We identified a carbohydrate metabolic operon (frz) that is highly associated with extraintestinal pathogenic Escherichia coli (ExPEC) strains. The frz operon codes for three subunits of a phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS) transporter of the fructose subfamily, for a transcriptional activator of PTSs of the MgA family, for two type II ketose-1,6-bisphosphate aldolases, for a sugar-specific kinase (repressor, open reading frame, kinase family [ROK]), and for a protein of the cupin superfamily. We proved that the frz operon promotes bacterial fitness under stressful conditions, such as oxygen restriction, late stationary phase of growth, or growth in serum or in the intestinal tract. Furthermore, we showed that frz is involved in adherence to and internalization in human type II pneumocytes, human enterocytes, and chicken liver cells by favoring the ON orientation of the fim operon promoter and thus acting on the expression of type 1 fimbriae, which are the major ExPEC adhesins. Both the PTS activator and the metabolic enzymes encoded by the frz operon are involved in these phenotypes.

BackgroundLocomotor disorders and infections by Escherichia coli represent major concerns to the poultry industry worldwide. Avian pathogenic E. coli (APEC) is associated with extraintestinal infections leading to respiratory or systemic disease known as colibacillosis. The most common lesions seen in cases of colibacillosis are perihepatitis, airsacculitis, pericarditis, peritonitis/salpingitis and arthritis. These diseases are responsible for significant economic losses in the poultry industry worldwide. E. coli has been recently isolated from vertebral osteomyelitis cases in Brazil and there are no data on molecular and phenotypic characteristics of E. coli strains isolated from lesions in the locomotor system of broilers. This raised the question whether specific E. coli strains could be responsible for bone lesions in broilers. The aim of this study was to assess these characteristics of E. coli strains isolated from broilers presenting vertebral osteomyelitis and arthritis in Brazil.ResultsFifteen E. coli strains from bone lesions were submitted to APEC diagnosis and setting of ECOR phylogenic group, O serogroup, flagella type, virulence genes content, genetic patterns by Pulsed Field Gel Electrophoresis (PFGE) and Multilocus Sequence Typing (MLST). In addition, bacterial isolates were further characterized through a lethality test, serum resistance test and antibiotic resistance profile. E. coli strains harbored different genetic pattern as assessed by PFGE, regardless of flock origin and lesion site. The strains belonged to seven sequence types (STs) previously described (ST117, ST101, ST131, ST 371 and ST3107) or newly described in this study (ST5766 and ST5856). ECOR group D (66.7 %) was the most frequently detected. The strains belonged to diverse serogroups (O88, O25, O12, and O45), some of worldwide importance. The antibiotic resistance profile confirmed strains’ diversity and revealed a high proportion of multidrug-resistant strains (73 %), mainly to quinolones and beta-lactams, including third generation cephalosporin. The percentage of resistance to tetracycline was moderate (33 %) but always associated with multidrug resistance.ConclusionsOur results demonstrated that vertebral osteomyelitis and arthritis in broilers can be associated with highly diverse E. coli based on molecular and phenotypic characteristics. There was no specific virulence patterns of the E. coli strains associated with vertebral osteomyelitis or arthritis. Also, E. coli strains were frequently multidrug resistant and belonged to STs commonly shared by APEC and human ExPEC strains.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-016-0762-0) contains supplementary material, which is available to authorized users.

Escherichia coli strains that cause septicemia of poultry often possess F1 (type 1) fimbriae (encoded by pil [fim] homologous gene clusters) and/or P fimbriae (encoded by pap homologous gene clusters). These fimbriae are thought to be involved in infection and colonization. To study the dynamics of infection due to E. coli with different virulence determinant profiles and to examine the expression of these fimbriae in vivo, three pathogenic E. coli isolates--O1 (pil+/pap+), O2 (pil+/pap), and O78 (pil+/pap+)--were administered intratracheally to 1.5-week-old chickens. Chickens were euthanatized from 3 to 144 hr after infection. The three isolates caused lesions in 30 to 55% of birds. Colonization rates of the trachea, lungs, internal organs, and pericardial fluid were similar for all three isolates, whereas significant differences among isolates were observed in colonization of the air sacs and blood. Bacteria appeared rapidly in the blood, liver, and spleen, whereas presence in the pericardial fluid generally occurred only after 24 hr postinoculation. The dynamics of colonization of the air sacs varied among isolates. Immunofluorescence of frozen tissue sections demonstrated F1 fimbriae (pil expressed) but not P fimbriae on all three isolates colonizing the trachea and on the O1 and O78 isolates colonizing the air sacs. Results suggest that F1 fimbriae are involved in the early stages of development of colisepticemia by promoting association of pathogenic E. coli with the trachea and air sacs of chickens.

IbeA in extraintestinal pathogenic Escherichia coli (ExPEC) strains was previously described for its role in invasion. Here we investigated the role of IbeA and IbeT, encoded by a gene located downstream of ibeA, in the adhesion of the avian ExPEC strain BEN2908 to human brain microvascular endothelial cells (HBMEC). The ⌬ibeA mutant was less adhesive to HBMEC than the wild-type strain BEN2908 was. Because strain BEN2908 also expresses type 1 fimbriae, we measured the adhesion specifically due to IbeA by comparing the adhesive properties of a ⌬fim derivative of strain BEN2908 to those of a double ⌬fim ⌬ibeA mutant. No differences were observed, indicating that the reduction of adhesion in BEN2908 ⌬ibeA could be due to a decrease in type 1 fimbria expression. We indeed showed that the decreased adhesion of BEN2908 ⌬ibeA was correlated with a decrease in type 1 fimbria expression. Accordingly, more bacteria had a fim promoter orientated in the off position in a culture of BEN2908 ⌬ibeA than in a culture of BEN2908. Expression of fimB and fimE, two genes encoding recombinases participating in controlling the orientation of the fim promoter, was decreased in BEN2908 ⌬ibeA. A reduction of type 1 fimbria expression due to a preferential orientation of the fim promoter in the off position was also seen in an ibeT mutant of strain BEN2908. We finally suggest a role for IbeA and IbeT in modulating the expression of type 1 fimbriae through an as yet unknown mechanism.Extraintestinal pathogenic Escherichia coli (ExPEC) strains are responsible for a wide range of diseases in humans and animals. In humans, almost 80% of urinary tract infections, as well as almost 20% of newborn meningitis cases, are caused by ExPEC strains (23,45). In chickens, ExPEC strains are responsible for avian colibacillosis, which results in different syndromes, ranging from superficial dermatitis to respiratory infections that frequently develop into systemic infections (12,32). Phylogenetic studies have shown that avian ExPEC strains are closely related to human ExPEC strains (40, 44). Additionally, avian ExPEC strains share common virulence genes with ExPEC strains isolated from patients with urinary tract infections or meningitis (16,40,44). Several potential virulence factors have been described for ExPEC strains. These virulence factors confer different properties, such as adhesion to host cells through type 1 and P fimbriae, iron acquisition, toxic activity toward eukaryotic cells (cytotoxins), and resistance to host defenses.ibeA is an ExPEC virulence gene that was first described for strain RS218, isolated from a patient with human newborn meningitis (26,46). ibeA encodes a 50-kDa protein and is located on the GimA genomic island. This island is inserted between yjiD and yjiE and is predicted to contain four operons, three of them potentially involved in carbohydrate metabolism (24). In addition to ibeA, the GimA4 operon is predicted to contain two other genes, ibeR and ibeT. ibeR encodes a potential transcriptional activator homologous to t...

Mammalian type I interferons (IFNα/β) are known to modulate inflammatory processes in addition to their antiviral properties. Indeed, virus-induced type I interferons regulate the mammalian phagocyte immune response to bacteria during superinfections. However, it remains unresolved whether type I IFNs similarly impact the chicken macrophage immune response. We first evidenced that IFNα and IFNβ act differently in terms of gene expression stimulation and activation of intracellular signaling pathways in chicken macrophages. Next, we showed that priming of chicken macrophages with IFNα increased bacteria uptake, boosted bacterial-induced ROS/NO production and led to an increased transcriptional expression or production of NOS2/NO, IL1B/IL-1β and notably IFNB/IFNβ. Neutralization of IFNβ during bacterial challenge limited IFNα-induced augmentation of the pro-inflammatory response. In conclusion, we demonstrated that type I IFNs differently regulate chicken macrophage functions and drive a pro-inflammatory response to bacterial challenge. These findings shed light on the diverse functions of type I IFNs in chicken macrophages.

Extra-intestinal pathogenic Escherichia coli (ExPEC) strains are responsible for a wide range of diseases in humans and animals. Using in vitro invasion assays and transmission electron microscopy, we showed that BEN2908, an ExPEC strain of avian origin (also termed APEC for Avian Pathogenic E. coli), is able to usurp cellular endocytic pathways to invade A549 human type II pneumocytes and LMH avian hepatocytes where it is able to survive over several days. Although type 1 fimbriae are the major adhesin of BEN2908, proportions of adherent fimbriated or afimbriated bacteria that entered cells were comparable. Internalization of BEN2908 into human pneumocytes reinforces previous studies indicating that APEC strains could represent a zoonotic risk.

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Summary :Although vertical transmission of Pneumocystis in human or animal hosts has often been suspected, no evidence demonstrating this infection route has been furnished until now. This widespread parasite is constantly found in the lungs of rabbits, which spontaneously develop a benign pneumocystosis at weaning.However, the infection source, the method of entry of Pneumocystis organisms into the rabbit and when this mammal is infected, remain to be known. As a few parasites have been