Short-term effects of amoxicillin on bacterial communities in manured soil

Abstract

Antibiotic-resistant bacteria, nutrients and antibiotics that enter the soil by means of manure may enhance the proportion of bacteria displaying antibiotic resistance among soil bacteria and may affect bacterial community structure and function. To investigate the effect of manure and amoxicillin added to manure on soil bacterial communities, microcosm experiments were performed with two soil types and the following treatments: (1) nontreated, (2) manure-treated, (3) treated with manure supplemented with 10 mg amoxicillin kg(-1) soil and (4) treated with manure supplemented with 100 mg amoxicillin kg(-1) soil, with four replicates per treatment. Manure significantly increased the total CFU count and the amoxicillin-resistant CFU count of both soil types. However, only the soil with a history of manure treatment showed a significant increase in the relative number of amoxicillin-resistant bacteria as a result of amoxicillin amendment. The majority of plasmids exogenously isolated from soil originated from soil treated with amoxicillin-supplemented manure. All 16 characterized plasmids carried the bla-TEM gene, and 10 of them belonged to the IncN group. The bla-TEM gene was detected in DNA directly extracted from soil by dot-blot hybridization of PCR amplicons and showed an increased abundance in soil samples treated with manure. Molecular fingerprint analysis of 16S rRNA gene fragments amplified from soil DNA revealed significant effects of manure and amoxicillin on the bacterial community of both soils.

Disturbance and change in biodiversity

“…Effects of disturbance on biodiversity have been studied in a great variety of ecosystems ranging from tundra communities (Jorgenson et al 2010) to coral reefs (Graham et al 2009), a range of organisms extending from bacteria (Binh et al 2007) to primates (Bicknell & Peres 2010) and at multiple levels of organization including molecular pathways (Spagnuolo et al 2009) and ecosystem functioning (Hotes et al 2010). The types of disturbance involved include everything from single tree-falls (Brokaw 1985) to ecological catastrophes (Hughes 1994).…”

Accumulation of Sulfonamide Resistance Genes in Arable Soils Due to Repeated Application of Manure Containing Sulfadiazine

“…Feeding experiments performed with 14 C-labeled SDZ showed that more than 96% of the SDZ administered to pigs was excreted within 10 days and did not decrease during storage of the manure over 6 months (13). A survey of 15 field-scale piggery manures showed that piggery manure represents a hot spot for antibiotic resistance genes as well as broad-host-range plasmids (2)(3)(4). In a soil microcosm experiment, significant effects of manure containing SDZ on the abundance of the sulfonamide resistance genes sul1 and sul2 were detected even 2 months after application, compared to the abundance in untreated soil or soil treated with manure devoid of antibiotics (14,15).…”

Phenotypic and genotypic characterization of antibiotic-resistant soil and manure bacteria adjacent to swine production facilities

“…Studies show that subinhibitory concentrations of antibiotics would likely enhance the frequency of resistance gene transfer (13,14). Horizontal gene transfer is recognized as playing an important role in spreading antibiotic resistance genes in soil microbial communities (14,15). Studies also suggest that manuretreated environments exhibit a wide range of bacteria hosting diverse genetic elements (14,16).…”

“…Horizontal gene transfer is recognized as playing an important role in spreading antibiotic resistance genes in soil microbial communities (14,15). Studies also suggest that manuretreated environments exhibit a wide range of bacteria hosting diverse genetic elements (14,16).…”

“…However, selection pressure of antibiotic persistence is not the only mechanism increasing the antibiotic resistance rate in environmental bacteria (5,12). Studies show that subinhibitory concentrations of antibiotics would likely enhance the frequency of resistance gene transfer (13,14). Horizontal gene transfer is recognized as playing an important role in spreading antibiotic resistance genes in soil microbial communities (14,15).…”