Dairy cattle are routinely treated with antibiotics, and the resulting manure or composted manure is commonly used as a soil amendment for crop production, raising questions regarding the potential for antibiotic resistance to propagate from “farm to fork.” The objective of this study was to compare the microbiota and “resistomes” (i.e., carriage of antibiotic resistance genes [ARGs]) associated with lettuce leaf and radish taproot surfaces grown in different soils amended with dairy manure, compost, or chemical fertilizer only (control). Manure was collected from antibiotic-free dairy cattle (DC) or antibiotic-treated dairy cattle (DA), with a portion composted for parallel comparison. Amendments were applied to loamy sand or silty clay loam, and lettuce and radishes were cultivated to maturity in a greenhouse. Metagenomes were profiled via shotgun Illumina sequencing. Radishes carried a distinct ARG composition compared to that of lettuce, with greater relative abundance of total ARGs. Taxonomic species richness was also greater for radishes by 1.5-fold. The resistomes of lettuce grown with DC compost were distinct from those grown with DA compost, DC manure, or fertilizer only. Further, compost applied to loamy sand resulted in twofold-greater relative abundance of total ARGs on lettuce than when applied to silty clay loam. The resistomes of radishes grown with biological amendments were distinct from the corresponding fertilizer controls, but effects of composting or antibiotic use were not measureable. Cultivation in loamy sand resulted in higher species richness for both lettuce and radishes than when grown in silty clay loam by 2.2-fold and 1.2-fold, respectively, when amended with compost. IMPORTANCE A controlled, integrated, and replicated greenhouse study, along with comprehensive metagenomic analysis, revealed that multiple preharvest factors, including antibiotic use during manure collection, composting, biological soil amendment, and soil type, influence vegetable-borne resistomes. Here, radishes, a root vegetable, carried a greater load of ARGs and species richness than lettuce, a leafy vegetable. However, the lettuce resistome was more noticeably influenced by upstream antibiotic use and composting. Network analysis indicated that cooccurring ARGs and mobile genetic elements were almost exclusively associated with conditions receiving raw manure amendments, suggesting that composting could alleviate the mobility of manure-derived resistance traits. Effects of preharvest factors on associated microbiota and resistomes of vegetables eaten raw are worthy of further examination in terms of potential influence on human microbiomes and spread of antibiotic resistance. This research takes a step toward identifying on-farm management practices that can help mitigate the spread of agricultural sources of antibiotic resistance.

Enterococcus mundtii CUGF08, a lactic acid bacterium isolated from alfalfa sprouts, was found to produce mundticin L, a new class IIa bacteriocin that has a high level of inhibitory activity against the genus Listeria. The plasmid-associated operons containing genes for the mundticin L precursor, the ATP binding cassette (ABC) transporter, and immunity were cloned and sequenced. The fifth residue of the conservative consensus sequence YGNGX in the mature bacteriocin is leucine instead of valine in the sequences of the homologous molecules mundticin KS (ATO6) and enterocin CRL35. The primary structures of the ABC transporter and the immunity protein are homologous but unique.Bacteriocins are ribosomally synthesized proteinaceous compounds that inhibit closely related bacteria (19). Due to consumer concerns with chemical and irradiation preservation methods and due to the rising demand for minimally processed food products, alternative methods for shelf life extension and enhanced safety are needed. Bacteriocins are considered "natural" antimicrobials since many bacteriocins are produced by food grade lactic acid bacteria, which are generally recognized as safe. Bacteriocins can be divided into three main classes: the class I lanthionine-containing lantibiotics, exemplified by nisin; the class II non-lanthionine-containing bacteriocins; and the class III heat-labile, large proteins (6). Class III bacteriocins have limited application due to their thermal instability and cytolytic activity against eukaryotic cells. Class II can be further divided into class IIa containing pediocin-like bacteriocins, class IIb containing two-peptide bacteriocins, and class IIc containing other bacteriocins (8). Class IIa bacteriocins have been extensively studied since pediocin PA-1 was first discovered (12) and characterized (20). Currently, only nisin in class I has been approved by the FDA as a natural food additive. Bacteriocins belonging to class IIa are promising alternative antimicrobials since they are more stable over a broader range of heating regimens and pH conditions. In addition, these bacteriocins exhibit stronger antimicrobial activity against the genus Listeria than nisin (17) but have a narrower antimicrobial spectrum.The potential applications of class IIa bacteriocins in both meat and plant-based foods as a means to provide protection against potential food-borne pathogens and extend shelf life continue to expand. In an attempt to use biological methods for controlling food-borne pathogens on fresh sprouts, a number of food grade lactic acid bacteria were isolated from the indigenous microbiota on alfalfa sprouts. Some of these isolates were found to be bacteriocinogenic. This study describes a new class IIa bacteriocin, mundticin L produced by Enterococcus mundtii CUGF08 isolated from alfalfa sprouts.Bacteriology. The mundticin L producer E. mundtii CUGF08 was obtained from alfalfa sprouts. The genus and species were determined by BLAST homology analysis (http://blast.ncbi.nlm .nih.gov/blast.cgi) of the 16S rRNA...

Curation of antibiotic resistance gene (ARG) databases is labor intensive and requires expert knowledge to manually collect, correct, and/or annotate individual genes.Consequently, most existing ARG databases contain only a small number of ARGs (~5k genes) and updates to these databases tend to be infrequent, commonly requiring years for completion and often containing inconsistencies. Thus a new approach is needed to achieve a truly comprehensive ARG database while also maintaining a high level of accuracy. Here we propose a new web-based curation system, ARGminer, that 1 .

Cattle are commonly administered antibiotics, resulting in excretion of antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic resistance genes (ARGs). The aim of this study was to determine if the use of dairy manure collected during antibiotic administration influences the bacterial microbiota of lettuce and radishes, including carriage of ARB and ARGs, when applied as a soil amendment and if composting mitigates the effects. Lettuce and radishes were grown in field-plots amended with raw manure from antibiotic-treated (cephapirin, pirlimycin) cows, composted manure from antibiotic-treated cows, composted manure from antibiotic-free cows, or an inorganic chemical fertilizer (control; 12 plots, n = 3). Surficial vegetable bacteria and antibiotic resistomes (i.e., total ARGs) were characterized using heterotrophic plate counts (HPCs) on antibiotic-containing media, 16S rRNA gene amplicon sequencing, quantitative polymerase chain reaction (qPCR), and shotgun metagenomics. The different manure and compost amendments did not result in significant changes to the surficial vegetable bacteria at the phylum level; however, some minor changes at the class and family level were observed. Beta-diversities of the ARGs detected by shotgun metagenomic sequencing were distinctly different between vegetable type (R = 0.30, p = 0.04), with small separations between the resistomes associated with amendment type in unrarefied analysis (R = 0.27, p = 0.02), but not rarefied analysis, of the data. Network analysis highlighted that multi-drug ARG classes commonly co-occurred with plasmid-associated genes and could be a driver of co-and cross-selection of ARGs in the different conditions. Carriage of sul1 and tet(W) ARGs on vegetables quantified by qPCR were strong indicators of manure-based amendment relative to chemical fertilizer, with some reduction incurred via composting (p < 0.05). Also, increased HPCs resistant/tolerant to clindamycin, a class of antibiotics administered to cattle, were on lettuce grown in biological soil amendments relative to chemical fertilizer (p < 0.05). This study demonstrates that amending soil with raw manure collected from dairy cows during Fogler et al. Biological Amendment Affects Vegetable Resistome antibiotic administration may affect the composition of microbiota and resistomes associated with vegetable surfaces. Composting may be an important strategy to reduce some ARGs on fresh produce, but differences in the resistomes of lettuce and radishes suggest the extent of soil contact should be considered.

There is interest in understanding effects of amending soil with manure in a cultivation setting and if composting can provide benefits. Raw or composted manure from cattle administered with and without sulfamethazine, chlortetracycline, and tylosin was amended to loamy sand and silty clay loam soils, where lettuce (Lactuca sativa L.), radish (Raphanus sativus L.), and broccoli (Brassica oleracea L. var. italica) were cultivated and compared with those grown in soil amended with fertilizer as a control. Upon plant maturation, rhizosphere and bulk soils were analyzed for antibiotics, and sul1, ermB, tet(W), and intI1 genes were quantified. Antibiotic concentrations in compost‐amended soils were below detection limits. For soils amended with manure containing antibiotics, sulfamethazine ranged from 1.1 to 3.1 μg kg−1 in the bulk soils but was below detection limits in the rhizosphere soils. Chlortetracycline (2.8–9.3 μg kg−1) was two times lower in the rhizosphere than in the bulk soil. Levels of tylosin in the rhizosphere soil were similar to the bulk soil. Soil texture or vegetable type did not have significant influence on antibiotic concentration differences between the bulk and rhizosphere soils. Relative abundances of tet(W) and intI1 in the fertilizer‐amended soil were significantly lower than in those amended with manure or compost (p < 0.05), whereas ermB was not detected in any soils. Rhizosphere zone has no significant effect on the detected antibiotic resistance genes. It is suggested that plant roots may have a substantial effect on the fate of certain antibiotics in manure‐amended fields, but less of an effect on antibiotic resistance and mobility genes. Core Ideas Composting reduces antibiotic inputs to soils relative to direct manure application. Antibiotic concentrations in manure generally decrease in amended soils. Dissipation of sulfamethazine and chlortetracycline is enhanced in the rhizosphere. Antibiotic fate in bulk and rhizosphere soils was similar for three vegetables and two soils. Resistance and mobility genes were greater in manure ‐ than fertilizer‐amended soil.