The Yersinia High-Pathogenicity Island Encodes a Siderophore-Dependent Copper Response System in Uropathogenic Escherichia coli.

Siderophores are iron chelators used by microbes to bind and acquire iron, which, once in the cell, inhibits siderophore production through feedback repression mediated by the ferric uptake repressor (Fur). Yersiniabactin (Ybt), a siderophore associated with enhanced pathogenic potential among Enterobacteriaceae, also binds copper ions during human and experimental murine infections. In contrast to iron, we found that extracellular copper ions rapidly and selectively stimulate Ybt production in extraintestinal pathogenic Escherichia coli. The stimulatory pathway requires formation of an extracellular copper-Ybt (Cu(II)-Ybt) complex, internalization of Cu(II)-Ybt entry through the canonical TonB-dependent outer membrane transporter, and Fur-independent transcriptional regulation by the specialized transcription factor YbtA. Dual regulation by iron and copper is consistent with a multifunctional metallophore role for Ybt. Feed-forward regulation is typical of stress responses, implicating Ybt in prevention of, or response to, copper stress during infection pathogenesis. IMPORTANCE Interactions between bacteria and transition metal ions play an important role in encounters between humans and bacteria. Siderophore systems have long been prominent mediators of these interactions. These systems secrete small-molecule chelators that bind oxidized iron(III) and express proteins that specifically recognize and import these complexes as a nutritional iron source. While E. coli and other Enterobacteriaceae secrete enterobactin, clinical isolates often secrete an additional siderophore, yersiniabactin (Ybt), which has been found to also bind copper and other non-iron metal ions. The observation here that an extraintestinal E. coli isolate secretes Ybt in a copper-inducible manner suggests an important gain of function over the enterobactin system. Copper recognition involves using Ybt to bind Cu(II) ions, consistent with a distinctively extracellular mode of copper detection. The resulting Cu(II)-Ybt complex signals upregulation of Ybt biosynthesis genes as a rapid response against potentially toxic extracellular copper ions. The Ybt system is distinguishable from other copper response systems that sense cytosolic and periplasmic copper ions. The Ybt dependence of the copper response presents an implicit feed-forward regulatory scheme that is typical of bacterial stress responses. The distinctive extracellular copper recognition-response functionality of the Ybt system may enhance the pathogenic potential of infection-associated Enterobacteriaceae.

Determination of B- and T- cell epitopes for Helicobacter pylori cagPAI: An in silico approach.

BACKGROUND/AIMS: Helicobacter pylori is classified as a gram-negative bacteria and can cause significant diseases, including gastric cancer, mucosa-associated lymphoid tumor, peptic ulcer, and chronic gastritis. Recent studies have shown that some autoimmune diseases are also associated with H. pylori. In the past decades, polymorphisms of certain genes of H. pylori, mechanisms and strains of H. pylori, and new therapeutic approaches have continued to be defined. Bioinformatic tools continue to be used in drug design and vaccine design. This study aimed to investigate the cag pathogenicity island (cagPAI) of H. pylori using an in silico approach, which could contribute to vaccine studies. MATERIALS AND METHODS: The pathogenicity island of H. pylori was obtained from GenBank and analyzed with ClustalW software. Structures of cag Virb11 (Hp0525) and an inhibitory protein (Hp1451) were obtained, and codon optimization and secondary and tertiary structure prediction for the cagPAI of H. pylori were analyzed using Garnier-Osguthorpe-Rabson IV secondary structure prediction method and self-optimized prediction method with alignment software. The BcePred prediction server was used to distinguish linear B-cell epitopes, and prediction of T-cell was obtained with NetCTL and MHCPred. RESULTS: According to the physicochemical parameters, the cagPAI of H. pylori was analyzed and found to be stable, and 2 B-cell epitopes of cagPAI of H. pylori and 2 T-cell epitopes of cagPAI were found in this study. CONCLUSION: B- and T-cell epitopes that we have identified can induce both humoral and cellular immune responses. Thus, these epitopes have a potential for vaccine studies. Consequently, this in silico analysis should be combined with other pieces of evidence, including experimental data, to assign function.

Multivalent Fusion DNA Vaccine against Brucella abortus.

As an alternative brucellosis prevention method, we evaluated the immunogenicity induced by new multivalent DNA vaccines in BALB/c mice. We constructed the vaccines by fusion of BAB1_0273 and/or BAB1_0278 open reading frames (ORFs) from genomic island 3 (GI-3) and the Brucella abortus 2308 sodC gene with a link based on prolines and alanines (pV273-sod, pV278-sod, and pV273-278-sod, resp.). Results show that immunization with all tested multivalent DNA vaccines induced a specific humoral and cellular immune response. These novel multivalent vaccines significantly increased the production of IgM, IgG, and IgG2a antibodies as well as IFN-γ levels and the lymphoproliferative response of splenocytes. Although immunization with these multivalent vaccines induced a typical T-helper 1- (Th1-) dominated immune response, such immunogenicity conferred low protection levels in mice challenged with the B. abortus 2308 pathogenic strain. Our results demonstrated that the expression of BAB1_0273 and/or BABl_0278 antigens conjugated to SOD protein can polarize mice immunity to a Th1-type phenotype, conferring low levels of protection.

Francisella tularensis Live Vaccine Strain deficient in capB and overexpressing the fusion protein of IglA, IglB, and IglC from the bfr promoter induces improved protection against F. tularensis respiratory challenge.

A safer and more effective vaccine than the unlicensed Francisella tularensis Live Vaccine Strain (LVS) is needed to protect against the biowarfare agent F. tularensis. Previously, we developed an LVS ΔcapB mutant that is significantly safer than LVS and provides potent protective immunity against F. tularensis respiratory challenge when administered intranasally but limited protection when administered intradermally unless as part of a prime-boost vaccination strategy. To improve the immunogenicity and efficacy of LVS ΔcapB, we developed recombinant LVS ΔcapB (rLVS ΔcapB) strains overexpressing various F. tularensis Francisella Pathogenicity Island (FPI) proteins - IglA, IglB and IglC, and a fusion protein (IglABC) comprising immunodominant epitopes of IglA, IglB, and IglC downstream of different Francisella promoters, including the bacterioferritin (bfr) promoter. We show that rLVS ΔcapB/bfr-iglA, iglB, iglC, and iglABC express more IglA, IglB, IglC or IglABC than parental LVS ΔcapB in broth and in human macrophages, and stably express FPI proteins in macrophages and mice absent antibiotic selection. In response to IglC and heat-inactivated LVS, spleen cells from mice immunized intradermally with rLVS ΔcapB/bfr-iglC or bfr-iglABC secrete greater amounts of interferon-gamma and/or interleukin-17 than those from mice immunized with LVS ΔcapB, comparable to those from LVS-immunized mice. Mice immunized with rLVS ΔcapB/bfr-iglA, iglB, iglC or iglABC produce serum antibodies at levels similar to LVS-immunized mice. Mice immunized intradermally with rLVS ΔcapB/bfr-iglABC and challenged intranasally with virulent F. tularensis Schu S4 survive longer than sham- and LVS ΔcapB-immunized mice. Mice immunized intranasally with rLVS ΔcapB/bfr-iglABC - but not with LVS - just before or after respiratory challenge with F. tularensis Schu S4 are partially protected; protection is correlated with induction of a strong innate immune response. Thus, rLVS ΔcapB/bfr-iglABC shows improved immunogenicity and protective efficacy compared with parental LVS ΔcapB and, in contrast to LVS, has partial efficacy as immediate pre- and post-exposure prophylaxis.

A gut-vascular barrier controls the systemic dissemination of bacteria.

In healthy individuals, the intestinal microbiota cannot access the liver, spleen, or other peripheral tissues. Some pathogenic bacteria can reach these sites, however, and can induce a systemic immune response. How such compartmentalization is achieved is unknown. We identify a gut-vascular barrier (GVB) in mice and humans that controls the translocation of antigens into the blood stream and prohibits entry of the microbiota. Salmonella typhimurium can penetrate the GVB in a manner dependent on its pathogenicity island (Spi) 2-encoded type III secretion system and on decreased ß-catenin-dependent signaling in gut endothelial cells. The GVB is modified in celiac disease patients with elevated serum transaminases, which indicates that GVB dismantling may be responsible for liver damage in these patients. Understanding the GVB may provide new insights into the regulation of the gut-liver axis.

Ethanolamine Signaling Promotes Salmonella Niche Recognition and Adaptation during Infection.

Chemical and nutrient signaling are fundamental for all cellular processes, including interactions between the mammalian host and the microbiota, which have a significant impact on health and disease. Ethanolamine is an essential component of cell membranes and has profound signaling activity within mammalian cells by modulating inflammatory responses and intestinal physiology. Here, we describe a virulence-regulating pathway in which the foodborne pathogen Salmonella enterica serovar Typhimurium (S. Typhimurium) exploits ethanolamine signaling to recognize and adapt to distinct niches within the host. The bacterial transcription factor EutR promotes ethanolamine metabolism in the intestine, which enables S. Typhimurium to establish infection. Subsequently, EutR directly activates expression of the Salmonella pathogenicity island 2 in the intramacrophage environment, and thus augments intramacrophage survival. Moreover, EutR is critical for robust dissemination during mammalian infection. Our findings reveal that S. Typhimurium co-opts ethanolamine as a signal to coordinate metabolism and then virulence. Because the ability to sense ethanolamine is a conserved trait among pathogenic and commensal bacteria, our work indicates that ethanolamine signaling may be a key step in the localized adaptation of bacteria within their mammalian hosts.

Intraspecies competition for niches in the distal gut dictate transmission during persistent Salmonella infection.

In order to be transmitted, a pathogen must first successfully colonize and multiply within a host. Ecological principles can be applied to study host-pathogen interactions to predict transmission dynamics. Little is known about the population biology of Salmonella during persistent infection. To define Salmonella enterica serovar Typhimurium population structure in this context, 129SvJ mice were oral gavaged with a mixture of eight wild-type isogenic tagged Salmonella (WITS) strains. Distinct subpopulations arose within intestinal and systemic tissues after 35 days, and clonal expansion of the cecal and colonic subpopulation was responsible for increases in Salmonella fecal shedding. A co-infection system utilizing differentially marked isogenic strains was developed in which each mouse received one strain orally and the other systemically by intraperitoneal (IP) injection. Co-infections demonstrated that the intestinal subpopulation exerted intraspecies priority effects by excluding systemic S. Typhimurium from colonizing an extracellular niche within the cecum and colon. Importantly, the systemic strain was excluded from these distal gut sites and was not transmitted to naïve hosts. In addition, S. Typhimurium required hydrogenase, an enzyme that mediates acquisition of hydrogen from the gut microbiota, during the first week of infection to exert priority effects in the gut. Thus, early inhibitory priority effects are facilitated by the acquisition of nutrients, which allow S. Typhimurium to successfully compete for a nutritional niche in the distal gut. We also show that intraspecies colonization resistance is maintained by Salmonella Pathogenicity Islands SPI1 and SPI2 during persistent distal gut infection. Thus, important virulence effectors not only modulate interactions with host cells, but are crucial for Salmonella colonization of an extracellular intestinal niche and thereby also shape intraspecies dynamics. We conclude that priority effects and intraspecies competition for colonization niches in the distal gut control Salmonella population assembly and transmission.

Helicobacter pylori-induced IL-1ß secretion in innate immune cells is regulated by the NLRP3 inflammasome and requires the cag pathogenicity island.

Infection with the gram-negative bacterium Helicobacter pylori is the most prevalent chronic bacterial infection, affecting ∼50% of the world's population, and is the main risk factor of gastric cancer. The proinflammatory cytokine IL-1ß plays a crucial role in the development of gastric tumors and polymorphisms in the IL-1 gene cluster leading to increased IL-1ß production have been associated with increased risk for gastric cancer. To be active, pro-IL-1ß must be cleaved by the inflammasome, an intracellular multiprotein complex implicated in physiological and pathological inflammation. Recently, H. pylori was postulated to activate the inflammasome in murine bone marrow-derived dendritic cells; however, the molecular mechanisms as well as the bacterial virulence factor acting as signal 2 activating the inflammasome remain elusive. In this study, we analyzed the inflammasome complex regulating IL-1ß upon H. pylori infection as well as the molecular mechanisms involved. Our results indicate that H. pylori-induced IL-1ß secretion is mediated by activation of the nucleotide-binding oligomerization domain-like receptor family, pyrin domain-containing 3 inflammasome. We also show that reactive oxygen species, potassium efflux, and lysosomal destabilization are the main cellular mechanisms responsible of nucleotide-binding oligomerization domain family, pyrin domain-containing 3 inflammasome activation upon H. pylori infection, and identify vacuolating cytotoxin A and cag pathogenicity island as the bacterial virulence determinants involved. Moreover, in vivo experiments indicate an important role for the inflammasome in the onset and establishment of H. pylori infection and in the subsequent inflammatory response of the host.

A Salmonella Typhimurium-Typhi genomic chimera: a model to study Vi polysaccharide capsule function in vivo.

The Vi capsular polysaccharide is a virulence-associated factor expressed by Salmonella enterica serotype Typhi but absent from virtually all other Salmonella serotypes. In order to study this determinant in vivo, we characterised a Vi-positive S. Typhimurium (C5.507 Vi(+)), harbouring the Salmonella pathogenicity island (SPI)-7, which encodes the Vi locus. S. Typhimurium C5.507 Vi(+) colonised and persisted in mice at similar levels compared to the parent strain, S. Typhimurium C5. However, the innate immune response to infection with C5.507 Vi(+) and SGB1, an isogenic derivative not expressing Vi, differed markedly. Infection with C5.507 Vi(+) resulted in a significant reduction in cellular trafficking of innate immune cells, including PMN and NK cells, compared to SGB1 Vi(-) infected animals. C5.507 Vi(+) infection stimulated reduced numbers of TNF-α, MIP-2 and perforin producing cells compared to SGB1 Vi(-). The modulating effect associated with Vi was not observed in MyD88(-/-) and was reduced in TLR4(-/-) mice. The presence of the Vi capsule also correlated with induction of the anti-inflammatory cytokine IL-10 in vivo, a factor that impacted on chemotaxis and the activation of immune cells in vitro.

Tolerance rather than immunity protects from Helicobacter pylori-induced gastric preneoplasia.

BACKGROUND & AIMS: Chronic infection with the bacterial pathogen Helicobacter pylori causes gastric disorders, ranging from chronic gastritis to gastric adenocarcinoma. Only a subset of infected persons will develop overt disease; most remains asymptomatic despite lifelong colonization. This study aims to elucidate the differential susceptibility to H pylori that is found both across and within populations. METHODS: We have established a C57BL/6 mouse model of H pylori infection with a strain that is capable of delivering the virulence factor cytotoxin-associated gene A (CagA) into host cells through the activity of a Cag-pathogenicity island-encoded type IV secretion system. RESULTS: Mice infected at 5-6 weeks of age with CagA(+)H pylori rapidly develop gastritis, gastric atrophy, epithelial hyperplasia, and metaplasia in a type IV secretion system-dependent manner. In contrast, mice infected during the neonatal period with the same strain are protected from preneoplastic lesions. Their protection results from the development of H pylori-specific peripheral immunologic tolerance, which requires transforming growth factor-ß signaling and is mediated by long-lived, inducible regulatory T cells, and which controls the local CD4(+) T-cell responses that trigger premalignant transformation. Tolerance to H pylori develops in the neonatal period because of a biased ratio of T-regulatory to T-effector cells and is favored by prolonged low-dose exposure to antigen. CONCLUSIONS: Using a novel CagA(+)H pylori infection model, we report here that the development of tolerance to H pylori protects from gastric cancer precursor lesions. The age at initial infection may thus account for the differential susceptibility of infected persons to H pylori-associated disease manifestations.

Helicobacter pylori exploits cholesterol-rich microdomains for induction of NF-kappaB-dependent responses and peptidoglycan delivery in epithelial cells.

Infection with Helicobacter pylori cag pathogenicity island (cagPAI)-positive strains is associated with more destructive tissue damage and an increased risk of severe disease. The cagPAI encodes a type IV secretion system (TFSS) that delivers the bacterial effector molecules CagA and peptidoglycan into the host cell cytoplasm, thereby inducing responses in host cells. It was previously shown that interactions between CagL, present on the TFSS pilus, and host α(5)ß(1) integrin molecules were critical for CagA translocation and the induction of cytoskeletal rearrangements in epithelial cells. As the α(5)ß(1) integrin is found in cholesterol-rich microdomains (known as lipid rafts), we hypothesized that these domains may also be involved in the induction of proinflammatory responses mediated by NOD1 recognition of H. pylori peptidoglycan. Indeed, not only did methyl-ß-cyclodextrin depletion of cholesterol from cultured epithelial cells have a significant effect on the levels of NF-κB and interleukin-8 (IL-8) responses induced by H. pylori bacteria with an intact TFSS (P < 0.05), but it also interfered with TFSS-mediated peptidoglycan delivery to cells. Both of these effects could be restored by cholesterol replenishment of the cells. Furthermore, we demonstrated for the first time the involvement of α(5)ß(1) integrin in the induction of proinflammatory responses by H. pylori. Taking the results together, we propose that α(5)ß(1) integrin, which is associated with cholesterol-rich microdomains at the host cell surface, is required for NOD1 recognition of peptidoglycan and subsequent induction of NF-κB-dependent responses to H. pylori. These data implicate cholesterol-rich microdomains as a novel platform for TFSS-dependent delivery of bacterial products to cytosolic pathogen recognition molecules.

Clinical pathogenesis of typhoid fever.

Human infections with Salmonella enterica results in two major groups of diseases: gastroenteritis and typhoid fever. Clinical observations suggest that gastroenteritis, caused by non-typhoidal Salmonella serovars, is characterized by a massive neutrophil influx, which keeps the infection localized to the intestinal mucosa. In contrast, the absence of neutrophilic intestinal infiltrates in the acute phase of typhoid fever suggests a propensity for typhoidal Salmonella serovars (S. Typhi, S. Paratyphi A, S. Paratyphi B and S. Paratyphi C) to evade aspects of the innate immune response and cause a systemic infection. The fact that there are no virulence genes shared by typhoidal Salmonella serovars that are absent from non-typhoidal Salmonella serovars, suggests that this innate immune evasion is mediated by different mechanisms in different typhoidal serovars. This review discusses what is known about the clinical pathogenesis of typhoid fever.

Injection of flagellin into the host cell cytosol by Salmonella enterica serotype Typhimurium.

Bacterial flagellins are potent inducers of innate immunity. Three signaling pathways have been implicated in the sensing of flagellins; these involve toll-like receptor 5 (TLR5) and the cytosolic proteins Birc1e/Naip5 and Ipaf. Although the structural basis of TLR5-flagellin interaction is known, little is known about how flagellin enters the host cell cytosol to induce signaling via Birc1e/Naip5 and Ipaf. Here we demonstrate for the first time the translocation of bacterial flagellin into the cytosol of host macrophages by the vacuolar pathogen, Salmonella enterica serotype Typhimurium. Translocation of flagellin into the host cell cytosol was directly demonstrated using beta-lactamase reporter constructs. Flagellin translocation required the Salmonella Pathogenicity Island 1 Type III secretion system (SPI-1 T3SS) but not the flagellar T3SS.

Presence of virulence and fitness gene modules of enterohemorrhagic Escherichia coli in atypical enteropathogenic Escherichia coli O26.

Enterohemorrhagic Escherichia coli (EHEC) strains of serogroup O26 cause hemolytic-uremic syndrome (HUS) whereas atypical enteropathogenic E. coli (aEPEC) O26 typically cause uncomplicated diarrhea but have been also isolated from HUS patients. To gain insight into the virulence of aEPEC O26, we compared the presence of O island (OI) 122, which is associated with enhanced virulence in EHEC strains, among aEPEC O26 and EHEC O26 clinical isolates. We also tested these strains for the high pathogenicity island (HPI) which is a fitness island. All 20 aEPEC O26 and 20 EHEC O26 investigated contained virulence genes located within OI-122 (efa1/lifA, nleB, nleE, ent). In both aEPEC O26 and EHEC O26, OI-122 was linked to the locus for enterocyte effacement, forming a mosaic island which was integrated in pheU. Moreover, strains of these two pathotypes shared a conserved HPI. These data support a close relatedness between aEPEC O26 and EHEC O26 and have evolutionary implications. The presence of OI-122 in aEPEC O26 might contribute to their pathogenic potential.

Identification of novel genomic islands coding for antigenic pilus-like structures in Streptococcus agalactiae.

We have recently reported the presence of covalently linked pilus-like structures in the human pathogen, Group B Streptococcus (GBS). The pilus operon codes for three proteins which contain the conserved amino acid motif, LPXTG, associated with cell wall-anchored proteins together with two genes coding for sortase enzymes. Analysis of the eight sequenced genomes of GBS has led to the identification of a second, related genomic island of which there are two variants, each containing genes coding for proteins with LPXTG motifs and sortases. Here we show that both variant islands also code for pilus-like structures. Furthermore, we provide a thorough description and characterization of the genomic organization of the islands and the role of each protein in the assembly of the pili. For each pilus, polymerization of one of the three component proteins is essential for incorporation of the other two proteins into the pilus structure. In addition, two sortases are required for complete pilus assembly, each with specificity for one of the pilus components. A component protein of one of the newly identified pili is also a previously identified protective antigen and a second component of this pilus is shown to confer protection against GBS challenge. We propose that pilus-like structures are important virulence factors and potential vaccine candidates.

RrgA and RrgB are components of a multisubunit pilus encoded by the Streptococcus pneumoniae rlrA pathogenicity islet.

The rlrA pathogenicity islet in Streptococcus pneumoniae TIGR4 encodes three surface proteins, RrgA, RrgB, and RrgC, and three sortase enzymes. Using transmission electron microscopy, cell fractionation, cell wall sorting signal domain swapping, and Western blotting, we show that RrgA and RrgB are incorporated into a multisubunit pilus in S. pneumoniae.

Molecular mechanisms used by Salmonellato interfere with Dendritic Cell function

Las Células Dendríticas (DCs) son células presentadoras deantígeno profesionales, capaces de reconocer y degradar antígenosbacterianos que son presentados a linfocitos T vírgenes paraasí iniciar la respuesta inmune específica contra los antígenos derivadosde patógenos. Por esta razón, algunos microorganismospatógenos han adquirido mecanismos de virulencia que interfierencon la función de la DC y evitan la activación de la respuestainmune específica. Salmonella entericaserovar Typhimurium, elagente causal en el ratón de una enfermedad similar a fiebre tifoidea,es capaz de escapar de la presentación de antígenos mediadapor la DC al evitar su degradación lisosomal. Esta capacidadvirulenta de Salmonellarequiere la expresión funcional de un Sistemade Secreción de Tipo III (TTSS) y de otras proteínas de virulenciacodificadas por la Isla de Patogenicidad 2 (SPI-2). En estarevisión discutimos estudios recientes que han demostrado queel impedimento de la función de la DC, debido a la actividad delos productos génicos de la SPI-2 y a la evasión de la fusión fagosoma-lisosoma, es crucial para la patogénesis de Salmonella

Dendritic cells (DCs) are professional antigen presenting cellswith the ability to recognize and degrade bacterial antigens, whichare presented to naïve T cells to initiate the adaptive immune responseagainst pathogen-derived antigens. For this reason, somebacterial pathogens have acquired virulence mechanisms thatinterfere with DC function and avoid the adaptive immune responseactivation. Salmonella entericaserovar Typhimurium, thecausative agent of typhoid-like disease in the mouse, is able toescape from DC-mediated antigen presentation by avoiding lysosomaldegradation. This feature of virulent Salmonellarequiresthe functional expression of the Type Three Secretion System(TTSS) and other virulence proteins encoded within the SalmonellaPathogenicity Island 2 (SPI-2). In this review we discuss recentstudies showing that impairment of DC function by the activityof SPI-2 gene products and the avoidance of phagosome-lysosomefusion in these cells are crucial for Salmonellapathogenesis

Unraveling Brucella genomics and pathogenesis in immunocompromised IRF-1-/- mice.

PROBLEM: Brucellosis causes abortion in domestic animals and Malta fever in humans. Comparison of Brucella species genomes may reveal potential virulence mechanisms. Engineering bioluminescent Brucella would permit monitoring bacterial dissemination. METHOD OF STUDY: Microarray of the B. melitensis genome allowed comparison of gene content from six Brucella species. Bioluminescent B. melitensis strains were developed using transposon mutagenesis permitting the study of pathogenic Brucella in mice. Monitoring bacterial dissemination as well as organ localization permits evaluating the role of genes and genomic islands in mutant bacteria. RESULTS: Comparative genomic analysis revealed 217 ORFs altered in five Brucella species and were often found in islands. Bioluminescent bacteria disseminated from the injection site to liver, spleen, inguinal lymph nodes, testes and submanibular region. CONCLUSIONS: Genomic islands contribute to Brucella pathogenicity. Biophotonic imaging suggests that Brucella dissemination in mice parallels acute and chronic infections of humans.

Assessment of the cag pathogenicity island status of Helicobacter pylori infections with serology and PCR.

The serological characterisation of Helicobacter pylori strains has been questioned, e.g., when the presence or absence of the cag pathogenicity island (PAI) is determined. This study compared CagA-reactive serum antibodies, assessed with immunoblot, with cag PAI status, as determined by PCR. CagA serology results were available for 101 individuals contributing 202 bacterial samples for cag PAI PCR. There was a high degree of correlation between the two methods (kappa coefficient, 0.82; 95% confidence interval, 0.68-0.97). Combined with suggested biological explanations for the discrepancies, this finding supports the application of well-evaluated serological assays in the assessment of the cag PAI status of H. pylori infections in clinical and epidemiological studies.