Radiation force on a bubble located near an interface

The presence of a boundary produces marked changes in the oscillation amplitudes and types of bubble distortion modes excited by an external acoustic field. In the majority of cases, the radiation force can be determined based on the linearized equations of motion. Bispherical coordinates are used to obtain an analytical description of linearized bubble dynamics at distances from the interface comparable to those of the bubble size. In the limit of weak dissipation, explicit formulas have been derived that describe the dependence of the radiation force on the separation distance between the bubble and the interface, the material parameters of the contacting media, and the angle of incidence of the incoming wave. The component of the radiation force directed to the interface has been shown to exhibit qualitative changes when the direction of the incoming field passes through the angle of the total internal reflection.

Genotoxic effect of 2,2'-bis(bicyclo[2.2.1] heptane) on bacterial cells

The toxic effect of strained hydrocarbon 2,2'-bis (bicyclo[2.2.1]heptane) (BBH) was studied using whole-cell bacterial lux-biosensors based on Escherichia coli cells in which luciferase genes are transcriptionally fused with stress-inducible promoters. It was shown that BBH has the genotoxic effect causing bacterial SOS response however no alkylating effect has been revealed. In addition to DNA damage, there is an oxidative effect causing the response of OxyR/S and SoxR/S regulons. The most sensitive to BBH lux-biosensor was E. coli pSoxS-lux which reacts to the appearance of superoxide anion radicals in the cell. It is assumed that the oxidation of BBH leads to the generation of reactive oxygen species, which provide the main contribution to the genotoxicity of this substance.

A Beam from Protvino to the Mediterranean Sea

The report overviews preliminary results on the feasibility to produce a neutrino beam based on the U-70 proton synchrotron at Protvino for a very long baseline experiment with the deep water ORCA detector in the Mediterranean Sea.

Besnoitia tarandi in Canadian woodland caribou - Isolation, characterization and suitability for serological tests

In the present study, we report the first in vitro isolation of Besnoitia tarandi from North America and the second of B. tarandi at all. The parasite was isolated directly from the skin of a Canadian woodland caribou from the migratory ecotype. The animal belonged to the Leaf River Herd, in Northern Quebec, Canada. The isolate was designated Bt-CA-Quebec1.

Sequencing of the 3’-end of the 18S rRNA gene, the complete sequence of the ITS1 and the 5’-end of the 5.8S rRNA gene of Bt-CA-Quebec1 revealed only minor differences to rDNA gene fragments of B. besnoiti. In contrast, the patterns for the microsatellite loci Bt-20 and Bt-21 varied substantially from those reported for B. besnoiti and B. bennetti. Surprisingly, the typing results in the loci Bt-6 and Bt-7 differed between Bt-CA-Quebec1 and results obtained for skin samples from caribou of the Canadian regions of Nunavut and the Northwest Territories reported by other investigators. This indicates that differences might exist among B. tarandi in caribou from different regions in Canada.

Mice (γ-interferon knockout) intraperitoneally inoculated with 1.2 × 10⁶ or 1.5 × 10⁶ bradyzoites mechanically released from skin tissue cysts fell ill 8, 9 or 18 days post inoculation. GKO mice inoculated with 3.0 × 10⁴ tachyzoites isolated from the peritoneal cavity of a bradyzoites-inoculated mouse became ill earlier, i.e. 5 days post inoculation. Lung was the predilection site in all mice.

Bt-CA-Quebec1 tachyzoites rapidly grew in MARC-145 cells and were used for antigen production. Comparative Western blot analyses revealed only a few differences between B. tarandi Bt-CA-Quebec1 and B. besnoiti Evora antigen when probed with sera collected from chronically infected caribou.

Due to its fast growth in vitro, the Bt-CA-Quebec1 isolate may represent an interesting antigen source to establish B. tarandi-specific serological tools and to study the biology of this parasite species further.

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Besnoitia tarandi was in vitro-isolated directly from the skin of a Canadian woodland caribou.

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Microsatellite typing revealed differences to existing Bt-6, Bt-7 and Bt-21 patterns of B. tarandi.

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The isolate Bt-CA-Quebec1 caused disease in γ-interferon knockout mice.

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Bt-CA-Quebec1 rapidly grows in MARC-145 cells.

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Antigens of Bt-CA-Quebec1 are similar but not identical to those of Besnoitia besnoiti.

Naturally acquired bovine besnoitiosis: Differential distribution of parasites in the skin of chronically infected cattle

Bovine besnoitiosis is caused by Besnoitia besnoiti, an apicomplexan parasite closely related to Toxoplasma gondii and Neospora caninum. In the acute stage of besnoitiosis, cattle suffer from pyrexia, swollen lymph nodes, anorexia and subcutaneous edema. In the chronic stage, tissue cysts are formed in a variety of tissues including the skin. Knowledge about the distribution of tissue cysts of different parts of the skin of infected animals is scarce. Four chronically infected cattle were euthanized and skin samples were taken from a total of 77 standardized cutaneous locations per animal. Portions of the dermis were taken, from which DNA was extracted and examined by real-time PCR. Cycle of transition (Ct) values reflecting the amount of parasite DNA in the samples were determined. For statistical analysis, samples were attributed to 11 larger skin regions ('OuterHindlegDistal', 'Rump, ForelegMiddle', 'NoseFrontEars', 'CheekEye', 'SideLowerPart', 'ForelegDistal', 'SideUpperPart', 'LegsInner', 'VentralHeadNeck', 'DorsalNeckWithersBackTail'). While all samples revealed a positive result in three female cattle, only 63.6% (49/77) of the samples of a bull showed positive results. For statistical analysis, a Ct value of 45 was assumed for samples with a negative result. The dams showed median Ct values of 16.1, 17.5 and 19.4, while in skin samples of the bull a median Ct value of 37.6 was observed. To determine the differences in DNA concentrations between different locations of the skin of the animals, a relative Ct (relCt) was determined by subtracting for each animal indv the MedianCtindv from each sample Ct. Analyses of the relCt values showed that the highest relative parasite DNA concentrations were observed in the categories 'OuterHindlegDistal', 'Rump', 'ForelegMiddle' and 'NoseFrontEars'. The relCt values in these categories differed statistically significantly from those determined for the categories 'VentralHeadNeck' and 'DorsalNeckWithersBackTail'. The analysis showed clear differences in the distribution and the detectability of parasite DNA in the skin of cattle infected with B. besnoiti. In all four animals, samples from the 'Rump' region (Regio fermoris) showed high parasite DNA concentrations. Because this region is also easily accessible for veterinarians, this skin location appears to be optimal for taking skin biopsies for detection or isolation of B. besnoiti.

Serotyping of Toxoplasma gondii in cats (Felis domesticus) reveals predominance of type II infections in Germany

Background

Cats are definitive hosts of Toxoplasma gondii and play an essential role in the epidemiology of this parasite. The study aims at clarifying whether cats are able to develop specific antibodies against different clonal types of T. gondii and to determine by serotyping the T. gondii clonal types prevailing in cats as intermediate hosts in Germany.

Methodology

To establish a peptide-microarray serotyping test, we identified 24 suitable peptides using serological T. gondii positive (n=21) and negative cat sera (n=52). To determine the clonal type-specific antibody response of cats in Germany, 86 field sera from T. gondii seropositive naturally infected cats were tested. In addition, we analyzed the antibody response in cats experimentally infected with non-canonical T. gondii types (n=7).

Findings

Positive cat reference sera reacted predominantly with peptides harbouring amino acid sequences specific for the clonal T. gondii type the cats were infected with. When the array was applied to field sera from Germany, 98.8% (85/86) of naturally-infected cats recognized similar peptide patterns as T. gondii type II reference sera and showed the strongest reaction intensities with clonal type II-specific peptides. In addition, naturally infected cats recognized type II-specific peptides significantly more frequently than peptides of other type-specificities. Cats infected with non-canonical types showed the strongest reactivity with peptides presenting amino-acid sequences specific for both, type I and type III.

Conclusions

Cats are able to mount a clonal type-specific antibody response against T. gondii. Serotyping revealed for most seropositive field sera patterns resembling those observed after clonal type II-T. gondii infection. This finding is in accord with our previous results on the occurrence of T. gondii clonal types in oocysts shed by cats in Germany.

Development of a multiplex real time PCR to differentiate Sarcocystis spp. affecting cattle

Cattle are intermediate hosts of Sarcocystis cruzi, Sarcocystis hirsuta and Sarcocystis hominis which use canids, felids or primates as definitive hosts (DH), respectively, and in addition of Sarcocystis sinensis from which the DH is unknown. The aims of the present study were to develop and optimize a multiplex real time PCR for a sensitive and specific differentiation of Sarcocystis spp. affecting cattle and to estimate the prevalence of Sarcocystis spp. in Argentinean cattle. The 18S rRNA genes from individual sarcocysts were amplified and cloned to serve as controls. For the amplification of bovine Sarcocystis spp. a total of 3 primers were used in combination with specific individual probes. Each assay was evaluated and optimized individually and subsequently combined in a multiplex assay (BovSarcoMultiplex real time PCR). The analytical specificity of the multiplex assay was assessed using 5 ng of DNA of heterologous Sarcocystis spp. and other apicomplexan parasites, and no positive reactions were observed other than for the species the PCR targeted. The analytical sensitivity ranged between 0.0125 and 0.125 fg of plasmid DNA (equivalent to the DNA of 2-20 plasmid DNA copies) or resembling DNA of 0.1-0.3 bradyzoites. A total of 380 DNA loin samples from Argentina were tested and 313, 29, 14 and 2 were positive for S. cruzi, S. sinensis, S. hirsuta and S. hominis, respectively. S. sinensis was the most prevalent species among thick walled Sarcocystis spp. in Argentinean cattle. Mixed infections were detected in 8.9% of all samples. Diagnostic sensitivity and specificity for the BovSarcoMultiplex real time PCR relative to previous microscopic examination for thin and thick-walled cyst were 91.5% and 41.7%, 36.3% and 95.9% respectively. Improved DNA extraction methods may allow to further increase the specific and sensitive detection of Sarcocystis spp. in meat samples.

Novel tools for the diagnosis and differentiation of acute and chronic bovine besnoitiosis

Diagnosis of acute bovine besnoitiosis is a major diagnostic problem. We developed diagnostic tests to serologically diagnose and differentiate acute and chronic cases of bovine besnoitiosis using affinity purified antigens of Besnoitia besnoiti tachyzoites in immunoblots and in both, a conventional ELISA and an avidity ELISA. Sera of acutely and chronically infected cattle were investigated using these tests. Acutely infected cattle initially recognised an antigen of 74 kDa relative molecular mass, followed by reactions with increasing intensity against 81 and 28 kDa antigens. In addition, faint reactions against antigens with 36, 37, 39 and 42 kDa molecular mass started soon after seroconversion and increased over time. An antigen of 45 kDa molecular mass was transiently recognised early after infection but not or only weakly in the chronic stage. At least two antigens, the 39 and the 42 kDa antigens, seem to be located on the surface of B. besnoiti tachyzoites as determined by biotinylation. Affinity purified antigen was used to establish an APure-BbELISA which showed excellent sensitivity (100%) relative to a serological reference system in naturally, most likely chronically, infected cattle. Specificity was also high (99.8%) as determined in cattle from herds with Neospora caninum-associated abortions. The antibody levels in APure-BbELISA were correlated with the parasite load in the skin or the mucous membrane of the vestibulum vaginae as determined by real-time PCR. In acute cases of bovine besnoitiosis (confirmed by the detection of low avidity IgG in the APure-BbELISA) first specific antibodies were detected by ELISA in all animals except one, at the same time or earlier than in the serological reference system. The detection of parasite DNA in skin by real-time PCR was clearly superior to serological analysis in detecting infected cattle during acute besnoitiosis.

Toxoplasma gondii sexual cross in a single naturally infected feline host: generation of highly mouse-virulent and avirulent clones, genotypically different from clonal types I, II and III

Tachyzoite clones obtained from a single Toxoplasma gondii oocyst field sample were genotyped and characterized regarding mouse virulence. PCR-RFLP genotyping of tachyzoites initially isolated from interferon-γ-knockout (GKO) mice, BALB/c mice and VERO cell culture using the nine independent, unlinked genetic markers nSAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico revealed mixed T. gondii infections showing combinations of type II and type III alleles at different loci. Forty-five individual clones were obtained from all mixed T. gondii tachyzoite cell cultures by limiting dilution. Sixteen T. gondii clones showed type III alleles at all loci and 29 clones displayed a combination of type II and type III alleles at different loci. Five clone groups were identified in total, four of which include T. gondii clones that showed a non-canonical allele pattern and have never been described in natural infections before. All tested clones, except two, were highly virulent in BALB/c mice. The isolation of different non-canonical T. gondii clones originating from an oocyst sample of a single naturally infected cat demonstrate that sexual recombination as well as re-assortment of chromosomes via a sexual cross of T. gondii occur under natural conditions and result in the emergence of clones with increased virulence in mice.

Analysis of clonal type-specific antibody reactions in Toxoplasma gondii seropositive humans from Germany by peptide-microarray

Background

Different clonal types of Toxoplasma gondii are thought to be associated with distinct clinical manifestations of infections. Serotyping is a novel technique which may allow to determine the clonal type of T. gondii humans are infected with and to extend typing studies to larger populations which include infected but non-diseased individuals.

Methodology

A peptide-microarray test for T. gondii serotyping was established with 54 previously published synthetic peptides, which mimic clonal type-specific epitopes. The test was applied to human sera (n = 174) collected from individuals with an acute T. gondii infection (n = 21), a latent T. gondii infection (n = 53) and from T. gondii-seropositive forest workers (n = 100).

Findings

The majority (n = 124; 71%) of all T. gondii seropositive human sera showed reactions against synthetic peptides with sequences specific for clonal type II (type II peptides). Type I and type III peptides were recognized by 42% (n = 73) or 16% (n = 28) of the human sera, respectively, while type II–III, type I–III or type I–II peptides were recognized by 49% (n = 85), 36% (n = 62) or 14% (n = 25) of the sera, respectively. Highest reaction intensities were observed with synthetic peptides mimicking type II-specific epitopes. A proportion of the sera (n = 22; 13%) showed no reaction with type-specific peptides. Individuals with acute toxoplasmosis reacted with a statistically significantly higher number of peptides as compared to individuals with latent T. gondii infection or seropositive forest workers.

Conclusions

Type II-specific reactions were overrepresented and higher in intensity in the study population, which was in accord with genotyping studies on T. gondii oocysts previously conducted in the same area. There were also individuals with type I- or type III-specific reactions. Well-characterized reference sera and further specific peptide markers are needed to establish and to perform future serotyping approaches with higher resolution.

Comparison of different commercial DNA extraction kits to detect Toxoplasma gondii oocysts in cat faeces

The cat is the definitive host of Toxoplasma gondii and plays an important role in the transmission of this and other coccidian parasites, e.g. Hammondia hammondi, a protozoon closely related and morphologically similar to T. gondii. A number of techniques to detect T. gondii nucleic acids in feline faeces are described and several extraction kits for isolating pathogen DNA from faeces or soil are commercially available. To compare the performance of such kits with regard to isolating oocyst DNA, a feline sample that had tested negative for coccidian parasites including T. gondii and H. hammondi was spiked with 10(4), 10(3), 10(2), 50 and 10 H. hammondi oocysts. Several ready-to-use stool or soil kits and an in-house method were then used to extract parasite DNA from these spiked faecal samples. Of six kits tested, two were found suitable for the detection of H. hammondi oocysts DNA by the polymerase chain reaction (PCR) in faecal samples with a detection limit of 250 oocysts per 1 g of faecal sample. These two kits revealed a similar, even slightly lower detection limit (50 oocysts per 1 g of sample) when tested with faecal samples spiked with T gondii oocysts.

Toxoplasma gondii infection in sentinel and free-range chickens from Argentina

This study aimed at isolating and genotyping Toxoplasma gondii from serologically positive free-range chickens from Argentina, and to evaluate the use of sentinel animals during a short time period of exposure to determine environmental contamination with T. gondii oocysts. Two groups of chickens on six farms were compared in this study: (i) young, 2-3 month-old broiler-type chickens reared as sentinel animals on the farms and (ii) adult chickens reared on the same farms for more than one year. Seroconversion rates of 7.0% or 5.7% were observed in sentinel broiler chickens reared for a period of 74 days (January-April 2010) or 88 days (August-November 2010) respectively, as shown by a T. gondii specific immunofluorescent antibody test. Fifty-three percent (17 of 32) of adult chickens were positive and showed higher titres than sentinel animals. Isolation of T. gondii from tissues (brain and heart) of serologically positive chickens was achieved from six of seven free-range adult birds with IFAT titres of 200 and higher. The isolated parasites were analysed by multi-locus polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The isolated T. gondii showed three different genotypes: two genotypes consisted in atypical allele combinations, and the remaining genotype had exclusively clonal type II alleles. All isolates obtained at a single farm, corresponded to the same genotype. The T. gondii genotypes observed are identical to those described in cats, dogs, chickens and capybaras elsewhere in South America. Two isolates, which showed different allele combinations in PCR-RFLP, were characterized in a mouse virulence assay. While one isolate showed a low virulence a second isolate was of intermediate virulence to mice.

Quantitative real time polymerase chain reaction assays for the sensitive detection of Besnoitia besnoiti infection in cattle

Bovine besnoitiosis, an economically important disease in cattle in some countries of Africa and Asia, is emerging in Europe. The definitive host of Besnoitia besnoiti, the causative agent of bovine besnoitiosis, is unknown and the transmission of the parasite is not completely understood. Sensitive and quantitative DNA detection methods are needed to determine whether serologically positive animals are infectious and to examine the role of vectors (e.g. haematophagous insects) in the transmission of the parasite. To this end, we established two different 5'-nuclease quantitative assays to detect B. besnoiti infection in cattle and to estimate the parasite load in samples (BbRT1 and BbRT2). These PCRs are based on the sequence of the internal transcribed spacer region 1 (ITS-1) of the ribosomal RNA gene. Tests with serial dilutions of B. besnoiti genomic DNA in a buffer containing 100 ng/μl bovine DNA revealed a detection limit of 0.01 pg genomic B. besnoiti DNA. Reliable quantification was possible in samples containing ≥1 pg B. besnoiti genomic DNA with a coefficient of variation of ≤ 2%. To estimate the diagnostic sensitivity of the tests, skin biopsies and scrapings from the mucous membrane of the vestibulum vaginae (vaginal scrapings) were taken from cattle with clinical signs of chronic besnoitiosis. Regardless of the real time PCR assay used, 90.7% (39/43) of these animals were positive in at least one of two samples (skin or vaginal scrapings). Antibody titers, as determined by an immunofluorescent antibody test, and the threshold cycle values of the real time PCR obtained for skin samples and vaginal scrapings, were significantly correlated. The specificity of the PCRs was confirmed using genomic DNA from related parasites, including genomic DNA of Besnoitia spp., Neospora caninum, Toxoplasma gondii, Hammondia hammondi, Hammondia heydorni, Isospora spp., Sarcocystis spp., Eimeria bovis, Cryptosporidium parvum, and Trypanosoma brucei brucei. Since the sequence of the ITS-1 region of B. besnoiti is identical with that of Besnoitia species isolated from donkeys (Besnoitia bennetti), and reindeer (Besnoitia tarandi), both real time PCRs detected also DNA of these parasites. One of the B. besnoiti real time PCRs, BbRT1, but not BbRT2, cross-reacted with Besnoitia darlingi, Besnoitia oryctofelisi, and Besnoitia neotomofelis when large amounts of genomic DNA (10 ng) were used. The other B. besnoiti real time PCR assay (BbRT2) was specific for B. besnoiti, B. bennetti and B. tarandi, but did not react when 10 ng DNA of other related parasite species from the genus Besnoitia or other genera were subjected to analysis.