Assessment of Antimicrobial Activity of Ethanolic and Aqueous Extracts of Aesculus hippocastanum L. (Horse Chestnut) Bark against Bacteria Isolated from Urine of Patients Diagnosed Positive to Urinary Tract Infections.

The search for new antimicrobials is essential to address the worldwide issue of antibiotic resistance. The present work aimed at assessing the antimicrobial activity of Aesculus hippocastanum L. (horse chestnut) bark against bacteria involved in urinary tract infections (UTIs). Bioactive compounds were extracted from A. hippocastanum bark using water and ethanol as solvents. The extracts were tested against 10 clinical uropathogenic strains including five Gram-positive and five Gram-negative bacteria. Staphylococcus aureus ATCC 6538 and Escherichia coli ATCC 25922 were used as reference bacteria. The susceptibility to antibiotics was assessed using the Kirby Bauer disc diffusion method and the antibacterial activity of the extracts was evaluated using the well diffusion method. The Minimum inhibitory concentration (MIC) and the minimum bactericidal concentrations (MBC) were asseded by the microdilution method. A. hippocastanum bark possessed a dry matter content of 65.73%. The aqueous extract (AE) and ethanolic extract (EE) showed a volume yield of 77.77% and 74.07% (v/v), and a mass yields of 13.4% and 24.3% (w/w) respectively. All the bacteria were susceptible to amoxiclav, imipenem and ceftriaxone but the clinical strains were resistant to at least one antibiotic. Kocuria rizophilia 1542 and Corynebacterium spp 1638 were the most resistant bacteria both with multidrug resistance index of 0.45. Except AE on Proteus Mirabilis 1543 and Enterococcus faecalis 5960 (0 mm), both AE and EE were active against all the microorganisms tested with inhibition diameters (mm) which ranged from 5.5-10.0 for AE and 8.0-14.5 for EE. The MICs of EEs varied from 1-4 mg/mL while those of AEs varied from 4-16 mg/mL. The ethanolic extracts (EE) were overall more active than the aqueous ones. The A. hippocastanum bark extracts had overall weak antibacterial activity (MIC ≥0.625 mg/mL) and bacteriostatic potential (MBC/MIC ≥16) on both Gram-positive and Gram-negative bacteria.

Antibacterial activity of grapefruit peel extracts and green-synthesized silver nanoparticles.

BACKGROUND AND AIM: The gradual loss of efficacy of conventional antibiotics is a global issue. Plant material extracts and green-synthesized nanoparticles are among the most promising options to address this problem. Therefore, the aim of this study was to assess the antibacterial properties of aqueous and hydroalcoholic extracts of grapefruit peels as well as their inclusion in green-synthesized silver nanoparticles (AgNPs). MATERIALS AND METHODS: Aqueous and hydroalcoholic extracts (80% v/v) were prepared, and the volume and mass yields were determined. The synthesis of AgNPs was done in an eco-friendly manner using AgNO3 as a precursor. The nanoparticles were characterized by ultraviolet-vis spectrometry and photon cross-correlation spectroscopy. The antibacterial activity of the extracts was tested on three Gram-positive bacteria (Staphylococcus aureus ATCC 6538, clinical Enterococcus faecalis, and S. aureus) and two Gram-negative bacteria (two clinical Escherichia coli) using various concentrations of extracts (100, 50, 25, 12, and 5 mg/mL and 5% dimethyl sulfoxide as negative control). Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined using the microdilution method. Modulation of cefazoline and ampicillin on resistant E. coli and S. aureus strains was added to the mixture design response surface methodology with extreme vertices design, with the diameters of inhibition and the fractional inhibitory concentration index as responses and factors, respectively. The antibiotic, the ethanolic extract, and water varied from 0.1 MIC to 0.9 MIC for the first two and from 0 to 0.8 in proportion for the third. Validating the models was done by calculating the absolute average deviation, bias factor, and accuracy factor. RESULTS: The volume yield of the EE and aqueous extract (AE) was 96.2% and 93.8% (v/v), respectively, whereas their mass yields were 7.84% and 9.41% (m/m), respectively. The synthesized AgNPs were very uniform and homogeneous, and their size was dependent on the concentration of AgNO3. The antibacterial activity of the two extracts was dose-dependent, and the largest inhibition diameter was observed for the Gram-positive bacteria (S. aureus ATCC 6538; AE, 12; EE, 16), whereas AgNPs had a greater effect on Gram-negative bacteria. The MICs (mg/mL) of the AEs varied from 3.125 (S. aureus ATCC 6538) to 12.5 (E. coli 1 and E. coli 2), whereas the MICs of the EEs varied from 1.5625 (S. aureus 1, S. aureus ATCC 6538, and E. faecalis) to 6.25 (E. coli 1). There was a significant difference between the MICs of AEs and EEs (p=0.014). The MBCs (mg/mL) of the AEs varied from 12.5 (S. aureus ATCC 6538) to 50 (S. aureus 1), whereas those of the EEs varied from 6.25 (S. aureus 1) to 25 (E. coli 1 and E. faecalis). Ethanolic grapefruit extracts demonstrated an ability to modulate cefazolin on E. coli and S. aureus but were completely indifferent to ampicillin on E. coli. CONCLUSION: Grapefruit peel extracts and their AgNPs exhibit antibacterial properties that can be exploited for the synthesis of new antimicrobials and their EEs may be efficiently used synergistically with other antibiotics against bacteria with intermediate susceptibility.

The use of probiotics in animal feeding for safe production and as potential alternatives to antibiotics.

Although the production of safe food for human consumption is the primary purpose for animal rearing, the environment and well-being of the animals must also be taken into consideration. Based on microbiological point of view, the production of healthy food from animals involves considering foodborne pathogens, on the one hand and on the other hand, the methods used to fight against germs during breeding. The conventional method to control or prevent bacterial infections in farming is the use antibiotics. However, the banning of these compounds as growth promoters caused many changes in animal breeding and their use has since been limited to the treatment and prevention of bacterial infections. In this function, their importance no longer needs to be demonstrated, but unfortunately, their excessive and abusive use have led to a double problem which can have harmful consequences on consumer health: Resistance to antibiotics and the presence of antibiotic residues in food. The use of probiotics appears to be a suitable alternative to overcome these problems because of their ability to modulate the immune system and intestinal microflora, and further considering their antagonistic role against certain pathogenic bacteria and their ability to play the role of growth factor (sometimes associated with prebiotics) when used as feed additives. This review aims to highlight some of the negative effects of the use of antibiotics in animal rearing as well as emphasize the current knowledge on the use of probiotics as a feed additive, their influence on animal production and their potential utility as an alternative to conventional antibiotics, particularly in poultry, pig, and fish farming.