Two new bioassay techniques for nitrofurans: Bacteroides fragilis and rec-Escherichia coli as indicator strains

Techniques for the microbiological assay of nitrofurans are described. In one the indicator strain is Bacteroides fragilis; use of this system enables concentrations of nifuratel and furazolidone of down to 0.7 micrograms/ml to be estimated. The other system uses a recombination-deficient (recA-uvrA-) mutant of Escherichia coli; with this indicator, concentrations of 0.2 micrograms/ml, or less, of five nitrofurans can be assayed.