Antibiotic Resistance Genes in the Guts of Vegetarians vs. Meat-Eaters

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There are nearly a million salmonella and campylobacter infections in children 10 and younger each year in the United States. Some of these infections are severe, causing meningitis and death, and requiring treatment with antibiotics. The problem is that there’s an increasing problem of antibiotic resistance among these bugs that threatens our ability to treat them. Part of the problem is that the same lifesaving miracle drug antibiotics are being squandered for use in food animals for things like growth promotion in such unhygienic, crowded conditions, which increases the likelihood that pathogens like salmonella or campylobacter will become resistant––and I’ve done a bunch of videos on that.

There’s another problem. The resistance determinants, the genes that encode antibiotic resistance, may be transmitted from food animals to humans through the food supply. See, most resistant bacteria have mobile genetic elements, like these little circles of DNA called plasmids, that carry the resistance genes that they can pass on to other bacteria, including those in our own gut.

Food animals are, therefore, a reservoir of antibiotic resistance genes, and a potential vector for transmission of antibiotic resistance genes to the human intestinal microbiota. In this study, transfer of an antibiotic resistance plasmid from an E. coli originating from a chicken raised for meat to human gut bugs was assessed by using a model that mimics the human intestines. And, it happened within two hours. This spread of antibiotic resistance genes presents an alarming scenario, a growing concern that antibiotic-resistant bacteria present on food can transfer their resistance genes to the inherent gut microbiota of the consumer. But you don’t know, until you put it to the test. Assessing antibiotic resistance gene loads in vegan vs. vegetarian vs. omnivore gut bacteria.

You’d think the results might be obvious, but antibiotic resistance genes are spread due to manure application on agricultural fields of fruits and vegetables. Yes, massive antibiotic use in animal farming is considered as the greatest contributor to the presence of antibiotic-resistant bacteria (ARB) in food of animal origin: meats, eggs, and dairy. Nevertheless, sewage from treated animals may impact on vegetables grown on fertilized fields, but it was largely unknown whether, and to what extent, antibiotic-resistant bacteria are being transferred to vegetables, and then to the human gut, until now. Researchers looked for antibiotic-resistant genes (ARGs) against sulfa drugs like bactrim, tetracyclines, penicillins and cephalosporins, and streptomycin-type antibiotics. And…both omnivores and vegetarians showed a significantly higher antibiotic-resistant gene load in their guts as compared with vegans.

There wasn’t a significant difference between omnivores and vegetarians, but significantly lower loads in vegans compared to omnivores, and vegans compared to vegetarians––the first evidence that a vegan lifestyle is associated with a reduced load of human gut antibiotic-resistant genes, but not the last. Fewer tetracycline resistance genes in vegan guts and more vancomycin resistance genes in the guts of those who eat meat. No surprise, since they found a correlation between tetracycline resistance genes and the intake of eggs, milk, and cheese (I like how there are so many types of milk these days they have to specify “milk from animal source”), and a higher incidence of vancomycin resistance genes was found in consumers of eggs, poultry, fish, and seafood. And vancomycin is one of our antibiotics of last resort, used to treat serious life-threatening strep and staph infections like MRSA.

Despite the links to dairy and eggs, just cutting out meat has indeed been shown to offer an advantage in some studies, as bacteria obtained from meat-eater poop samples showed resistance to a greater number of antibiotics, and carried more tested antibiotic resistance genes compared to the vegan or vegetarian poop.

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• Angulo FJ, Baker NL, Olsen SJ, Anderson A, Barrett TJ. Antimicrobial use in agriculture: controlling the transfer of antimicrobial resistance to humans. Semin Pediatr Infect Dis. 2004;15(2):78-85.
• Lambrecht E, Van Coillie E, Van Meervenne E, Boon N, Heyndrickx M, Van de Wiele T. Commensal E. coli rapidly transfer antibiotic resistance genes to human intestinal microbiota in the Mucosal Simulator of the Human Intestinal Microbial Ecosystem (M-SHIME). Int J Food Microbiol. 2019;311:108357.
• Losasso C, Di Cesare A, Mastrorilli E, et al. Assessing antimicrobial resistance gene load in vegan, vegetarian and omnivore human gut microbiota. Int J Antimicrob Agents. 2018;52(5):702-5.
• Heuer H, Schmitt H, Smalla K. Antibiotic resistance gene spread due to manure application on agricultural fields. Curr Opin Microbiol. 2011;14(3):236-43.
• Milanović V, Osimani A, Aquilanti L, et al. Occurrence of antibiotic resistance genes in the fecal DNA of healthy omnivores, ovo-lacto vegetarians and vegans. Mol Nutr Food Res. 2017;61(9).
• Milanović V, Osimani A, Cardinali F, et al. Erythromycin-resistant lactic acid bacteria in the healthy gut of vegans, ovo-lacto vegetarians and omnivores. PLoS One. 2019;14(8):e0220549.

Motion graphics by Avo Media

• antibiotics
• Campylobacter
• children
• dairy
• eggs
• factory farming practices
• fish
• fruit
• gut flora
• meat
• microbiome
• Plant-Based Diets
• poultry
• Salmonella
• seafood
• vegans
• vegetables
• vegetarians