Scientists monitored antibiotic residues in manure from three different pig farms. They found plenty, but not at exceptionally high levels.
Tiedje then tested those manure samples, looking for genes that make bacteria resistant to particular antibiotics. That’s when he hit the jackpot: He found more than 100 different resistance genes. The concentration of resistance genes was almost 200 times higher in these samples, compared to manure from a pig farm that had never used antibiotics.
Interestingly, composting appears to reduce the microbe population:
The study indicates that treating the manure after it leaves the farm can significantly reduce the potential for this manure to spread antibiotic resistance to other bacteria in the surrounding environment. Composting it, for instance, cuts the total population of microbes in manure – which means fewer microbes carrying antibiotic resistance genes.
I wonder if the study shows that the resistant microbes are reduced at the same rate as the susceptible, or if compost reduces them at a different rate. Haven’t read the original study yet. Have you? Let’s discuss!