Avian pathogenic Escherichia coli (APEC) strains cause severe respiratory and systemic diseases, threatening food security and avian welfare worldwide. Intensification of poultry production and the ...quick expansion of free-range production systems will increase the incidence of colibacillosis through greater exposure of birds to pathogens and stress. Therapy is mainly based on antibiotherapy and current vaccines have poor efficacy. Serotyping remains the most frequently used diagnostic method, only allowing the identification of a limited number of APEC strains. Several studies have demonstrated that the most common virulence factors studied in APEC are all rarely present in the same isolate, showing that APEC strains constitute a heterogeneous group. Different isolates may harbor different associations of virulence factors, each one able to induce colibacillosis. Despite its economical relevance, pathogenesis of colibacillosis is poorly understood. Our knowledge on the host response to APEC is based on very descriptive studies, mostly restricted to bacteriological and histopathological analysis of infected organs such as lungs. Furthermore, only a small number of APEC isolates have been used in experimental studies. In the present review, we discuss current knowledge on APEC diversity and virulence, including host response to infection and the associated inflammatory response with a focus on pulmonary colibacillosis.
In the present review, we discuss current knowledge on APEC diversity and virulence, including host response to infection and the associated inflammatory response with a focus on pulmonary colibacillosis.
Bacterial wilt caused by the Ralstonia solanacearum species complex (RSSC) is among the most important plant diseases worldwide, severely affecting a high number of crops and ornamental plants in ...tropical regions. Only a limited number of phages infecting R. solanacearum have been isolated over the years, despite the importance of this bacterium and the associated plant disease. The antibacterial effect or morphological traits of these R. solanacearum viruses have been well studied, but not their genomic features, which need deeper consideration. This study reports the full genome of 23 new phages infecting RSSC isolated from agricultural samples collected in Mauritius and Reunion islands, particularly affected by this plant bacterial pathogen and considered biodiversity hotspots in the Southwest Indian Ocean. The complete genomic information and phylogenetic classification is provided, revealing high genetic diversity between them and weak similarities with previous related phages. The results support our proposal of 13 new species and seven new genera of R. solanacearum phages. Our findings highlight the wide prevalence of phages of RSSC in infected agricultural settings and the underlying genetic diversity. Discoveries of this kind lead more insight into the diversity of phages in general and to optimizing their use as biocontrol agents of bacterial diseases of plants in agriculture.
Avian pathogenic Escherichia coli (APEC) causes colibacillosis, the main bacterial disease in poultry leading to significant economic losses worldwide. Antibiotic treatments favor the emergence of ...multidrug-resistant bacteria, and preventive measures are insufficient to control the disease. There is increasing interest in using the potential of bacteriophages, not only for phage therapy but also for prevention and biocontrol. This study aimed to evaluate the efficacy of a phage cocktail administered in ovo to prevent avian colibacillosis in chicks. When 4 different phages (REC, ESCO3, ESCO47, and ESCO58), stable under avian physiological conditions, were combined and inoculated at 17 embryogenic days (ED), they were transmitted to the newly hatched chicks. In a second trial, the 4-phage cocktail was inoculated into the allantoic fluid at ED16 and after hatch 1-day-old chicks were challenged with the O2 APEC strain BEN4358 inoculated subcutaneously. Two phages (REC and ESCO3) were still detected in the ceca of surviving chicks at the end of the experiment (7-days postinfection). Chicks that received the phages in ovo did not develop colibacillosis lesions and showed a significant decrease in intestinal BEN4358 load (8.00 × 107 CFU/g) compared to the challenged chicks (4.52 × 108 CFU/g). The majority of the reisolated bacteria from the ceca of surviving chicks had developed full resistance to ESCO3 phage, and only 3 were resistant to REC phage. The partially or complete resistance of REC phage induced a considerable cost to bacterial virulence. Here, we showed that phages inoculated in ovo can partially prevent colibacillosis in 1-wk-old chicks. The reduction in the APEC load in the gut and the decreased virulence of some resistant isolates could also contribute to control the disease.
Poultry production is an important agricultural sector for human food worldwide. Chicks after hatch often face health problems leading to economic losses that are deleterious for breeders. Avian ...defensin 2 (AvBD2) is a prominent host defense peptide of the intestinal mucosa of caecum and is involved in the resistance of poultry to bacterial pathogens. This peptide could thus represent an innate immunity marker of robustness of birds. To test this hypothesis by comparing fast-growing and slow-growing lines in different conditions of breeding, the chick's caecal AvBD2 content was analysed according to animal quality and immunity indicators. Chick's caecal tissue sections labelled by immuno-histo-chemistry with newly developed specific antibodies revealed the localization of AvBD2 in the mucosa with high individual variability, without showing differences attributable to quality indicators, but interestingly showing inverse correlation with seric IgM levels in the fast-growing line. The availability of our anti-AvBD2 antibodies to the scientific community opens perspectives to identify the cellular sources of this defensin in the caecal mucosa and to investigate the organisation and function of innate immune arsenal of birds.
The avian respiratory tract is a common entry route for many pathogens and an important delivery route for vaccination in the poultry industry. Immune responses in the avian lung have mostly been ...studied in vivo due to the lack of robust, relevant in vitro and ex vivo models mimicking the microenvironment. Precision-cut lung slices (PCLS) have the major advantages of maintaining the 3-dimensional architecture of the lung and includes heterogeneous cell populations. PCLS have been obtained from a number of mammalian species and from chicken embryos. However, as the embryonic lung is physiologically undifferentiated and immunologically immature, it is less suitable to examine complex host-pathogen interactions including antimicrobial responses. Here we prepared PCLS from immunologically mature chicken lungs, tested different culture conditions, and found that serum supplementation has a detrimental effect on the quality of PCLS. Viable cells in PCLS remained present for ≥ 40 days, as determined by viability assays and sustained motility of fluorescent mononuclear phagocytic cells. The PCLS were responsive to lipopolysaccharide stimulation, which induced the release of nitric oxide, IL-1β, type I interferons and IL-10. Mononuclear phagocytes within the tissue maintained phagocytic activity, with live cell imaging capturing interactions with latex beads and an avian pathogenic Escherichia coli strain. Finally, the PCLS were also shown to be permissive to infection with low pathogenic avian influenza viruses. Taken together, immunologically mature chicken PCLS provide a suitable model to simulate live organ responsiveness and cell dynamics, which can be readily exploited to examine host-pathogen interactions and inflammatory responses.
Gut microbiota is of considerable importance for each host. Despite this, germ-free animals can be obtained and raised to sexual maturity and consequences of the presence or absence of gut microbiota ...on gene expression of the host remain uncharacterised. In this study, we performed an unbiased study of protein expression in the caecum of germ-free and colonised chickens. The major difference between these two groups was in the expression of immunoglobulins which were essentially absent in the germ-free chickens. Microbiota also caused a minor decrease in the expression of focal adhesion and extracellular matrix proteins and an increase in the expression of argininosuccinate synthase ASS1, redox potential sensing, fermentative metabolic processes and detoxification systems represented by sulfotransferases SULT1C3 or SULT1E1. Since we also analysed expression in the caecum of E. coli Nissle and E. faecium DSM7134 mono-associated chickens, we concluded that at least immunoglobulin expression and expression of cystathionine synthase (CBS) was dependent on microbiota composition with E. coli Nissle stimulating more immunoglobulin and PIGR expression and E. faecium DSM7134 stimulating more CBS expression. Gut microbiota and its composition therefore affected protein expression in the chicken caecum though except for immunoglobulin production, the remaining differences were unexpectedly low.
Avian pathogenic
(APEC) cause severe respiratory and systemic disease in chickens, commonly termed colibacillosis. Early immune responses after initial infection are highly important for the outcome ...of the infection. In this study, the early interactions between
-expressing APEC strains of serotypes O1:K1:H7 and O2:K1:H5 and phagocytic cells in the lung of
-reporter transgenic chickens were investigated.
-reporter transgenic chickens express fluorescent protein under the control of elements of the
promoter and enhancer, such that cells of the myeloid lineage can be visualized
and sorted. Chickens were separately inoculated with APEC strains expressing
and culled 6 h post-infection. Flow cytometric analysis was performed to phenotype and sort the cells that harbored bacteria in the lung, and the response of the sorted cells was defined by transcriptomic analysis. Both APEC strains were mainly detected in
-transgene
(
-tg
) and
-tg
MHC II
MRC1L-B
cells and low numbers of APEC were detected in
-tg
MHC II
MRC1L-B
cells. Transcriptomic and flow cytometric analysis identified the APEC
-tg
and
-tg
cells as heterophils and the APEC
-tg
cells as macrophages and dendritic cells. Both APEC strains induced strong inflammatory responses, however in both
-tg
and
-tg
cells, many immune related pathways were repressed to a greater extent or less activated in birds inoculated with APEC O2-
compared to APEC O1-
inoculated birds. Comparison of the immune pathways revealed the aryl hydrocarbon receptor (
) pathway,
and
signaling, heterophil recruitment pathways and the acute phase response, are modulated particularly post-APEC O2-
inoculation. In contrast to
data, APEC O2-
was more invasive in
-tg
cells
than APEC O1-
and had higher survival rates for up to 6 h post-infection. Our data indicate significant differences in the responses induced by APEC strains of prevalent serotypes, with important implications for the design and interpretation of future studies. Moreover, we show that bacterial invasion and survival in phagocyte populations
is not predictive of events in the chicken lung.
Extraintestinal pathogenic Escherichia coli (ExPEC) strains of human and avian origin show similarities that suggest that the avian strains potentially have zoonotic properties. However, the ...phylogenetic relationships between avian and human ExPEC strains are poorly documented, so this possibility is difficult to assess. We used PCR-based phylotyping and multilocus sequence typing (MLST) to determine the phylogenetic relationships between 39 avian pathogenic E. coli (APEC) strains of serogroups O1, O2, O18, and O78 and 51 human ExPEC strains. We also compared the virulence genotype and pathogenicity for chickens of APEC strains and human ExPEC strains. Twenty-eight of the 30 APEC strains of serogroups O1, O2, and O18 were classified by MLST into the same subcluster (B2-1) of phylogenetic group B2, whereas the 9 APEC strains of serogroup O78 were in phylogenetic groups D (3 strains) and B1 (6 strains). Human ExPEC strains were closely related to APEC strains in each of these three subclusters. The 28 avian and 25 human strains belonging to phylogenetic subcluster B2-1 all expressed the K1 antigen and presented no significant differences concerning the presence of other virulence factors. Moreover, human strains of this phylogenetic subcluster were highly virulent for chicks, so no host specificity was identified. Thus, APEC strains of serotypes O1:K1, O2:K1, and O18:K1 belong to the same highly pathogenic clonal group as human E. coli strains of the same serotypes isolated from cases of neonatal meningitis, urinary tract infections, and septicemia. These APEC strains constitute a potential zoonotic risk.
The increase in antibiotic-resistant avian-pathogenic Escherichia coli (APEC), the causative agent of colibacillosis in poultry, warrants urgent research and the development of alternative therapies. ...This study describes the isolation and characterization of 19 genetically diverse, lytic coliphages, 8 of which were tested in combination for their efficacy in controlling
APEC infections. Genome homology analysis revealed that the phages belong to nine different genera, one of them being a novel genus (
). One phage, REC, was derived from a recombination event between two
phages (ESCO5 and ESCO37) isolated in this study. Twenty-six of the 30 APEC strains tested were lysed by at least one phage. Phages exhibited varying infectious capacities, with narrow to broad host ranges. The broad host range of some phages could be partially explained by the presence of receptor-binding protein carrying a polysaccharidase domain. To demonstrate their therapeutic potential, a phage cocktail consisting of eight phages belonging to eight different genera was tested against BEN4358, an APEC O2 strain.
, this phage cocktail fully inhibited the growth of BEN4358. In a chicken lethality embryo assay, the phage cocktail enabled 90% of phage-treated embryos to survive infection with BEN4358, compared with 0% of nontreated embryos, indicating that these novel phages are good candidates to successfully treat colibacillosis in poultry.
Colibacillosis, the most common bacterial disease affecting poultry, is mainly treated by antibiotics. Due to the increased prevalence of multidrug-resistant avian-pathogenic Escherichia coli, there is an urgent need to assess the efficacy of alternatives to antibiotherapy, such as phage therapy. Here, we have isolated and characterized 19 coliphages that belong to nine phage genera. We showed that a combination of 8 of these phages was efficacious
to control the growth of a clinical isolate of E. coli. Used
, this phage combination allowed embryos to survive APEC infection. Thus, this phage combination represents a promising treatment for avian colibacillosis.
PDF
