Abstract:In this study, two strains with sulfonamide-sensitive strains H1 and H2 were screened by UV mutagenesis. After DNA identification, the two strains were of the genus Bacillus, a species of Geobacillus stearothermophilus. Using H1 and H2 as the indicator bacteria, the total amount of sulfonamide residues in milk was detected, and the obtained results showed that these two strains exhibited different sensitivities to different kinds of sulfa drugs. When the total colony ratio of spore suspension for H1 and H2 was 3:4, the test kit had good sensitivity: sulfonamide, 30 μg/L; sulfadiazine, 30 μg/L; sulfamethazine, 30 μg/L; sulfamethazine, 30 μg/L; sulfonamide, 60 μg/L; sulfathiazole, 45 μg/L; sulfachloropyridazine, 80 μg/L; sulfamethoxazole, 75 μg/L; sulfazone, 75 μg/L. Under these conditions, the two strains were simultaneously passaged, and the effect of strain passage on the sensitivity of the test kit was investigated. The results showed that the test kit lost sensitivities to sulfonamide and sulfaguanidine when the fourth generation bacteria was used as the indicator. The sensitivity to sulfachloropurazine or sulfamethoxazole also lost when the sixth generation was used. Whereas, the sensitivity to sulfonamides, sulfadiazine, sulfamethazine or sulfathiazole remained constant till the seventh generation. Compared with domestic and overseas commercial kits, this kit had a higher sensitivity than the domestic kits, and showed advantage in detection time over the overeas kits.
