Food Additive Mediated Biosynthesis of AgNPs with Antimicrobial Activity Against Hypermucoviscous Enterotoxigenic Foodborne Klebsiella pneumoniae

Abstract

This study was aimed to adopt an ecofriendly method to synthesize nanoparticles with an effective antibacterial and anti-biofilm activity. A food origin hypermucoviscous Klebsiella pneumoniae was isolated from food samples and identified using biochemical tests and the Vitek system. A string test was depended on to identify hypermucoviscous isolates. Enterotoxicity of foodborne hypermucoviscous K. pneumoniae isolates was detected phenotypically using suckling mouse bioassay. Biofilm forming ability was tested for all the isolated bacteria using the Microtiter plate method and Congo Red Agar. A natural food additive Syzygium aromaticum (clove) aqueous extract was used for the biosynthesis of silver nanoparticles in optimized conditions. The biosynthesized clove-silver nanoparticles (Clove-AgNps) were characterized by several techniques, and their antimicrobial and antibiofilm activity was determined. The results of this study revealed that the isolation of 28 K. pneumoniae isolates were isolated from 200 food samples. String test results showed that 16/28 (57.14%) K. pneumoniae isolates were hypermucoviscous. Eleven of these isolates (68.75%) were enterotoxigenic. Using clove aqueous extract as a biological agent was successful in the biosynthesis of AgNPs with an average diameter of 14.12 nm as measured by AFM. The optimum biosynthesis conditions were: 1mM of AgNO3 concentration, pH 7, at 37 °C, and 24 hours. The minimum inhibitory concentration of the clove-AgNPs was detected as 62.5 µg.mL-1. Sub-inhibitory concentration of 31.25 µg.mL-1 of Clove-AgNPs resulted in: 91% decrease in the formed biofilm. It can be concluded that using Syzygium aromaticum is an effective ecofriendly method for AgNPs biosynthesis with excellent antibacterial and anti-biofilm activity against enterotoxigenic hypermucoviscous K. pneumoniae.