Biogenic silver nanoparticles affect motility and eradicate the biofilm in yersinia enterocolitica

Abstract

Yersinia enterocolitica is a Gram-negative cocobacillus, not sporulated, mobile at 25 °C but immobile at 37 °C. This pathogenic specie is widely distributed in nature and animals, being the pig the main reservoir of pathogenic strains for humans. Y. enterocolitica can cause numerous diseases, usually at gastrointestinal level but various complications can be manifested especially in immunocompromised people, being the cases where antibacterial therapy is needed. Biofilms are communities of microorganisms that grow irreversibly adhered to living or inert substrates, contained in a polymer matrix secreted by themselves. The most important property of the biofilm forms in clinical medicine is the enhanced resistance to antimicrobial agents. The flagellar motility is crucial initially for surface attachment and subsequently for biofilm formation in Y. enterocolitica. In addition, the fliA gene is a regulator gene necessary for the expression of flagella. The objective of this work was to determine if silver nanoparticles (AgNPs) phytosynthesized from the aqueous extract of Bothriochloa laguroides are capable of inhibiting motility modifying the expression of the fliA gene and eradicating mature biofilm of Y. enterocolitica. Two strains were used: Y. enterocolitica 8081 bio/serotype 1B/O:4 and Y. enterocolitica ME110 1A/O:5. The swimming and swarming motility was determined in a culture medium containing 0.3 and 0.6 % p/v of agar respectively, the fliA gene expression was carried out by RT-PCR and the mature biofilm eradication was determined by the crystal violet technique. The swimming and swarming motility was effectively reduced by AgNPs at 7.8 pM in the two tested strains. The decrease in swimming was 90.38 % for Y. enterocolitica 8081 and 74.27 % for Y. enterocolitica ME110, while for swarming it was 79.16 % and 89.28, respectively. Furthermore, AgNPs at 31.25 pM significantly reduce (p<0.05) the expression of the fliA gene in the two Y. enterocolitica strains. In addition, the AgNPs were able to eradicate mature biofilm at a concentration of 500 pM, with an eradication percentage of 99.33 % for Y. enterocolitica 8081 and 92.95 % for Y. enterocolitica ME110. The AgNPs were able to decrease the motility in Y. enterocolitica and to eradicate the mature biofilm, for which they could be used in the future not only to prevent the formation of biofilm but also to eradicate formed biofilms.