UCLA

The rising level of antibiotic resistance worldwide is a critical public health challenge. Antibiotic resistance genes (ARGs) and mobile genetic elements allow for bacteria to confer resistance to antibiotics in as little as a year. Antibiotics utilized for growth promotion in confined animal feeding operations (CAFOs) generates manure that is an anthropogenic source of ARGs into the environment. In this study, 10 potting soils, 7 garden soils, 4 food amendments, 4 lawn amendments, 6 manure-based soils, 5 natural soils, 3 community soils, and 3 compost soils were surveyed for antibiotic resistance gene ermF, mobile genetic element intI1, and proxy for bacterial content 16S rRNA. The ARGs were quantified through quantitative polymerase chain reaction (qPCR) to per gram of fertilizer and per gene copies of 16S rRNA. Most soils contained detectable levels of ermF and intI1, ranging from 9.66 x 10-7 to 8.31 x 10-2 gene copies ermF/copies of 16S rRNA and 8.92 x 10-7 to 6.21 x 10-2 gene copies intI1/copies of 16S rRNA. Natural soils were significantly lower in ermF and intI1 than the other soil types. Natural soils ranged from 10-7 to 10-5 gene copies per copies of 16S rRNA while the other types ranged from 10-7 to 10-2 gene copies per copies of 16S rRNA. There was no strong correlation between intI1 and ermF.