Source+6

[|http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0020232#pmed-0020232-b1](antibiotic uses, overuse, where antibiotics and resistant bacteri are located, pathogens, new type of resistance)
 * Smith DL, Dushoff J, Morris JG Jr. //Agricultural Antibiotics and Human Health//. PloS Magazine. July 2005.
 * "Evidence suggests that antibiotic use in agriculture has contributed to antibiotic resistance in the pathogenic bacteria of humans, but the chain from cause to effect is long and complicated." (paragraph 1)
 * "Antibiotic use clearly selects for antibiotic resistance, but how far do these effects extend beyond the population where antibiotics are used? Antibiotics and antibiotic-resistant bacteria (ARB) are found in the air and soil around farms, in surface and ground water, in wild animal populations, and on retail meat and poultry [[|2�9]]." (paragraph 2)
 * "ARB are carried into the kitchen on contaminated meat and poultry, where other foods are cross-contaminated because of common unsafe handling practices [[|10],[|11]]. Following ingestion, bacteria occasionally survive the formidable but imperfect gastric barrier, and colonize the gut [[|12]]." (paragraph 2)
 * "To emerge as human pathogens, new strains of ARB must (1) evolve, originating from mutations or gene transfer; (2) spread, usually horizontally among humans or animals, but occasionally heterospecifically; and (3) cause disease." (paragraph 4)
 * The emergence of a new type of resistance is a highly random event, which can't be predicted accurately, and may involve multiple steps that preclude perfect understanding even after the fact. Spread is equally complicated and may obscure the origins of resistance. (paragraph 5)
 * "The rate of horizontal transmission among humans is determined by the underlying biology of the pathogen, medical antibiotic use, and hospital infection control, but not by agricultural antibiotic use" (paragraph 6)
 * "On the other hand, a farm where multiple antibiotics are used routinely, universally, and in low quantities for growth promotion is likely to be an excellent environment for the evolution of multiple resistance factors, including some variants that might never have evolved in humans." (paragraph 6)
 * "Thus, even very rare transmission resulting from agricultural antibiotics may have a medical impact by introducing new resistant variants to the human population. The epidemiology of spread in the human population dictates how the impact of agricultural antibiotic use should be assessed." (paragraph 6)
 * "Zoonotic pathogens, such as Campylobacter and Salmonella, are generally regarded as having low horizontal transmission rates in human populations" (paragraph 7)
 * "While resistance in zoonotic infections should be directly attributable to resistance in the zoonotic reservoir, the impact of agricultural antibiotic use remains controversial [[|18],[|27–29]]." (paragraph 7)
 * "Zoonotic species could acquire resistance genes from human commensal bacteria during the infection process, but this hypothesis is difficult to test." (paragraph 7)
 * "For pathogens with high horizontal transmission rates, resistant bacteria will spread rapidly once they have emerged, and prevalence will be maintained at a steady state by horizontal transmission." (paragraph 8)
 * "Thus, the impact of subsequent heterospecific transmission is limited ([|Figure 1])." (paragraph 8)
 * "Nevertheless, one or two heterospecific transmission events could be sufficient to cause the appearance of a highly successful ARB genotype in humans, affecting the timing, nature, and extent of spread within the human population [[|22]]." (paragraph 8)