| Summary: | Thesis (M.A.)--Boston University === Because of the importance in abdominal surgery of finding an antibiotic or combinations of antibiotics which will be effective in suppressing the fecal flora, many workers have studied each new agent from this standpoint. Loh (1), in doing counts of organisms in the feces of normal humans during the oral administration of aureomycin, found a decrease in coliform bacteria in many of his subjects. This decrease was often followed by a rise to or above pre-drug level. The question arose - were resistant organisms emerging? Four of his subjects were studied for sensitivity to aureomycin of the coliform organisms.
The minimum inhibitory concentration of aureomycin for Escherichia increased slightly from 0.78-3.12 ug/ml in two of the subjects but showed essentially no change remaining at a minimum inhibitory concentration of 3.12 ug/ml throughout the study of the other two subjects. The slight variation was hardly more than that noticed in the control culture. There appeared to be essentially no development of resistant organisms.
During the course of these studies, the coliform population in two of Loh's subjects changed from Escherichia before therapy to Klebsiella during or directly after treatment and back to Escherichia after the drug was stopped. In order to determine whether this might be a common change during aureomycin therapy, eight more persons were studied.
The cultures of the fecal specimens of five of the eight subjects did show a decrease in numbers of Escherichia organisms during the oral administration of aureomycin. This was accompanied by an increase in numbers of Klebsiella and/or paracolon organisms with a subsequent rise in Escherichia numbers. One subject had too few cultures studied for definite conclusions to be made but those that were obtained suggested a similar shift. The cultures of one subject showed the opposite shift, an increase in Escherichia with a decrease in Klebsiella and paracolons and a return of Escherichia to about the original level. The specimens of one subject differed from the rest in that they contained nothing but paracolon organisms before, during and after the oral administration of aureomycin.
The initial cultures taken before administration of aureomycin were of interest in that they varied so greatly. Escherichia predominated in most of these initial cultures and was the only kind of organism isolated from two. Usually Escherichia was accompanied by Klebsiella or paracolons or both and in three subjects Proteus also appeared.
Escherichia organisms had different biochemical reactions before and after therapy in four of the twelve subjects. This change was from non-mucoid to mucoid colonies in the cultures of two subjects, from non-motile to motile organisms in the cultures of one subject and from a citrate utilizing Escherichia to a mixture of the same citrate utilizing variety plus Escherichia with typical biochemical reactions.
This change in biochemical reactions suggested a possible antigenic change in the Escherichia organisms isolated before and after the administration of aureomycin. This possibility is being studied further.
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