Nothing is definitely known of the agencies by which Spirochaeta pallida produces the lesions of syphilis. Some of the symptoms of the disease suggest the production and activity of toxins by the organism, but these have not been demonstrated.
In my experiments, Mandler and Berkefeld filtrates of ascites-agar-kidney and ascites-bouillon-kidney cultures of Noguchi strains of Spirochaeta pallida grown for from three to eight weeks were found relatively nontoxic for rabbits by intratesticular injection and for young guinea-pigs by intraperitoneal inoculation. Slight local inflammatory reactions and loss in weight were no more marked than those observed with control filtrates of sterile mediums incubated for the same period and injected in similar amounts per kilogram of weight.
These experiments indicated that cultures of spirochetes alleged or believed to be Spirochaeta pallida do not produce demonstrable amounts of soluble or exogenous toxins in vitro, although the results are of limited value since it
KOLMER JA. TOXIN PRODUCTION BY SPIROCHAETA PALLIDA. Arch Derm Syphilol. 1929;20(2):189-190. doi:10.1001/archderm.1929.01440020041008