Extracts of selected xerographic toners and copies were found to be mutagenic in the Salmonella assay. The activity was independent of the xerographic hardware and process and was traced to nitropyrenes present as impurities in the carbon black, the toner colorant. Manufacturing process changes resulted in a substantial reduction of the nitropyrene content of the carbon black and thus in the mutagenicity of the corresponding toners. Nitropyrenes are potent frameshift mutagens, and possible mechanisms for their biological action are discussed.

A glycoprotein responsible for the antiphagocytic properties of Campylobacter fetus has been identified by comparing cells of a wild-type strain with those of a mutant lacking this substance. The antiphagocytic component is demonstrable through electron microscopy as a discrete, negatively charged structure on the periphery of the cell. CLT is readily removed from the cell by mild extraction procedures and contributes to the inagglutinability in O antiserum normally displayed by C. fetus. Cells possessing this antigen are refractory to ingestion by macrophages except in the presence of specific antiserum. In its absence maximum phagocytosis occurs without a requirement for opsonins. It is concluded that the antiphagocytic component comprises a critical virulence factor of the bacterium.

A total of 63 chemicals were tested for mutagenicity in Salmonella typhimurium strains TA98, TA100, TA1535, TA1537, and TA1538, and Escherichia coli WP2 uvrA in a four-laboratory study. Sixty of the chemicals had been tested for carcinogenicity by the National Cancer Institute or the National Toxicology Program. All chemicals were tested for mutagenicity without metabolic activation and with liver S-9 preparations from uninduced and Aroclor 1254-induced F344 rats, B6C3F1 mice, and Syrian hamsters. The intra- and interlaboratory reproducibility of the Salmonella assay with regard to the overall judgment of mutagenic or nonmutagenic was good. The results in the E coli strain, however, exhibited a high degree of variability between laboratories. With one or two exceptions, the mutagens were detected with S-9 preparations from all three species. The uninduced liver S-9 preparations did not activate any chemicals to mutagens that were not also activated by induced S-9, but some chemicals were detected as mutagens only when induced S-9 was used. A positive mutagenic response in Salmonella was predictive of carcinogenicity 69% of the time; when equivocal carcinogens and borderline mutagens were included, the predictivity increased to 83%. Conversely, 76% of the carcinogens were mutagens. When the equivocal carcinogens were included, the proportion dropped to 75%. Relatively few chemicals (18%) were mutagenic in E coli. Not all the carcinogens induced tumors in both rats and mice, and the species-specific carcinogenicity could not be predicted from the S-9-specific mutagenicity.

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Tris(2,3-dibromopropyl) phosphate, a widely used flame-retardant additive for textiles, is mutagenic to histidine-requiring strains of Salmonella typhimurium. Extracts of fabrics treated with this compound are also capable of inducing mutations in these bacterial strains.