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Antibiotic activity in serum from a model for type II diabetes was similar to that in normal sera or media containing cholesterol but lacking glucose, insulin, or both. The ratio of effects of broth plus obese-rat serum to effects of broth plus lean-rat serum supplemented with cholesterol approached or equaled 1.The interactions of antibiotics with serum components, including serum proteins and cholesterol, have been demonstrated to be important determinants of their activity in serum. It has been well documented that the levels and types of proteins found in serum can profoundly affect antibiotic activity, especially that of penicillin and others of the 1-lactam class (1,2). Another serum component, cholesterol, which is commonly elevated in persons in Western society, can act as a competitive inhibitor for members of the polyene class of antibiotics, such as amphotericin B (6, 11). Obesity is often associated with changes in the levels of serum components. In obesity-associated type II diabetes, both serum insulin and glucose can be elevated. Altered levels of cholesterol, triglycerides, free fatty acids, and lipoproteins are also commonly associated with obesity and type II diabetes (3,10,13,14). The effect that these skewed levels of serum components have on antibiotic activity is not known.In this study, we

The addition to the diet daily of 10% (v/w) of a high level (28 × 109 cells) of a viable culture consisting of two strains of beta hemolytic enterococci sensitive to 10 and 30 μgm./ml. of chlortetracycline HCl respectively caused a highly significant reduction in growth of chicks. The reduction in growth was accompanied by an increase in numbers of enterococci in the ceca and a decrease in coliforms in the ileum and ceca as well as a decrease in lactobacilli in all segments of the intestine examined. The addition of 40 gm. of crystalline chlortetracycline HCl to the diet overcame the reduction in growth caused by the high level of dietary enterococci and resulted in a decrease in numbers of enterococci in the ileum and ceca.

Using selective media, an examination of 2400 hens' eggs was made to determine the incidence of Salmonella types in the egg or on the shell. The contents of 1000 eggs laids by a flock of presumably normal hens did not yield any representatives of the Salmonella group. Of a similar number of eggs produced by a flock of 55 known pullorum reactors, 61 were found to contain S. pullorum; no other Salmonella organisms were isolated. The exteriors of an additional 400 eggs obtained from the latter source failed to produce any Salmonella types.

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