Compost That Manure! & Maybe Feeding Food Animals Antibiotics is Ok After All…

I apologize for missing a couple of posts. Conferences just get busier when you go from grad student to new professor trying to meet everyone and identify potential future students as well as catch up with old friends.

Maybe using antibiotics in agriculture is ok after all… (Tuesday)

One proposed source of antibiotic-resistant bacteria has been livestock farming. Conventional (non-organic) farmers are allowed to dose their animals (dairy and beef cattle, pigs, chickens, etc) with small amounts of antibiotics as a preventative measure, so they’re less likely to fall ill. These aren’t the same antibiotics used in humans, but they usually work by the same general method. They also sometimes use the same antibiotics we use in humans on sick animals. So one hypothesis was that a bacterium which developed resistance to these antibiotics might also be less susceptible to the human forms. Another potential problem is that antibiotic resistance genes (think computer programs/apps) are often picked up in clusters by bacteria. So a bacterium which is resistant to an animal antibiotic could be more likely to also have a resistance gene against a human antibiotic. Consequently, a link between constant on-farm usage of antibiotics and antibiotic resistance in the bacteria which infect humans seemed plausible.

However, the panelists disagreed with these assumptions, arguing that any evidence which could tie on-farm use of antibiotics to antibiotics not working in sick humans was thin at best.

So we can stop worrying about use and overuse of antibiotics in farm animals?

Not really. The panelists agreed that moving away from using any antibiotics which might be important for human health either to prevent or cure illness in farm animals was a good and important step (it’s in progress). They also were careful to note that further research was needed to be sure that farm use of antibiotics wasn’t contributing to antibiotic treatment failures in humans. Nonetheless, they added a wrinkle to the antibiotic resistance debate.

Keep composting (Wednesday)

A talk on Wednesday looked at whether using animal manure as a fertilizer increased the amount of antibiotic resistance genes in the soil. What they found was that using raw animal manure as fertilizer did increase the presence of antibiotic resistance genes to the soil (which could be picked up by any bacteria in the soil). However, properly composted manure didn’t as much, probably because the heat involved in composting killed most bacteria and disintegrated their DNA. So composting manure was a good way to prevent the spread of antibiotic resistance genes from animals to soil.

Takeaway: if you use animal manure as fertilizer in your garden, keep composting

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