Plasmids providing antibiotic resistance are abundant in manure and manured soil
Plasmids are small circular DNA molecules that occur in bacteria. They carry genetic information that is not essential for bacterial cell growth; however, it is advantageous in harsh conditions, e.g. presence of antibiotics. Plasmids often contain antibiotic resistance genes and may constitute an important way of antibiotic resistance spreading. They represent a significant thread to mankind as they allow for resistance interchange among unrelated bacterial species. They contribute, therefore, to dramatic reduction of the effectiveness of infectious disease treatment. Importantly, antibiotic resistance can easily spread not only in the environment, but also in human bodies via ingestion of resistance bearing bacteria with food.
New variant of so called LowGC plasmid encoding resistance to the antibiotics streptomycine and tetracycline was isolated from dairy cow feces in the Czech Republic. Researchers from the Department of Soil Microbiology, Biology Centre CAS., read the whole genetic information of the plasmid using next generation sequencing. Analyses of feces, manure and soil sampled at the studied dairy farm revealed that this type of plasmid was very abundant in manure and manured soil, suggesting that plasmid transfer could occur between manure and soil bacteria, from which the plasmid can be spread further.
Additional genetic analyses suggested that genetic exchange could occur among LowGC plasmids and bacteria of the genus Acinetobacter. Acinetobacters were also isolated from dairy cow feces and are considered to be natural hosts of Low GC plasmids. Importantly, some species of the genus Acinetobacter cause severe nosocomial infections and hence LowGC plasmids became suspected from antibiotic resistance transfer from the environment to human pathogens.
Kyselková M, Chrudimský T, Husník F, Chroňáková A, Heuer H, Smalla K, Elhottová D. Characterization of tet(Y)-carrying LowGC plasmids exogenously captured from cow manure at a conventional dairy farm. FEMS Microbiol Ecol. 2016 Jun;92(6). pii: fiw075. doi: 10.1093/femsec/fiw075. Epub 2016 Apr 15.