Determination of MIC, MPC, and MSW of Ilex paraguariensis against non-typhoidal Salmonella with identification of the mechanisms of resistance and pathogenicity factors

Abstract

This study investigated the antibacterial activity of the aqueous extract of Ilex paraguariensis against 32 different strains of nontyphoidal Salmonella (NTS) through the determination of the minimum inhibitory concentration (MIC), mutant prevention concentration (MPC), and mutant selection window (MSW) and the detection of virulence genes by multiplex PCR assays. The MIC values of Ilex paraguariensis against Salmonella spp. strains varied between 0.78 mg/ml and 6.25 mg/ml with a MIC90 of 3.12 mg/ml. The highest MPC in this study was 48 mg/ml yielding a mutant selection window of 41.75 mg/ml. The MSW values of the remaining strains varied between 1.56 and 8.87 mg/ml. Genes of pathogenicity detected in Salmonella spp. isolates were most commonly the stn, sdiA, invA, sopB, invH, and sopE genes. The antibacterial activity of yerba mate extract was not affected by the antimicrobial resistance patterns or pathogenicity genes expressed. More work is needed to identify the active antibacterial compound(s) responsible for the antibacterial activity.

Keywords: Antibacterial activity; Antimicrobial resistance; Ilex paraguariensis; Salmonella; Virulence genes.