Chromogenic enzyme substrates based on [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives for the detection of nitroreductase activity in clinically important microorganisms.

A series of [2-(nitroaryl)ethenyl]pyridinium and quinolinium derivatives have been synthesised as potential indicators of microbial nitroreductase activity. When assessed against a selection of 20 clinically important pathogenic microorganisms, microbial colonies of various colours (yellow, green, red, brown, black) were produced and attributed to nitroreductase activity. Most substrates elicited colour responses with Gram-negative microorganisms. In contrast, the growth of several species of Gram-positive microorganisms and yeasts was often inhibited by the substrates and hence coloured responses were not seen.

2-Arylbenzothiazole, benzoxazole and benzimidazole derivatives as fluorogenic substrates for the detection of nitroreductase and aminopeptidase activity in clinically important bacteria.

A series of 2-(2-nitrophenyl)benzothiazole 7, 2-(2-nitrophenyl)benzoxazole 10 and 2-(2-nitrophenyl)benzimidazole 13 derivatives have been synthesised and assessed as indicators of nitroreductase activity across a range of clinically important Gram negative and Gram positive bacteria. The majority of Gram negative bacteria produced strongly fluorescent colonies with substrates 7 and 10 whereas fluorescence production in Gram positive bacteria was less widespread. The l-alanine 16 and 19 and ß-alanine 21 and 23 derivatives have been prepared from 2-(2-aminophenyl)benzothiazole 14 and 2-(2-aminophenyl)benzoxazole 17. These four compounds have been evaluated as indicators of aminopeptidase activity. The growth of Gram positive bacteria was generally inhibited by these substrates but fluorescent colonies were produced with the majority of Gram negative bacteria tested.