Comparative evaluation of the Ridascreen Verotoxin enzyme immunoassay for detection of Shiga-toxin producing strains of Escherichia coli (STEC) from food and other sources

AIMS

To evaluate the suitability of the commercially distributed Ridascreen Verotoxin enzyme immunoassay (EIA) for detection of known genetic types of the Vero (Shiga) toxins 1 (Stx1) and 2 (Stx2) families and to determine its relative sensitivity and specificity.

METHODS AND RESULTS

The Ridascreen-EIA was compared with the Vero cell assay, a P(1)-glycoprotein receptor EIA and with stx gene-specific PCs for detection of Stx with 43 Shiga toxin-producing strains of Escherichia coli (STEC) reference strains and with 241 test strains. The Ridascreen-EIA detects strains producing Stx1 and variants Stx1c and Stx1d, as well as Stx2 and variants Stx2d1, Stx2d2, Stx2e, Stx2d, Stx2-O118 (Stx2d-ount), Stx2-NV206, Stx2f and Stx2g. The assay showed a relative sensitivity of 95.7% and a relative specificity of 98.7%. Some of the Stx2-O118-, Stx2e- and Stx2g-producing STEC were not detected with the Ridascreen-EIA probably because of low amount of toxin produced by these strains.

CONCLUSIONS

The Ridascreen-EIA is able to detect all known types of Stx and is applicable for routine screening of bacterial isolates owing to its high specificity. It is less applicable for testing samples where low amounts of Stx are expected, such as mixed cultures and certain Stx2 variants.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study presents a first comprehensive evaluation of the Ridascreen-EIA, a rapid standardized STEC screening test for routine diagnostic laboratories. Data are presented on the type of the spectrum of Stx that are detected with this immunoassay and its advantages and limits for practical use.

Probably anti-Tr associated paraneoplastic cerebellar degeneration as initial presentation of a squamous cell carcinoma of the lung

Paraneoplastic cerebellar degeneration (PCD) is the most frequent paraneoplastic syndrome affecting the brain. Until now, anti-Tr associated PCD was only seen in patients with Hodgkin's disease. We report a male patient who presented with a progressive ataxia, affecting predominantly the lower limbs and a cerebellar dysarthria. Extensive diagnostic approach initially showed no evidence of tumor. The patient was found to have anti-Tr antibodies in his serum. Fourteen months after onset of symptoms a whole body PET-scan showed a pathological focus at the right hilus of the lungs. A mediastinoscopy was performed and peribronchial node sampling was done. The anatomopathological analysis revealed a non-well differentiated squamous cell carcinoma. This is the first report about the association between an anti-Tr associated PCD and squamous cell carcinoma.

Central nervous system metastases of pulmonary adenocarcinoma mimicking neurofibromatosis type 2

We report a case of a 51-year-old man presenting with rapidly progressive unilateral tinnitus, hearing loss and imbalance. Neuroimaging revealed bilateral VIIIth cranial nerve masses and multiple cerebral and spinal cord lesions that were interpreted as being acoustic schwannomas and multiple meningeomas. An initial tentative diagnosis of neurofibromatosis type 2 (NF2) was made. Both clinical and radiological evolution were atypical for NF2 and the initial diagnosis of NF2 was questioned. Additional technical investigations demonstrated a pulmonary adenocarcinoma. Postmortem examination confirmed that this patient had multiple central nervous system metastases of a primary pulmonary adenocarcinoma, presenting clinically and neuroradiologically as a probable neurofibromatosis type 2. Clinicians should be aware of the rare possibility of central nervous system metastases mimicking NF2.

Evaluation of different methods to discriminate Bacillus anthracis from other bacteria of the Bacillus cereus group

AIMS

To evaluate different methods that are useful for rapid and definitive discrimination of Bacillus anthracis from other bacteria of the Bacillus cereus group in environmental samples like letters claimed to contain anthrax spores.

METHODS AND RESULTS

Characterized strains and bacteria from environmental samples were analysed by microbiological and molecular methods (PCR and restriction analysis). Environmental isolates often shared several microbiological features with B. anthracis, e.g. lack of beta-haemolysis and phospholipase C activity, and only the gamma phage assay was specific for B. anthracis. PCR assays targeting markers from the virulence plasmids exclusively detected B. anthracis, but other PCR targets were also detected in nonanthrax isolates. Additionally, the restriction pattern in an AluI restriction analysis of the SG-749 fragment is not 100% specific. The loci used for multiple-locus variable-number tandem repeat analysis of B. anthracis are also present in other members of the B. cereus group, but amplicon sizes are usually different.

CONCLUSIONS

Environmental samples often contain borderline isolates closely related to B. anthracis both on microbiological and genetic levels. Real-time PCR targeting plasmidal and chromosomal markers should be used for rapid and definitive exclusion of a virulent strain of B. anthracis in such samples.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study gives an overview of the current microbiological and molecular methods used for identification of B. anthracis and shows that most assays have limits when borderline isolates present in environmental samples are analysed.

Lipidic implants for controlled release of bioactive insulin: effects on cartilage engineered in vitro

Controlled release systems for growth factors and morphogens are potentially powerful tools for the engineering or the treatment of living tissues. However, due to possible instabilities of the protein during manufacture, storage, and release, in the development of new release systems it is paramount to investigate into the maintenance of bioactivity of the protein. Within this study, recently developed protein releasing lipid matrix cylinders of 2 mm diameter and 2 mm height made from glycerol tripalmitate were manufactured in a compression process without further additives. Insulin in different concentrations (0.2%, 1%, and 2%) served as model protein. The bioactivity of the protein released from the matrices was investigated in a long-term cartilage engineering culture for up to four weeks; additionally, the release profiles were determined using ELISA. Insulin released from the matrices increased the wet weights of the cartilaginous cell-polymer constructs (up to 3.2-fold), the amount of GAG and collagen in the constructs (up to 2.4-fold and 3.2-fold, respectively) and the GAG and collagen content per cell (1.8-fold and 2.5-fold, respectively), compared to the control. The dose-dependent effects on tissue development correlated well with release profiles from the matrices with different insulin loading. In conclusion, the lipid matrices, preserving the bioactivity of incorporated and released protein, are suggested as a suitable carrier system for use in tissue engineering or for the localized treatment of tissues with highly potent protein drugs such as used in the therapy of brain cancer or neurodegenerative CNS diseases.

Studies of the efficacy of Enterocoliticin, a phage-tail like bacteriocin, as antimicrobial agent against Yersinia enterocolitica serotype O3 in a cell culture system and in mice

The efficacy of enterocoliticin, a phage tail-like bacteriocin, as antimicrobial compound against infections with pathogenic Yersinia enterocolitica serotype O3 strains was assessed. In cell cultures, which were infected with the Y. enterocolitica strains 13 169 or 6471/76, bactericidal activity of enterocoliticin was found for bacteria adhering to the surface of eukaryotic cells, whereas bacteria, which had invaded the eukaryotic cells, were not accessible to the bacteriocin. The interaction of enterocoliticin with Y. enterocolitica was further examined in animals. Female BALB/c mice were experimentally infected with the two Y. enterocolitica strains and enterocoliticin was applied as antimicrobial compound by the oral route. Experimental variations concerning the infectious doses of the Y. enterocolitica strains and the time points of application of the bacteriocin were investigated. The increase of the Yersinia CFU titre in animals was retarded at time points shortly after the application of enterocoliticin indicating that the particles were effective on recently introduced Yersinia. The repeated application of enterocoliticin, however, did not prevent the colonization of the gastrointestinal tract by Yersinia.

Effiziente Abtötung von Milzbrandsporen durch wässrige und alkoholische Peressigsäure–Lösungen

We analysed the sporicidal effect of different concentrations of aqueous and alcoholic peracetic acid (PAA) solutions on anthrax spores in suspension and germ carrier tests. In activation of anthrax spores in suspension assays was achieved in less than 2 min using 1% PAA solution and in less than 3 min using 0.5% PAA solution, respectively. In contrast, in germ carrier as says, a test under practical conditions, spores on 38% of the germ carriers survived treatment with 1% PAA solution for 15 min. The use of PAA in 80% ethyl alcohol outclassed the sporicidal effect of aqueous PAA solutions in both suspension and germ carrier assays. Anthrax spores on 14% of germ carriers tested survived 30 min of treatment with a 1% aqueous PAA solution. In contrast anthrax spores were reliably inactivated under the same test procedure using a 1% alcoholic PAA solution for 30 min. The proven enhancement of the sporicidal effect of alcoholic PAA solutions should be kept in mind when using disinfectants in practice. In further surveys we will optimise the test conditions.

Use of a quantitative TaqMan-PCR for the fast quantification of mycobacteria in broth culture, eukaryotic cell culture and tissue

The quantification of slow-growing mycobacteria such as Mycobacterium tuberculosis or M. bovis from in vitro and in vivo samples is complicated by their long generation time, their ability to form aggregates, and their capacity to persist in a state of dormancy. We compared different methods for the establishment of growth curves for broth cultures of M. bovis bacille Calmette-Guérin (BCG). A quantitative TaqMan-PCR yielded results comparable with those obtained by protein quantification and measurement of the ATP content of the cultures. The quantitative TaqMan-PCR furthermore turned out to be particularly suitable for the measurement of multiplication of BCG within eukaryotic cells. Furthermore, it is a fast method allowing an estimation of the mycobacterial load in tissue long before colony counts can be obtained.

Bone morphogenetic protein 9: a potent modulator of cartilage development in vitro

Few publications describe the activity of bone morphogenetic protein-9 (BMP-9), but the consensus of these largely in vivo studies is that while BMP-9 can induce ectopic bone formation at relatively large concentrations, it is primarily active in non-skeletal locations--including the liver, nervous system and marrow. To study the effects of BMP-9 on chondrogenesis in a well-defined environment, calf articular chondrocytes were seeded onto biodegradable PGA scaffolds. The resulting cell-polymer constructs were cultured in either control medium or medium supplemented with 1, 10, 50 or 100 ng/ml of BMP-9. After 4 weeks of in vitro culture, all concentrations of BMP-9 increased the total mass of the constructs, and the amounts of collagen, glycosaminoglycans (GAG) and cells per construct. On a mass percentage basis, BMP-9 tended to increase GAG, to decrease the relative amount of collagen and had little effect on the relative amount of cells. BMP-9 elicited qualitatively similar responses as BMP-2, -12 and -13. However, in contrast to BMP-12 and -13, BMP-9 (at concentrations > or = 10 ng/ml) induced hypertrophic chondrocyte formation and was the only BMP tested to induce mineralization. Taken together, these data suggest that BMP-9 is a potent modulator of cartilage development in vitro.

[The relationship of plasmids from environmental Yersinia isolates and the virulence plasmid of enteropathogenic Yersinia strains]

The human pathogenic strains of Yersinia harbour a conserved plasmid carrying the Yop virulon. The virulence plasmid of Yersinia enterocolitica strains belonging to the serogroups O:3 and O:9 were used as probes to detect homologous sequences in plasmids of "avirulent" Yersinia strains. "Avirulent" Yersinia strains (Y. enterocolitica biogroup 1A, Y. intermedia, Y. kristensenii and Y. frederiksenii) lack the virulence plasmid. They are widely distributed in the environment and can frequently be isolated from clinical samples. Hybridisation experiments revealed a number of common genetic elements of the virulence plasmid and the plasmids of "avirulent" Yersinia strains. These elements were identified as genes involved in plasmid replication, as an endonuclease gene and as mobile genetic elements. However, none of the plasmid encoded virulence genes was present in the plasmids of "avirulent" Yersinia strains. The frequent occurrence and the possible etiological relevance of "avirulent" isolates will be discussed.

Characterization of enterocoliticin, a phage tail-like bacteriocin, and its effect on pathogenic Yersinia enterocolitica strains

Yersinia enterocolitica 29930 (biogroup 1A; serogroup O:7,8) produces a bacteriocin, designated enterocoliticin, that shows inhibitory activity against enteropathogenic strains of Y. enterocolitica belonging to serogroups O:3, O:5,27 and O:9. Enterocoliticin was purified, and electron micrographs of enterocoliticin preparations revealed the presence of phage tail-like particles. The particles did not contain nucleic acids and showed contraction upon contact with susceptible bacteria. Enterocoliticin addition to logarithmic-phase cultures of susceptible bacterial strains led to a rapid dose-dependent reduction in CFU. Calorimetric measurements of the heat output of cultures of sensitive bacteria showed a complete loss of cellular metabolic activity immediately upon addition of enterocoliticin. Furthermore, a dose-dependent efflux of K(+) ions into the medium was determined, indicating that enterocoliticin has channel-forming activity.

Taxonomic studies of predatory bdellovibrios based on 16S rRNA analysis, ribotyping and the hit locus and characterization of isolates from the gut of animals

The aim of our study was to obtain data for the molecular characterization of bdellovibrio bacteria, which were recently split into the genus Bdellovibrio and the newly designated genus Bacteriovorax. We determined the 16S rDNA sequences of five reference strains and performed a phylogenetic analysis including published 16S rRNA sequences of bdellovibrios. A comparison of the secondary structure showed significant differences in two regions of the 16S rRNAs of the species Bdellovibrio bacteriovorus, Bacteriovorax starrii, and Bacteriovorax stolpii. In addition, ribotyping techniques gave specific hybridization patterns and revealed that two rRNA operons are present in the investigated strains. A hybridization probe derived from the genetic locus hit, associated with the host independent (HI) phenotype of B. bacteriovorus, was found to be specific for this species. Sequence comparison of the hit locus revealed few base pair changes between host independent (HI) and host dependent (HD) strains. Ribotyping and hybridization experiments using the hit probe were applied to characterize bdellovibrio strains isolated from the gut of animals and humans and one isolate from sewage.

Isolation of a lysogenic bacteriophage carrying the stx(1(OX3)) gene, which is closely associated with Shiga toxin-producing Escherichia coli strains from sheep and humans

A specific PCR for the detection of a variant of the gene encoding Shiga toxin 1 (stx(1)) called stx(1(OX3)) (GenBank accession no. Z36901) was developed. The PCR was used to investigate 148 Stx(1)-producing Escherichia coli strains from human patients (n = 72), cattle (n = 27), sheep (n = 48), and a goat (n = 1) for the presence of the stx(1(OX3)) gene. The stx(1(OX3)) gene was present in 38 Shiga toxin-producing E. coli (STEC) strains from sheep belonging to serogroups O5, O125, O128, O146, and OX3 but was absent from Stx(1)-positive ovine STEC O91 strains. The stx(1(OX3)) gene was also detected in 22 STEC strains from humans with nonbloody diarrhea and from asymptomatic excreters. Serotypes O146:H21 and O128:H2 were most frequently associated with stx(1(OX3))-carrying STEC from sheep and humans. In contrast, Stx(1)-producing STEC strains from cattle and goats and 50 STEC strains from humans were all negative for the stx(1(OX3)) gene. The stx(1(OX3))-negative strains belonged to 13 serotypes which were different from those of the stx(1(OX3))-positive STEC strains. Moreover, the stx(1(OX3)) gene was not associated with STEC belonging to enterohemorrhagic E. coli (EHEC) serogroups O26, O103, O111, O118, O145, and O157. A bacteriophage carrying the stx(1(OX3)) gene (phage 6220) was isolated from a human STEC O146:H21 strain. The phage was able to lysogenize laboratory E. coli K-12 strain C600. Phage 6220 shared a similar morphology and a high degree of DNA homology with Stx(2)-encoding phage 933W, which originates from EHEC O157. In contrast, few similarities were found between phage 6220 and Stx(1)-encoding bacteriophage H-19B from EHEC O26.

A highly homologous 68 kbp plasmid found in Vibrio vulnificus strains virulent for eels

Vibrio vulnificus serovar E (biotype 2) strains are virulent for eels and have also been reported to cause illness in humans. Studies on the plasmid content of serovar E strains revealed the existence of a plasmid of approximately 70 kbp present in most of these strains. In this study we characterized the 70 kbp plasmids of seven biotype 2 strains isolated from seawater, diseased eels and wound infections in humans. We determined the exact size of the high molecular weight plasmids to be 68 kbp. A comparison of the plasmids of the seven strains by restriction length polymorphism and hybridization analysis showed them to be almost identical.

Comparative study of temperate bacteriophages isolated from Yersinia

170 Yersinia strains belonging to various species were investigated for the presence of temperate bacteriophages. By induction with mitomycin C seven phages were isolated from Y. enterocolitica strains and one phage from a Y. frederiksenii strain. The phages were characterized on the basis of their morphology, host range, genome size, DNA homology, and protein composition. They belong to different phage families and reveal narrow to moderate wide host ranges. Some of the isolated phages were able to infect pathogenic as well as nonpathogenic strains of Y. enterocolitica. The genomes of all isolated phages were found to be composed of double stranded DNA ranging from about 40 to 60 kb. In addition to the analysed phages, a number of putative phages were induced in strains of Y. frederiksenii, Y. kristensenii, Y. intermedia, and Y. mollaretii. The putative phages were identified by isolation of phage DNA from cell free lysates but could not be propagated on indicator strains. Southern hybridization experiments revealed relationships between phages belonging to different families. Moreover, DNA homologies were observed between phages isolated from nonpathogenic Yersinia strains and a phage which was isolated from a pathogenic Y. enterocolitica serogroup O:3 strain.

Isolation of a new insertion element of Yersinia intermedia closely related to remnants of mobile genetic elements present on Yersinia plasmids harboring the Yop virulon

A new insertion element present in two alleles, designated IS1635.1 and IS1635.2, was identified on a plasmid of a Yersinia intermedia strain by hybridization with the Yersinia enterocolitica pYV virulence plasmid. IS1635.1 and IS1635.2 are 861 bp long, carry imperfect inverted terminal repeats and possess a single open reading frame encoding a putative transposase of the IS6 family. A truncated IS1635 element is present immediately downstream of element IS1635.2. The capacity of the IS1635 elements to mediate transposition in Yersinia was demonstrated with a R6K-derived suicide vector, where a kanamycin resistance gene had been inserted between IS1635.1 and IS1635.2. Hybridization and sequence alignments showed that remnants of IS1635-like insertion elements harboring large deletions and point mutations are present on the Yop virulon harboring plasmids of pathogenic Yersinia strains. In a few cases, the IS1635 element has also been found on plasmids of apathogenic Yersinia strains.

Zebrafish neural induction and patterning

Formation of a functional nervous system requires that distinct types of cells develop at quite precise times and places. A goal of developmental neurobiologists is to understand the nature of the patterning mechanisms that specify neural cells for particular fates. In recent years, zebrafish has emerged as new model system for investigating vertebrate neural development, offering a unique combination of genetic, cellular, and molecular tools. Studies using zebrafish provide important new insights concerning the source and nature of molecular signals that induce and pattern the central nervous system.

Is natural genetic transformation a mechanism of horizontal gene transfer in Yersinia?

We investigated the capacity of different Yersinia strains with emphasis to Yersinia enterocolitica to take up and incorporate DNA by natural genetic transformation. Our studies were initiated by the observation of partial homology between the virulence plasmid of a pathogenic Y. enterocolitica strain (O: 3, biovar 4) and plasmids indiginous to different a pathogenic Y. enterocolitica biovar 1A strains revealed by hybridization studies. Furthermore, an observation of natural genetic transformation in a strain of Y. enterocolitica has been published by CALLAHAN and KOROMA (1979). To detect an uptake and incorporation of DNA, we incubated potential recipient strains with naked DNA under varying experimental conditions. The parameters tested were--the recipient strain,--the markers used to detect a DNA transfer,--the condition of the transforming DNA,--the nutrient availability,--the temperature,--the growth phase, and--the influence of stress. In our experiments, we could not identify conditions under which Y. enterocolitica could be naturally transformed. We thus conclude that natural transformation is unlikely to be an important mechanism for horizontal gene transfer in Yersinia.

A giant prolactinoma presenting with unilateral exophthalmos: effect of cabergoline and review of the literature

We report the case of a 45-year-old male presenting with unilateral exophthalmos due to a large tumoral mass invading the skull base. Ophthalmologic examination did not show any visual field defects. Imaging techniques demonstrated extension of a huge tumor (approx. 8x8x8 cm) into the right orbit and nasopharynx. Endocrine work-up revealed grossly elevated serum prolactin (PRL) levels (26,466 microg/l, nl. < 12), pointing to a large, invasive macroprolactinoma. Stimulation tests indicated associated partial adrenal and growth hormone deficiencies. Planned surgery was abandoned, and the patient was instead treated with the long-acting dopamine agonist, cabergoline. Over a period of one year, serum PRL dropped to 131 microg/l, while the tumor mass shrank to less than 50% of its original volume (with 3.5 mg/week of cabergoline). The exophthalmos disappeared, and the patient did not develop rhinorrhea or any other side effects from treatment with cabergoline. The efficacy was maintained throughout the second year (ultimate serum PRL 74 microg/l, and final size less than 10% of the original). With reference to this case, we review other macroprolactinomas reported in the recent literature for associated exophthalmos, grossly elevated serum PRL levels (> or = 15,000 microg/l), and/or "giant" size (> or = 4 cm in maximum diameter). We highlight the use of dopamine agonists in the treatment of prolactinomas with such unusual characteristics.

Use of a plasmid of a yersinia enterocolitica biogroup 1A strain for the construction of cloning vectors

A plasmid with a size of 2,682 base pairs isolated from the Yersinia enterocolitica biogroup 1A strain # 29807 was characterized in respect to its suitability as a basic replicon for cloning vectors. The copy number of the plasmid was determined to be approximately 14 copies per cell and it was shown to be compatible with vectors with an origin of replication derived from ColE1 and p115A. The replication region of the plasmid encodes a primer RNAI and countertranscript RNAII. Two vectors, pIV1 and pIV2, containing a kanamycin resistance gene and the lacZalpha fragment with the multiple cloning site of pBluescriptSK + were constructed. A mobilizable derivative was successfully introduced into different bacteria belonging to the family Enterobacteriacea. To prove the applicability of the novel vectors for cloning purposes, a 13 kb hemolysin operon of Escherichia coli was inserted into pIV1, and the resulting recombinant plasmid was stably maintained and expressed in E. coli and Y. enterocolitica.