 It has been shown experimentally that 20 million virulent 
2 q group A streptococci are required in order to establish 
21 a pharyngitis in human volunteers; and a million coagulase 
22 positive staphylococci can be injected into healthy human 
23 skin without causing disease, whereas the presence of an 
24 inert foreign body, such as a suture, in that skin 
25 suddenly allows 100 staph to establish purulent infection. 
[112] 
