Human Therapeutic and Agricultural Uses of Antibacterial Drugs and Resistance of the Enteric Flora of Humans

Abstract

Fecal samples were collected from five groups of people differing in the manner of their exposure to antibacterial drugs. The groups included: (i) people working on farms who were continuously in contact with the predominantly resistant florae of farm animals receiving rations containing antibacterial drugs, (ii) people residing on the same farms with no direct exposure to the farm animals, (iii) people treated with antibacterial drugs, (iv) untreated people residing with treated individuals, and (v) untreated people with no exposure to farm animals or treated individuals. The samples were examined by quantitative plating for proportions of antibiotic-resistant, gram-negative enteric organisms. Individual isolates were also examined for their susceptibility to 11 different antibacterial drugs. The results indicate that enteric florae unexposed directly to the selective effects of antibacterial drugs may be affected by contact with predominantly resistant florae directly exposed to antibacterial drugs.Antibacterial drugs are widely used for production purposes on livestock and poultry farms. This practice has been questioned because it might create conditions detrimental to animal and human health. It has been established that the enteric florae of farm animals are largely composed of drug-resistant organisms as a result of the continuous exposure to antibacterial agents (5, 7-10). Due to the transmissible nature of drug resistance in gramnegative enteric organisms, it has been postulated that the resident animal flora may comprise a reservoir of resistance for animal and human pathogens.A central question to an objective assessment of the possible danger to public health posed by the agricultural use of antibacterial drugs is whether or not organisms and/or R factors originating on the farm can become established in the florae of human beings who have consumed food of animal origin. An investigation relating to this question was conducted to determine whether or not enteric florae continuously exposed to antibacterial drugs and composed largely of antibiotic-resistant organisms influenced epidemiologically associated enteric florae unexposed to antibacterial drugs. A previous paper reported the high proportions of antibiotic-resistant, gram-negative enteric organisms in fecal samples from Illinois farm animals given feeds containing antibacterial drugs (7). This paper reports the proportions of resist- ' (BBL) was used for all broth cultures. Nutrient agar (Difco) slants were used for isolate storage.Antibiotics. The following concentrations of antibacterial drugs in MacConkey agar were used: nalidixic acid, 40 ,ug/ml; oxytetracycline, 20 tg/ml; dihydrostreptomycin, 25 ug/ml; and ampicillin, 50 jug/ml. Concentrations of oxytetracycline, dihydrostreptomycin, and ampicillin were selected to provide the best possible correlations between KirbyBauer disk susceptibility tests and growth on agar.Fecal samples. Ten-to 20-g fecal samples were collected into 40-ml -quantities of sterile, pH 7.2, buffered-glycerol-s...

Direct transmission of Escherichia coli from poultry to humans

“…Transmission of E. coli from poultry to man 521 intestinal tract of poultry (5,8,12,14,27,30). Where the resistance factor contains genes for resistance to more than one antibiotic, the use of a single agent will select for multiple resistance (31) and this may complicate the therapy of veterinary as well as human infections.…”

“…Such non-therapeutic uses have been of major concern to those engaged in the treatment of infectious diseases, especially as a correlation has been found between the widespread use of antimicrobial drugs and the emergence of drug resistance (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18). Thus, resistance patterns of animal E. coli isolates have been found to be similar to those found among the isolates from humans who were closely associated with the animals (7,14,(17)(18)(19)(20).…”

The Effect of Tetracycline upon the Spread of Bacterial Resistance from Calves to Man1

“…Whether this was due to the relatively short period of time the human subjects were in contact with tetracycline and/ or the calves, or the highly restrictive measures taken by the human subjects to preclude transfer of microorganisms out of the isolation unit (e.g., changing clothes), is not known. Epidemiologic studies have shown that contact with animals on antimicrobials is reflected to a high degree in the resistance of the enteric flora (Linton et al, 1972;Wells and James, 1973;Siegel et al, 1975). Human subjects in these studies had long term contact with the animals.…”

“…Numerous attempts have been made to draw a relationship between the R factor gene pool in animals, antimicrobic pressures exerted on the pool, and the occurrence of resistance genes in the enteric microorganisms in the enteric tract of man. Most of the investigations have been indirect and epidemiological in scope (Linton et al, 1972;Wells and James, 1973;Fein et al, 1974;Dorn et al, 1975;Siegel et al, 1975). All these studies have shown that a direct correlation exists between animal contact, antimicrobic usage, and the occurrence of multiply-resistant flora in the enteric tracts of the human contacts.…”

Role of Plasmids in the Antibiotic Resistance of Bacteria in Asir Province

“…We describe the results of a study that was designed to: (1) show the magnitude of antibiotic resistance in selected bacteria isolated from patients admitted to a hospital in the Asir region of Saudi Arabia; (2) screen these strains for plas-mid-borne antibiotic resistance; and (3) test the feasibility of using the plasmid profile analysis to show strain relationships and demonstrate the potential of the technique in tracing cross infections.…”