| Abstract: | Some of the physiological and biochemical characteristics of a type F strain recently isolated from the United States were studied and compared with those of the prototype Langeland type F strain. The recent isolates were nonproteolytic, fermented sucrose and ribose, produced spores of low thermal resistance, produced a protoxin activated by trypsin, and grew and produced toxin at 38 F (3.3 C) from a spore inoculum. The prototype Langeland strain was proteolytic, did not ferment sucrose or ribose, and produced spores of relatively high thermal resistance, and the toxin of 3-day-old cultures was not activated by trypsin. Approximately two to three times the minimal lethal dose (MLD) of type F toxin from either Langeland or nonproteolytic strains was cross-neutralized by 1,000 anti-MLD of type E antitoxin. Antitoxin serums prepared by immunizing rabbits with the toxoid of the nonproteolytic type F isolate neutralized the toxin of the Langeland strain, but did not show cross-neutralization with the toxins of other types of Clostridium botulinum. |
