Oligodendrocyte differentiation

In the nervous system, axons transmit information in the form of electrical impulses over long distances. The speed of impulse conduction is enhanced by myelin, a lipid-rich membrane that wraps around axons. Myelin also is required for the long-term health of axons by providing metabolic support. Accordingly, myelin deficiencies are implicated in a wide range of neurodevelopmental and neuropsychiatric disorders, intellectual disabilities, and neurodegenerative conditions. Central nervous system myelin is formed by glial cells called oligodendrocytes. During development, oligodendrocyte precursor cells migrate from their origins to their target axons, extend long membrane processes that wrap axons, and produce the proteins and lipids that provide myelin membrane with its unique characteristics. Myelination is a dynamic process that involves intricate interactions between multiple cell types. Therefore, an in vivo myelination model, such as the zebrafish, which allows for live observation of cell dynamics and cell-to-cell interactions, is well suited for investigating oligodendrocyte development. Zebrafish offer several advantages to investigating myelination, including the use of transgenic reporter lines, live imaging, forward genetic screens, chemical screens, and reverse genetic approaches. This chapter will describe how these tools and approaches have provided new insights into the regulatory mechanisms that guide myelination.

Virulence and antimicrobial resistance determinants of verotoxigenic Escherichia coli (VTEC) and of multidrug-resistant E. coli from foods of animal origin illegally imported to the EU by flight passengers

The aim of this study was to reveal phenotype/genotype characteristics of verotoxigenic Escherichia coli (VTEC) and multidrug resistant E. coli in food products of animal origin confiscated as illegal import at Austrian, German and Slovenian airports. VTEC isolates were obtained by using ISO guidelines 16654:2001 for O157 VTEC or ISO/ TS13136:2012 for non-O157 VTEC, with additional use of the RIDASCREEN® Verotoxin immunoassay. The testing of 1526 samples resulted in 15 VTEC isolates (1.0%) primarily isolated from hard cheese from Turkey and Balkan countries. Genotyping for virulence by using a miniaturized microarray identified a wide range of virulence determinants. One VTEC isolate (O26:H46) possessing intimin (eae) and all other essential genes of Locus of Enterocyte Effacement (LEE) was designated as enterohemorrhagic E. coli (EHEC). None of the other VTEC strains belonged to serogroups O157, O145, O111, O104 or O103. VTEC strains harbored either stx(1) (variants stx1(a) or stx(1c)) or st(x2) (variants stx(2a), stx(2b), stx(2a/d) or stx(2c/d)) genes. Pulsed field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) demonstrated high genetic diversity and identified three new sequence types (STs): 4505, 4506 and 4507. Food samples collected from the Vienna airport were also tested for E. coli quantities using the ISO 16649:2001, and for detection of multidrug resistant phenotypes and genotypes. The resulting 113 commensal E. coli isolates were first tested in a pre-screening against 6 selected antimicrobials to demonstrate multidrug resistance. The resulting 14 multidrug resistant (MDR) E. coli isolates, representing 0.9% of the samples, were subjected to further resistance phenotyping and to microarray analyses targeting genetic markers of antimicrobial resistance and virulence. Genotyping revealed various combinations of resistance determinants as well as the presence of class 1, class 2 integrons. The isolates harbored 6 to 11 antibiotic resistance genes as well as 1 to 14 virulence genes. In this panel of 14 MDR E. coli two strains proved to carry CTX-M type ESBLs, and one single isolate was identified as enteropathogenic E. coli (EPEC). In general, isolates carrying a high number of resistance determinants had lower number of virulence genes and vice versa. In conclusion, this first pilot study on the prevalence of VTEC and of MDR/ESBL E. coli in illegally imported food products of animal origin suggests that these strains could represent reservoirs for dissemination of potentially new types of pathogenic and MDR E. coli in Europe.

Survey of systems for comparative ranking of agents that pose a bioterroristic threat

Strong efforts are made to improve preparedness for the prevention and counteraction of possible deliberate release of highly pathogenic biological agents at national and international level. An objective risk assessment for highly pathogenic biological agents is urgently needed for the purpose of prioritizing measures, evaluating the vulnerabilities and supporting rapid decisions on a scientific base in case of an emergency. Hitherto, several differing ranking schemes were developed. In general, the purpose of such ranking schemes is a comparative classification of agents under consideration of different transmission paths as well as agents threatening human and/or animal health. The analysed prioritization methods differ from qualitative to (semi-)quantitative with each its benefits and disadvantages in preciseness of the result, complexity and duration of the assessment but also in comprehensibility. Mainly, risk was defined as the product of probability and impact. In this survey, factors frequently used for the assessment of the probability and impact of a deliberate agent release were identified. Main criteria for the probability of an application were the history of use, the accessibility of the agent and possible paths of introduction and contamination as well as the feasibility of agent production. For the estimation of the impact, mainly the agent's effects on human and/or veterinary public health, depending on the target population, were examined. This includes the morbidity and mortality rates as well as the severity of induced illness, possible measures for diagnosis, and treatment and prevention. Furthermore, the economic and socioeconomic consequences were considered. In this review, the authors give an overview on open-source publications dealing with risk ranking of biological agents by outlining the criteria that were applied for risk ranking.

Emerging antimicrobial resistance in commensal Escherichia coli with public health relevance

In 2009, 1462 Escherichia coli isolates were collected in a systematic resistance monitoring approach from primary production, slaughterhouses and at retail and evaluated on the basis of epidemiological cut-off values. Besides resistance to antimicrobial classes that have been extensively used for a long time (e.g. sulphonamides and tetracyclines), resistance to (fluoro)quinolones and third-generation cephalosporins was observed. While in the poultry production chain the majority (60%) of isolates from laying hens was susceptible to all antimicrobials tested, most isolates from broilers, chicken meat and turkey meat showed resistance to at least one (85-93%) but frequently even to several antimicrobial classes (73-84%). In the cattle and pig production chain, the share of isolates showing resistance to at least one antimicrobial was lowest (16%) in dairy cows, whereas resistance to at least one antimicrobial ranged between 43% and 73% in veal calves, veal and pork. Resistance rates to ciprofloxacin and nalidixic acid in isolates from broilers were 41.1% and 43.1%, respectively. Likewise, high resistance rates to (fluoro)quinolones were observed in isolates from chicken meat and turkey meat. In contrast, ciprofloxacin resistance was less frequent in E. coli isolates from the cattle and pig production chain with highest rate in veal calves (13.3%). Highest resistance rates to cephalosporins were observed in broilers and chicken meat, with 5.9% and 6.2% of the isolates showing resistance. In dairy cattle and veal, no isolates with cephalosporin resistance were detected, whereas 3.3% of the isolates from veal calves showed resistance to ceftazidime. Resistance to (fluoro)quinolones and cephalosporins in E. coli isolates is of special concern because they are critically important antimicrobials in human antimicrobial therapy. The emergence of this resistance warrants increased monitoring. Together with continuous monitoring of antimicrobial usage, management strategies should be regularly assessed and adapted.

Quo vadis? - Monitoring Campylobacter in Germany

Campylobacter is a poorly recognized foodborne pathogen, leading the statistics of bacterially caused human diarrhoea in Europe during the last years. In this review, we present qualitative and quantitative German data obtained in the framework of specific monitoring programs and from routine surveillance. These also comprise recent data on antimicrobial resistances of food isolates. Due to the considerable reduction of in vitro growth capabilities of stressed bacteria, there is a clear discrepancy between the detection limit of Campylobacter by cultivation and its infection potential. Moreover, antimicrobial resistances of Campylobacter isolates established during fattening of livestock are alarming, since they constitute an additional threat to human health. The European Food Safety Authority (EFSA) discusses the establishment of a quantitative limit for Campylobacter contamination of broiler carcasses in order to achieve an appropriate level of protection for consumers. Currently, a considerable amount of German broiler carcasses would not comply with this future criterion. We recommend Campylobacter reduction strategies to be focussed on the prevention of fecal contamination during slaughter. Decontamination is only a sparse option, since the reduction efficiency is low and its success depends on the initial contamination concentration.

Livestock associated methicillin-resistant Staphylococcus aureus (LaMRSA) isolated from lesions of pigs at necropsy in northwest Germany between 2004 and 2007

An increasing number of reported detections of methicillin-resistant Staphylococcus aureus (MRSA) in food animals since 2007 has led to the assumption that there is an emerging zoonotic problem with livestock associated (la)MRSA potentially aggravating the MRSA problem in humans. It was the objective of the study to investigate, whether MRSA was present in clinical specimens of pigs collected at post-mortem since 2004 and to further characterize these isolates. We studied 138 isolates of S. aureus collected between 2004 and 2007 from various pathological lesions of pigs at necropsy. Potential MRSA were identified by growth on selective chromogenic media. Isolates were confirmed as MRSA using multiplex PCR. Confirmed isolates were spa- and SCCmec-typed and were tested for antimicrobial resistance. Overall, 60 (43%) S. aureus isolates were identified as MRSA. The majority (57/60) of the MRSA isolates found in the altered porcine tissues were spa-types associated with MRSA ST398. Three MRSA were ST97 isolates, a type that has not been described as an MRSA in pigs before. Other clonal complexes (ST9, ST30) dominated among the methicillin-sensitive S. aureus. MRSA were found in similar frequency in all 4 years. We assume that MRSA in pigs may have occurred earlier than 2004 and might be not really 'emerging', but rather have been overlooked until recently. The potentially causative role of the MRSA in the lesions warrants further investigation.

High heterogeneity within methicillin-resistant Staphylococcus aureus ST398 isolates, defined by Cfr9I macrorestriction-pulsed-field gel electrophoresis profiles and spa and SCCmec types

During recent years, the animal-associated methicillin-resistant Staphylococcus aureus clone ST398 has extensively been studied. The DNA of these isolates turned out to be refractory to SmaI restriction, and consequently, SmaI is unsuitable for subtyping this clone by standard pulsed-field gel electrophoresis (PFGE). Very recently, ST398 DNA was shown to be digested by Cfr9I, a neoschizomer of SmaI. In the present study, we employed Cfr9I PFGE on 100 German and 5 Dutch ST398 isolates and compared their PFGE profiles, protein A gene variable repeat regions (spa types), and types of the staphylococcal cassette chromosome mec (SCCmec). The isolates (from healthy carrier pigs, clinical samples from pigs, dust from farms, milk, and meat) were assigned to 35 profiles, which were correlated to the SCCmec type. A dendrogram with the Cfr9I patterns assigned all profiles to two clusters. Cluster A grouped nearly all isolates with SCCmec type V, and cluster B comprised all SCCmec type IVa and V* (a type V variant first identified as III) carriers plus one isolate with SCCmec type V. Both clusters also grouped methicillin-susceptible S. aureus isolates. The association of the majority of isolates with SCCmec type V in one large cluster indicated the presence of a successful subclone within the clonal complex CC398 from pigs, which has diversified. In general, the combination of Cfr9I PFGE with spa and SCCmec typing demonstrated the heterogeneity of the series analyzed and can be further used for outbreak investigations and traceability studies of the MRSA ST398 emerging clone.

Prevalence of MRSA types in slaughter pigs in different German abattoirs

To investigate the prevalence of types of meticillin-resistant Staphylococcus aureus (MRSA) in slaughter pigs in German abattoirs, nasal swabs were collected from a total of 1026 pigs in five abattoirs after stunning in the course of two studies, and examined for MRSA. Study 1 included four abattoirs; study 2 was carried out in one large abattoir. Isolates were tested for antimicrobial susceptibility and characterised using spa-typing, multilocus sequence typing (MLST) and typing of the staphylococcal cassette chromosome, SCCmec. Overall, MRSA was isolated from 70.8 per cent of 520 samples in study 1 and from 49.0 per cent of 506 samples in study 2. The proportion of positive samples varied substantially between the abattoirs in study 1. Most isolates belonged to spa-types t011 and t034 and SCCmec types III and V. MLST of selected isolates revealed that they were all MLST ST398. Besides beta-lactams, 100 per cent of the isolates were resistant to tetracycline, 80.5 per cent were resistant to erythromycin and 80.7 per cent were resistant to clindamycin. Less than 5 per cent of the isolates were resistant to other antimicrobials.

Comparative examination and validation of ELISA test systems for Salmonella typhimurium diagnosis of slaughtering pigs

The most frequently isolated Salmonella serotype from pork in Germany is S. typhimurium, especially phagetype DT 104. The monitoring programs on Salmonella in swine are based on enzyme-linked immunoadsorbent assay (ELISA) detecting antibodies in serum or meat juice. These serological results are used to classify swine herds in three categories to assess the hygienic status of farm regarding Salmonella infection in pigs. The object of this study was the comparative evaluation of four indirect Salmonella ELISA tests approved in Germany to detect Salmonella typhimurium infection of swine. Three tests (A-C) are based on LPS-antigen and directed against specific IgG-antibodies. The fourth test (D) bases on a whole-cell-lysate antigen and discriminates between Salmonella specific IgA-, IgM- and IgG-antibodies. In a longitudinal study sixteen 6 weeks old weaning pigs were orally infected with S. typhimurium DT 104. During an observation period of 138d clinical and bacteriological parameters were monitored and serum samples obtained at regular intervals as well as meat juice samples taken at slaughter were examined by the respective ELISA systems. Study results reveal that all tested ELISA systems are able to detect S. typhimurium infection in pigs in both sample matrices, blood serum and meat juice whereas test D showed the highest sensitivity to detect Salmonella antibodies in pigs. The sensitivity to detect Salmonella antibodies varied between tests A and C according to the used cut-off (test specific cut-off vs. recommended surveillance cut-off) resulting in a change of seroprevalence and hence may influence the Salmonella status of the farm.

Serotypes and virutypes of enteropathogenic and enterohaemorrhagic Escherichia coli strains from stool samples of children with diarrhoea in Germany

AIMS

To investigate the prevalence of traditional and emerging types of enteropathogenic (EPEC) and enterohaemorrhagic Escherichia coli (EHEC) strains in stool samples from children with diarrhoea and to characterize their virulence genes involved in the attaching and effacing (A/E) phenotype.

METHODS AND RESULTS

Serological and PCR-based methods were used for detection and isolation of EPEC and EHEC strains from 861 stool samples from diarrhoeic children. Agglutination with traditional EPEC and EHEC O-group-specific antisera resulted in detection of 38 strains; 26 of these carried virulence factors of EPEC or EHEC. PCR screening for the eae gene resulted in isolation of 97 strains, five carried genes encoding Shiga toxins (stx), one carried the bfpA gene and 91 were atypical EPEC. The 97 EPEC and EHEC strains were divided into 36 O-serogroups and 21 H-types, only nine strains belonged to the traditional EPEC O-groups O26, O55, O86 and O128. In contrast, EPEC serotypes O28:H28, O51:H49, O115:H38 and O127:H40 were found in multiple cases. Subtyping the virulence factors intimin, Tir and Tir-cytoskeleton coupling effector protein (TccP)/TccP2 resulted in further classification of 93.8% of the 97 strains.

CONCLUSIONS

Our findings show a clear advantage of the eae-PCR over the serological detection method for identification of EPEC and EHEC strains from human patients.

SIGNIFICANCE AND IMPACT OF THE STUDY

Molecular detection by the eae-PCR followed by serotyping and virutyping is useful for monitoring trends in EPEC and EHEC infections and to discover their possible reservoirs.

The pyruvate kinase isoenzyme M2 (Tu M2-PK) as a tumour marker for renal cell carcinoma

The M2 isoenzyme of pyruvate kinase (M2-PK) is specially expressed by tumour cells (Tu M2-PK) and has been detected in the peripheral blood of patients with renal cell carcinoma (RCC). We analysed the benefit of using Tu M2-PK as a tumour marker for primary detection of RCC by receiver operating characteristic (ROC) analysis. The area under the curve was 0.674, and the sensitivity, specificity and positive predictive value (PPV) were 44.4%, 87.5% and 88%, respectively, at the ROC optimal cut-off of 28.2 kU/L. We examined 71 patients. Since the marker sensitivity for detection of the early stages T1 and T2 was only 47% it is not suggested to use this marker for primary diagnosis of RCC. Its use as part of the confirmatory preoperative evaluation might be considered in view of its high PPV.

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.