Abstract
Practices in intensive animal farming such as the extensive use of antimicrobials have significant impacts on the genetic make-up of bacterial communities, especially on that of human/animal commensals. In this report, whole genome sequencing of two vancomycin-resistant enterococci (VRE) isolates from a cattle feedlot in the North West Province, South Africa, was used to highlight the threats that extensive antimicrobial usage in intensive animal rearing represents for environmental microbiomes and the food chain. The genomic DNA of the studied strains was extracted using a DNA extraction kit. Whole-genome sequencing was performed through next-generation sequencing. The genomes of Enterococcus durans strain NWUTAL1 and Enterococcus gallinarum strain S52016 consisted of 3,279,618 and 2,374,946 bp, respectively with G + C contents of 40.76 and 43.13%, respectively. Antibiotic resistance genes (ARG), plasmids and virulence factors (involved in biofilm formation, colonization and copper/silver efflux system), were detected in the genomes of both strains. The presence of these genetic determinants in the studied strains is a cause for concern as they may disseminate and find their way into the food chain via horizontal gene transfer amongst bacteria of the different ecological niches. Issues of this nature cannot be undermined and are relevant as far as food safety is concerned.
Highlights
The discovery of antibiotics was a significant hallmark in the evolution of mankind as they became important life-saving compounds both for animals and humans (Gonzalez-Zorn and Escudero, 2012)
The aim of the study was to analyze the whole genomes of two vancomycin-resistant enterococcal strains, E. durans NWUTAL1 and E. gallinarum S52016 isolated from a feedlot and further, demonstrate the impact of antimicrobial usage in animal farming on the genetic constitution of these strains and the risk that such strains represent for food safety
Two vancomycin-resistant strains, E. durans NWUTAL1 was recovered from fecal samples obtained from cattle while E. gallinarum S52016 was recovered from samples obtained from feedlot soil in Rooigrond, North-West Province, South Africa (Tatsing and Ateba, 2019), and stored at −80◦C in Luria-Bertani broth supplemented with 50% (v/v) glycerol
Summary
The discovery of antibiotics was a significant hallmark in the evolution of mankind as they became important life-saving compounds both for animals and humans (Gonzalez-Zorn and Escudero, 2012). Antimicrobials have impacted significantly on society and the health of humans and animals mainly because life expectancy could be ameliorated as common infections have become curable, promoting rapid growth of the population (Gonzalez-Zorn and Escudero, 2012). According to Marshall and Levy (2011), subtherapeutic doses of certain antibiotics that are used as growth promoters improve feed conversion, animal growth and diminish mortality and morbidity rates that arise. There are studies that highlight that resistant bacteria and resistance mechanisms were present long before antibiotics were produced or used in clinical practise (Boxall et al, 2002; Acar et al, 2012)
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