Flore Chirila

Influence of phytochemical profile on antibacterial activity of different medicinal plants against gram-positive and gram-negative bacteria

Nettle (Urtica dioica), basil (Ocimum basilicum), thyme (Thymus serphyllium), costmary (Chrysanthemum balsamita) and yarrow (Achillea millefolium) are used worldwide as aromatic herbs and medicinal plants. The alcoholic macerates of these plants were prepared and their chemical composition was investigated by spectrophotometric methods and HPLC chromatography with photodiode array detection. Alcoholic extracts were tested also in vitro against 5 pathogenic bacterial strains: 2 Gram-positive (Staphyloccocus aureus and Bacillus cereus) and 3 Gram-negative (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium). Minimum inhibitory concentrations for the extracts against all the microorganisms were determined by serial dilutions method. All the extracts demonstrated antibacterial activity against Gram-positive bacteria and partially against Gram-negative bacteria. In addition, nettle extract possessed the highest polyphenolic and flavonoid content. The results obtained indicated that these plants represent a potential source of natural antibacterial substances and can be used for the production of natural antibacterial formulations.

Concerning Increase in Antimicrobial Resistance in Shiga Toxin-Producing Escherichia coli Isolated from Young Animals during 1980–2016

This study was conducted in order to assess the antimicrobial resistance patterns of E. coli isolated from young animals affected between 1980 and 2016. The selected isolates for this study (n=175) carried stx1/stx2 genes and the most prevalent type of pathogenic E. coli found belonged to serogroup O101, antigen (K99)–F41 positive. All STEC-positive isolates were tested for susceptibility to 11 antimicrobials. Multidrug resistance (MDR) increased from 11% during the 1980s to 40% between 2000 and 2016. Resistance to tetracycline and streptomycin was the most frequent co-resistance phenotype (37%). Co-resistance to tetracycline and sulfonamide was found in 21% of E. coli isolates, while the MDR pattern to tetracycline, sulfonamide, and streptomycin was observed in 12% of the strains tested. Only 8% of isolates were co-resistant to tetracycline, ampicillin, streptomycin, and sulfonamide. The most common resistance genes found were those encoding for tetracycline, sulphonamides, and streptomycin, with 54% (n=95) of the tested isolates containing at least one of the genes encoding tetracycline resistance. A total of 87% of E. coli that tested positive for tetracycline (tetA, tetB, and tetC) and sulphonamide (sul1) resistance genes were isolated between 2000 and 2016. A large number of isolates (n=21) carried int1 and a nucleotide sequence analysis revealed that all class 1 integron gene cassettes carried sul1, tet, and dfrA1 resistance genes. An increase was observed in the level of resistance to antimicrobials in Romania, highlighting the urgent need for a surveillance and prevention system for antimicrobial resistance in livestock in Eastern Europe.