Abstract
Worldwide antimicrobial resistance is partly caused by the overuse of antibiotics as growth promoters. Based on the known bactericidal effect of silver, a new material containing silver in a clay base was developed to be used as feed additive. An in vitro genotoxicity evaluation of this silver-kaolin clay formulation was conducted, which included the mouse lymphoma assay in L5178Y TK+/− cells and the micronucleus test in TK6 cells, following the principles of the OECD guidelines 490 and 487, respectively. As a complement, the standard and Fpg-modified comet assays for the evaluation of strand breaks, alkali labile sites and oxidative DNA damage were also performed in TK6 cells. The formulation was tested without metabolic activation after an exposure of 3 h and 24 h; its corresponding release in medium, after the continuous agitation of the silver-kaolin for 24 h was also evaluated. Under the conditions tested, the test compound did not produce gene mutations, chromosomal aberrations or DNA damage (i.e., strand breaks, alkali labile sites or oxidized bases). Considering the results obtained in the present study, the formulation seems to be a promising material to be used as antimicrobial in animal feed.
Highlights
Accepted: 3 March 2022Antimicrobial resistance is an economic and security threat which will reach worrying dimensions by 2050 unless solutions are found [1–3]
Given the evidence of in vitro genotoxic effects of AgNPs and the promising application of kaolin as an inert support, the aim of this study is to demonstrate the reduction of genotoxicity of AgNPs when they are formulated as a combinationwith kaolin
Micrographs obtained by field emission scanning electron microscopy (FESEM) (Figure S1 in Supplementary Information) showed the laminar structure of kaolinite microparticles decorated with spheroidal silver nanoparticles with diameters ranging from 2 to 90 nm
Summary
Antimicrobial resistance is an economic and security threat which will reach worrying dimensions by 2050 unless solutions are found [1–3]. One of the main reasons of antimicrobial resistance development is the therapeutic and non-therapeutic overuse of antimicrobials in humans, agriculture, and companion and food animals [1,2,5]. The use of long-term and low-dose antimicrobials in animal production as growth promoters is an important contributor to antimicrobial resistance occurrence and its spread between animals, humans, and the environment [5–8]. In 1999, the European commission highlighted the need of facing antimicrobials use as growth promoters. Silver nanoparticles (AgNPs) are turning out to be a good alternative to antibiotics and their use has increased in the food sector [12–15]. AgNPs have demonstrated to exert bactericidal activity against both Gram-positive and Gram-negative antibiotic-resistant bacteria [16–23]. It has been demonstrated that AgNPs are effective against species that cause infectious diseases in poultry, such as Bacillus subtilis, Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Pseudomonas aeruginosa [23]
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