In vivoinfluence ofin vitroup-regulated genes in the virulence of an APEC strain associated with swollen head syndrome

An overview of the structure and function of the flagellar hook FlgE protein

The flagellum is an important organelle for the survival of bacteria and consists of a basal body, hook, and filament. The FlgE protein is the subunit of the hook that connects the basal body and the filament and determines the motility of bacteria. Also, flgE gene plays an essential role in flagellar biosynthesis, swimming ability and biofilm formation. Although the intact flagella and the major component filament have been extensively studied, so far, little is known about the comprehensive understanding of flagellar hook and FlgE. Here in this review, we summarize the structures of flagellar hook and its subunit FlgE in various species and physiological functions of FlgE, including the hook assembly, the structural characteristics of flagellar hook, the mechanical properties of hook, and the similarities and differences between FlgE (hook) and FlgG (distal rod), with special attention on the interaction of FlgE with other molecules, the antigenicity and pro-inflammatory effect of FlgE, and cross-linking of FlgE in spirochetes. We hope our summary of this review could provide a better understanding of the FlgE protein and provide some useful information for developing new effective antibacterial drugs in the future work.

Whatever makes them stick - Adhesins of avian pathogenic Escherichia coli

Avian pathogenic Escherichia coli (APEC) is associated with extraintestinal infections and the development of colibacillosis, causing high mortality in farm birds and extensive losses in the poultry industry worldwide. The virulence of APEC is a complex phenomenon associated with numerous mechanisms involving a variety of extracellular and intracellular structures to overcome host barriers. Initial bacterial attachment or adhesion to host cells is vital to bacterial pathogenesis and is determined by various adhesins. These proteins protect pathogens against possible host defense mechanisms, enabling the effective use of other virulence attributes. Considering this property, the current review provides a systematic and in-depth analysis of the latest information on adhesins analyzed in APEC strains. This review discusses in detail each of the adhesin types, such as fimbrial chaperone-usher, fimbrial curli, nonfimbrial and atypical adhesins, and their components, presenting an opportunity to gain a better understanding of different adhesins and mechanisms employed in pathogenesis. Additionally, the article scrutinizes and notes missing information and potential studies that need to be undertaken to develop a complete understanding of APEC adhesion.

Avian Pathogenic Escherichia coli (APEC): An Overview of Virulence and Pathogenesis Factors, Zoonotic Potential, and Control Strategies

Avian pathogenic Escherichia coli (APEC) causes colibacillosis in avian species, and recent reports have suggested APEC as a potential foodborne zoonotic pathogen. Herein, we discuss the virulence and pathogenesis factors of APEC, review the zoonotic potential, provide the current status of antibiotic resistance and progress in vaccine development, and summarize the alternative control measures being investigated. In addition to the known virulence factors, several other factors including quorum sensing system, secretion systems, two-component systems, transcriptional regulators, and genes associated with metabolism also contribute to APEC pathogenesis. The clear understanding of these factors will help in developing new effective treatments. The APEC isolates (particularly belonging to ST95 and ST131 or O1, O2, and O18) have genetic similarities and commonalities in virulence genes with human uropathogenic E. coli (UPEC) and neonatal meningitis E. coli (NMEC) and abilities to cause urinary tract infections and meningitis in humans. Therefore, the zoonotic potential of APEC cannot be undervalued. APEC resistance to almost all classes of antibiotics, including carbapenems, has been already reported. There is a need for an effective APEC vaccine that can provide protection against diverse APEC serotypes. Alternative therapies, especially the virulence inhibitors, can provide a novel solution with less likelihood of developing resistance.

Acquired mucoid phenotype of Acinetobacter baumannii: Impact for the molecular characteristics and virulence

Mucoid phenotype is an important adaptive defense response for Acinetobacter baumannii (A. baumannii). The aim of this study was to analyze the impact of mucoid phenotype for the molecular characteristics and virulence of A. baumannii. We observed that the colonies of mucoid A. baumannii were moist, with an elevated surface, and the wire drawing result was positive. Transmission electron microscopy data showed that the outer wall of the mucoid colonies was not smooth, had protruding pseudopodia, and was surrounded by a layer of unknown material. Antibiotic susceptibility testing showed that the mucoid strains were multidrug resistant. Notably, the mucoid phenotype and antibiotic resistance were not correlated with the amount of biofilm produced by A. baumannii. MLST data demonstrated that the mucoid A. baumannii strains belonged to type ST2. Most (82.6 %, 38/46) of the multidrug-resistant nonmucoid strains also belonged to the molecular type ST2 and to other types, including ST129, ST158, ST195, ST80 and ST3. Moreover, mucoid A. baumannii strains were more virulent than nonmucoid isolates in a mouse model. The comparative transcriptomic data indicated that 15 genes, especially IX87_RS16955 (acnA), IX87_RS10800 (XanP), IX87_RS12875 (GlmM), IX87_RS00885 and IX87_RS12395 (bfr), were possibly associated with the phenotype and virulence of mucoid A. baumannii. In conclusions, the study comprehensively describes the molecular characteristics and virulence regulatory mechanism of mucoid A. baumannii, and provides novel insights for the prevention and treatment of infections associated with these strains.

Novel biotechnological approaches for monitoring and immunization against resistant to antibiotics Escherichia coli and other pathogenic bacteria

The application of next-generation molecular, biochemical and immunological methods for developing new vaccines, antimicrobial compounds, probiotics and prebiotics for zoonotic infection control has been fundamental to the understanding and preservation of the symbiotic relationship between animals and humans. With increasing rates of antibiotic use, resistant bacterial infections have become more difficult to diagnose, treat, and eradicate, thereby elevating the importance of surveillance and prevention programs. Effective surveillance relies on the availability of rapid, cost-effective methods to monitor pathogenic bacterial isolates. In this opinion article, we summarize the results of some research program initiatives for the improvement of live vaccines against avian enterotoxigenic Escherichia coli using virulence factor gene deletion and engineered vaccine vectors based on probiotics. We also describe methods for the detection of pathogenic bacterial strains in eco-environmental headspace and aerosols, as well as samples of animal and human breath, based on the composition of volatile organic compounds and fatty acid methyl esters. We explain how the introduction of these low-cost biotechnologies and protocols will provide the opportunity to enhance co-operation between networks of resistance surveillance programs and integrated routine workflows of veterinary and clinical public health microbiology laboratories.