15 
were absent because of protective vaccination. P_. pestis is a fragile 
organism requiring a considerable respiratory dose, as is evident from 
Pike's report (12) of only 4 laboratory cases in the United States and 6 
worldwide. The Genetics Branch worked only with nonpathogens, although there 
was one hospitalized case of Salmonellosis, ascribed to mouth pipetting. 
The Bacterial Nutrition and Microphysiology Branches examined a variety of 
bacteria using Class I cabinets. During the 10 years there was only one 
infection, in 1963 - severe pulmonary coccidioidomycosis with a cavity in 
the lung. This was the consequence of using a shaker with a dry spore 
sediment and glass beads, inside a Class I cabinet with an inserted four 
porthole panel without attached arm length gloves. The staph enterotoxin 
unit had 4 illnesses, ascribable to a procedure most unlikely to be dupli- 
cated in any studies with recombinant DNA. This procedure involved exposing 
the heads of monkeys to an aerosol of solubilized aerosolized staph entero- 
< . . 
toxin, using a Henderson apparatus in a modified Class I cabinet (54). 
No respiratory protection was worn during transportation of the monkeys 
(the fur on their heads obviously was shedding enterotoxin) to the animal 
room, where they were held in open cages. 
Nevertheless, a summary made in June 1966 concerning the biohazards in 
the study of staph enterotoxin does show that Class I hoods were protective. 
Portions of the summary are reproduced below, from a contractor's report: 
"Toxic reactions of personnel engaged in purification studies 
of the enterotoxin on an open laboratory bench have included mild 
cold symptoms, conjunctivitis, and dermatitis. The latter has been 
severe when concentrated material was contacted by the skin. A 
tolerance is developed after repeated exposure; however, skin reactions 
to the concentrated material continue." 
[ 386 ] 
