Effect of Nitrofurans and Chlortetracycline on Microorganisms Associated with Shrimp

Abstract

Nitrofuran AF-2 displayed greater inhibitory effect than did nitrofuran Z when a mixed bacterial culture, including several proteolytic bacteria, isolated from shrimp was subjected to these compounds in vitro. Nitrofuran Z exhibited greater bactericidal properties than did chlortetracycline in all cultures used. Only 10 μg of nitrofuran AF-2 per ml was sufficient to inhibit the growth of mixed bacteria in nutrient broth, whereas 50 μg of nitrofuran Z per ml was necessary to accomplish the same inhibition. A 50-μg amount of chlortetracycline per ml displayed about the same inhibitory effect as either 10 μg of AF-2 per ml or 20 μg of Z per ml. The isolated proteolytic bacteria showed greater suppression of growth when subjected to AF-2 than when subjected to Z; however, both nitrofurans were effective in preventing growth. The addition of either 1 μg of AF-2 per ml or 5 μg of Z per ml to nutrient broth inhibited the growth of Achromobacter aquarmarinus, whereas chlortetracycline was less effective, requiring about 20 μg to suppress growth to the same degree.