Multiplex PCR for detection of virulence markers of Vibrio vulnificus.

UNLABELLED: Vibrio vulnificus is a Gram-negative pathogen found in coastal and estuarine waters worldwide that can cause life threatening diseases. Characterization of the vcg (virulence correlated gene) or 16S rRNA alleles is used to distinguish virulent (clinical (C)-type) from presumably avirulent (environmental (E)-type) strains. However, some studies reported a significant number of clinical strains belonging to the E-type. In recent years more potential virulence markers have been identified, that are useful for the identification of potentially pathogenic isolates of the E-type. In this study, we successfully combined detection of pathogenicity region XII, nanA and a mannitol fermentation operon with the virulence associated alleles of the 16S rRNA and vcg genes in one multiplex PCR. Additionally, toxR primers for species confirmation and internal amplification control were included. Validation of multiplex amplification was performed with a total of 132 bacterial strains, including V. vulnificus (n = 71), other Vibrionaceae (n = 50) and non-Vibrio isolates (n = 11). Multiplex PCR showed reliable amplification of four of the five virulence markers with a high sensitivity and specificity. Amplification of the 16S rRNA type B allele was not completely reliable with conventional PCR assays, however, the positive predictive value of this marker was 100 %. SIGNIFICANCE AND IMPACT OF THE STUDY: A multiplex PCR for simultaneous detection and characterization of potentially virulent strains of Vibrio vulnificus was developed and validated. Monitoring programs will benefit from this cost and time effective method when screening large strain collections. Application of the multiplex PCR simplifies determination of risks emanating from V. vulnificus in recreational waters or mussel primary production.

Genetic and phenotypic analysis of Vibrio cholerae non-O1, non-O139 isolated from German and Austrian patients.

Vibrio cholerae belonging to the non-O1, non-O139 serogroups are present in the coastal waters of Germany and in some German and Austrian lakes. These bacteria can cause gastroenteritis and extraintestinal infections, and are transmitted through contaminated food and water. However, non-O1, non-O139 V. cholerae infections are rare in Germany. We studied 18 strains from German and Austrian patients with diarrhea or local infections for their virulence-associated genotype and phenotype to assess their potential for infectivity in anticipation of possible climatic changes that could enhance the transmission of these pathogens. The strains were examined for the presence of genes encoding cholera toxin and toxin-coregulated pilus (TCP), as well as other virulence-associated factors or markers, including hemolysins, repeats-in-toxin (RTX) toxins, Vibrio seventh pandemic islands VSP-1 and VSP-2, and the type III secretion system (TTSS). Phenotypic assays for hemolysin activity, serum resistance, and biofilm formation were also performed. A dendrogram generated by incorporating the results of these analyses revealed genetic differences of the strains correlating with their clinical origin. Non-O1, non-O139 strains from diarrheal patients possessed the TTSS and/or the multifunctional autoprocessing repeats-in-toxin (MARTX) toxin, which were not found in the strains from ear or wound infections. Routine matrix-assisted laser desorption/ionization (MALDI-TOF) mass spectrometry (MS) analysis of all strains provided reliable identification of the species but failed to differentiate between strains or clusters. The results of this study indicate the need for continued surveillance of V. cholerae non-O1, non-O139 in Germany, in view of the predicted increase in the prevalence of Vibrio spp. due to the rise in surface water temperatures.

Characterization of a Yersinia enterocolitica biotype 1A strain harbouring an ail gene.

AIMS: The chromosomal ail gene (attachment and invasion locus) is commonly used as target gene for the detection of pathogenic Y. enterocolitica strains in food testing. The ail PCR does not detect strains of biotype 1A (BT1A), which are regarded as non-pathogenic because BT1A strains lack the virulence plasmid and chromosomally encoded virulence genes. In some recent reports, however, BT1A strains were discovered that harboured the ail gene. We isolated an ail-positive strain and characterized this strain with phenotypic and genotypic methods to study its possible relation to pathogenic Y. enterocolitica strains. METHODS AND RESULTS: The ail region of the BT1A strain was sequenced and compared with the corresponding region of nonpathogenic BT1A strains and pathogenic strains. Pulsed field gel electrophoresis (PFGE) analysis was applied revealing no similarity of the PFGE pattern of this strain to the patterns of pathogenic strains. Virulence-gene-based PCR analyses showed the strain to be positive for ystB, but negative for virulence genes ystA, virF and yadA. Whole-cell MALDI-TOF MS combined with a shrinkage discriminant analysis approach was applied and clearly classified the ail-positive biotype 1A strain within the cluster of BT1A strains. CONCLUSIONS: PCR detection of ail sequences in food matrices should be followed by the isolation of the responsible strain and its characterization using phenotypic or genotypic methods. SIGNIFICANCE AND IMPACT OF THE STUDY: The ail gene may be present in Y. enterocolitica BT1A strains, which are commonly considered as nonpathogenic. Efficient methods such as PCR typing of other virulence genes or rapid MALDI-TOF MS-based bacterial profiling allow a more comprehensive assessment of the pathogenicity potential of Yersinia strains.

[Vibrio infections from food and sea water. Introducing the "VibrioNet"]. / Vibrio-Infektionen durch Lebensmittel und Meerwasser. Das Netzwerk "VibrioNet" stellt sich vor.

Vibrio is a genus of bacteria present in surface and coastal waters as well as in marine organisms worldwide. In many countries, pathogenic Vibrio species are a main cause of bacterial diarrhea, which may result from comsumption of contaminated seafood and fish products or from drinking contaminated water. Vibrio infections may also gain in importance in our regions due to global warming and the increase in the world trade of seafood. The research network "VibrioNet" studies pathogenic Vibrios in the marine environment and in seafood consumed by humans as a potential, new emerging zoonotic agent. An assessment of the risk arising from pathogenic non-cholera-vibrios in central Europe is the target of a multidisciplinary research effort. The research network will be strengthened by cooperations with international partners from countries in which Vibrio infections play a major role (Bangladesh, Chile, India, Thailand, and Vietnam).

Rapid identification and characterization of Vibrio species using whole-cell MALDI-TOF mass spectrometry.

AIMS: Vibrio identification by means of traditional microbiological methods is time consuming because of the many biochemical tests that have to be performed to distinguish closely related species. This work aimed at evaluating the use of MALDI-TOF mass spectrometry for the rapid identification of Vibrio (V.) spp. as an advantageous application to rapidly discriminate the most important Vibrio spp. and distinguish Vibrio spp. from closely related bacterial species like Photobacterium damselae and Grimontia hollisae and other aquatic bacteria like Aeromonas spp. METHODS AND RESULTS: Starting from sub-colony amounts of pure cultures grown on agar plates, a very simple sample preparation procedure was established and combined with a rapid and automated measurement protocol that allowed species identification within minutes. Closely related species like Vibrio alginolyticus and Vibrio parahaemolyticus or Vibrio cholerae and Vibrio mimicus could thus be differentiated by defining signatures of species-identifying biomarker ions (SIBIs). As a reference method for species designation and for determination of relationships between strains with molecular markers, partial rpoB gene sequencing was applied. CONCLUSIONS: The MALDI-TOF MS-based method as well as the rpoB sequence-based approach for Vibrio identification described in this study produced comparable classification results. The construction of phylogenetic trees from MALDI-TOF MS and rpoB sequences revealed a very good congruence of both methods. SIGNIFICANCE AND IMPACT OF THE STUDY: Our results suggest that whole-cell MALDI-TOF MS-based proteometric characterization represents a powerful tool for rapid and accurate classification and identification of Vibrio spp. and related species.

A pan-European ring trial to validate an International Standard for detection of Vibrio cholerae, Vibrio parahaemolyticus and Vibrio vulnificus in seafoods.

Globally, vibrios represent an important and well-established group of bacterial foodborne pathogens. The European Commission (EC) mandated the Comite de European Normalisation (CEN) to undertake work to provide validation data for 15 methods in microbiology to support EC legislation. As part of this mandated work programme, merging of ISO/TS 21872-1:2007, which specifies a horizontal method for the detection of V. parahaemolyticus and V. cholerae, and ISO/TS 21872-2:2007, a similar horizontal method for the detection of potentially pathogenic vibrios other than V. cholerae and V. parahaemolyticus was proposed. Both parts of ISO/TS 21872 utilized classical culture-based isolation techniques coupled with biochemical confirmation steps. The work also considered simplification of the biochemical confirmation steps. In addition, because of advances in molecular based methods for identification of human pathogenic Vibrio spp. classical and real-time PCR options were also included within the scope of the validation. These considerations formed the basis of a multi-laboratory validation study with the aim of improving the precision of this ISO technical specification and providing a single ISO standard method to enable detection of these important foodborne Vibrio spp.. To achieve this aim, an international validation study involving 13 laboratories from 9 countries in Europe was conducted in 2013. The results of this validation have enabled integration of the two existing technical specifications targeting the detection of the major foodborne Vibrio spp., simplification of the suite of recommended biochemical identification tests and the introduction of molecular procedures that provide both species level identification and discrimination of putatively pathogenic strains of V. parahaemolyticus by the determination of the presence of theromostable direct and direct related haemolysins. The method performance characteristics generated in this have been included in revised international standard, ISO 21872:2017, published in July 2017.

Cloning of a phosphinothricin N-acetyltransferase gene from Streptomyces viridochromogenes Tü494 and its expression in Streptomyces lividans and Escherichia coli.

Phosphinothricin-tripeptide (Ptt), also known as bialaphos, contains phosphinothricin (Pt), a potent inhibitor of glutamine synthetase. A 4.0-kb Bam HI fragment coding for Ptt resistance was cloned in Streptomyces lividans TK23. The fragment was isolated from a Ptt-resistant mutant of Streptomyces viridochromogenes Tü494. Subcloning experiments revealed that Ptt resistance can be assigned to a 0.8-kb Bg/II fragment. This fragment was shown to include the Ptt-resistance promoter. Subcloning this fragment downstream from the lacZ promoter conferred Ptt resistance to Escherichia coli JM83 in one of the two possible orientations. Biochemical investigations revealed that the Bg/II fragment codes for a Pt N-acetyltransferase.

Nucleotide sequence of the phosphinothricin N-acetyltransferase gene from Streptomyces viridochromogenes Tü494 and its expression in Nicotiana tabacum.

The phosphinothricin (Pt) N-acetyltransferase gene (pat) of Streptomyces viridochromogenes Tü494 is located on a 0.8-kb BglII fragment [Strauch et al., Gene 63 (1988) 65-74]. By sequencing a 1.3-kb BglII-SstII fragment, an open reading frame representing the pat gene was found. It encodes a polypeptide of 183 amino acids with an Mr of 20,621. The base composition of the pat gene is typical for Streptomyces [70.1 mol% (G + C) in total and 93.5 mol% (G + C) in the third position]. Translation of pat is initiated by a GTG codon which was identified by frameshift mutations in Escherichia coli as well as in Streptomyces lividans. Significant homology of the pat gene was found to the bialaphos-resistance gene (bar) of Streptomyces hygroscopicus [Thompson et al., EMBO J. 9 (1987) 2519-2523]. However, variations were detected in the 5'-noncoding region of the two resistance genes which may reflect differences in regulation. Since Pt is a potent herbicide, the pat gene was modified and introduced into Nicotiana tabacum by Agrobacterium-mediated leaf-disc transformation. The GTG start codon of pat was replaced by ATG. Subsequently the modified pat-coding region was fused to the 35S promoter of the cauliflower mosaic virus. Transgenic plants could directly be selected on Pt-containing medium.

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.

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.

Combined hyperthermia and immunotherapy treatment of multiple pulmonary metastases in mice.

The combination of immunotherapy and hyperthermia results in a greater reduction in tumour growth compared to either therapy used alone in a murine subcutaneous tumour model. To evaluate this combination further we tested it in a murine pulmonary metastasis model. Mice were given 5 x 10(5) MCA-105 sarcoma cells on day 0 intravenously resulting in the formation of pulmonary metastases. Mice were treated with local hyperthermia to the left hemithorax with a transcutaneous microwave applicator or with whole-body hyperthermia to 41 degrees C for 30 min on days 3 and 6. Immunotherapy included 5 x 10(7) syngeneic LAK cells administered on days 3 and 6 and interleukin-2 given intraperitoneally three times daily on days 3-7. Animals were killed on day 12 and pulmonary nodules enumerated. While the addition of whole-body hyperthermia to immunotherapy had no significant effect on tumour growth, the combination of local hyperthermia and immunotherapy significantly decreased the number of pulmonary nodules by 94% compared to controls in combined experiments. The mechanism of this beneficial effect may be related to increased trafficking of immune active cells to the tumour-bearing site, an increase in the sensitivity of tumour cells to lysis, or perhaps a local release of cytokines induced by hyperthermia. This study established the efficacy of combined immunotherapy and hyperthermia for the treatment of visceral metastases and provides impetus for the initiation of clinical trials.

Bronchial hyperresponsiveness to 4.5% hypertonic saline indicates a past history of asthma-like symptoms in children.

SUMMARY. To evaluate the importance of a past history of asthma-like symptoms over a period of 2 years and current bronchial hyperreactivity (BHR), 538 randomly selected schoolchildren, initially aged 7-8 years, were examined. At yearly intervals, three standardized questionnaires, including items from the ISAAC panel, were answered by parents. Following the last questionnaire, BHR to 4.5% hypertonic saline (HS) was recorded. In survey 1, lifetime prevalence of asthma was 4.9%. During the 12-month period, prevalence of wheeze and dyspnea ranged between 9.3 and 5.2% (Survey 1) and 5.9% and 4.4% (Survey 2). Among children with wheeze or dyspnea in Survey 3, BHR (defined as a fall of baseline FEV(1) > or = 15%) was significantly more frequent (50.0% and 60.7%, respectively) than among children without these symptoms (12.8%, P < 0.001, and 12.8%, P < 0.001, respectively). The negative predictive value of BHR to have neither wheeze nor dyspnea was about 88% and did not vary throughout the study (Survey 1, 87%; Survey 2, 88%; Survey 3, 88%). The relative risk of showing BHR was significantly increased in children with wheeze (survey 2, odds ratio (OR) 3.0 (95% confidence interval (CI) 1.0-8.7)) or dyspnea (Survey 1: OR 5.9 (95% CI 1.9-18.5), Survey 3: 5.2 (1.7-16.2), but not in children with dry cough or nocturnal cough (data not shown). Wheeze and dyspnea occurred repeatedly in the same individuals with BHR in a high percentage of children (83.3% and 76.5%, respectively). In conclusion, there is a strong association between recent and previous dyspnea and current BHR, and it indicates intraindividual persistence of symptom history.

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.

Characterization of plasmid regions of foodborne Yersinia enterocolitica biogroup 1A strains hybridizing to the Yersinia enterocolitica virulence plasmid.

The aim of our study was to find out if plasmids of foodborne Yersinia enterocolitica biogroup 1A strains harbour genes related to the virulence genes located on the virulence plasmid pYV of Yersinia enterocolitica. The foodborne strains were isolated from pork, as pigs are considered as an important reservoir for enteropathogenic Y. enterocolitica 0:3 and 0:9 strains. The plasmids of the foodborne strains were characterized by restriction enzyme analysis and hybridized to the virulence plasmid pYV of pathogenic Y. enterocolitica strains (0:3 biogroup 4; 0:9 biogroup 2). In several cases the plasmids of the foodborne strains showed homologies to parts of the pYV plasmid. Analysis of the hybridizing regions revealed that genes involved in replication, sequences of transposable elements and an endonuclease gene caused the observed hybridization to the virulence plasmid. In cause of the study also a remnant of a Tn3-like transposon was shown to be present adjacent to the yadA gene on the pYV plasmid. Although there is evidence that at least some strains of Y. enterocolitica biogroup 1A might possess pathogenic properties none of the well known plasmid encoded virulence genes were present on the plasmids of the investigated foodborne biogroup 1A strains.

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.

Characterization of a Shiga toxin-encoding temperate bacteriophage of Shigella sonnei.

A Shiga toxin (Stx)-encoding temperate bacteriophage of Shigella sonnei strain CB7888 was investigated for its morphology, DNA similarity, host range, and lysogenization in Shigella and Escherichia coli strains. Phage 7888 formed plaques on a broad spectrum of Shigella strains belonging to different species and serotypes, including Stx-producing Shigella dysenteriae type 1. With E. coli, only strains with rough lipopolysaccharide were sensitive to this phage. The phage integrated into the genome of nontoxigenic S. sonnei and laboratory E. coli K-12 strains, which became Stx positive upon lysogenization. Moreover, phage 7888 is capable of transducing chromosomal genes in E. coli K-12. The relationships of phage 7888 with the E. coli Stx1-producing phage H-19B and the E. coli Stx2-producing phage 933W were investigated by DNA cross-hybridization of phage genomes and by nucleotide sequencing of an 8,053-bp DNA region of the phage 7888 genome flanking the stx genes. By these methods, a high similarity was found between phages 7888 and 933W. Much less similarity was found between phages H-19B and 7888. As in the other Stx phages, a regulatory region involved in Q-dependent expression is found upstream of stxA and stxB (stx gene) in phage 7888. The morphology of phage 7888 was similar to that of phage 933W, which shows a hexagonal head and a short tail. Our findings demonstrate that stx genes are naturally transferable and are expressed in strains of S. sonnei, which points to the continuous evolution of human-pathogenic Shigella by horizontal gene transfer.

Development of a plasmid-cloning system for Streptomyces viridochromogenes Tü494.

A plasmid-cloning system was developed for Streptomyces viridochromogenes Tü494, a producer of the tripeptide antibiotic phosphinothricyl-alanyl-alanine (PTT). Parameters affecting protoplast formation and transformability of S. viridochromogenes were investigated in detail. A procedure giving rise to transformation efficiencies of 10(4)-10(5) transformants per microgram DNA was worked out. Several Streptomyces plasmid vectors such as pIJ350, pIJ61, pEB2, pGM4 and pSW2 were tested in S. viridochromogenes. Some of these vectors (pGM4, pEB2) showed a high copy number, whereas the copy number of others (pIJ350, pIJ61 and pSW2) was markedly lower. Under non-selective conditions some of the vectors (pIJ350, pEB2) were not stably maintained, in contrast to the vectors pGM4 and pSW2 which did not require any selection pressure for stable maintenance. Therefore, the plasmid vectors pGM4 and pSW2 derived from endogenous replicons of Streptomyces ghanaensis strains represent appropriate plasmid vehicles for cloning experiments in S. viridochromogenes.

Retropsoas hernia as a cause of chronic abdominal pain: CT diagnosis.

Congenital retropsoas small bowel herniation is reported as the cause of long-standing recurrent abdominal pain in a teenage girl. Knowledge of this entity is important for differential diagnosis of abdominal pain, mass, or retroperitoneal gas and fluid, and for avoiding complications of percutaneous renal interventions.

[The relationship of plasmids from environmental Yersinia isolates and the virulence plasmid of enteropathogenic Yersinia strains]. / Untersuchungen zur Verwandtschaft der Plasmide aus Yersinia-Umweltisolaten und dem Virulenzplasmid enteropathogener Yersinien.

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.