The RyfA small RNA regulates oxidative and osmotic stress responses and virulence in uropathogenic Escherichia coli.

Urinary tract infections (UTIs) are a common bacterial infectious disease in humans, and strains of uropathogenic Escherichia coli (UPEC) are the most frequent cause of UTIs. During infection, UPEC must cope with a variety of stressful conditions in the urinary tract. Here, we demonstrate that the small RNA (sRNA) RyfA of UPEC strains is required for resistance to oxidative and osmotic stresses. Transcriptomic analysis of the ryfA mutant showed changes in expression of genes associated with general stress responses, metabolism, biofilm formation and genes coding for cell surface proteins. Inactivation of ryfA in UPEC strain CFT073 decreased urinary tract colonization in mice and the ryfA mutant also had reduced production of type 1 and P fimbriae (pili), adhesins which are known to be important for UTI. Furthermore, loss of ryfA also reduced UPEC survival in human macrophages. Thus, ryfA plays a key regulatory role in UPEC adaptation to stress, which contributes to UTI and survival in macrophages.

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.

Fimbrial adhesins promote bacterial adherence and biofilm formation. Sequencing of avian pathogenic Escherichia coli (APEC) strain QT598 identified new fimbriae belonging to the π group, which we named PL (P-like) fimbriae since the genetic organization and sequence are similar to those of P and related fimbriae. Genes encoding PL fimbriae located on IncF plasmids are present in diverse E. coli isolates from poultry, human systemic infections, and other sources. As with P fimbriae, PL fimbriae exhibit divergence in adhesin-encoding genes and could be divided into 5 classes based on sequence differences in the PlfG adhesin. plf genes from two predominant PlfG adhesin classes, PlfG class I (PlfGI) and PlfGII, were cloned. PL fimbriae were visualized by electron microscopy, associated with increased biofilm, demonstrated distinct hemagglutination profiles, and promoted adherence to human bladder and kidney epithelial cells. The genes encoding hybrid fimbriae were comprised of genes from plfQT598, wherein plfG was replaced by papG; the adhesin-encoding genes were also functional and mediated adherence to epithelial cells, demonstrating compatibility between the components of these two types of fimbriae. Deletion of plf genes did not reduce colonization of the mouse urinary tract in a single-strain infection model. In contrast, loss of plf genes significantly reduced competitive colonization in the mouse kidneys. Furthermore, plf gene expression was increased over 40-fold in the bladder compared to during in vitro culture. Overall, PL fimbriae represent a new group of fimbriae demonstrating both functional differences from and similarities to P fimbriae, which mediated adherence to host cells and improved competitive colonization of the mouse kidney. IMPORTANCE Fimbriae are important colonization factors in many bacterial species. The identification of a new type of fimbriae encoded on some IncF plasmids in E. coli was investigated. Genomic sequences demonstrated these fimbrial gene clusters have genetic diversity, particularly in the adhesin-encoding plfG gene. Functional studies demonstrated differences in hemagglutination specificity, although both types of Plf adhesin under study mediated adherence to human urinary epithelial cells. A plf mutant also showed decreased colonization of the kidneys in a mouse competitive infection model. PL fimbriae may represent previously unrecognized adhesins that could contribute to host specificity and tissue tropism of some E. coli strains.

The Serine Protease Autotransporters TagB, TagC, and Sha from Extraintestinal Pathogenic Escherichia coli Are Internalized by Human Bladder Epithelial Cells and Cause Actin Cytoskeletal Disruption.

TagB, TagC (tandem autotransporter genes B and C), and Sha (Serine-protease hemagglutinin autotransporter) are recently described members of the SPATE (serine protease autotransporters of Enterobacteriaceae) family. These SPATEs can cause cytopathic effects on bladder cells and contribute to urinary tract infection in a mouse model. Bladder epithelial cells form an important barrier in the urinary tract. Some SPATEs produced by pathogenic E. coli are known to breach the bladder epithelium. The capacity of these newly described SPATEs to alter bladder epithelial cells and the role of the serine protease active site were investigated. All three SPATE proteins were internalized by bladder epithelial cells and altered the distribution of actin cytoskeleton. Sha and TagC were also shown to degrade mucin and gelatin respectively. Inactivation of the serine catalytic site in each of these SPATEs did not affect secretion of the SPATEs from bacterial cells, but abrogated entry into epithelial cells, cytotoxicity, and proteolytic activity. Thus, our results show that the serine catalytic triad of these proteins is required for internalization in host cells, actin disruption, and degradation of host substrates such as mucin and gelatin.

The Periplasmic Trehalase Affects Type 1 Fimbria Production and Virulence of Extraintestinal Pathogenic Escherichia coli Strain MT78.

Extraintestinal pathogenic Escherichia coli (ExPEC) is responsible for various infections outside the gastrointestinal tract in humans and other animals. ExPEC strain MT78 is invasive to various nonphagocytic cells and highly virulent in vivo To identify genes required for invasion of nonphagocytic cells by this strain, we applied signature-tagged mutagenesis to generate a library of mutants and tested them for invasion of avian fibroblasts. Mutants showing reduced cellular invasion included those with insertions in the fim operon, encoding type 1 fimbriae. Another attenuated mutant showed a disruption in the treA gene, which encodes a periplasmic trehalase. The substrate of TreA, trehalose, can be metabolized and used as a carbon source or can serve as an osmoprotectant under conditions of osmotic stress in E. coli K-12. We generated and characterized mutant MT78ΔtreA In contrast to the wild type, MT78ΔtreA was able to grow under osmotic stress caused by 0.6 M urea but not in minimal M9 medium with trehalose as the only carbon source. It presented decreased association and invasion of avian fibroblasts, decreased yeast agglutination titer, and impaired type 1 fimbria production. In a murine model of urinary tract infection, MT78ΔtreA was less able to colonize the bladder. All phenotypes were rescued in the complemented mutant. Our results show that the treA gene is needed for optimal production of type 1 fimbriae in ExPEC strain MT78 and that loss of treA significantly reduces its cell invasion capacity and colonization of the bladder in a murine model of urinary tract infection.

Altered Regulation of the Diguanylate Cyclase YaiC Reduces Production of Type 1 Fimbriae in a Pst Mutant of Uropathogenic Escherichia coli CFT073.

The pst gene cluster encodes the phosphate-specific transport (Pst) system. Inactivation of the Pst system constitutively activates the two-component regulatory system PhoBR and attenuates the virulence of pathogenic bacteria. In uropathogenic Escherichia coli strain CFT073, attenuation by inactivation of pst is predominantly attributed to the decreased expression of type 1 fimbriae. However, the molecular mechanisms connecting the Pst system and type 1 fimbriae are unknown. To address this, a transposon library was constructed in the pst mutant, and clones were tested for a regain in type 1 fimbrial production. Among them, the diguanylate cyclase encoded by yaiC (adrA in Salmonella) was identified to connect the Pst system and type 1 fimbrial expression. In the pst mutant, the decreased expression of type 1 fimbriae is connected by the induction of yaiC This is predominantly due to altered expression of the FimBE-like recombinase genes ipuA and ipbA, affecting at the same time the inversion of the fim promoter switch (fimS). In the pst mutant, inactivation of yaiC restored fim-dependent adhesion to bladder cells and virulence. Interestingly, the expression of yaiC was activated by PhoB, since transcription of yaiC was linked to the PhoB-dependent phoA-psiF operon. As YaiC is involved in cyclic di-GMP (c-di-GMP) biosynthesis, an increased accumulation of c-di-GMP was observed in the pst mutant. Hence, the results suggest that one mechanism by which deletion of the Pst system reduces the expression of type 1 fimbriae is through PhoBR-mediated activation of yaiC, which in turn increases the accumulation of c-di-GMP, represses the fim operon, and, consequently, attenuates virulence in the mouse urinary tract infection model.IMPORTANCE Urinary tract infections (UTIs) are common bacterial infections in humans. They are mainly caused by uropathogenic Escherichia coli (UPEC). We previously showed that interference with phosphate homeostasis decreases the expression of type 1 fimbriae and attenuates UPEC virulence. Herein, we identified that alteration of the phosphate metabolism increases production of the signaling molecule c-di-GMP, which in turn decreases the expression of type 1 fimbriae. We also determine the regulatory cascade leading to the accumulation of c-di-GMP and identify the Pho regulon as new players in c-di-GMP-mediated cell signaling. By understanding the molecular mechanisms leading to the expression of virulence factors, we will be in a better position to develop new therapeutics.

HlyF Produced by Extraintestinal Pathogenic Escherichia coli Is a Virulence Factor That Regulates Outer Membrane Vesicle Biogenesis.

Escherichia coli can cause extraintestinal infections in humans and animals. The hlyF gene is epidemiologically associated with virulent strains of avian pathogenic E. coli and human neonatal meningitis-associated E. coli. We demonstrated that culture supernatants of E. coli expressing HlyF induced autophagy in eukaryotic cells. This phenotype coincided with an enhanced production of outer membrane vesicles (OMVs) by bacteria expressing HlyF. The HlyF protein displays a predicted catalytic domain of the short-chain dehydrogenase/reductase superfamily. This conserved domain was involved the ability of HlyF to promote the production of OMVs. The increased production of OMVs was associated with the release of toxins. hlyF was shown to be expressed during extraintestinal infection and to play a role in the virulence of extraintestinal pathogenic E. coli in a chicken model of colibacillosis. This is the first evidence that pathogenic bacteria produce a virulence factor directly involved in the production of OMVs.

The Bacterial Stress-Responsive Hsp90 Chaperone (HtpG) Is Required for the Production of the Genotoxin Colibactin and the Siderophore Yersiniabactin in Escherichia coli.

The genotoxin colibactin, synthesized by Escherichia coli, is a secondary metabolite belonging to the chemical family of hybrid polyketide/nonribosomal peptide compounds. It is produced by a complex biosynthetic assembly line encoded by the pks pathogenicity island. The presence of this large cluster of genes in the E. coli genome is invariably associated with the high-pathogenicity island, encoding the siderophore yersiniabactin, which belongs to the same chemical family as colibactin. The E. coli heat shock protein HtpG (Hsp90Ec) is the bacterial homolog of the eukaryotic molecular chaperone Hsp90, which is involved in the protection of cellular proteins against a variety of environmental stresses. In contrast to eukaryotic Hsp90, the functions and client proteins of Hsp90Ec are poorly known. Here, we demonstrated that production of colibactin and yersiniabactin is abolished in the absence of Hsp90Ec We further characterized an interplay between the Hsp90Ec molecular chaperone and the ClpQ protease involved in colibactin and yersiniabactin synthesis. Finally, we demonstrated that Hsp90Ec is required for the full in vivo virulence of extraintestinal pathogenic E. coli This is the first report highlighting the role of heat shock protein Hps90Ec in the production of two secondary metabolites involved in E. coli virulence.

Comprehensive analysis of flagellin glycosylation in Campylobacter jejuni NCTC 11168 reveals incorporation of legionaminic acid and its importance for host colonization.

Campylobacter jejuni is the leading cause of bacterial gastroenteritis. It relies on several virulence factors for host colonization, including glycosylated flagella. C. jejuni NCTC 11168 modifies its flagellins with pseudaminic acid derivatives. It is also presumed to modify these proteins with legionaminic acid, although no glycopeptide evidence was available at the onset of this study. The enzyme encoded by cj1319 can be used to make legionaminic acid in vitro, but the pathway for legionaminic acid synthesis partially inferred by knockout mutagenesis in Campylobacter coli VC167 excludes Cj1319. To address this contradiction, we examined the presence of legionaminic acid in flagellin glycopeptides of wild-type (WT) C. jejuni NCTC 11168 and of a cj1319 knockout mutant. We used high-energy collision-induced dissociation to obtain amino acid sequences while also visualizing signature sugar oxonium ions. Data analysis was performed with PEAKS software, and spectra were manually inspected for glycopeptide determination and verification. We showed that legionaminic acid is present on the flagellins of C. jejuni NCTC 11168 and that flagellin glycosylation is highly heterogeneous, with up to six different sugars singly present at a given site. We found that the cj1319 mutant produces more legionaminic acid than WT, thus excluding the requirement for Cj1319 for legionaminic acid synthesis. We also showed that this mutant has enhanced chicken colonization compared with WT, which may in part be attributed to the high content of legionaminic acid on its flagella.

Role of capsular modified heptose in the virulence of Campylobacter jejuni.

The Campylobacter jejuni capsular polysaccharide is important for virulence and often contains a modified heptose. In strain ATCC 700819 (a.k.a. NCTC 11168), the modified heptose branches off from the capsular backbone and is directly exposed to the environment. We reported previously that the enzymes encoded by wcaG, mlghB and mlghC are involved in heptose modification. Here, we show that inactivation of any of these genes leads to production of capsule lacking modified heptose and alters the transcription of other capsule modification genes differentially. Inactivation of mlghB or mlghC, but not of wcaG, decreased susceptibility to bile salts and abrogated invasion of intestinal cells. All mutants showed increased sensitivity to serum killing, especially wcaG::cat, and had defects in colonization and persistence in chicken intestine, but did not show significant differences in adhesion, phagocytosis and intracellular survival in murine macrophages. Together, our findings suggest that the capsular heptose modification pathway contributes to bacterial resistance against gastrointestinal host defenses and supports bacterial persistence via its role in serum resistance and invasion of intestinal cells. Our data further suggest a dynamic regulation of expression of this pathway in the gastrointestinal tract.

The small RNA RyhB contributes to siderophore production and virulence of uropathogenic Escherichia coli.

In Escherichia coli, the small regulatory noncoding RNA (sRNA) RyhB and the global ferric uptake regulator (Fur) mediate iron acquisition and storage control. Iron is both essential and potentially toxic for most living organisms, making the precise maintenance of iron homeostasis necessary for survival. While the roles of these regulators in iron homeostasis have been well studied in a nonpathogenic E. coli strain, their impact on the production of virulence-associated factors is still unknown for a pathogenic E. coli strain. We thus investigated the roles of RyhB and Fur in iron homeostasis and virulence of the uropathogenic E. coli (UPEC) strain CFT073. In a murine model of urinary tract infection (UTI), deletion of fur alone did not attenuate virulence, whereas a ΔryhB mutant and a Δfur ΔryhB double mutant showed significantly reduced bladder colonization. The Δfur mutant was more sensitive to oxidative stress and produced more of the siderophores enterobactin, salmochelins, and aerobactin than the wild-type strain. In contrast, while RyhB was not implicated in oxidative stress resistance, the ΔryhB mutant produced lower levels of siderophores. This decrease was correlated with the downregulation of shiA (encoding a transporter of shikimate, a precursor of enterobactin and salmochelin biosynthesis) and iucD (involved in aerobactin biosynthesis) in this mutant grown in minimal medium or in human urine. iucD was also downregulated in bladders infected with the ΔryhB mutant compared to those infected with the wild-type strain. Our results thus demonstrate that the sRNA RyhB is involved in production of iron acquisition systems and colonization of the urinary tract by pathogenic E. coli.

Avian extraintestinal Escherichia coli exhibits enterotoxigenic-like activity in the in vivo rabbit ligated ileal loop assay.

Avian pathogenic Escherichia coli (APEC) strains harbor a number of virulence genes and cause extraintestinal diseases, such as septicemia, swollen-head syndrome, salpingitis, and omphalitis in poultry. APEC strains are not known to cause intestinal diseases. Herein, for the first time, it is reported that APEC strains were able to induce an enterotoxigenic-like effect in rabbit ligated ileal loops. Strain SEPT362 caused cell detachment of the intestinal villi, which also showed a flattened and wilted appearance, but the integrity of the tight junctions was maintained. Additionally, this strain did not adhere to enterocytes in vivo, although adhesin encoding genes ( fimH, csgA, lpfA2-3, and ECP) were present while other lpfA types, sfa, afa, papC, and ral genes were not. This enterotoxigenic-like activity was conserved after thermal treatment of the supernatant at 65°C but not at 100°C. Moreover, experiments based on filtering with different molecular weight cut-off (MWCO) pore sizes demonstrated that the component associated with the observed biological effect has a molecular weight >100 kDa. Blast search and polymerase chain reaction assays for known E. coli virulence factors showed that strain SEPT362 harbors the gene encoding for the toxin EAST-1 and the serine protease autotransporter (SPATE) Tsh, but is negative for genes encoding for the toxins LT-I, STh, STp, Stx1, Stx2, CNF-1, CNF-2, CDT and the SPATEs Sat, Pic, Vat, SigA, SepA, EatA, EspP, or EspC. A cloned copy of the tsh gene in E. coli K-12 was also tested and was shown to have an enterotoxic effect. These results suggest that APEC might induce fluid accumulation in the rabbit gut. The Tsh autotransporter seems to be one of the factors associated with this phenotype.

Multimodal vaccination targeting the receptor binding domains of Clostridioides difficile toxins A and B with an attenuated Salmonella Typhimurium vector (YS1646) protects mice from lethal challenge.

Developing a vaccine against Clostridioides difficile is a key strategy to protect the elderly. Two candidate vaccines using a traditional approach of intramuscular (IM) delivery of recombinant antigens targeting C. difficile toxins A (TcdA) and B (TcdB) failed to meet their primary endpoints in large phase 3 trials. To elicit a mucosal response against C. difficile, we repurposed an attenuated strain of Salmonella Typhimurium (YS1646) to deliver the receptor binding domains (rbd) of TcdA and TcdB to the gut-associated lymphoid tissues, to elicit a mucosal response against C. difficile. In this study, YS1646 candidates with either rbdA or rbdB expression cassettes integrated into the bacterial chromosome at the attTn7 site were generated and used in a short-course multimodal vaccination strategy that combined oral delivery of the YS1646 candidate(s) on days 0, 2, and 4 and IM delivery of recombinant antigen(s) on day 0. Five weeks after vaccination, mice had high serum IgG titers and increased intestinal antigen-specific IgA titers. Multimodal vaccination increased the IgG avidity compared to the IM-only control. In the mesenteric lymph nodes, we observed increased IL-5 secretion and increased IgA+ plasma cells. Oral vaccination skewed the IgG response toward IgG2c dominance (vs IgG1 dominance in the IM-only group). Both oral alone and multimodal vaccination against TcdA protected mice from lethal C. difficile challenge (100% survival vs 30% in controls). Given the established safety profile of YS1646, we hope to move this vaccine candidate forward into a phase I clinical trial.IMPORTANCEClostridioides difficile remains a major public health threat, and new approaches are needed to develop an effective vaccine. To date, the industry has focused on intramuscular vaccination targeting the C. difficile toxins. Multiple disappointing results in phase III trials have largely confirmed that this may not be the best strategy. As C. difficile is a pathogen that remains in the intestine, we believe that targeting mucosal immune responses in the gut will be a more successful strategy. We have repurposed a highly attenuated Salmonella Typhimurium (YS1646), originally pursued as a cancer therapeutic, as a vaccine vector. Using a multimodal vaccination strategy (both recombinant protein delivered intramuscularly and YS1646 expressing antigen delivered orally), we elicited both systemic and local immune responses. Oral vaccination alone completely protected mice from lethal challenge. Given the established safety profile of YS1646, we hope to move these vaccine candidates forward into a phase I clinical trial.

The osmoregulated metabolism of trehalose contributes to production of type 1 fimbriae and bladder colonization by extraintestinal Escherichia coli strain BEN2908.

In Escherichia coli, the disaccharide trehalose can be metabolized as a carbon source or be accumulated as an osmoprotectant under osmotic stress. In hypertonic environments, E. coli accumulates trehalose in the cell by synthesis from glucose mediated by the cytosolic enzymes OtsA and OtsB. Trehalose in the periplasm can be hydrolyzed into glucose by the periplasmic trehalase TreA. We have previously shown that a treA mutant of extraintestinal E. coli strain BEN2908 displayed increased resistance to osmotic stress by 0.6 M urea, and reduced production of type 1 fimbriae, reduced invasion of avian fibroblasts, and decreased bladder colonization in a murine model of urinary tract infection. Since loss of TreA likely results in higher periplasmic trehalose concentrations, we wondered if deletion of otsA and otsB genes, which would lead to decreased internal trehalose concentrations, would reduce resistance to stress by 0.6 M urea and promote type 1 fimbriae production. The BEN2908ΔotsBA mutant was sensitive to osmotic stress by urea, but displayed an even more pronounced reduction in production of type 1 fimbriae, with the consequent reduction in adhesion/invasion of avian fibroblasts and reduced bladder colonization in the murine urinary tract. The BEN2908ΔtreAotsBA mutant also showed a reduction in production of type 1 fimbriae, but in contrast to the ΔotsBA mutant, resisted better than the wild type in the presence of urea. We hypothesize that, in BEN2908, resistance to stress by urea would depend on the levels of periplasmic trehalose, but type 1 fimbriae production would be influenced by the levels of cytosolic trehalose.

Salmonella Typhimurium expressing chromosomally integrated Schistosoma mansoni Cathepsin B protects against schistosomiasis in mice.

Schistosomiasis threatens hundreds of millions of people worldwide. The larval stage of Schistosoma mansoni migrates through the lung and adult worms reside adjacent to the colonic mucosa. Several candidate vaccines are in preclinical development, but none is designed to elicit both systemic and mucosal responses. We have repurposed an attenuated Salmonella enterica Typhimurium strain (YS1646) to express Cathepsin B (CatB), a digestive enzyme important for the juvenile and adult stages of the S. mansoni life cycle. Previous studies have demonstrated the prophylactic and therapeutic efficacy of our plasmid-based vaccine. Here, we have generated chromosomally integrated (CI) YS1646 strains that express CatB to produce a viable candidate vaccine for eventual human use (stability, no antibiotic resistance). 6-8-week-old C57BL/6 mice were vaccinated in a multimodal oral (PO) and intramuscular (IM) regimen, and then sacrificed 3 weeks later. The PO + IM group had significantly higher anti-CatB IgG titers with greater avidity and mounted significant intestinal anti-CatB IgA responses compared to PBS control mice (all P < 0.0001). Multimodal vaccination generated balanced TH1/TH2 humoral and cellular immune responses. Production of IFNγ by both CD4+ and CD8+ T cells was confirmed by flow cytometry (P < 0.0001 & P < 0.01). Multimodal vaccination reduced worm burden by 80.4%, hepatic egg counts by 75.2%, and intestinal egg burden by 78.4% (all P < 0.0001). A stable and safe vaccine that has both prophylactic and therapeutic activity would be ideal for use in conjunction with praziquantel mass treatment campaigns.

Decreased expression of type 1 fimbriae by a pst mutant of uropathogenic Escherichia coli reduces urinary tract infection.

The pstSCAB-phoU operon encodes the phosphate-specific transport system (Pst). Loss of Pst constitutively activates the Pho regulon and decreases bacterial virulence. However, specific mechanisms underlying decreased bacterial virulence through inactivation of Pst are poorly understood. In uropathogenic Escherichia coli (UPEC) strain CFT073, inactivation of pst decreased urinary tract colonization in CBA/J mice. The pst mutant was deficient in production of type 1 fimbriae and showed decreased expression of the fimA structural gene which correlated with differential expression of the fimB, fimE, ipuA, and ipbA genes, encoding recombinases, mediating inversion of the fim promoter. The role of fim downregulation in attenuation of the pst mutant was confirmed using a fim phase-locked-on derivative, which demonstrated a significant gain in virulence. In addition, the pst mutant was less able to invade human bladder epithelial cells. Since type 1 fimbriae contribute to UPEC virulence by promoting colonization and invasion of bladder cells, the reduced bladder colonization by the pst mutant is predominantly attributed to downregulation of these fimbriae. Elucidation of mechanisms mediating the control of type 1 fimbriae through activation of the Pho regulon in UPEC may open new avenues for therapeutics or prophylactics against urinary tract infections.

Identification and mechanism of evolution of new alleles coding for the AIDA-I autotransporter of porcine pathogenic Escherichia coli.

Autotransporters are a large family of virulence factors of Gram-negative bacterial pathogens. The autotransporter adhesin involved in diffuse adherence (AIDA-I) is an outer membrane protein of Escherichia coli, which allows binding to epithelial cells as well as the autoaggregation of bacteria. AIDA-I is glycosylated by a specific heptosyltransferase encoded by the aah gene that forms an operon with the aidA gene. aidA is highly prevalent in strains that cause disease in pigs. Nevertheless, there are only two published whole-length sequences for this gene. In this study, we sequenced the aah and aidA genes of 24 aidA-positive porcine strains harboring distinct virulence factor profiles. We compared the obtained sequences and performed phylogenetic and pulsed-field electrophoresis analyses. Our results suggest that there are at least 3 different alleles for aidA, which are associated with distinct virulence factor profiles. The genes are found on high-molecular-weight plasmids and seem to evolve via shuffling mechanisms, with one of the sequences showing evidence of genetic recombination. Our work suggests that genetic plasticity allows the evolution of aah-aidA alleles that are selected during pathogenesis.

Increased Pho regulon activation correlates with decreased virulence of an avian pathogenic Escherichia coli O78 strain.

Avian pathogenic Escherichia coli (APEC) strains are associated with respiratory infections, septicemia, cellulitis, peritonitis, and other conditions, since colibacillosis manifests in many ways. The Pho regulon is jointly controlled by the two-component regulatory system PhoBR and by the phosphate-specific transport (Pst) system. To determine the specific roles of the PhoBR regulon and the Pst system in the pathogenesis of the APEC O78 strain χ7122, different phoBR and pst mutant strains were tested in vivo in chickens and in vitro for virulence traits. Mutations resulting in constitutive activation of the Pho regulon rendered strains more sensitive than the wild type to hydrogen peroxide and to the bactericidal effects of rabbit serum. In addition, production of type 1 fimbriae was also impaired in these strains. Using a chicken competitive infection model, all PhoB constitutive mutants were outcompeted by the wild-type parent, including strains containing a functional Pst system. Cumulative inactivation of the Pst system and the PhoB regulator resulted in a restoration of virulence. In addition, loss of the PhoB regulator alone did not affect virulence in the chicken infection model. Interestingly, the level of attenuation of the mutant strains correlated directly with the level of activation of the Pho regulon. Overall, results indicate that activation of the Pho regulon rather than phosphate transport by the Pst system plays a major role in the attenuation of the APEC O78 strain χ7122.

Roles of the extraintestinal pathogenic Escherichia coli ZnuACB and ZupT zinc transporters during urinary tract infection.

Roles of the ZnuACB and ZupT transporters were assessed in Escherichia coli K-12 and uropathogenic E. coli (UPEC) CFT073. K-12 and CFT073 Deltaznu DeltazupT mutants demonstrated decreased (65)Zn(2+) uptake and growth in minimal medium. CFT073Deltaznu demonstrated an intermediate decrease of (65)Zn(2+) uptake and growth in minimal medium, whereas the CFT073DeltazupT mutant grew as well as CFT073 and exhibited a less marked decrease in (65)Zn(2+) uptake. CFT073 mutants grew as well as the wild type in human urine. In competitive infections in CBA/J mice, the DeltazupT mutant demonstrated no disadvantage during urinary tract infection. In contrast, the UPEC Deltaznu and Deltaznu DeltazupT strains demonstrated significantly reduced numbers in the bladders (mean 4.4- and 30-fold reductions, respectively) and kidneys (mean 41- and 48-fold reductions, respectively). In addition, in single-strain infection experiments, the Deltaznu and Deltaznu DeltazupT mutants were reduced in the kidneys (P = 0.0012 and P < 0.0001, respectively). Complementation of the CFT073 Deltaznu DeltazupT mutant with the znuACB genes restored growth in Zn-deficient medium and bacterial numbers in the bladder and kidneys. The loss of the zinc transport systems decreased both motility and resistance to hydrogen peroxide, which could be restored by supplementation with zinc. Overall, the results indicate that Znu and ZupT are required for growth in zinc limited-conditions, that Znu is the predominant zinc transporter, and that the loss of Znu and ZupT has a cumulative effect on fitness during UTI, which may in part be due to reduced resistance to oxidative stress and motility.

Chiropractic Management of a Patient With Radial Nerve Entrapment Symptoms: A Case Study.

OBJECTIVE: This report describes the case of a patient with chronic radial nerve entrapment symptoms managed with chiropractic care. We propose a complementary functional neurologic assessment of muscle function in different positions that could reveal muscle dysfunctions absent with standard test position. CLINICAL FEATURES: A 45-year-old man presented to a private chiropractic clinic with a throbbing pain 5 cm above the right lateral elbow epicondyle radiating onto the back of the lower arm and increasing after using a mouse when working on a computer. A Mill test and a Cozen test created pain near the lateral epicondylitis. The use of complementary functional neurologic assessment for radial nerve entrapment showed changes in manual muscle testing after tests were done in different positions to increase the compression on the nerve. INTERVENTION AND OUTCOME: Chiropractic management was performed, including myofascial therapy, spinal and proximal radioulnar joint adjustments, neural mobilization, and the use of a splint. After 7 days (2 treatments), the patient showed no elbow pain even if he worked on his computer using a mouse. After a 2-year follow-up, no recurrence was reported. CONCLUSION: In this case of radial nerve entrapment symptoms, the patient benefited from chiropractic management using standard chiropractic, applied kinesiology, and neural mobilization techniques. The complementary functional neurologic assessment of radial nerve entrapment proposed revealed muscles dysfunctions absent with the standard test position. These changes in manual muscle testing were useful to determine the possible sites of entrapment in order to direct the therapeutic efforts to these locations.

yqhG Contributes to Oxidative Stress Resistance and Virulence of Uropathogenic Escherichia coli and Identification of Other Genes Altering Expression of Type 1 Fimbriae.

Urinary tract infections (UTIs) are common bacterial infections and the vast majority of UTIs are caused by extraintestinal pathogenic Escherichia coli (ExPEC) strains referred to as uropathogenic E. coli (UPEC). Successful colonization of the human urinary tract by UPEC is mediated by secreted or surface exposed virulence factors-toxins, iron transport systems, and adhesins, such as type 1 fimbriae (pili). To identify factors involved in the expression of type 1 fimbriae, we constructed a chromosomal transcriptional reporter consisting of lux under the control of the fimbrial promoter region, fimS and this construct was inserted into the reference UPEC strain CFT073 genome at the attTn7 site. This fimS reporter strain was used to generate a Tn10 transposon mutant library, coupled with high-throughput sequencing to identify genes that affect the expression of type 1 fimbriae. Transposon insertion sites were linked to genes involved in protein fate and synthesis, energy metabolism, adherence, transcriptional regulation, and transport. We showed that YqhG, a predicted periplasmic protein, is one of the important mediators that contribute to the decreased expression of type 1 fimbriae in UPEC strain CFT073. The ΔyqhG mutant had reduced expression of type 1 fimbriae and a decreased capacity to colonize the murine urinary tract. Reduced expression of type 1 fimbriae correlated with an increased bias for orientation of the fim switch in the OFF position. Interestingly, the ΔyqhG mutant was more motile than the WT strain and was also significantly more sensitive to hydrogen peroxide. Taken together, loss of yqhG may decrease virulence in the urinary tract due to a decrease in production of type 1 fimbriae and a greater sensitivity to oxidative stress.