Escherichia coli isolates causing asymptomatic bacteriuria in catheterized and noncatheterized individuals possess similar virulence properties

Urinary tract infections (UTIs) are among the most common infectious diseases of humans, with Escherichia coli being responsible for >80% of all cases. Asymptomatic bacteriuria (ABU) occurs when bacteria colonize the urinary tract without causing clinical symptoms and can affect both catheterized patients (catheter-associated ABU [CA-ABU]) and noncatheterized patients. Here, we compared the virulence properties of a collection of ABU and CA-ABU nosocomial E. coli isolates in terms of antibiotic resistance, phylogenetic grouping, specific UTI-associated virulence genes, hemagglutination characteristics, and biofilm formation. CA-ABU isolates were similar to ABU isolates with regard to the majority of these characteristics; exceptions were that CA-ABU isolates had a higher prevalence of the polysaccharide capsule marker genes kpsMT II and kpsMT K1, while more ABU strains were capable of mannose-resistant hemagglutination. To examine biofilm growth in detail, we performed a global gene expression analysis with two CA-ABU strains that formed a strong biofilm and that possessed a limited adhesin repertoire. The gene expression profile of the CA-ABU strains during biofilm growth showed considerable overlap with that previously described for the prototype ABU E. coli strain, 83972. This is the first global gene expression analysis of E. coli CA-ABU strains. Overall, our data suggest that nosocomial ABU and CA-ABU E. coli isolates possess similar virulence profiles.

Virulence properties of asymptomatic bacteriuria Escherichia coli

In asymptomatic bacteriuria (ABU), bacteria colonize the urinary tract without provoking symptoms. Here, we compared the virulence properties of a collection of ABU Escherichia coli strains to cystitis and pyelonephritis strains. Specific urinary tract infection (UTI)-associated virulence genes, hemagglutination characteristics, siderophore production, hemolysis, biofilm formation, and the ability of strains to adhere to and induce cytokine responses in epithelial cells were analyzed. ABU strains were phylogenetically related to strains that cause symptomatic UTI. However, the virulence properties of the ABU strains were variable and dependent on a combination of genotypic and phenotypic factors. Most ABU strains adhered poorly to epithelial cells; however, we also identified a subgroup of strongly adherent strains that were unable to stimulate an epithelial cell IL-6 cytokine response. Poor immune activation may represent one mechanism whereby ABU E. coli evade immune detection after the establishment of bacteriuria.

Virulence properties and antimicrobial susceptibility of Shiga toxin-producing Escherichia coli strains isolated from healthy cattle from Parana State, Brazil

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Prevalence and virulence properties of Vibrio cholerae non-O1, Aeromonas spp. and Plesiomonas shigelloides isolated from Cambe Stream (State of Parana, Brazil)

The incidence of Vibrio cholerae, Aeromonas spp, and Plesiomonas shigelloides was determined in Rater samples from Cambe Stream. The samples were collected from seven different sites. The serogroups, virulence markers and drug resistance profiles were also evaluated. Twelve. Aer. hydrophila, 12 Aer. caviae, eight Aer. sobria, seven Ple. shigelloides and two V. cholerae non-O1 were isolated. They belonged to different serogroups and all produced haemolysis in different assays. Five of the Aeromonas strains and one of V, cholerae non-O1 were positive for enterotoxin activity. Haemagglutination and its inhibition, using erythrocytes of different origins, was variable for Aeromonas spp and V. cholerae, while none of the Plt. shigelloides haemagglutinated in association with any type of erythrocyte. All isolates exhibited multiple drug resistance. These results indicate that the occurrence of V. cholerae non-O1, Aeromonas spp, and Ple. shigelloides, in water used for vegetable irrigation, human recreation and animal consumption, among others, represents a potential risk for humans.

Comparison of selected methods for measuring the virulence properties of Listeria spp.

The comparative ability of different methods to assess virulence of Listeria species was investigated in ten Listeria strains. All strains were initially subjected to pulsed-field gel electrophoresis analysis to determine their relatedness. Virulence characteristics were subsequently tested for by (i) determining the presence of six virulence genes by polymerase chain reaction; (ii) testing for the production of listeriolysin O, phosphatidylcholine phospholipase C, and phosphatidylinositol-specific phospholipase C; (iii) investigating the hydrophobicity of the strains; (iv) determining the strains ability to attach to, enter, and replicate within the Caco-2 cells. Variations in most of the virulence characteristics were obvious across the strains for the range of tests performed. A wide range of anomalous results among methods were apparent. In particular, the presence of virulence genes was found to be unrelated to the production of virulence-associated proteins in vitro, while virulence protein production and hydrophobicity in Listeria monocytogenes were found to be unrelated or marginally related, respectively, to the ability to invade the Caco-2 cell line. It was concluded that the methods investigated were unable to consistently and unequivocally measure the differences in the virulence properties of the strains.

Functional heterogeneity of the UpaH autotransporter protein from Uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is responsible for the majority of urinary tract infections (UTI). To cause a UTI, UPEC must adhere to the epithelial cells of the urinary tract and overcome the shear flow forces of urine. This function is mediated primarily by fimbrial adhesins, which mediate specific attachment to host cell receptors. Another group of adhesins that contributes to UPEC-mediated UTI is autotransporter (AT) proteins. AT proteins possess a range of virulence properties, such as adherence, aggregation, invasion, and biofilm formation. One recently characterized AT protein of UPEC is UpaH, a large adhesin-involved-in-diffuse-adherence (AIDA-I)-type AT protein that contributes to biofilm formation and bladder colonization. In this study we characterized a series of naturally occurring variants of UpaH. We demonstrate that extensive sequence variation exists within the passenger-encoding domain of UpaH variants from different UPEC strains. This sequence variation is associated with functional heterogeneity with respect to the ability of UpaH to mediate biofilm formation. In contrast, all of the UpaH variants examined retained a conserved ability to mediate binding to extracellular matrix (ECM) proteins. Bioinformatic analysis of the UpaH passenger domain identified a conserved region (UpaHCR) and a hydrophobic region (UpaHHR). Deletion of these domains reduced biofilm formation but not the binding to ECM proteins. Despite variation in the upaH sequence, the transcription of upaH was repressed by a conserved mechanism involving the global regulator H-NS, and mutation of the hns gene relieved this repression. Overall, our findings shed new light on the regulation and functions of the UpaH AT protein.

Suolistopatogeenisten Escherichia coli -bakteerien esiintyvyys ripulipotilailla ja raa’oissa lihatuotteissa Burkina Fasossa sekä enterohemorraagisten E. coli -kantojen karakterisointi

Suolistopatogeeniset Escherichia coli -bakteerit eli ripulikolit aiheuttavat ihmisellä suolistoinfektioita. Kuten normaalimikrobiston E. coli -bakteerit, ne esiintyvät ihmisen lisäksi muiden nisäkkäiden, etenkin märehtijöiden, ja lintujen suolistossa. Lisäksi ne voivat esiintyä maaperässä ja vesistöissä. Ihminen voi saada tartunnan eläinperäisten elintarvikkeiden välityksellä tai juomalla eläinten tai ihmisen ulosteilla saastunutta vettä. Ripulikolit voidaan jakaa ainakin viiteen ryhmään perustuen niiden erilaisiin virulenssiominaisuuksiin: enteropatogeeninen E. coli (EPEC), enterotoksigeeninen E. coli (ETEC), enterohemorraaginen E. coli (EHEC), enteroinvasiivinen E. coli (EIEC) ja enteroaggregatiivinen E. coli (EAEC). EPEC aiheuttaa etenkin kehitysmaissa pikkulapsille ripulia. ETEC aiheuttaa turistiripulia ja vastasyntyneiden ripulia kehitysmaissa. EHEC aiheuttaa ripulia tai veriripulia, joka voi varsinkin pienillä lapsilla johtaa hemolyyttis-ureemiseen oireyhtymään (HUS) ja munuaisten vaurioitumiseen. EIEC aiheuttaa Shigellan kaltaista ripulia, joka voi olla veristä. EAEC on yhdistetty lähinnä pitkittyneisiin ripuleihin. Tutkimuksessa selvitettiin suolistopatogeenisten E. coli -bakteerien esiintyvyyttä Burkina Fasossa, josta ei ole saatavilla aikaisempaa tietoa ripulikolien esiintymisestä ihmisissä ja elintarvikkeissa. Ulostenäytteitä otettiin ripulia sairastavilta alle viisivuotiailta lapsilta maaseudulta kahdesta kylästä, Boromosta ja Gourcysta, ja maan pääkaupungista Ouagadougousta (110 näytettä). Lihanäytteitä (kanaa, nautaa, lammasta ja naudan suolta, jota käytetään ihmisravinnoksi) otettiin Ouagadougoun toreilla myytävistä kypsentämättömistä lihoista (120 näytettä). Näytteistä saadut bakteerisekaviljelmät tutkittiin monialukkeisella PCR-menetelmällä, joka tunnistaa viiden ripulikoliryhmän virulenssigeenejä. Lisäksi lihanäytteistä eristettiin 20 EHEC-kantaa shigatoksiinin stx-geenin havaitsemiseen perustuvalla pesäkehybridisaatiolla ja PCR-seulonnalla, ja karakterisoitiin mahdollisten virulenssiominaisuuksien selvittämiseksi. Tutkimus osoitti, että ripulikolien aiheuttamat suolistoinfektiot ovat yleisiä ripulia sairastavilla pikkulapsilla Burkina Fasossa. Ulostenäytteistä 59 % oli positiivisia. Useimmiten lapsilla esiintyi EAEC- (32 %) ETEC- (31 %) ja EPEC-patoryhmiä (20 %). EIEC- (2 %) ja EHEC-patoryhmiä (1 %) esiintyi vähän. Myös useamman patoryhmän sekainfektiot olivat yleisiä (24 %). Eri paikkakuntien välillä oli tilastollisesti merkitseviä eroja ripulikolien esiintymisessä. Gourcyssa ripulikoleja esiintyi useammin kuin Ouagadougoussa ja Boromossa. Tutkimuksessa kävi ilmi, että Ouagadougoun toreilla myytävissä lihoissa on paljon ripulikoleja. Lihanäytteistä 43 % oli positiivisia. Yleisimmin lihoissa esiintyi EHEC (28 %), EPEC (20 %), ETEC (8 %) ja EAEC (5 %). EIEC-ryhmää ei havaittu lihoissa. Myös useamman patoryhmän sekakontaminaatioita löytyi (17 %) lihoista. Ripulikolien esiintyvyydessä eri lihojen välillä ei ollut tilastollisesti merkitseviä eroja, kun tarkasteltiin kaikkia patoryhmiä yhdessä. Eri patoryhmien esiintyvyyttä tarkasteltaessa EHEC-patoryhmää ei esiintynyt ollenkaan kanassa ja ero oli tilastollisesti merkitsevä muihin lihoihin verrattuna. Lihoista eristetyt 20 EHEC-kantaa kuuluivat 14 eri serotyyppiin, joista osa on aikaisemmin eristetty suolistoinfektioihin ja HUSoireyhtymään sairastuneilta ihmisiltä. Kaikki kannat olivat stx1-positiivisia ja puolella oli lisäksi stx2-geeni, jota pidetään shigatoksiinin virulentimpana muotona. Kahdelta EHEC-kannalta löytyi myös ETECpatoryhmän lämpöstabiilin enterotoksiini Ia:n geeni eli kannat olivat kahden patoryhmän välimuotoa ja osoitus geenien siirtymisestä eri patoryhmien välillä. Vaikka nuorimmat näytteen antaneet lapsipotilaat tuskin söivät lihaa, sen voidaan ajatella silti olevan edustava näyte lasten elinympäristöstä, sillä lasten ruoka valmistetaan usein samoissa oloissa, joissa raakaa lihaa käsitellään. Saastunut liha voi siten olla pikkulasten ripulikoli-infektioiden aiheuttaja.

Relative contributions of lipooligosaccharide inner and outer core modifications to nontypeable Haemophilus influenzae pathogenesis

Nontypeable Haemophilus influenzae (NTHi) is a frequent commensal of the human nasopharynx that causes opportunistic infection in immunocompromised individuals. Existing evidence associates lipooligosaccharide (LOS) with disease, but the specific and relative contributions of NTHi LOS modifications to virulence properties of the bacterium have not been comprehensively addressed. Using NTHi strain 375, an isolate for which the detailed LOS structure has been determined, we compared systematically a set of isogenic mutant strains expressing sequentially truncated LOS. The relative contributions of 2-keto-3-deoxyoctulosonic acid, the triheptose inner core, oligosaccharide extensions on heptoses I and III, phosphorylcholine, digalactose, and sialic acid to NTHi resistance to antimicrobial peptides (AMP), self-aggregation, biofilm formation, cultured human respiratory epithelial infection, and murine pulmonary infection were assessed. We show that opsX, lgtF, lpsA, lic1, and lic2A contribute to bacterial resistance to AMP; lic1 is related to NTHi self-aggregation; lgtF, lic1, and siaB are involved in biofilm growth; opsX and lgtF participate in epithelial infection; and opsX, lgtF, and lpsA contribute to lung infection. Depending on the phenotype, the involvement of these LOS modifications occurs at different extents, independently or having an additive effect in combination. We discuss the relative contribution of LOS epitopes to NTHi virulence and frame a range of pathogenic traits in the context of infection.

Identification of enteropathogenic and enterohaemorrhagic Escherichia coli strains by immunoserological detection of intimin

Aims: To evaluate the sensitivity and specificity of polyclonal and monoclonal antibodies (Mabs) against intimin in the detection of enteropathogenic and enterohaemorrhagic Escherichia coli isolates using immunoblotting. Methods and Results: Polyclonal and Mabs against the intimin-conserved region were raised, and their reactivities were compared in enteropathogenic E. coli (EPEC) and enterohaemorrhagic E. coli (EHEC) isolates using immunoblotting analysis. In comparison with rat antiserum, rabbit anti-intimin IgG-enriched fraction had a stronger recognition pattern to a wide spectrum of intimin types in different EPEC and EHEC serotypes. On the other hand, murine monoclonal IgG2b specific to intimin, with dissociation constant of 1 center dot 3 x 10-8 mol l-1, failed in the detection of some of these isolates. Conclusion: All employed antibodies showed 100% specificity, not reacting with any of the eae-negative isolates. The sensitivity range was according to the employed antisera, and 97% for rabbit anti-intimin IgG-enriched fraction, followed by 92% and 78% sensitivity with rat antisera and Mab. Significance and Impact of the Study: The rabbit anti-intimin IgG-enriched fraction in immunoblotting analysis is a useful tool for EPEC and EHEC diagnoses.

Identificação e fatores de virulência de Candida spp isoladas da cavidade bucal de transplantados renais do hospital universitário Onofre Lopes em Natal-RN

Despite Candida species are often human commensals isolated from various oral sites such as: tongue, cheek and palatal mucosa plus subgingival region, there are some properties linked to the organism commonly known as virulence factors which confer them the ability to produce disease. Oral candidiasis is one of the main oral manifestations reported in literature related to kidney transplant patients. The objectives of the present study were to identify and investigate virulence factors of yeasts isolated from the oral cavity of kidney transplant recipients admitted at the Hospital Universitário Onofre Lopes, in Natal RN. Seventy Candida species isolated from 111 kidney transplant recipients were investigated in this study. Identification of the isolates was performed by using the evidence of germ tube formation, hypertonic broth, tolerance to grow at 42°C, micromorphology and biochemical profiles. We observed a high rate of isolation of yeasts from the oral cavity of kidney transplant recipients (63.1%) being C. albicans was the most prevalent species. Oral candidiasis was diagnosed in 14.4% of transplant recipients. We evaluated virulence properties of the isolates regarding to: biofilm formation on polystyrene microplates as well as XTT reduction, adherence to acrylic resin and human buccal epithelial cells and proteinase activity. Most isolates were able to form biofilm by the method of adhesion to polystyrene. All isolates of Candida spp. remained viable during biofilm formation when analyzed by the method of XTT reduction. The number of CFU attached to the acrylic resin suggested high adherence for C. parapsilosis. C. albicans isolates showed higher median adherence to human buccal epithelial cells than non-C. albicans Candida isolates. Nevertheless, this difference was not statistically significant. C. dubliniensis showed low ability to adhere to plastic and epithelial cells and biofilm formation. Proteolytic activity was observed for all the isolates investigated, including the unique isolate of C. dubliniensis. There was a statistically significant association between proteinase production and the presence of oral candidiasis. Studies related to oral candidiasis in renal transplant recipients are limited to clinical and epidemiological data, but investigations concerning Candida spp. virulence factor for this group of individuals are still scarce. We emphasize the importance of studies related to virulence factors of yeasts isolated from this population to contribute to the knowledge of microbiological aspects of oral candidiasis

Ice as a vehicle for diarrheagenic Escherichia coli

In a recent study of the microbiological quality of commercial ice, 50 Escherichia coli isolates belonging to different serotypes were found. The potential hazard from these isolates was examined by testing their adherence patterns ill HeLa cells and searching for the presence of DNA sequences related to E. coli virulence properties. Twelve potentially diarrheagenic isolates were found and classified as enteroaggregative E. coli (EAEC) based oil their ability to produce aggregative adherence to HeLa cells. The remaining isolates were devoid of the virulence properties searched for. The EAEC isolates belonged to 10 different serotypes, among which O128ab:H35 is often found in diarrheic feces. None of these isolates reacted with a specific EAEC DNA probe or carried any of the known EAEC virulence genes. These data indicate that ice may be all important vehicle for transmission of enteropathogens, especially of the EAEC group. (C) 2003 Elsevier B.V. All rights reserved.

High prevalence of aggregative adherent Escherichia coli strains in the mucosa-associated microbiota of patients with inflammatory bowel diseases

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Influência das proteínas Yops de Yersinia pseudotuberculosis na resposta imune humoral murina

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Retroviroses em felinos domésticos

The retrovirus are recognized as pathogenic group of virus for domestic animals. The particularitities of these viruses are the necessity of the enzyme transcriptase reversa, for the conversion of the viral RNA in viral DNA (provirus) and the incorporation in the DNA of the cell, what it confers to the infection the lifetime character, due to all the infected cells present the provirus our DNA. Among the retroviruses in domestic felines, the leukaemia and immunossupressive virus represent the more important diseases. The main form of transmission of the virus of the FeLV is occur by close contact and the saliva presents high viral concentration. For the FIV, the main form of transmission is represented by wounds of bite. The retrovírus, replicate mainly in high metabolization cells. The infection for FeLV cause mieloproliferativas and degenerative illnesses, while the FIV are related imunossupressora illness. The treatment for these retroviroses is symptomatic associated to imunomodulatory drugs, none of these drugs are capable to eliminate the virus. For the prevention of these retrovirus are used vaccines. However only the vaccine against FeLV have showed efficiency. Thus , the more important measures in control of these diseases is prevent the contact between infected and health felines. The ain of present study was reviewed the more important aspects of retroviruses in domestic felines, with emphasis to virulence properties, epidemiology, fisiopathogeny, clinical manifestations, methods of diagnosis, therapy, and control measures