Perspectives for Uses of Propolis in Therapy against Infectious Diseases

Propolis has gained wide popularity over the last decades in several parts of the world. In parallel, the literature about propolis composition and biological properties increased markedly. A great number of papers have demonstrated that propolis from different parts of the world is composed mainly of phenolic substances, frequently flavonoids, derived from plant resins. Propolis has a relevant role in increasing the social immunity of bee hives. Experimental evidence indicates that propolis and its components have activity against bacteria, fungi, and viruses. Mechanisms of action on bacteria, fungi, and viruses are known for several propolis components. Experiments have shown that propolis may act synergistically with antibiotics, antifungals, and antivirus drugs, permitting the administration of lower doses of drugs and higher antimicrobial effects. The current trend of growing resistance of microbial pathogens to the available drugs has encouraged the introduction of propolis in therapy against infectious diseases. Because propolis composition is widely variable, standardized propolis extracts have been produced. Successful clinical trials have included propolis extracts as medicine in dentistry and as an adjuvant in the treatment of patients against COVID-19. Present world health conditions encourage initiatives toward the spread of the niche of propolis, not only as traditional and alternative medicine but also as a relevant protagonist in anti-infectious therapy. Production of propolis and other apiary products is environmentally friendly and may contribute to alleviating the current crisis of the decline of bee populations. Propolis production has had social-economic relevance in Brazil, providing benefits to underprivileged people.     

A Multi-component All-DNA Biosensing System Controlled by a DNAzyme

We report on a programmable all-DNA biosensing system that centers on the use of a 4-way junction (4WJ) to transduce a DNAzyme reaction into an amplified signal output. A target acts as a primary input to activate an RNA-cleaving DNAzyme, which then cleaves an RNA-containing DNA substrate that is designed to be a component of a 4WJ. The formation of the 4WJ controls the release of a DNA output that becomes an input to initiate catalytic hairpin assembly (CHA), which produces a second DNA output that controls assembly of a split G-quadruplex as a fluorescence signal generator. The 4WJ can be configured to produce either a turn-off or turn-on switch to control the degree of CHA, allowing target concentration to be determined in a quantitative manner. We demonstrate this approach by creating a sensor for E. coli that could detect as low as 50 E. coli cells mL⁻¹ within 85 min and offers an amplified bacterial detection method that does not require a protein enzyme.     

Segmented continuous-flow multiplex polymerase chain reaction microfluidics for high-throughput and rapid foodborne pathogen detection

High-throughput and rapid identification of multiple foodborne bacterial pathogens is vital in global public health and food industry. To fulfill this need, we propose a segmented continuous-flow multiplex polymerase chain reaction (SCF-MPCR) on a spiral-channel microfluidic device. The device consists of a disposable polytetrafluoroethylene (PTFE) capillary microchannel coiled on three isothermal blocks. Within the channel, n segmented flow regimes are sequentially generated, and m-plex PCR is individually performed in each regime when each mixture is driven to pass three temperature zones, thus providing a rapid analysis throughput of m × n. To characterize the performance of the microfluidic device, continuous-flow multiplex PCR in a single segmented flow has been evaluated by investigating the effect of key reaction parameters, including annealing temperatures, flow rates, polymerase concentration and amount of input DNA. With the optimized parameters, the genomic DNAs from Salmonella enterica, Listeria monocytogenes, Escherichia coli O157:H7 and Staphylococcus aureus could be amplified simultaneously in 19 min, and the limit of detection was low, down to 10² copies μL⁻¹. As proof of principle, the spiral-channel SCF-MPCR was applied to sequentially amplify four different bacterial pathogens from banana, milk, and sausage, displaying a throughput of 4 × 3 with no detectable cross-contamination.     

A phage-displayed chicken single-chain antibody fused to alkaline phosphatase detects Fusarium pathogens and their presence in cereal grains

Fusarium and its poisonous mycotoxins are distributed worldwide and are of particular interest in agriculture and food safety. A simple analytical method to detect pathogens is essential for forecasting diseases and controlling mycotoxins. This article describes a proposed method for convenient and sensitive detection of Fusarium pathogens that uses the fusion of single-chain variable fragment (scFv) and alkaline phosphatase (AP). A highly reactive scFv antibody specific to soluble cell wall-bound proteins (SCWPs) of F. verticillioides was selected from an immunized chicken phagemid library by phage display. The antibody was verified to bind on the surface of ungerminated conidiospores and mycelia of F. verticillioides. The scFv–AP fusion was constructed, and soluble expression in bacteria was confirmed. Both the antibody properties and enzymatic activity were retained, and the antigen-binding capacity of the fusion was enhanced by the addition of a linker. Surface plasmon resonance measurements confirmed that the fusion displayed 4-fold higher affinity compared with the fusion's parental scFv antibody. Immunoblot analyses showed that the fusion had good binding capacity to the components from SCWPs of F. verticillioides, and enzyme-linked immunosorbent assays revealed that the detection limit of the fungus was below 10⁻² μg mL⁻¹, superior to the scFv antibody. The fusion protein was able to detect fungal concentrations as low as 10⁻³ mg g⁻¹ of maize grains in both naturally and artificially contaminated samples. Thus, the fusion can be applied in rapid and simple diagnosis of Fusarium contamination in field and stored grain or in food.     

Direct growth of hierarchically structured titanate nanotube filtration membrane for removal of waterborne pathogens

A hierarchical titanate nanotube based filtration membrane was fabricated and successfully applied for bacteria removal. A facile and effective membrane fabrication method was developed to directly grow a hierarchical titanate nanotube selective layer onto a porous metal membrane substrate. The method is a one-pot synthesis method, eliminates the needs for tedious and costly multiple-coating approach. The resultant membrane possesses a unique porous structure with strong mechanical strength, intrinsically free of cracks and pinholes, and can be readily regenerated by a simple pressure driven back-flushing process. Successful separation of E. coli demonstrates the applicability of the titanate nanotube membrane for waterborne pathogens removal, which would be of a great interest to the water purification applications, especially for the purified recycling water applications. The high selectivity and flux of the nanotube membrane in addition to its excellent biocompatibility and nontoxic nature make such a membrane highly attractive to medical applications for removal of pathogens and other unwanted biological constituents with sizes greater than 50 nm from highly complex medium.     

Effects of Insecticides and Microbiological Contaminants on Apis mellifera Health

Over the past two decades, there has been an alarming decline in the number of honey bee colonies. This phenomenon is called Colony Collapse Disorder (CCD). Bee products play a significant role in human life and have a huge impact on agriculture, therefore bees are an economically important species. Honey has found its healing application in various sectors of human life, as well as other bee products such as royal jelly, propolis, and bee pollen. There are many putative factors of CCD, such as air pollution, GMO, viruses, or predators (such as wasps and hornets). It is, however, believed that pesticides and microorganisms play a huge role in the mass extinction of bee colonies. Insecticides are chemicals that are dangerous to both humans and the environment. They can cause enormous damage to bees’ nervous system and permanently weaken their immune system, making them vulnerable to other factors. Some of the insecticides that negatively affect bees are, for example, neonicotinoids, coumaphos, and chlorpyrifos. Microorganisms can cause various diseases in bees, weakening the health of the colony and often resulting in its extinction. Infection with microorganisms may result in the need to dispose of the entire hive to prevent the spread of pathogens to other hives. Many aspects of the impact of pesticides and microorganisms on bees are still unclear. The need to deepen knowledge in this matter is crucial, bearing in mind how important these animals are for human life.     

儿茶素-稀土配合物的合成、表征及抗菌活性

以稀土(Re³⁺)和儿茶素(C)为原料,由液相合成法制备了3种(La³⁺-C、Gd³⁺-C、Er³⁺-C)配合物,结合傅里叶变换红外光谱、紫外光谱、X射线光电子能谱及配位数测定对配合物结构进行表征,确定了配合物的配位数为8。并采用牛津杯法、最小抑菌浓度(MIC)及最小杀菌浓度(MBC)等三种方法测定了Re³⁺-C对大肠杆菌、金黄色葡萄球菌、绿脓杆菌、沙门氏菌4种食源性细菌的抗菌性能。结果表明,这3种稀土配合物对各试验菌株均表现不同程度的抑制能力,相较Re³⁺和C而言,Re³⁺-C配合物的抑菌性能均有显著的提高。Re³⁺-C的抑菌活性顺序为：Gd³⁺-C > La³⁺-C > Er³⁺-C,其中Gd³⁺-C对4种细菌的MIC值分别为：1.550、0.097、0.780、1.550 μmol·mL⁻¹,MBC值分别为3.100、0.194、1.550、1.550 μmol·mL⁻¹,Gd³⁺-C对金黄色葡萄球菌表现出最佳的抑菌和杀菌能力。     

表面增强拉曼光谱技术在快速、灵敏检测食源性致病菌中的应用

食源性致病菌的快速、灵敏检测是食品和药品安全领域关注的重点.表面增强拉曼光谱(SERS)技术凭借其检测速度快、信息丰富、灵敏度高、无损等优势在食源性致病菌的快速、灵敏检测中受到广泛关注.本文从SERS检测基底材料入手,综述了液相基底、刚性固相基底、柔性固相基底等材料的特点和性能,并对其在致病菌快速、灵敏检测中的应用进行...     

Antimicrobial activity of spices essential oils and its effectiveness on mature biofilms of human pathogens

Abstract

The antibacterial activity of Pimpinella anisum L., Cinnamomum zeylanicum, Syzygium aromaticum, and Cuminum cyminum L. essential oils (EOs) against some common pathogenic microorganisms (Staphylococcus aureus ATCC 6538, Staphylococcus epidermidis ATCC 14990, Enterococcus faecalis ATCC 29212, Streptococcus pyogenes ATCC 1915, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853, Aeromonas hydrophila ATCC 7966, Proteus mirabilis ATCC 10005, Klebsiella pneumoniae ATCC 13883, and Candida albicans ATCC 10231) and their biofilms was studied. The EOs inhibitory effects were evaluated by both Agar Well Diffusion assay and Minimum Inhibitory Concentration (MIC) determination. The most active EOs, cinnamon and cloves, were also tested on 18, 24, 48, 72?hours mature biofilms. Cinnamon and cloves exhibited the best results showing a significant activity against all the tested bacteria. Concerning biofilm, results suggest that Cinnamomum zeylanicum oil may be a useful approach to impair the biofilm produced by the tested Gram-negative bacteria.      

Food microbiology update emerging foodborne pathogens

A review of three “emerging” foodborne pathogen groups is presented, includingCampylobacter jejuni/coli, Yersinia enterocolitica, and foodborneVibrio sp.