Natalya Doroshenko

Staphylococcus epidermidis biofilm formation is responsible for the persistence of orthopedic implant infections. Previous studies have shown that exposure of S. epidermidis biofilms to sub-MICs of antibiotics induced an increased level of biofilm persistence. BODIPY FL-vancomycin (a fluorescent vancomycin conjugate) and confocal microscopy were used to show that the penetration of vancomycin through sub-MIC-vancomycin-treated S. epidermidis biofilms was impeded compared to that of control, untreated biofilms. Further experiments showed an increase in the extracellular DNA (eDNA) concentration in biofilms preexposed to sub-MIC vancomycin, suggesting a potential role for eDNA in the hindrance of vancomycin activity. Exogenously added, S. epidermidis DNA increased the planktonic vancomycin MIC and protected biofilm cells from lethal vancomycin concentrations. Finally, isothermal titration calorimetry (ITC) revealed that the binding constant of DNA and vancomycin was 100-fold higher than the previously reported binding constant of vancomycin and its intended cellular d-Ala-d-Ala peptide target. This study provides an explanation of the eDNA-based mechanism of antibiotic tolerance in sub-MIC-vancomycin-treated S. epidermidis biofilms, which might be an important factor for the persistence of biofilm infections.

Cationic diblock copolymer spheres, worms and vesicles are synthesised <italic>via</italic> polymerisation-induced self-assembly; worms form soft, thermoresponsive anti-bacterial gels at 20 °C.

Microbial keratitis can arise from penetrating injuries to the cornea. Corneal trauma promotes bacterial attachment and biofilm growth, which decrease the effectiveness of antimicrobials against microbial keratitis. Improved therapeutic efficacy can be achieved by reducing microbial burden prior to antimicrobial therapy. This paper assesses a highly-branched poly(N-isopropyl acrylamide) with vancomycin end groups (HB-PNIPAM-van), for reducing bacterial attachment and biofilm formation. The polymer lacked antimicrobial activity against Staphylococcus aureus, but significantly inhibited biofilm formation (p = 0.0008) on plastic. Furthermore, pre-incubation of S. aureus cells with HB-PNIPAM-van reduced cell attachment by 50% and application of HB-PNIPAM-van to infected ex vivo rabbit corneas caused a 1-log reduction in bacterial recovery, compared to controls (p = 0.002). In conclusion, HB-PNIPAM-van may be a useful adjunct to antimicrobial therapy in the treatment of corneal infections.

The paper is devoted to improving the elements of the technology of clonal micropropagation of Pukhlyakovsky grapevine variety in order to increase the efficiency of its content in the in vitro collection. The introduction of an osmotically active substance ‒ sorbitol into the culture medium in the concentration range of 5-30 g/l in comparison with sucrose of 10 g/l was studied. The research was carried out in 2021-2022 on the collection of grapevine plants in vitro of the All-Russian Research Institute for Viticulture and Winemaking named after Ya.I. Potapenko in Novocherkassk (Rostov region). Cultivation was carried out in conditions of illumination of 3.0 thousand lux, temperature +25 ° C, photoperiod of 16/8 hours, air humidity 60 %. Morphometric parameters of shoots were evaluated: the number and length of shoots, shoot height, number of leaves, inhibition of growth processes was noted in all experimental variants in comparison with the control. The maximum safety indicators were recorded in the variant with a sorbitol concentration of 10 g/l. The minimum safety was observed in the control (43.3 %) and the variant with the maximum sorbitol content ‒ 30 g/l (36.7 %). The calculation of the economic efficiency of keeping plants in the collection in vitro on a medium with sucrose and sorbitol was carried out. Depositing on a medium with sorbitol is 17 % more economical due to an increase in the interval between subcultivations from 6 months to 12. The positive effect of the drug sorbitol on the safety and quality characteristics of plants was established, the maximum safety (86.7 %) and moderate inhibition of growth were recorded in the variant with a concentration of the drug 10 g/l. We consider this concentration to be optimal for use when depositing Puhlyakovsky grape plants in the in vitro collection under conditions of slow growth.