Influence of pig gut microbiota on Mycoplasma hyopneumoniae susceptibility.

This study investigated the influence of gut microbiome composition in modulating susceptibility to Mycoplasma hyopneumoniae in pigs. Thirty-two conventional M. hyopneumoniae free piglets were randomly selected from six different litters at 3 weeks of age and were experimentally inoculated with M. hyopneumoniae at 8 weeks of age. Lung lesion scores (LS) were recorded 4 weeks post-inoculation (12 weeks of age) from piglet lungs at necropsy. Fecal bacterial community composition of piglets at 3, 8 and 12 weeks of age were targeted by amplifying the V3-V4 region of the 16S rRNA gene. The LS ranged from 0.3 to 43% with an evident clustering of the scores observed in piglets within litters. There were significant differences in species richness and alpha diversity in fecal microbiomes among piglets within litters at different time points (p < 0.05). The dissimilarity matrices indicated that at 3 weeks of age, the fecal microbiota of piglets was more dissimilar compared to those from 8 to 12 weeks of age. Specific groups of bacteria in the gut that might predict the decreased severity of M. hyopneumoniae associated lesions were identified. The microbial shift at 3 weeks of age was observed to be driven by the increase in abundance of the indicator family, Ruminococcaceae in piglets with low LS (p < 0.05). The taxa, Ruminococcus_2 having the highest richness scores, correlated significantly between litters showing stronger associations with the lowest LS (r = -0.49, p = 0.005). These findings suggest that early life gut microbiota can be a potential determinant for M. hyopneumoniae susceptibility in pigs.

A novel two-component signaling system facilitates uropathogenic Escherichia coli's ability to exploit abundant host metabolites.

Two-component signaling systems (TCSs) are major mechanisms by which bacteria adapt to environmental conditions. It follows then that TCSs would play important roles in the adaptation of pathogenic bacteria to host environments. However, no pathogen-associated TCS has been identified in uropathogenic Escherichia coli (UPEC). Here, we identified a novel TCS, which we termed KguS/KguR (KguS: α-ketoglutarate utilization sensor; KguR: α-ketoglutarate utilization regulator) in UPEC CFT073, a strain isolated from human pyelonephritis. kguS/kguR was strongly associated with UPEC but was found only rarely among other E. coli including commensal and intestinal pathogenic strains. An in vivo competition assay in a mouse UTI model showed that deletion of kguS/kguR in UPEC CFT073 resulted in a significant reduction in its colonization of the bladders and kidneys of mice, suggesting that KguS/KguR contributed to UPEC fitness in vivo. Comparative proteomics identified the target gene products of KguS/KguR, and sequence analysis showed that TCS KguS/KguR and its targeted-genes, c5032 to c5039, are encoded on a genomic island, which is not present in intestinal pathogenic E. coli. Expression of the target genes was induced by α-ketoglutarate (α-KG). These genes were further shown to be involved in utilization of α-KG as a sole carbon source under anaerobic conditions. KguS/KguR contributed to the regulation of the target genes with the direct regulation by KguR verified using an electrophoretic mobility shift assay. In addition, oxygen deficiency positively modulated expression of kguS/kguR and its target genes. Taken altogether, this study describes the first UPEC-associated TCS that functions in controlling the utilization of α-ketoglutarate in vivo thereby facilitating UPEC adaptation to life inside the urinary tract.

FNR regulates expression of important virulence factors contributing to pathogenicity of uropathogenic Escherichia coli.

Uropathogenic Escherichia coli (UPEC) is responsible for the majority of urinary tract infections (UTIs), which are some of the world's most common bacterial infections of humans. Here, we examined the role of FNR (fumarate and nitrate reduction), a well-known global regulator, in the pathogenesis of UPEC infections. We constructed an fnr deletion mutant of UPEC CFT073 and compared it to the wild type for changes in virulence, adherence, invasion, and expression of key virulence factors. Compared to the wild type, the fnr mutant was highly attenuated in the mouse model of human UTI and showed severe defects in adherence to and invasion of bladder and kidney epithelial cells. Our results showed that FNR regulates motility and multiple virulence factors, including expression of type I and P fimbriae, modulation of hemolysin expression, and expression of a novel pathogenicity island involved in α-ketoglutarate metabolism under anaerobic conditions. Our results demonstrate that FNR is a key global regulator of UPEC virulence and controls expression of important virulence factors that contribute to UPEC pathogenicity.

Hemolytic porcine intestinal Escherichia coli without virulence-associated genes typical of intestinal pathogenic E. coli.

Testing 1,666 fecal or intestinal samples from healthy and diarrheic pigs, we obtained hemolytic Escherichia coli isolates from 593 samples. Focusing on hemolytic E. coli isolates without virulence-associated genes (VAGs) typical for enteropathogens, we found that such isolates carried a broad variety of VAGs typical for extraintestinal pathogenic E. coli.

Comparative Analysis of Phylogenetic Assignment of Human and Avian ExPEC and Fecal Commensal Escherichia coli Using the (Previous and Revised) Clermont Phylogenetic Typing Methods and its Impact on Avian Pathogenic Escherichia coli (APEC) Classification.

The Clermont scheme has been used for subtyping of Escherichia coli since it was initially described in early 2000. Since then, researchers have used the scheme to type and sub-type commensal E. coli and pathogenic E. coli, such as extraintestinal pathogenic E. coli (ExPEC), and compare their phylogenetic assignment by pathogenicity, serogroup, distribution among ExPEC of different host species and complement of virulence and resistance traits. Here, we compare assignments of human and avian ExPEC and commensal E. coli using the old and revised Clermont schemes to determine if the new scheme provides a refined snapshot of isolate classification. 1,996 E. coli from human hosts and poultry, including 84 human neonatal meningitis E. coli isolates, 88 human vaginal E. coli, 696 human uropathogenic E. coli, 197 healthy human fecal E. coli, 452 avian pathogenic E. coli (APEC), 200 retail poultry E. coli, 80 crop and gizzard E. coli from healthy poultry at slaughter and 199 fecal E. coli from healthy birds at slaughter. All isolates were subject to phylogenetic analysis using the Clermont et al. (2000, 2013) schemes and compared to determine the effect of the new classification on strain designation. Most of the isolates' strain designation remained where they were originally assigned. Greatest designation change occurred in APEC where 53.8% of isolates were reclassified; while classification rates among human strains ranged from 8 to 14%. However, some significant changes were observed for UPEC associated strains with significant (P < 0.05) designation changes observed from A to C and D to E or F phylogenetic types; a similar designation change was noted among NMEC for D to F designation change. Among the APEC significant designation changes were observed from A to C and D to E and F. These studies suggest that the new scheme provides a tighter and more meaningful definition of some ExPEC; while the new typing scheme has a significant impact on APEC classification. A comparison of phylogenetic group assignment by content of virulence, resistance, replicon and pathogenicity island genes in APEC suggests that insertion of pathogenicity islands into the genome appears to correlate closely with revised phylogenetic assignment.

Complete Genome Sequence of the Avian-Pathogenic Escherichia coli Strain APEC O18.

Avian-pathogenic Escherichia coli (APEC) is the causative agent of colibacillosis, a disease that affects all facets of poultry production worldwide, resulting in multimillion dollar losses annually. Here, we report the genome sequence of an APEC O18 sequence type 95 (ST95) strain associated with disease in a chicken.

Complete Genome Sequence of the Neonatal Meningitis-Causing Escherichia coli Strain NMEC O18.

Neonatal meningitis Escherichia coli (NMEC) is a common agent of neonatal bacterial meningitis, causing high neonatal mortality and neurologic sequelae in its victims. Here, we present the complete genome sequence of NMEC O18 (also known as NMEC 58), a highly virulent (O18ac:K1, ST416) strain.

Complete Genomic Sequence of an Avian Pathogenic Escherichia coli Strain of Serotype O7:HNT.

Avian pathogenic Escherichia coli (APEC) is associated with colibacillosis in poultry. Here, we present the first complete sequence of an APEC strain of the O7:HNT serotype and ST73 sequence type, isolated from a broiler with cellulitis. Complete genomes of APEC with distinct genetic backgrounds may be useful for comparative analysis.

Genetic Characterization of ExPEC-Like Virulence Plasmids among a Subset of NMEC.

Neonatal Meningitis Escherichia coli (NMEC) is one of the most common causes of neonatal bacterial meningitis in the US and elsewhere resulting in mortality or neurologic deficits in survivors. Large plasmids have been shown experimentally to increase the virulence of NMEC in the rat model of neonatal meningitis. Here, 9 ExPEC-like plasmids were isolated from NMEC and sequenced to identify the core and accessory plasmid genes of ExPEC-like virulence plasmids in NMEC and create an expanded plasmid phylogeny. Results showed sequenced virulence plasmids carry a strongly conserved core of genes with predicted functions in five distinct categories including: virulence, metabolism, plasmid stability, mobile elements, and unknown genes. The major functions of virulence-associated and plasmid core genes serve to increase in vivo fitness by adding multiple iron uptake systems to the genetic repertoire to facilitate NMEC's survival in the host's low iron environment, and systems to enhance bacterial resistance to host innate immunity. Phylogenetic analysis based on these core plasmid genes showed that at least two lineages of ExPEC-like plasmids could be discerned. Further, virulence plasmids from Avian Pathogenic E. coli and NMEC plasmids could not be differentiated based solely on the genes of the core plasmid genome.

Serotype O18 avian pathogenic and neonatal meningitis Escherichia coli strains employ similar pathogenic strategies for the onset of meningitis.

Neonatal meningitis Escherichia coli K1 (NMEC) are thought to be transmitted from mothers to newborns during delivery or by nosocomial infections. However, the source of E. coli K1 causing these infections is not clear. Avian pathogenic E. coli (APEC) have the potential to cause infection in humans while human E. coli have potential to cause colibacillosis in poultry, suggesting that these strains may lack host specificity. APEC strains are capable of causing meningitis in newborn rats; however, it is unclear whether these bacteria use similar mechanisms to that of NMEC to establish disease. Using four representative APEC and NMEC strains that belong to serotype O18, we demonstrate that these strains survive in human serum similar to that of the prototypic NMEC strain E44, a derivative of RS218. These bacteria also bind and enter both macrophages and human cerebral microvascular endothelial cells (HCMEC/D3) with similar frequency as that of E44. The amino acid sequences of the outer membrane protein A (OmpA), an important virulence factor in the pathogenesis of meningitis, are identical within these representative APEC and NMEC strains. Further, these strains also require FcγRI-α chain (CD64) and Ecgp96 as receptors for OmpA in macrophages and HCMEC/D3, respectively, to bind and enter these cells. APEC and NMEC strains induce meningitis in newborn mice with varying degree of pathology in the brains as assessed by neutrophil recruitment and neuronal apoptosis. Together, these results suggest that serotype O18 APEC strains utilize similar pathogenic mechanisms as those of NMEC strains in causing meningitis.

Complete genome sequence of the avian pathogenic Escherichia coli strain APEC O78.

Colibacillosis, caused by avian pathogenic Escherichia coli (APEC), is a significant disease, causing extensive animal and financial losses globally. Because of the significance of this disease, more knowledge is needed regarding APEC's mechanisms of virulence. Here, we present the fully closed genome sequence of a typical avian pathogenic E. coli strain belonging to the serogroup O78.

Porcine E. coli: virulence-associated genes, resistance genes and adhesion and probiotic activity tested by a new screening method.

We established an automated screening method to characterize adhesion of Escherichia coli to intestinal porcine epithelial cells (IPEC-J2) and their probiotic activity against infection by enteropathogenic E. coli (EPEC). 104 intestinal E. coli isolates from domestic pigs were tested by PCR for the occurrence of virulence-associated genes, genes coding for resistances to antimicrobial agents and metals, and for phylogenetic origin by PCR. Adhesion rates and probiotic activity were examined for correlation with the presence of these genes. Finally, data were compared with those from 93 E. coli isolates from wild boars. Isolates from domestic pigs carried a broad variety of all tested genes and showed great diversity in gene patterns. Adhesions varied with a maximum of 18.3 or 24.2 mean bacteria adherence per epithelial cell after 2 or 6 hours respectively. Most isolates from domestic pigs and wild boars showed low adherence, with no correlation between adhesion/probiotic activity and E. coli genes or gene clusters. The gene sfa/foc, encoding for a subunit of F1C fimbriae did show a positive correlative association with adherence and probiotic activity; however E. coli isolates from wild boars with the sfa/foc gene showed less adhesion and probiotic activity than E. coli with the sfa/foc gene isolated from domestic pigs after 6 hour incubation. In conclusion, screening porcine E. coli for virulence associated genes genes, adhesion to intestinal epithelial cells, and probiotic activity revealed a single important adhesion factor, several probiotic candidates, and showed important differences between E. coli of domestic pigs and wild boars.