Therapeutic potential of Bulgarian Propolis against antibiotic-resistant Salmonella species

Abstract

The emergence of multidrug-resistant (MDR) Salmonella spp. has increased the need for investigation of antimicrobial alternatives. Ethanolic extract of propolis (EEP) has been identified to have wide-ranging medical applications related to its antimicrobial activity. The current study aimed to identify the major chemical components of EEP with antibacterial effects, evaluate the antibacterial efficacy of EEP against MDR Salmonella spp. isolates, and further examine the therapeutic efficacy of EEP against MDR S. Enteritidis infected mouse model. Bulgarian propolis EEP was prepared by using ethanol based extraction method. The chemical composition of EEP was characterized using the gas chromatography-mass spectroscopy (GC-MS). The in-vitro antibacterial activity of EEP against 20 isolates of MDR Salmonella spp. was investigated. Furthermore, the minimum inhibitory concentration (MIC) and minimum bactericidal concentrations (MBC) of EEP were determined along with in vivo therapeutic efficacy with reference to hematobiochemical and histological analyses. The main identified compounds belonged to flavonoids, aromatic acids, and esters which may be attributable to its antibacterial activity. Antimicrobial efficacy of EEP was detected against all isolates with variable bactericidal to bacteriostatic efficacy and with an MIC of ≤0.012-6.250 mg/mL (mean 1.294 ± 1.557) and an MBC of 1.563-12.50 mg/mL (mean 4.531 ± 2.678). A therapeutic efficacy against S. Enteritidis was also determined. Statistical analyses for hematological and serum biochemical tests have showed a significant increase due to infection effect in band neutrophil counts, eosinophil counts and serum alanine aminotransferase (ALT) levels in comparing two infected groups with two non-infected groups; simultaneously, there was no significant difference in between both infected groups and in between both non infected groups whereas the results were significant at (p value<0.05). As well as, there was no any evidence of significance regarding neither treatment nor infection*treatment interaction effects. In infected groups, histological examination of the liver revealed degenerative changes in hepatocytes; these changes had almost disappeared in the EEP-treated group. The current study demonstrated a potential therapeutic effect of Bulgarian propolis ethanolic extract on clinically recovered antibiotic-resistant S. Enteritidis from diarrheic goat, and the results herald a promising supplementary therapy of EEP during resistant Salmonella infection.