Comparisons on chemically-induced mutation among four bacterial strains, Salmonella typhimurium TA102 and TA2638, and Escherichia coli WP2/pKM101 and WP2 uvrA/pKM101: collaborative study II.

A collaborative study of chemically-induced mutation was performed using the four bacterial strains Salmonella typhimurium TA102 and TA2638, and Escherichia coli WP2/pKM101 and WP2 uvrA/pKM101, used in the previous successive studies in order to compare the specific spectrum of response to chemicals among the four strains and to determine the usefulness (sensitivity) of each strain. Twenty-two laboratories participated in this study. Following the previous study, 28 compounds were selected consisting of oxidative agents or crosslinking agents. These compounds were tested for mutagenicity using the plate incorporation method with or without metabolic activation. The tests were performed in two laboratories per chemical. The number of chemicals which showed positive results were 18, 17, 16 and 14 with WP2 uvrA/pKM101, TA2638, TA102 and WP2/pKM101, respectively. In all four strains 19/28 chemicals (68%) were either positive or negative while the remaining 9 chemicals showed a heterogeneous response. With TA102 and TA2638 89% (25/28) of the test chemicals showed the same response, while 75-79% (21-22/28) showed the same response in these two S. typhimurium strains and in WP2 uvrA/pKM101. In conclusion, WP2/pKM101 strain showed the least sensitivity to the chemicals used. Among the other three strains, WP2 uvrA/pKM101 was the most sensitive strain, although the difference in the number of chemicals which showed positive results was minor. Concerning the spectrum of response to chemicals, it is apparent that TA102 and TA2638 have almost the same sensitivity, but some chemicals induce different responses between the two S. typhimurium strains and WP2 uvrA/pKM101.