Comparison of the culture method with multiplex PCR for the confirmation of Legionella spp. and Legionella pneumophila

AIMS

The detection and enumeration of Legionella spp. in water samples are typically performed via a cultural technique standardized in ISO 11731. This method is time-consuming (up to 15 days), and the specificity of the confirmation step is questionable. This study proposes the use of multiplex polymerase chain reaction (PCR) to confirm presumptive Legionella colonies directly from the culture plate; this shortens the response time by 2-5 days while still reporting results in colony forming units (CFU).

METHODS AND RESULTS

Two laboratories analysed a total of 290 colonies to compare the confirmation step of Legionella spp. and Legionella pneumophila in accordance with ISO 11731 by culture growth and agglutination vs multiplex PCR. Discordant results were resolved by the swiss national reference laboratory. The data were evaluated following ISO 16140 and showed that the PCR-technique had higher specificity.

CONCLUSIONS

The confirmation of Legionella spp., L. pneumophila and L. pneumophila serogroup 1 by multiplex PCR allows detection of positive colonies more rapidly and with higher specificity.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study highlights a possibility to shorten the response time significantly during the enumeration of Legionella spp. and achieving a higher specificity while adhering to the legally recognized reporting in CFU.

All-Food-Seq (AFS): a quantifiable screen for species in biological samples by deep DNA sequencing

BACKGROUND

DNA-based methods like PCR efficiently identify and quantify the taxon composition of complex biological materials, but are limited to detecting species targeted by the choice of the primer assay. We show here how untargeted deep sequencing of foodstuff total genomic DNA, followed by bioinformatic analysis of sequence reads, facilitates highly accurate identification of species from all kingdoms of life, at the same time enabling quantitative measurement of the main ingredients and detection of unanticipated food components.

RESULTS

Sequence data simulation and real-case Illumina sequencing of DNA from reference sausages composed of mammalian (pig, cow, horse, sheep) and avian (chicken, turkey) species are able to quantify material correctly at the 1% discrimination level via a read counting approach. An additional metagenomic step facilitates identification of traces from animal, plant and microbial DNA including unexpected species, which is prospectively important for the detection of allergens and pathogens.

CONCLUSIONS

Our data suggest that deep sequencing of total genomic DNA from samples of heterogeneous taxon composition promises to be a valuable screening tool for reference species identification and quantification in biosurveillance applications like food testing, potentially alleviating some of the problems in taxon representation and quantification associated with targeted PCR-based approaches.

Determination of microbial transglutaminase in meat and meat products

Transglutaminase is an enzyme that can be used to cross-link pieces of meat, fish or meat products. The resulting product gives the optical impression of an intact chunk of meat. The usage of transglutaminase as a food additive is permitted in some countries. However, its utilisation has to be declared to ensure transparency for consumers. This paper describes two orthogonal analytical methods suited for the detection of technological relevant transglutaminase concentrations (around 25 mg pure enzyme in 1 kg of product) in meat and meat products. The mass spectrometry-based approach relies on a previous digestion with Achromobacter lyticus protease and LC-MS/MS separation and detection. Sufficient selectivity was obtained by monitoring four different peptides. The orthogonal (complementary and independent), ELISA-based approach relies on two commercially available bacterial transglutaminase-specific antibodies, combined to a sandwich ELISA. The two methods were tested by analysing some 60 samples obtained from the market.

Immediate-early protein BICP22 of bovine herpesvirus 1 trans-represses viral promoters of different kinetic classes and is itself regulated by BICP0 at transcriptional and posttranscriptional levels

Bovine herpesvirus 1 (BHV-1) encodes four immediate-early (IE) proteins. The transactivators BICP0 and BICP4 are key regulatory elements in viral replication, and circ is a myristylated virion component, whereas BICP22--originating from a spliced 1.7-kb transcript synthesized with dual IE and late kinetics--has not yet been characterized as a protein. In this study, Western blot and immunofluorescence analysis using antisera against a C-terminal oligopeptide revealed major 50-kDa and minor 35-kDa species of BICP22, predominantly located in the nuclei of BHV-1 infected cells. In transient expression assays, BICP22 acted as transrepressor protein on viral promoters of different kinetic classes, e.g. the IE promoter of the BICP4/BICP0 gene, early promoter of the BICP0 gene, and late promoter of the gC gene. The BICP22 gene promoter itself was not repressed by BICP22; it could be dissected into a proximal region stimulated by BICP0 and a distal region stimulated by BHV-1 alpha-transinducing factor. Replacement of the BICP22 promoter by cytomegalovirus IE promoter revealed an additional posttranscriptional level of regulation whereby more BICP22 accumulated in cells when functional BICP0 was present. Interplay of BICP22 and BICP0 might involve the recently described nuclear domains (ND10) and ubiquitin-dependent pathway.

Construction and characterization of a stably transformed HeLa cell line in which the expression of bovine herpesvirus 1 ICP0 (BICP0) is induced by tetracycline

To explore the effects BICP0 (a principal transactivator of BHV-1 gene expression) on viral promoter elements, we established a cell line in which the expression of BICP0 is regulated by tetracycline. A hybrid promoter containing reiterated copies of the tet-operator (tet-O) and a minimal herpesviral alpha gene transinducing factor (alpha TIF) responsive element (minimal human cytomegalovirus immediate early promoter) was fused to the BICP0 gene and used to transform a HeLa cell line which expressed a fusion protein consisting of the repressor of the tet-O and the transactivating domain of alpha TIF. Simultaneously, the hygromycin resistance gene was transfected to select cells in media containing either hygromycin alone or both hygromycin and tetracycline. Immunofluorescent assays indicated that BICP0 was synthesised in the transformed cell lines solely upon induction of the gene by tetracycline removal. Only cells which had been kept constantly in medium containing tetracycline were able to synthesise BICP0 upon induction. Induced cell lines transactivated the native BICP0 promoter as well as the herpes simplex virus thymidine kinase promoter and the long terminal repeat sequences of human immunodeficiency virus in a dose dependent manner. These cell lines may help to further explore the functions of BICP0 as well as to investigate the molecular basis of interactions between herpes- and retroviruses.

Recombinant bovine herpesvirus-1 (BHV-1) lacking transactivator protein BICPO entails lack of glycoprotein C and severely reduced infectivity

The immediate-early transactivator protein BICPO is a key regulatory element of bovine herpesvirus 1 (BHV-1) replication based on transient expression assays. To examine BICPO function in the context of the viral genome, we created recombinant BHV-1 expressing beta-galactosidase instead of BICPO. To complement the defect, a neomycin resistant MDBK cell line (M164) expressing BICPO was established, permitting selection of a blue-staining BHV-1 recombinant (A2G2). Southern blot and PCR analysis confirmed that the BICPO gene was interrupted by the beta-galactosidase gene and that wt progeny was absent. Compared with wt BHV-1, A2G2 reached lower titers in M164 cells but replicated with similar kinetics. Once isolated, A2G2 also grew in MDBK cells although the titer was reduced a further 10-fold and the virus remained strongly cell-associated. Thus, BICPO is not absolutely required for replication in cell culture. Gene expression of A2G2 was investigated by Western blots and immunofluorescence. Surprisingly, not only was BICPO absent, but glycoprotein C (gC) was also missing. Other viral genes were expressed normally. Semiquantitative PCR showed that A2G2 produced similar amounts of viral DNA as wt but a much smaller number of infectious particles. Cotransfection of A2G2 DNA and a plasmid containing the BICPO gene yielded revertant virus with fully restored wt properties. We conclude that BICPO is required for gC expression, and that the missing gC partly accounts for the reduced A2G2 infectivity.

[The effectiveness of preventive use of antibiotics in Cesarean section with a single dose: comparison of cefotaxime with amoxicillin plus clavulanic acid]

The effectiveness of a single prophylactic dose of two broad spectrum antibiotics, during Caesarean section, was compared and evaluated. In 119 consecutive cases at the Cantonal Hospital in Winterthur, Switzerland, either 1 g i.v. cefotaxime or 1,2 g amoxicillin plus clavulanic acid were administered after clamping the umbilical cord during Caesarean section. The study shows that single dose prophylaxis of either regimen provides adequate cover in preventing morbidity in Caesarean section, in both high-risk and low-risk groups.

[Approaches in computer-assisted surgical planning in hip dislocation]

From a sequence of planar CT pictures of the hip joint the diagnostically relevant contours are extracted on a graphic monitor by means of an image-analysis process. To do this an image preprocessing is necessary to improve the quality of the CT pictures. These contour data permit a mathematical surface model of the hip joint to be derived using well-known methods of simulating an osteotomy. Three-dimensional reconstruction of the cartilage surface by MRI will be possible in the future. It will then be possible to plan computer-aided osteotomies with high accuracy.

[External version of breech presentation--a possibility for lowering the rate of cesarean section and infant morbidity]

Between 1979 and 1985 a total of 8641 children were born at the gynecological clinic in Winterthur, 388 of them (4.5%) from breech presentation. All of these were evaluated with regard to external version, and conditions for an attempt at version were satisfied in 97 cases. The principal prerequisite was a gestational age of at least 37 weeks. External version was accomplished in 39 of the 97 cases (40.2%). Complications encountered were drops in fetal heart tone or bradycardias in 26 cases (26.8%); the attempt at version was abandoned for this reason in 22 cases. In one case premature detachment of the normally implanted placenta occurred 6 days after successful external version, and in one case an emergency cesarean section had to be performed owing to persistent bradycardia. In a further case intrauterine fetal death was established 18 hours after successful version on the basis of an absence of fetal movement, though no cause of death could be found. Among the 39 cases in which version was successful a cesarean section was only necessary in one (2.5%), as opposed to 21 in the 58 cases (36.2%) in which the attempt at version failed. Neonatal fetal condition (Apgar score and umbilical blood gas analysis) revealed that neonates born from vertex presentation are subject to very considerably less stress. The international literature is discussed and compared. It is found that there has been a change of trend from a tendency to reject external version in the 1970s to a majority favoring it in the 1980s.(ABSTRACT TRUNCATED AT 250 WORDS)

[CT image analysis for surface reconstruction of the hip joint]

From a sequence of planar CT-pictures of the hip joint the diagnostically relevant contours are extracted on a graphic monitor by means of an image analysis process. To enable this an image-preprocessing has been needed to improve quality of the CT-pictures. From theses contour data, a mathematical surface model of the hip joint will be derived with well-known methods to simulate osteotomy.

[Lowering the cesarean section rate by exclusion of cardiotocographically suspected acidosis using fetal blood gas analysis]

In 871 deliveries out of a total of 3980 effected during 1980-1982 at the Winterthur Gynaecological Hospital, we found it necessary to perform one or several microanalyses of blood (blood gas analyses) sub partu. Among these, we found retrospectively that in 22 cases the microanalysis of the blood gas had prevented us from performing caesarean section which would have seemed necessary if we had relied on the cardiotocographical findings alone. Micro-analysis of blood gas made it possible to exclude the presence of pre-acidosis or acidosis which would have made Caesarean section imperative; in all these cases, normal delivery via the vagina was achieved, and in no case did this result in severe acidosis. All newborn had a 5-minute Apgar score of 7 and higher. We can conclude from these results, therefore, that the indication for an immediate termination of delivery via Caesarean section should not depend solely on a pathological cardiotocogram; the final decision should be arrived at only after micro-analyses of blood gas have confirmed the presence of foetal pre-acidosis or acidosis.