Evaluation of the in vitro effects of concentrations of antibiotics on three Enterobacteriaceae isolates.

Due to the misuse and overuse of antibiotics, bacteria are now exposed to sub-minimum inhibitory concentrations (sub-MICs) of antibiotics in various environments. In recent years, exposure of bacteria to sub-MICs of antibiotics has led to the widespread emergence of antibiotic-resistant bacteria. In this study, three bacterial species from the Enterobacteriaceae family (Raoultella ornithinolytica, Pantoea agglomerans and Klebsiella quasivariicola) were isolated from water. The antibiotic susceptibility of these bacteria to 16 antibiotics was then investigated. The effects of sub-MICs of four selected antibiotics (kanamycin, chloramphenicol, meropenem, and ciprofloxacin) on the growth, biofilm formation, surface polysaccharide production, siderophore production, morphology, and expression of the translational/transcriptional regulatory transformer gene rfaH of these bacteria were analysed. The MICs of kanamycin, chloramphenicol, meropenem, and ciprofloxacin were determined to be 1, 2, 0.03 and 0.03 µg/mL for R. ornithinolytica; 0.6, 6, 0.03 and 0.05 µg/mL for P. agglomerans; and 2, 5, 0.04 and 0.2 µg/mL for K. quasivariicola. The growth kinetics and biofilm formation ability decreased for all three isolates at sub-MICs. The surface polysaccharides of R. ornithinolytica and P. agglomerans increased at sub-MICs. There was no significant change in the siderophore activities of the bacterial isolates, with the exception of MIC/2 meropenem in R. ornithinolytica and MIC/2 kanamycin in K. quasivariicola. It was observed that the sub-MICs of meropenem and ciprofloxacin caused significant changes in bacterial morphology. In addition, the expression of rfaH in R. ornithinolytica and K. quasivariicola increased with the sub-MICs of the selected antibiotics.

Comprehensive Evaluation of Three Important Herbs for Kombucha Fermentation.

Research background: Kombucha is consumed worldwide for its beneficial health effects. Kombucha teas fermented with various herbal infusions have become very important nowadays. Although black tea is used for kombucha fermentation, kombucha teas fermented with different herbal infusions have gained great importance. In this study, three different traditional medicinal plants, namely hop (Humulus lupulus L.), madimak (Polygonum cognatum) and hawthorn (Crataegus monogyna) were used for the fermentation of kombucha beverages, and the bioactivity of these beverages was investigated extensively. Experimental approach: The microbiological profile, bacterial cellulose formation, antibacterial, antiproliferative and antioxidant activities, sensory properties, total phenolic content and flavonoid content of kombucha beverages were investigated. Liquid chromatography-coupled mass spectrometry analysis was used to identify and quantify specific polyphenolic compounds in the samples. Results and conclusions: According to the results, the hawthorn-flavoured kombucha, which has lower free radical scavenging activity than the other samples, came into prominence in terms of sensory properties. All examined kombucha beverages showed a strong cytotoxic effect on Mahlavu and HCT116 cell lines, but only the madimak-flavoured kombucha sample, which had a higher total phenolic/flavonoid content, had antibacterial activity against all microorganisms used in the study. Novelty and scientific contribution: Considering the results of this study, madimak could be an effective herb for the development of new kombucha beverages, although its sensory properties still need to be improved. This study contributes to science in terms of producing new fermented beverages with improved beneficial health effects.

Alterations of growth, biofilm-forming, and gene expression of Bordetella pertussis by antibiotics at sub-minimum inhibitory concentrations.

Bordetella pertussis is the primary agent of the acute respiratory disease pertussis. It has been reported that the disease has recently become more common, especially in adults and adolescents, and adaptation of the pathogen is thought to have an important influence on the recurrence of the disease. This study aims to determine the effect of erythromycin, azithromycin, and trimethoprim-sulfamethoxazole used in the treatment of pertussis on the virulence gene expressions (prn, ptxS1, fhaB), biofilm-forming and growth of B. pertussis. In this study, the minimum inhibitory concentration (MIC) values of azithromycin and erythromycin in B. pertussis local strain Saadet were determined to be 0.09 µg/mL and 0.3 µg/mL, respectively. However, the Tohama-I and Saadet strains were resistant to trimethoprim-sulfamethoxazole (MIC>32 µg/mL). The biofilm-forming of the Saadet strain decreased with the increase in antibiotic doses. It was observed that 1/32MIC erythromycin and 1/32MIC azithromycin upregulated the expression of fhaB in Tohama-I, whereas the expression of ptxS1 and prn significantly decreased in sub-MICs of erythromycin. In the Saadet strain, only ptxS1 was highly expressed at 1/16MIC azithromycin and erythromycin (p > 0.05). This is the first study to investigate the effect of sub-MIC antibiotics on the expression of virulence genes and biofilm-forming of B. pertussis.

Bordetella pertussis and outer membrane vesicles.

Bordetella pertussis is the causative agent of a respiratory infection called pertussis (whooping cough) that can be fatal in newborns and infants. The pathogen produces a variety of antigenic compounds which alone or simultaneously can damage various host cells. Despite the availability of pertussis vaccines and high vaccination coverage around the world, a resurgence of the disease has been observed in many countries. Reasons for the increase in pertussis cases may include increased awareness, improved diagnostic techniques, low vaccine efficacy, especially acellular vaccines, and waning immunity. Many efforts have been made to develop more effective strategies to fight against B. pertussis and one of the strategies is the use of outer membrane vesicles (OMVs) in vaccine formulations. OMVs are attracting great interest as vaccine platforms since they can carry immunogenic structures such as toxins and LPS. Many studies have been carried out with OMVs from different B. pertussis strains and they revealed promising results in the animal challenge and human preclinical model. However, the composition of OMVs differs in terms of isolation and purification methods, strains, culture, and stress conditions. Although the vesicles from B. pertussis represent an attractive pertussis vaccine candidate, further studies are needed to advance clinical research for next-generation pertussis vaccines. This review summarizes general information about pertussis, the history of vaccines against the disease, and the immune response to these vaccines, with a focus on OMVs. We discuss progress in developing an OMV-based pertussis vaccine platform and highlight successful applications as well as potential challenges and gaps.