Plasmid-mediated fitness advantage ofAcinetobacter baylyiin sulfadiazine-polluted soil

Abstract

LowGC-type plasmids conferring resistance to sulfonamides have been frequently isolated from manure and manured soil. However, knowledge on the dynamics of plasmid-carrying populations in soil and their response to the presence of sulfonamides is scarce. Here, we investigated effects of the sulfonamide resistance conferring plasmid pHHV216 on the fitness of Acinetobacter baylyi BD413 in soil after application of manure with or without the sulfonamide antibiotic sulfadiazine (SDZ). The persistence of A. baylyi BD413 pHHV216 in competition to its plasmid-free variant was followed in soil microcosms. CFU counts showed a decrease in A. baylyi BD413 in manured soils over the experimental period of 32 days by about 0.5 log units. The proportion of the plasmid-carrying populations decreased from 50 to < 40% in the absence of SDZ, while the proportion of plasmid-carrying BD413 increased from 50 to about 65% with SDZ added. The data suggest that SDZ introduced via manure into soil was bioaccessible, providing a fitness advantage for the plasmid-carrying population of BD413 in soil, while the plasmid conferred a fitness disadvantage when selective pressure by SDZ was absent. In future, this method may be used as a tool for the assessment of bioavailability of antibiotics in soil.

Ecotoxicological assessment of antibiotics: A call for improved consideration of microorganisms

“…Recombinant whole-cell bacterial bioreporters that respond to specific classes of antibiotics or report on specific stress responses in bacteria have also been constructed (Melamed et al, 2012;van der Meer and Belkin, 2010). Dual strain single-species assays employing both antibiotic-resistant and sensitive strains may further be developed to measure minimal selective concentrations for antibiotic resistance development (Gullberg et al, 2011) in various environmental matrices (Ashbolt et al, 2013;Jechalke et al, 2013).…”

Plasmid Detection, Characterization, and Ecology

“…In two independent competition experiments with plasmid-free and plasmid-carrying Acinetobacter baylyi BD413 performed in soil microcosms, Jechalke et al [72] demonstrated that the LowGC-type plasmid pHHV216 conferred a fitness advantage to Acinetobacter baylyi BD413 in soils that had received manure spiked with sulfonamide antibiotic sulfadiazine. Plasmid carriage had a disadvantage when the selective pressure by SDZ was absent.…”

Plasmid Detection, Characterization, and Ecology

“…In addition to the many competition studies performed in liquid cultures, recent work has shown the effect of antibiotic presence on the competitiveness of plasmid-bearing strains in soil. In two independent competition experiments with plasmid-free and plasmid-carrying Acinetobacter baylyi BD413 performed in soil microcosms, Jechalke et al [72] demonstrated that the LowGC-type plasmid pHHV216 conferred a fitness advantage to Acinetobacter baylyi BD413 in soils that had received manure spiked with sulfonamide antibiotic sulfadiazine. Plasmid carriage had a disadvantage when the selective pressure by SDZ was absent.…”