Irina Tanuwidjaja

The aim of this in vitro study was to investigate the effects of six phenolic acids applied individually and in combination at concentrations of 0–20 mM on Ambrosia artemisiifolia and soil bacteria. Chlorogenic acid (CGA), p-hydroxybenzoic acid (PHBA), and protocatechuic acid (PKA) were tested on both plants and bacteria, whereas p-coumaric (PCA), vanillic (VA), and ferulic (FA) acids were tested only on soil bacteria. The estimated EC₅₀ for radicle inhibition were 4.9 ± 0.1 mM for PHBA, 4.1 ± 0.7 mM for CGA, 6.6 ± 0.7 mM for PKA, 10.1 ± 0.9 mM for CGA + PHBA + PKA, 4.6 ± 0.4 mM for ferulic, vanillic, and p-coumaric acids (FA + VA + PCA), and 2.5 ± 0.3 mM for the combination of all six phenolic acids. Bacterial strains were less susceptible to individual phenolic acids compared to their combinations. PKA and CGA showed the strongest antibacterial activity, with PKA inhibiting 78% and killing 74% of strains at ≤10 mM, while CGA inhibited 61% and killed 57%. Conversely, PCA and VA had the weakest antibacterial effects, requiring ≥20 mM for complete inhibition. Among test genera, Stenotrophomonas, Bacillus, Peribacillus, and Pseudomonas were more susceptible than Enterobacter and Lelliottia. Subinhibitory concentrations of individual phenolic acids did not affect bacterial motility, except for PKA. The study suggests that VA, PCA and FA alone or combined and PHBA alone, appear promising for weed management. Reduced herbicide strategies may safely incorporate CGA and PKA at concentrations below 2.5 mM.

U ovom je radu istraženo antimikrobno djelovanje ozonirane vode, generirane u obliku kapljica (326 - 400 µm) i maglice (145 - 225 µm), u koncentracijama od 4 ppm i 2 ppm, prema šest karabapenem- i kolistin- rezistentnih sojeva Klebsiella pneumoniae podrijetlom iz otpadnih voda. Rezultati su pokazali izuzetno visoku djelotvornost ozonirane vode kao antimikrobnog sredstva. Broj bakterija K. pneumoniae statistički je značajno smanjen u odnosu na kontrolu i iznosi 76,38 - 99,77 % za ozon apliciran u obliku kapljica u koncentraciji od 4 ppm, te od 17,0 2- 98,71 % za 2 ppm ozona primijenjenog u obliku maglice. Najbolja djelotvornost ozonirane vode bila je vidljiva prema tri soja K. pneumoniae (SE_SC_COL_46, SE_SC_COL_86 i SE_SC_COL_96) te je redukcija brojnosti kod ovih sojeva, prilikom svakog od četiri tretmana, iznosila više od 9 5%. Međutim, neki sojevi K. pneumoniae preživjeli su u znatno većem postotku, ovisno o primijenjenom tretmanu. Najveće je odskakanje od prosječnih rezultata detektirano za soj SE_SC_COL_102 te je ozonirana voda koncentracije 2 ppm u obliku maglice reducirala samo 17,02 % ovih bakterija. Općenito, način aplikacije ozonirane vode, kao i koncentracija apliciranog ozona (4 ili 2 ppm), značajno utječu na udio inhibiranih bakterija, a efikasnost ovisi i o soju na koji se primjenjuje pojedini tretman. Iako je učinkovitost inaktivacije mikroorganizama primjenom obje koncentracije ozonirane vode bila izuzetno visoka, prosječno bolje rezultate pokazala je voda koncentracije ozona od 4 ppm, a prilikom aplikacije u obliku kapljica.

Ozon is considered an environmentally friendly, low-cost antimicrobial treatment and an effective alternative to chemical pesticides. Ozonated water in the form of droplets and mist has been used in two concentrations (4 and 2 mg/L) against three biomasses (10², 10⁴, and 10⁶ CFU/mL) of phytopathogenic bacteria Erwinia amylovora, Pseudomonas syringae, and Agrobacterium tumefaciens and fungus Botrytis cinerea that infest a wide range of crops worldwide and pose a threat to global food production. Regardless of concentration, ozone dissolved in water showed a pronounced inhibitory effect on phytopathogenic bacteria when applied in the form of droplets. However, the effect was only detected when the bacterial load was not higher than 10⁴ CFU/mL, indicating the necessity to treat the crops and plant materials when the bacterial load is still manageable. Unlike bacterial phytopathogens, B. cinerea was the most susceptible to treatment with aqueous ozone, regardless of the applied biomass, ozone concentration, or type of application. Total removal of high biomass of B. cinerea was achieved even with the lowest ozonated water concentration thus underlying the power of ozone in treating this particular fungal contamination.

The incidence of antibiotic resistance in pathogenic bacteria has become an alarming clinical and social problem. Therefore, the demand for alternative antimicrobial compounds has increased. In this study, a chemical profile of honey bee (Apis mellifera L.) venom (HBV) has been determined by HPLC and FTIR-ATR spectroscopy, and tested for antibacterial activity, as well as efficiency with regard to conventional antibiotics. The investigated HBV was of high quality with melittin and total protein contents of 70.10 ± 7.01%, and 84.44 ± 3.12 g/100 g, respectively. The purity of HBV was confirmed by FTIR-ATR spectral profiling, which revealed a unique pattern of absorption bands that are characteristic of its major fractions. In addition, HBV showed a broad spectrum of activity against all three tested biomasses of potentially pathogenic Gram-positive and Gram-negative bacteria with MIC values ranging between 12.5 and 200 µg/mL, and MBC between 12.5 and 400 µg/mL. When compared to conventional antibiotics, HBV (400 µg) showed up to 27.8% efficiency of tetracycline (30 µg), 52.2% erythromycin (15 µg), 21.2% ciprofloxacin (5 µg), and 34.6% of ampicillin-sulbactam (20 µg). The overall results demonstrate the therapeutic potential of the analyzed HBV.