Antibiotic Resistance

Rudy Baum’s editorial “None Too Bright” was right on target regarding the problem of antibiotic resistance development in the intestinal microflora of farm animals fed with growth-promoting levels of antibiotics (C&EN, June 6, page 5).

In the late 1960s, I was principal investigator of a Department of Agriculture-funded pilot study on chlortetracycline resistance in enteric microorganisms in chickens and swine at Battelle Memorial Institute.

The results of this study clearly indicated statistically significant increases in the chlortetracycline-resistant bacteria in the enteric flora of those animals fed with this antibiotic over the numbers of resistant bacteria present initially and over those in separately housed control animals. Furthermore, chlortetracycline resistance was transferred from a resistant strain of Escherichia coli isolated from chickens to a sensitive strain of the intestinal pathogen Salmonella typhimurium in gnotobiotic (germ-free) mice.

These results were presented in a seminar at the USDA Beltsville Agricultural Research Center that was attended by both USDA and Food & Drug Administration scientific staff members who agreed that this was a start but further action was needed. A follow-up paper was presented at the 1970 annual meeting of the Society for Industrial Microbiology and was published in “Developments in Industrial Microbiology” (Washington, D.C.: American Institute of Biological Sciences, 1971, Vol. 12, 376–391).

Numerous studies since that time have shown the importance, from a public health standpoint, of the rise of antibiotic-resistant pathogenic bacteria in the environment. Why has nothing been done after more than 40 years? As Baum points out, although the European Union has banned such uses of antibiotics, FDA has waffled on taking any action, undoubtedly owing to the influence of politically powerful agribusiness interests. Do we have to await a public health crisis before taking action on this problem?

By John H. Litchfield
Worthington, Ohio