Commercially available garden products as important sources of antibiotic resistance genes—a survey

Abstract

The dissemination of antibiotic resistance genes (ARGs) in the environment contributes to the global rise in antibiotic resistant infections. Therefore, it is of importance to further research the exposure pathways of these emerging contaminants to humans. This study explores commercially available garden products containing animal manure as a source of ARGs in a survey of 34 garden products, 3 recently landscaped soils, and 5 native soils. DNA was extracted from these soils and quantified for 5 ARGs, intI1, and 16S rRNA. This study found that both absolute and relative gene abundances in garden products ranged from approximately two to greater than four orders of magnitude higher than those observed in native soils. Garden products with Organic Materials Review Institute (OMRI) certification did not have significantly different ARG abundances. Results here indicate that garden products are important sources of ARGs to gardens, lawns, and parks. Graphical abstract

Influence of soil characteristics and metal(loid)s on antibiotic resistance genes in green stormwater infrastructure in Southern California

“…These comparisons indicate (Fig. 7): (1) relative gene abundances of sul1 and intI1 in GSI soils are higher in GSI soils compared to native soils collected from the Santa Monica Mountains near Los Angeles (Cira et al, 2021); (2) relative gene abundances of sul1 are lower in GSI soils compared to biosolids (Hung, 2020), commercially available manure fertilizers (Cira et al, 2021), and Los Angeles park soils (Echeverria--Palencia et al, 2017); and (3) relative gene abundances of intI1 in GSI soil also exhibit a similar pattern to relative gene abundances of sul1 (excluding San Diego park soils for which intI1 gene abundance measurements were not available) (Fig. 7).…”

“…DNA extracts were analyzed in triplicate for ARGs (sul1, sul2, tetA, tetW, and ermF), intI1 genes, and 16S rRNA genes (a proxy for total cells). These ARGs were chosen as representatives of resistance mechanisms to sulfonamides, tetracycline, and macrolides, respectively, due to the frequent occurrence in garden products (Cira et al, 2021). Each qPCR reaction was conducted in 96-well reaction plates using StepOne Plus qPCR system (Applied Biosystems, Foster City, CA, USA) with a final reaction volume of 25 μL, containing 1.25 μL of each primer, 12.5 μL of PowerUp SYBR Green Master Mix (Applied Biosystems, Foster City, CA, USA), 2 μL of soil DNA extracts (approximately 5-100 ng DNA), and 10 μL of molecular-grade water (Thermo Fisher Scientific, Waltham, MA, USA).…”

“…ARGs were frequently detected in GSI soil samples analyzed here. To place these results in context, we compared the relative sul1 and intI1 gene abundances measured in GSI soil samples to soils previously measured in wastewater treatment plant biosolids (Hung, 2020), Los Angeles park soils (Echeverria-Palencia et al, 2017), commercially available manure fertilizers, and native soils from nearby hiking trails (Cira et al, 2021) (Fig. 7).…”

“…GSI management may play a critical role in soil ARG abundances. Soil amendments and reclaimed water, both of which are reservoirs for ARGs (Cira et al, 2021;Fahrenfeld et al, 2013;Mao et al, 2014), are frequently used for fertilizing and irrigating GSI (Rottle, 2018(Rottle, , 2013. In the present study, MZ, SM, CUL, and SAN were irrigated with reclaimed water while VER and ACT were irrigated with potable water (Table 1).…”