Formalinized bacterial "antigens" as a potential infection hazard.

It is widely thought that after enteric bacteric have been "formalinized" (treated with an equal volume of 0.6% formalin) for 1 h, the bacteria become "antigens" and are no longer viable. None of the 27 cultures of Salmonella and other Enterobacteriaceae were entirely killed within 1 h after formalin was added, but all 27 were reduced from 10(9) viable cells per ml to less than 10(2) per ml within 7 h. Thus, mouth pipetting of cultures formalinized for only 1 h is a possible infection hazard.