A Newly Identified Group of P-like (PL) Fimbria Genes from Extraintestinal Pathogenic Escherichia coli (ExPEC) Encode Distinct Adhesin Subunits and Mediate Adherence to Host Cells

Ochoa S, Xicohtencatl-Cortes J. Pathogenesis and Immunomodulation of Urinary Tract Infections Caused by Uropathogenic Escherichia coli

Urinary tract infections (UTIs) are a leading cause of illness in children and adults of all ages, with uropathogenic Escherichia coli (UPEC) being the primary agent responsible. During colonization and subsequent infection of the urinary tract (UT), UPEC requires the expression of genes associated with virulence, such as those that encode the fimbrial adhesins FimH, PapG, and CsgA, as well as the presence of the TosA protein and the flagellar appendages of the bacteria. However, for colonization and infection to be successful, UPEC must overcome the host's immunological barriers, such as physical barriers, expressed peptides and proteins, and immune cells found in the UT. In this context, the UT functions as an integral system where these factors act to prevent the colonization of uropathogens. Significant genetic diversity exists among UPEC strains, and the clonal complex ST131 represents one of the key lineages. This lineage has a high content of virulence genes, multiple mechanisms of antibiotic resistance, and a high frequency of extended-spectrum β-lactamases (ESBLs). New knowledge regarding protein structures known as adhesins and their role in the infection process can help identify therapeutic targets and aid in the design of vaccines. These vaccines could be based on the development of chimeric fusion proteins (FimH + CsgA + PapG), which may significantly reduce the incidence of UTIs in pediatric and adult patients.

Antibacterial activity of the antimicrobial peptide PMAP-36 in combination with tetracycline against porcine extraintestinal pathogenic Escherichia coli in vitro and in vivo

The increase in the emergence of antimicrobial resistance has led to great challenges in controlling porcine extraintestinal pathogenic Escherichia coli (ExPEC) infections. Combinations of antimicrobial peptides (AMPs) and antibiotics can synergistically improve antimicrobial efficacy and reduce bacterial resistance. In this study, we investigated the antibacterial activity of porcine myeloid antimicrobial peptide 36 (PMAP-36) in combination with tetracycline against porcine ExPEC PCN033 both in vitro and in vivo. The minimum bactericidal concentrations (MBCs) of AMPs (PMAP-36 and PR-39) against the ExPEC strains PCN033 and RS218 were 10 μM and 5 μM, respectively. Results of the checkerboard assay and the time-kill assay showed that PMAP-36 and antibiotics (tetracycline and gentamicin) had synergistic bactericidal effects against PCN033. PMAP-36 and tetracycline in combination led to PCN033 cell wall shrinkage, as was shown by scanning electron microscopy. Furthermore, PMAP-36 delayed the emergence of PCN033 resistance to tetracycline by inhibiting the expression of the tetracycline resistance gene tetB. In a mouse model of systemic infection of PCN033, treatment with PMAP-36 combined with tetracycline significantly increased the survival rate, reduced the bacterial load and dampened the inflammatory response in mice. In addition, detection of immune cells in the peritoneal lavage fluid using flow cytometry revealed that the combination of PMAP-36 and tetracycline promoted the migration of monocytes/macrophages to the infection site. Our results suggest that AMPs in combination with antibiotics may provide more therapeutic options against multidrug-resistant porcine ExPEC.

The host specificity of pilus gene traA in Escherichia coli and its use in tracking human fecal pollution

A reliable and accurate fecal source tracking (FST) approach is important in water quality management and preventing foodborne and waterborne diseases. In this study, a genetic marker of Escherichia coli (E. coli) was identified and utilized to differentiate between human and animal sources of fecal contamination. Nucleotide polymorphisms of 14 genes coding for cellular surface proteins, mainly fimbriae, were analyzed using the 22 draft genomes of E. coli strains from human and three domestic animal sources in Japan. A signature sequence, traAh, within the pilin gene traA, was found to be highly associated with E. coli of human origin. Subsequently, an end-point polymerase chain reaction (PCR) assay, namely PCR-Htra, was developed, specifically targeting traAh. The high association between traAh and E. coli of human origin was validated through the PCR-Htra amplification. This encompassed 1045 E. coli strains isolated from surface water, human feces or sewages, and feces from 12 animal species, including domestic and wild animals in the states of Missouri and Virginia in the United States of America (USA). The data suggested that the sensitivity and specificity of PCR-Htra assay were 49.0 % and 99.5 % respectively in distinguishing human-origin E. coli from nonhuman-source ones. Furthermore, the result of our in silico analysis of GenBank® data suggests that traAh may have a global distribution as the sequence was found in human-origin E. coli isolated from at least 14 countries around the world. Thus, the PCR-Htra may provide a new FST tool for rapid and accurate detection of human-origin E. coli, serving as a means to identify human fecal contamination in water.

Bird immunobiological parameters in the dissemination of the biofilm-forming bacteria Escherichia coli

Background and Aim

With the development of industrial maintenance technology, a group of pathogens called avian pathogenic Escherichia coli (APEC) became very common. The initiation, development, and outcome of the infectious process mediated by virulent APEC strains occur through a decrease in the colonization resistance of the intestine, an immunobiological marker of homeostasis stability in susceptible species. This study focused on the pathogenetic features of colibacillosis and the morphological features of E. coli.

Materials and Methods

Clinical, immunological, bacteriological, and histological studies were conducted on 15-day-old white Leghorn birds (n = 20). The birds were divided into two groups: Control group (Group I; n = 10) with birds intranasally inoculated with 0.5 mL of 0.9% NaCl solution and experimental group (Group II; n = 10) with birds intranasally inoculated with 0.5 mL of an E. coli suspension at 1 billion/mL.

Results

During the biofilm formation, clusters of microcolonies were formed as a gel-like intercellular matrix that accumulated due to cell coagulation. The intercellular matrix "glues" heteromorphic cells together and forms a structure of densely packed heteromorphic cells arranged in an orderly manner and growing in different directions. During the experimental reproduction of E. coli, excessive growth was observed in material isolated from poultry. Pathogenic E. coli strains implementing virulence factors adhered to the receptors of erythrocytes, alveolocytes, and enterocytes. Multicellular heterogeneous biofilms, united by an intercellular matrix, were located at the apical poles of the respiratory tract alveolocytes and enterocytes of the terminal ileum villi. Many bacteria exudate containing desquamated epithelial cells with an admixture of mucus, and polymorphonuclear leukocytes were detected in the lumen of the birds' abdominal organs. Invasive bacteria damaged the epithelial layer, violated the endothelial layer of blood vessels, and developed inflammatory hyperemia of the lamina propria of the respiratory and digestive systems' mucous membrane. A correlative dependence of changes developed by the type of delayed hypersensitivity reaction was established. Signs of accidental transformation of the thymus, atrophy of the bursa of Fabricius, disseminated thrombosis, and septic spleen developed. Moreover, toxic cardiomyocyte dystrophy, signs of congestive vascular hyperemia, massive disintegration of lymphocytes, macrophage reactions, perivascular edema resulting from the release of plasma, and shaped blood elements were detected.

Conclusion

The development and outcome of the infectious process in escherichiosis primarily depend on the homeostasis stability of susceptible species and virulence factors of the pathogenic microorganisms. One of the selected strains, E. coli O78:K80 displayed the highest ability to form biofilms. Its strong adhesion ability to bird erythrocytes was demonstrated. Deepening the scientific knowledge of the interaction between eukaryotes and prokaryotes will contribute to a better understanding of the pathogenetic aspects of avian escherichiosis and eventually find promising anti-adhesive drugs that could reduce primary bacterial contamination in vivo and in vitro.