No abstract

The effect of hibernation on the caecal flora of the thirteen-lined ground squirrel (Citellua tridecemlineatua) was determined by comparing the flora of 7 active squirrels with that of 6 x 6 days hibernators and 2 x 42 days hibernators. Direct microscopical examination showed the presence of a wide variety of micro-organisms, including protozoa in all the animals. Using strict anaerobic techniques it was possible to isolate >BOX of the total flora of the active squirrels but only c. 30% in the hibernators.Several distinct types of anaerobic Gram negative, nonsporing rods predominated in both the active and hibernating animals. Gram positive, nonsporing rods and coccobacilli were present in the active squirrels but were not isolated from the 42 days hibernators. Atypical lactobacilli present a t 10e-108/g formed the major part of the aerobic flora of the active squirrels but were rediiood a t least 100-fold during hibernation.

Summary. Human volunteers were given orally 0, 50 or 1000 mg of tetracycline/day for the 4 days preceding and the 5 days following ingestion of 1–2 x 106 cells of tetracycline resistant Escherichia coli strain x‐314 of bovine origin. Of those receiving 0, 50 or 1000 mg of tetracycline/day, 9/13, 5/9 and 12/13, respectively, excreted the organism at least once during the 25‐day sampling period. Significant differences were not observed between subjects receiving 0 or 50 mg of tetracycline/day with respect to the length of time the coliform was recovered from faeces, or the maximum proportion of the total coliforms found to be E. coli x‐314. Those receiving 1000 mg of tetracycline/day shed E. coli x‐314 for longer periods and the latter's contribution to the coliform population was greater than in those subjects receiving 0 or 50 mg of tetracycline/day. It was concluded that 1000, but not 50 mg, of tetracycline/day taken orally potentiates the establishment of a tetracycline resistant E. coli in the enteric tract of man.

Serial samples of feces from normal human subjects were analyzed for tetracycline-resistant strains of Escherichia coli. Subjects were found to be excreting tetracycline-resistant strains in amounts fluctuating with time. Ingestion of tetracycline increased both the number of individuals excreting tetracycline-resistant strains of E. coli and the proportion of the total E. coli isolates resistant to the antibiotic.Studies show that tetracycline taken orally will increase the number of tetracycline-resistant bacteria excreted from the intestinal tract of humans (2-4). Little is known, however, concerning the change with time in the number of tetracycline-resistant bacteria in the same individual after oral ingestion of a therapeutic regimen of tetracycline. Therefore, it was the purpose of this study to determine the changes that occur in the proportion of tetracyclineresistant Escherichia coli cells excreted by normal human volunteers after a therapeutic regimen of tetracycline.Beginning 5 weeks prior to administration of tetracycline, fecal samples from 11 normal human subjects were analyzed for tetracyclineresistant strains of E. coli. Serial dilutions of the samples were plated on MacConkey agar and MacConkey agar containing 25 ug of tetracycline/ml. The subjects, who professed having no known immediate contact with an antimicrobial agent, ranged in age from 21 to 25 years. Tetracycline was administered at an oral dose of 1,000 mg per day (250 mg four times a day) for 9 days. Fecal samples were analyzed for tetracycline-resistant E. coli cells 4, 9, 16, 23, and 37 days after the subjects commenced ingesting the antibiotic.The results of the analysis of the fecal samples prior to tetracycline are shown in Table 1. Over the 5-week period, between 0 and 45% of the subjects at any one time were found to be excreting tetracycline-resistant strains of E. coli. Of those individuals shedding tetracyclineresistant strains of E. coli, 0.001 to 100% of the total number of E. coli cells shed in the feces were found to be tetracycline-resistant.All of the subjects shown to be shedding tetracycline-resistant E. coli cells prior to ingestion of the antibiotic, except one (no. 5), were shedding resistant E. coli cells during the time tetracycline was being ingested. Subject 3 cannot be evaluated during this interval because no samples were submitted. Of the four subjects not excreting tetracycline-resistant E. coli cells prior to tetracycline ingestion, only two were found to be shedding resistant E. coli cells during this time. During the 9 days of tetracycline administration, the proportion of the total E. coli cells found to be resistant increased in the feces of those subjects excreting tetracycline-resistant E. coli cells compared to that found the week prior to ingestion of the antibiotic.In the 2 weeks after cessation of the antibiotic, the ratio of tetracycline-resistant to total E. coli cells decreased in most subjects. Exceptions were no. 5 and 14, who did not excrete tetracycline-resistant E. coli cells during adm...