Synthesis of Amphiphilic Copolymers Containing Ciprofloxacin and Amine Groups and Their Antimicrobial Performances As Revealed by Confocal Laser-Scanning Microscopy and Atomic-Force Microscopy

In Situ-Gelling Antimicrobial Poly(oligoethylene glycol methacrylate)-Based Hydrogels Integrating Bound Quaternary Ammonia Compounds and Antibiotic Functionalities for Effective Infected Wound Healing

In situ-gelling antibacterial hydrogels are reported in which two antibacterial entities (quaternary ammonium (QA) groups and the antibiotic ciprofloxacin (CIP)) are tethered to a single precursor based on the anti-fouling polymer poly(oligoethylene glycol methacrylate) (POEGMA). Synergism between the QA and CIP tethers is demonstrated to enable broad-spectrum killing and/or disinfection of both gram-positive and gram-negative bacteria both in vitro and in vivo while also supporting improved functional recovery of uninjured skin morphology. Coupled with the suitable mechanics, swelling capacity, and stability of the gels, the multi-mechanism antibacterial properties of the hydrogels offer promise for treating or preventing infections of burn wounds.

Discovery of Novel Cinnamic Acid Derivatives as Fungicide Candidates

Structural diversity derivatization from natural products is an important and effective method of discovering novel green pesticides. Cinnamic acids are abundant in plants, and their unparalleled structures endow them with various excellent biological activities. A series of novel cinnamic oxime esters were designed and synthesized to develop high antifungal agrochemicals. The antifungal activity, structure-activity relationship, and action mechanism were systematically studied. Compounds 7i, 7u, 7v, and 7x exhibited satisfactory activity against Gaeumannomyces graminis var. tritici, with inhibition rates of ≥90% at 50 μg/mL. Compounds 7z and 7n demonstrated excellent activities against Valsa mali and Botrytis cinerea, with median effective concentration (EC50) values of 0.71 and 1.41 μg/mL, respectively. Compound 7z exhibited 100% protective and curative activities against apple Valsa canker at 200 μg/mL. The control effects of 7n against gray mold on tomato fruits and leaves were all >96%, exhibiting superior or similar effects to those of the commercial fungicide boscalid. Furthermore, the quantitative structure-activity relationship was established to guide the further design of higher-activity compounds. The preliminary results on the action mechanism revealed that 7n treatment could disrupt the function of the nucleus and mitochondria, leading to reactive oxygen species accumulation and cell membrane damage. Its primary biochemical mechanism may be inhibiting fungal ergosterol biosynthesis. The novel structure, simple synthesis, and excellent activity of cinnamic oxime esters render them promising potential fungicides.

Quantitative proteomic analysis reveals the mechanisms of polymyxin B toxicity to Escherichia coli

Polymyxin B is increasingly employed all over the world to treat patients who affected by multidrug-resistant Gram-negative bacteria. Although the mechanism of resistance to polymyxin B is well known, the metabolic role of bacteria in stress response to polymyxin B remains an important task and may help to better understand polymyxin B-related stress response. In this study, the proteome changes of Escherichia coli (E. coli) continuously induced in concentrations of 1.0 mg/L and 10.0 mg/L polymyxin B were revealed. Compared to E. coli (PMB₀), E. coli exposed to polymyxin B at 1.0 mg/L (PMB₁) and 10.0 mg/L (PMB₁₀) resulted in 89 and 314 differentially expressed proteins (DEPs), respectively. Such differences related to fatty acid degradation, quorum sensing and two-component regulatory system pathways. Based on absolute quantitative (iTRAQ) proteomics analysis, this study comprehensively studied the changes of E. coli proteome in culture with concentrations of 1.0 mg/L and 10.0 mg/L polymyxin B through confocal laser scanning microscopy observation, cell viability detection and reactive oxygen species analysis. The results showed that E. coli cultured at concentration of 10.0 mg/L polymyxin B increased the expression levels of multidrug-resistant efflux transporters and efflux pump membrane transporters, which might further improve the pathogens of polymyxin B-resistant bacteria lastingness and evolution. It has emerged globally to resist polymyxin B. The reuse of polymyxin B should be aroused public attention to avoid causing more serious environmental pollution. These findings could provide new insights into polymyxin B-related stress.

Pattern of Disinfection of Root Canal Dentin by Alternated Acid-Base Irrigating Regimen

Objective

To quantify Enterococcus faecalis density in root canal dentin after chemomechanical preparation (CMP) using alternated irrigating regimen.

Methodology

Root canals (RC) were contaminated with E. faecalis (ATCC 19433) for 3 weeks and evident biofilms were obtained. After initial sampling (S1), the CMP was aided by irrigants: saline solution (control; n=12), a conventional regimen (CR) (group 1; n=12) using 5.25% NaOCl and a final rinse with 17% EDTA, and an alternating regimen (AR) of intercalated use of NaOCl and EDTA (group 2, n=12), followed by a second sampling (S2). After 2 weeks, S3 was obtained. Two roots were analyzed by scanning electron microscopy. Each root was divided into cervical, mild, and apical segments and sampling of the superficial (n=90) and deep (n=90) dentin layers was obtained using Gates-Glidden burs. The E. faecalis density (CFU/mg) in log₁₀ was categorized as residual (0 > 0.2), moderate (0.2 ≥ 0.5), or elevated (> 0.5). The prevalence of positive samples in BHI and BHI-A was analyzed by Pearson's chi-square test. The data were normalized by a log₁₀ transformation of CFU and were analyzed by one-way ANOVA and Tukey's tests.

Results

Biofilms were observed only in the control root canal walls. Topographically, the controls and CR showed similar distributions of E. faecalis in the dentin. Microbiologically positive root canals harbored much E. faecalis in the adjacent dentin (p < 0.05). Irrigating saline provided moderate density of E. faecalis in the dentin while CR and AR resulted in a residual density of microorganisms (p < 0.05).

Conclusions

The Enterococcus faecalis density in dentin was influenced by the irrigating regimen and the microbiological status of the root canal. The CMP aided by the alternating regimen interfered with the recolonization of the root canal and topographic distribution of Enterococcus in root dentin.