Efstathios Giaouris

Campylobacter spp. are significant zoonotic agents, which cause annually millions of human cases of foodborne gastroenteritis worldwide. Their inclusion in biofilms on abiotic surfaces seems to play a pivotal role in their survival outside of the host, growth, and spread. To successfully mitigate the risks that arise with these bacteria, it is crucial to decrease their prevalence within the food production chain (from farm to the table), alongside the successful treatment of the resulting illness, known as campylobacteriosis. For this, the use of various antimicrobial agents remains actively in the foreground. A general-purpose biocide and cationic surfactant (benzalkonium chloride; BAC), a widely used macrolide antibiotic (erythromycin; ERY), and a naturally occurring organic acid (L(+)-lactic acid; LA) were comparatively evaluated in this work for their potential to inhibit both the planktonic and biofilm growth of 12 selected Campylobacter spp. (of which, seven were C. jejuni and five were C. coli) raw chicken meat isolates, all grown in vitro as monocultures. The inhibitory action of LA was also studied against four mixed-culture Campylobacter biofilms (each composed of three different isolates). The results showed that the individual effectiveness of the agents varied significantly depending on the isolate, growth mode (planktonic, biofilm), intercellular interactions (monocultures, mixed cultures), and the growth medium used (with special focus on blood presence). Thus, BAC exhibited minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), and minimum biofilm inhibitory concentrations (MBICs) that ranged from 0.5 to 16 μg/mL. Interestingly enough, these values varied widely from 0.25 to 1024 μg/mL for ERY. Concerning LA, the MICs, MBCs, and MBICs varied from 1024 to 4096 μg/mL, with mixed-culture biofilm formation always being more difficult to suppress when compared to biofilm monocultures. In addition, it was evident that intercellular interactions encountered within mixed-culture Campylobacter biofilms significantly influenced both the population dynamics and the tolerance of each consortium member to acid exposure. Overall, the findings of this study provide useful information on the comparative effectiveness of three well-known antimicrobial agents for the control of Campylobacter spp. under various growth modes (i.e., planktonic, biofilm, monocultures, mixed cultures) that could potentially be encountered in food production and clinical settings.

This study implemented kombucha fermentation of Olympus Mountain tea (Sideritis scardica) sweetened with honey (OMTWH) in order to investigate the potential for producing a novel beverage with functional properties. The increase in the total count of bacteria and yeast suggests that the OMTWH acts as a viable substrate for supporting the proliferation of the microorganisms of the Kombucha symbiotic culture. The fermentation resulted in a reduction in pH and increased total titratable acidity. After fermentation, a statistically significant increase in the vitamins C, B1, B2, B6, B7, and B12 content was observed (p < 0.05). Total phenolics and antioxidant activity of the fermented beverage was significantly enhanced, as assessed by the method of Folin–Ciocalteu and ABTS assay, respectively. Results revealed that OMTWH had a potent inhibitory activity of α-amylase, α-glucosidase, acetylcholinesterase, and butyrylcholinesterase; OMTWH fermented with a kombucha consortium exhibited even higher inhibition. Hence, the process of kombucha fermentation can convert OMTWH into a novel beverage with enhanced functional properties.