The Effects of Feeding Tetracycline, Nitrovin and Quindoxin on the Drug‐Resistance of Coli‐aerogenes Bacteria from Calves and Pigs

Abstract

A study of calves and pigs was made to compare the effects on intestinal coli‐aerogenes bacteria of feeding diets medicated with tetracycline, nitrovin or quindoxin. Results showed that even before the introduction of medicated diets, drug‐resistant coli‐aerogenes bacteria were present in surprisingly high numbers. However, it was clear with both animal species that only tetracycline had a selective effect. With calves a resistance to furazolidone was frequently present in tetracycline‐resistant organisms. Analysis of the resistance patterns supported the contention that the dominant coli‐aerogenes bacteria in the gut flora following use of certain growth‐promoters, resulted from suppression of fully sensitive organisms: the distribution of the various resistance patterns was independent of the agent used and whether or not the diet was medicated. There was no significant difference in the trans‐missibility of resistance genes between calves and pigs receiving either tetracycline or quindoxin or neither treatment. Results obtained with nitrovin were thought to be similar but, inexplicably, the control animals all gave low values.