Quantifying Attachment and Antibiotic Resistance of Escherichia coli from Conventional and Organic Swine Manure

Abstract

Broad-spectrum antibiotics are often administered to swine, contributing to the occurrence of antibiotic-resistant bacteria in their manure. During land application, the bacteria in swine manure preferentially attach to particles in the soil, affecting their transport in overland flow. However, a quantitative understanding of these attachment mechanisms is lacking, and their relationship to antibiotic resistance is unknown. The objective of this study is to examine the relationships between antibiotic resistance and attachment to very fine silica sand in collected from swine manure. A total of 556 isolates were collected from six farms, two organic and four conventional (antibiotics fed prophylactically). Antibiotic resistance was quantified using 13 antibiotics at three minimum inhibitory concentrations: resistant, intermediate, and susceptible. Of the 556 isolates used in the antibiotic resistance assays, 491 were subjected to an attachment assay. Results show that isolates from conventional systems were significantly more resistant to amoxicillin, ampicillin, chlortetracycline, erythromycin, kanamycin, neomycin, streptomycin, tetracycline, and tylosin ( < 0.001). Results also indicate that isolated from conventional systems attached to very fine silica sand at significantly higher levels than those from organic systems ( < 0.001). Statistical analysis showed that a significant relationship did not exist between antibiotic resistance levels and attachment in from conventional systems but did for organic systems ( < 0.001). Better quantification of these relationships is critical to understanding the behavior of in the environment and preventing exposure of human populations to antibiotic-resistant bacteria.

Comparison of different approaches to antibiotic restriction in food-producing animals: stratified results from a systematic review and meta-analysis

“…Of the 127 studies, 51 restricted all use of antibiotics (complete restriction),35–85 three restricted use of a single antibiotic class86–88 and seven restricted use of a single specific antibiotic 89–95. In all, 33 studies restricted use of antibiotics for all non-therapeutic purposes,48 96–127 and 19 restricted antibiotic growth promoters only 128–146.…”

Characterization of the Microbial Resistome in Conventional and “Raised Without Antibiotics” Beef and Dairy Production Systems

“…Traditionally, AMR in bacterial communities has been investigated using cultures of indicator organisms such as Escherichia coli , Campylobacter , and Salmonella (Luangtongkum et al, 2006; Sapkota et al, 2014; Zwonitzer et al, 2016), or by amplification of a limited number of antibiotic resistance genes (ARGs; Cohen et al, 2012; Guarddon et al, 2014; Beukers et al, 2018) detected via polymerase chain reaction (PCR) methods. These approaches offer limited findings and conclusions because they select for only a few specific indicator bacterial species via enrichment and are limited to only a few ARGs.…”

Allelic Variation in Outer Membrane Protein A and Its Influence on Attachment of Escherichia coli to Corn Stover

“…Single-strain attachment assays were performed according to previously described methods (Liu et al, 2011; Zwonitzer et al, 2016) with modifications that are briefly described here. Fifteen μl of cell suspension were added to a 15-ml centrifuge tube (120 mm in length) containing 15 ml of saturated CaCO 3 solution (pH ~ 8) and 1.06 mg l −1 corn stover.…”