Evaluation of ELISA in raw milk for detection of antibodies to Mycobacterium avium subsp. paratuberculosis in dairy herd.

Paratuberculosis (PTBC) is a chronic intestinal disease of animals caused by Mycobacterium avium paratuberculosis (MAP). MAP infection is diagnosed through indirect tests based on the immune response. The aims of this study were to compare the performance of two milk ELISA for the diagnosis of PTBC and to assess the bulk tank milk (BTM) MAP exposure in dairy cattle in Argentina. A total of 357 fecal, serum, and milk samples were collected. The fecal samples were processed by culture for MAP isolation, while both, serum and milk samples were used for the detection of antibodies by two different ELISA tests, "in-house" and commercial kit. MAP was isolated in 3.9% of fecal samples. For milk ELISA, poor concordances were obtained. Optimized cut-off points were calculated. The highest sensitivity and specificity values (64% and 80% respectively) were obtained with the combination of MAP isolation and commercial milk ELISA. The results indicate that the combination of different techniques to identify of dairy cattle infected with MAP increases the efficiency of diagnosis. In addition, BTM  samples (n=98) were evaluated to determine herd status using the commercial kit during two seasons, identifying 33.3% of positive samples in autumn and 35.4% in spring.

Bovine campylobacteriosis in heifer: pathogenesis study and insights in the conventional and molecular diagnosis in an experimental bovine model and field cases.

Campylobacter fetus spp. is a bacterium associated to reproductive losses in cattle worldwide. It is a venereal infectious disease known as bovine campilobacteriosis, with high impact mainly in countries with extensive production systems. Here, we show pathogenesis and diagnostic methods for Campylobacter fetus detection in cervico-vaginal mucus (CVM) samples from heifers experimentally infected and field cases from herds with low reproductive performance by campylobacteriosis infection. Bacterial culture, direct immunofluorescence test and qPCR were used as diagnostic methods to evaluate detection of C. fetus. In the experimental model 30 Aberdeen Angus and crossbred heifers and 4 Aberdeen Angus bulls for natural mating were assigned to 3 groups experimentally challenged with C. fetus subsp. fetus (Cff), C. fetus subsps venerealis (Cfv) and C. fetus subsp venerealis biovar intermedius (Cfvi), respectively, and a negative control group, all followed for 9 months. Also, field samples of CVM and aborted fetuses were recollected from seven beef cattle farms. Bacteriological culture had the higher C. fetus detection rate in CVM being the most appropriate, followed by qPCR (with commercial extraction DNA kit), direct immunofluorescence test and qPCR (with in-house extraction DNA method), in both, experimental model and field cases. From experimental model after natural mating, 62.5% and 25% heifers got pregnant from Cff and Cfvi groups, respectively, while from Cfv no pregnancy was detected. The strain more frequently detected was Cfvi, followed by Cff and Cfv. Colonization of Cff in female genital tract with high number of carriers and presence in aborted fetuses was evidenced, suggesting a high risk to bovine reproductive health. Bacteriemia was not detected after genital infection. Given the low detection rate of either test, we suggest the use of both, PCR based methods and bacterial culture could result in higher detection rate in farms with endemic campylobacteriosis.

Bovine campylobacteriosis in bulls: insights in the conventional and molecular diagnosis.

Campylobacter fetus is a gram-negative motile bacterium, with two subspecies relevant to cattle health: C. fetus subsp. venerealis (Cfv) and C. fetus subsp. fetus (Cff). Both subspecies are associated with reproductive losses in cattle. In this study, we evaluated the identification of C. fetus for the diagnosis of bovine campylobacteriosis through bacteriological culture, direct immunofluorescence (DIF) and molecular tests in preputial smegma (PS) samples of three Angus bulls challenged with Cfv, Cfv biovar intermedius (Cfvi) or Cff, respectively, in an experiment imitating the natural infection. Two DNA extraction protocols were tested (in-house thermal extraction and commercial kit). Aspiration and scraping collection for PS were compared by conventional tests. Additionally, bacteremia was also evaluated in blood samples. Bulls were challenged by natural mating with heifers that had been experimentally infected with C. fetus subspecies; which led to infection. The Cfv- and Cfvi-bulls were positive for at least 9 months. Although Cff is not considered a venereal strain, in this study it was transmissible to bull from heifers experimentally infected, as evidenced by its colonization and persistence in the preputial cavity for 5 to 6 months. This finding suggests a potential risk of dissemination within herds. The results obtained by bacteriological culture or direct immunofluorescence (DIF) showed no significant differences, regardless the sampling device used (aspiration with Cassou pipette, metal and plastic scraper). C. fetus qPCR, on the other hand, yielded better results with an in-house DNA extraction method than with a commercial kit (75% vs 66.6%). Furthermore, qPCR diagnosis was more efficient than culture (66.6%) or DIF (56%). Bacteremia in whole blood samples was negative by qPCR and bacteriological culture in all samples. Altogether, this study demonstrated the transmission of Cff from heifers to bull and also showed that PCR-based methods are promising for the diagnosis of Bovine Genital Campylobacteriosis from clinical samples of PS.

Phylogenetic and Multiple-Locus Variable number tandem repeat analysis of Mycobacterium avium subsp. paratuberculosis isolates from Argentina.

Paratuberculosis is a worldwide chronic enteric disease of ruminants, caused by Mycobacterium avium subsp. paratuberculosis (MAP). While MAP has been widely investigated all around the world, little is known about the different strains that circulate in each country. This study describes the genetic diversity of MAP isolates from different bovine and deer herds from Argentina, analyzed by Multiple-Locus Variable number tandem repeat Analysis (MLVA), as well as the phylogenetic relatedness between geographically distant isolates through Whole Genome Sequencing (WGS) and core-genome analysis. A total of 90 MAP isolates were analyzed. The results showed seven different MLVA genotypes, with almost 75% of them belonging to pattern INMV 1, described in all the herds studied. WGS results suggested the presence of a common INMV 1 strain circulating throughout the country. Our results allow confirming the coexistence of different strains in time and space and the mixed infections identified in some animals. These observations suggest the absence of animal monitoring prior to introduction to the herds and the need for a control program in the country. This study represents the first to report WGS of MAP strains in Argentina.

Spatial-temporal trends and economic losses associated with bovine abortifacients in central Argentina.

The aims of this work are, firstly, to provide the geolocalization of cases of bovine abortion with definitive diagnosis and, secondly, to estimate the economic losses due to the most frequent abortifacients diagnosed agents in cattle in Buenos Aires province, Argentina. The total beef and dairy cattle population at risk of abortion is 8,358,186 and 538,076, respectively. In beef cattle, the overall risk of abortion was estimated at 4.5% for all pregnancies, where 27.9% are due to Campylobacter fetus, Neospora caninum, Leptospira spp., Brucella abortus, and bovine viral diarrhea virus with economic losses of US$ 440 per abortion, being the annual loss to the beef industry of US$ 50,144,101. In dairy cattle, there was an 8.0% risk of suffering abortion, 26.1% produced by the same abortigenic agents. The economic losses were estimated at US$ 1,415 per abortion, which equals a total loss of US$ 17,298,498 for the dairy industry in the region. The results of this study show that infectious causes are highly prevalent in Buenos Aires province, and they caused severe economic impacts in the dairy and beef industries. Furthermore, changes in temporal trends of infectious abortion occurrence were detected, probably related to the inclusion of molecular diagnostic techniques with more sensitivity or different epidemiological or husbandry conditions in the region analyzed.

Campylobacter fetus releases S-layered and immunoreactive outer membrane vesicles

Abstract The study of outer membrane vesicles (OMVs) became relevant because of theirprobable important role in the transfer of virulence factors to host cells. Campylobacter fetusis mainly a mammal pathogen whose virulence characterization is still limited. The aim of thisstudy was to evaluate and to characterize the secretion of OMVs in this bacterium. By trans-mission electron microscopy, we confirmed the production of OMVs in all the strains assayed.Purified OMVs showed a spherical shape and variable size, although comparable to those ofother gram-negative bacteria. We also confirmed the presence of the S-layer on the surface ofthe OMVs of all the strains assayed with the exception of those derived from the NTCC referencestrain. In addition, we demonstrated their immunoreactivity by the dot-blot assay. Hence, C.fetus OMVs could contribute to the modulation of the host response and constitute a candidateto be evaluated as an adjuvant of current vaccines used in the veterinary field. This work rep-resents a platform to drive future studies towards the role of these subcellular structures in C.fetus-host interaction.

Resumen El estudio de las vesículas de membrana externa (VME) tomó un rol protagónico, yaque se las ha relacionado con la transferencia de factores de virulencia a la célula hospedadora.Campylobacter fetus es, principalmente, un patógeno de mamíferos cuya virulencia solo hasido caracterizada de forma limitada. El objetivo de este trabajo fue evaluar y caracterizar la secreción de VME en esta bacteria. Mediante microscopía electrónica de transmisión confir-mamos la producción espontánea de VME en todas las cepas estudiadas. Las VME purificadasmostraron una morfología esférica y un tama˜no variable, pero compatible con el reporte deotras bacterias gram negativas. Asimismo, hemos demostrado que estas vesículas conservanla capa S en todas las cepas, menos en la cepa de referencia NCTC y hemos confirmado suinmunorreactividad por dot-blot inmunoblot. Estas VME de C. fetus podrían contribuir a la mod-ulación de la respuesta del hospedador y constituir un buen candidato como adyuvante de lasactuales vacunas empleadas en el campo veterinario. Este trabajo representa una plataformapara impulsar estudios futuros en torno al rol de estas estructuras subcelulares en la interfaseC. fetus-hospedador.

Campylobacter fetus releases S-layered and immunoreactive outer membrane vesicles.

The study of outer membrane vesicles (OMVs) became relevant because of their probable important role in the transfer of virulence factors to host cells. Campylobacter fetus is mainly a mammal pathogen whose virulence characterization is still limited. The aim of this study was to evaluate and to characterize the secretion of OMVs in this bacterium. By transmission electron microscopy, we confirmed the production of OMVs in all the strains assayed. Purified OMVs showed a spherical shape and variable size, although comparable to those of other gram-negative bacteria. We also confirmed the presence of the S-layer on the surface of the OMVs of all the strains assayed with the exception of those derived from the NTCC reference strain. In addition, we demonstrated their immunoreactivity by the dot-blot assay. Hence, C. fetus OMVs could contribute to the modulation of the host response and constitute a candidate to be evaluated as an adjuvant of current vaccines used in the veterinary field. This work represents a platform to drive future studies towards the role of these subcellular structures in C. fetus-host interaction.

Isolation of Campylobacter fetus subsp. venerealis from seminal vesicle of a naturally challenged bull.

Campylobacter fetus is a well-recognized pathogen that affects reproductive rate in cattle. In the present study, two Angus bulls were kept (39 days) separately with a group of heifers experimentally infected with Campylobacter fetus subsp. venerealis (Cfv) and Campylobacter fetus subsp. venerealis biovar intermedius (Cfvi), respectively. Each bull resulted infected post-mating by its respective strain (Cfv and Cfvi). Semen samples collected from each bull at days 39, 82, 132 and 269 resulted positive for C. fetus by bacteriological culture and/or direct immunofluorescence (DIF) test, and confirmed by polymerase chain reaction (PCR) from colonies isolated. Diagnosis resulted better with bacteriological culture (100%) compared to DIF (37,5%). Campylobacter fetus was isolated from seminal vesicle and preputial mucosa by bacteriological culture and confirmed by PCR and DIF test from colonies previously isolated from these tissues (day 276). Microscopic lesions detected in both bulls showed moderate diffuse subepithelial lymphoplasmacytic postitis. None of the seminal vesicle presented relevant microscopic lesions. To our knowledge this is the first report of isolation of C. fetus from seminal vesicles in a bull. The experimental model herein described, mimicks the natural infection and constitutes a promising alternative for future studies of campylobacteriosis in cattle.

Phylogenomic analysis for Campylobacter fetus ocurring in Argentina.

BACKGROUND AND AIM: Campylobacter fetus is one of the most important pathogens that severely affects livestock industry worldwide. C. fetus mediated bovine genital campylobacteriosis infection in cattle has been associated with significant economic losses in livestock production in the Pampas region, the most productive area of Argentina. The present study aimed to establish the genomic relationships between C. fetus strains, isolated from the Pampas region, at local and global levels. The study also explored the utility of multi-locus sequence typing (MLST) as a typing technique for C. fetus. MATERIALS AND METHODS: For pangenome and phylogenetic analysis, whole genome sequences for 34 C. fetus strains, isolated from cattle in Argentina were downloaded from GenBank. A local maximum likelihood (ML) tree was constructed and linked to a Microreact project. In silico analysis based on MLST was used to obtain information regarding sequence type (ST) for each strain. For global phylogenetic analysis, a core genome ML-tree was constructed using genomic dataset for 265 C. fetus strains, isolated from various sources obtained from 20 countries. RESULTS: The local core genome phylogenetic tree analysis described the presence of two major clusters (A and B) and one minor cluster (C). The occurrence of 82% of the strains in these three clusters suggested a clonal population structure for C. fetus. The MLST analysis for the local strains revealed that 31 strains were ST4 type and one strain was ST5 type. In addition, a new variant was identified that was assigned a novel ST, ST70. In the present case, ST4 was homogenously distributed across all the regions and clusters. The global analysis showed that most of the local strains clustered in the phylogenetic groups that comprised exclusively of the strains isolated from Argentina. Interestingly, three strains showed a close genetic relationship with bovine strains obtained from Uruguay and Brazil. The ST5 strain grouped in a distant cluster, with strains obtained from different sources from various geographic locations worldwide. Two local strains clustered in a phylogenetic group comprising intercontinental Campylobacter fetus venerealis strains. CONCLUSION: The results of the study suggested active movement of animals, probably due to economic trade between different regions of the country as well as with neighboring countries. MLST results were partially concordant with phylogenetic analysis. Thus, this method did not qualify as a reliable subtyping method to assess C. fetus diversity in Argentina. The present study provided a basic platform to conduct future research on C. fetus, both at local and international levels.

Accurate and fast identification of Campylobacter fetus in bulls by real-time PCR targeting a 16S rRNA gene sequence.

Campylobacter fetus is an important animal pathogen that causes infectious infertility, embryonic mortality and abortions in cattle and sheep flocks. There are two recognized subspecies related with reproductive disorders in livestock: Campylobacter fetus subsp. fetus (Cff) and Campylobacter fetus subsp. venerealis (Cfv). Rapid and reliable detection of this pathogenic species in bulls is of upmost importance for disease control in dairy and beef herds as they are asymptomatic carriers. The aim of the present work was to assess the performance a real-time PCR (qPCR) method for the diagnosis of Campylobacter fetus in samples from bulls, comparing it with culture and isolation methods. 520 preputial samples were both cultured in Skirrow's medium and analyzed by qPCR. The estimated sensitivity of qPCR was 90.9% (95% CI, 69.4%-100%), and the specificity was 99.4% (95% CI, 98.6% - 100%). The proportion of C. fetus positive individuals was 2.1% by isolation and 2.5% by qPCR. Isolates were identified by biochemical tests as Cfv (n = 9) and Cff (n = 2). Our findings support the use of qPCR for fast and accurate detection of C. fetus directly from field samples of preputial smegma of bulls. The qPCR method showed to be suitable for massive screenings because it can be performed in pooled samples without losing accuracy and sensitivity.

Evidence of in utero infection by Mycobacterium avium subsp. paratuberculosis using Multiple-Locus Variable-number tandem-repeat Analysis: first report in Argentina / Evidência de infecção intra-uterina por Mycobacterium avium subsp. paratuberculosis usando Multiple-Locus Variable-number tandem-repeat Analysis: primeiro relato na Argentina

A pregnant heifer with an advanced clinical stage of paratuberculosis was reported in a herd in Argentina. Thus, the animal was euthanized and samples of organs of the cow and its fetus was taken and cultured for bacteriology in specific medium. Tissues were analyzed by histopathology (hematoxylin-eosin and Ziehl-Neelsen staining). Histopathological analysis of the cow's samples revealed the presence of lesions consistent with paratuberculosis, and Ziehl-Neelsen staining revealed the presence of acid-fast bacilli, whereas the fetal tissues showed absence of lesions but the presence of acid-fast bacilli by Ziehl-Neelsen staining. After growing in specific medium, colonies in tissues from both cow and fetus were positive for IS900-PCR, confirming the presence of Mycobacterium avium subsp. paratuberculosis (MAP). Finally, the isolates were typed by Multiple-Locus Variable-number tandem-repeat Analysis (MLVA), which confirmed the epidemiological link between them. This study is the first in Argentina to report the detection of MAP that shares an identical MLVA type in a pregnant cow and its fetus. The results of this study are consistent with previous reports and highlight the intra-uterine transmission of MAP as an important source of infection within herds.(AU)

Uma novilha prenha em estado clínico avançado de paratuberculose foi observada em um rebanho bovino na Argentina. O animal foi eutanasiado e foram colhidas amostras dos seus órgãos e dos órgãos feto as quais foram cultivadas para bacteriologia em meio específico. Os tecidos foram examinados por histopatologia (coloração de hematoxilina-eosina e Ziehl-Neelsen). Na histopatologia das amostras colhidas da novilha foram observadas lesões compatíveis com paratuberculose e a coloração de Ziehl-Neelsen revelou a presença de bacilos álcool-ácido resistentes, nos tecidos fetais não foram observadas lesões, porém a coloração de Ziehl-Neelsen revelou a presença de bacilos álcool-ácido resistentes. Após o crescimento em meio específico, as colônias foram positivas para o teste IS900-PCR nos tecidos de ambos, vaca e feto, confirmando a presença de Mycobacterium avium subsp. paratuberculosis. Por fim, os isolados foram tipados por Multiple-Locus Variable-number tandem-repeat Analysis, confirmando a relação epidemiológica entre eles. Este estudo relata a primeira detecção de Mycobacterium avium subsp. paratuberculosis na Argentina em que houve o compartilhamento de um tipo idêntico de MLVA em uma vaca prenhe e no seu feto. Os resultados deste estudo são consistentes com relatos anteriores e destacam a transmissão intra-uterina de Mycobacterium avium subsp. paratuberculosis como importante fonte de infecção nos rebanhos de bovinos.(AU)

L-cysteine transporter-PCR to detect hydrogen sulfide-producing Campylobacter fetus.

Phenotypic differences between Campylobacter fetus fetus and C. fetus venerealis subspecies allow the differential diagnosis of bovine genital campylobacteriosis. The hydrogen sulfide production, for example, is a trait exclusive to C. fetus fetus and C. fetus venerealis biovar intermedius. This gas that can be biochemically tested can be produced from L-cysteine (L-Cys). Herein, we report a novel multiplex-PCR to differentiate C. fetus based on the evaluation of a deletion of an ATP-binding cassette-type L-Cys transporter that could be involved in hydrogen sulfide production, as previously described. A wet lab approach combined with an in silico whole genome data analysis showed complete agreement between this L-Cys transporter-PCR and the hydrogen sulfide production biochemical test. This multiplex-PCR may complement the tests currently employed for the differential diagnosis of C. fetus.

Distinct Campylobacter fetus lineages adapted as livestock pathogens and human pathobionts in the intestinal microbiota.

Campylobacter fetus is a venereal pathogen of cattle and sheep, and an opportunistic human pathogen. It is often assumed that C. fetus infection occurs in humans as a zoonosis through food chain transmission. Here we show that mammalian C. fetus consists of distinct evolutionary lineages, primarily associated with either human or bovine hosts. We use whole-genome phylogenetics on 182 strains from 17 countries to provide evidence that C. fetus may have originated in humans around 10,500 years ago and may have "jumped" into cattle during the livestock domestication period. We detect C. fetus genomes in 8% of healthy human fecal metagenomes, where the human-associated lineages are the dominant type (78%). Thus, our work suggests that C. fetus is an unappreciated human intestinal pathobiont likely spread by human to human transmission. This genome-based evolutionary framework will facilitate C. fetus epidemiology research and the development of improved molecular diagnostics and prevention schemes for this neglected pathogen.

Assessing the intra-species genetic variability in the clonal pathogen Campylobacter fetus: CRISPRs are highly polymorphic DNA markers.

Campylobacter fetus is a Gram-negative, microaerophilic bacterium that infects animals and humans. The subspecies Campylobacter fetus subsp. fetus (Cff) affects a broad range of vertebrate hosts and induces abortion in cows and sheep. Campylobacter fetus subsp. venerealis (Cfv) is restricted to cattle and causes the endemic disease bovine genital campylobacteriosis, which triggers reproductive problems and is responsible for major economic losses. Campylobacter fetus subsp. testudinum (Cft) has been isolated mostly from apparently healthy reptiles belonging to different species but also from ill snakes and humans. Genotypic differentiation of Cff and Cfv is difficult, and epidemiological information is scarce because there are few methods to study the genetic diversity of the strains. We analyze the efficacy of MLST, ribosomal sequences (23S gene and internal spacer region), and CRISPRs to assess the genetic variability of C. fetus in bovine and human isolates. Sequences retrieved from complete genomes were included in the analysis for comparative purposes. MLST and ribosomal sequences had scarce or null variability, while the CRISPR-cas system structure and the sequence of CRISPR1 locus showed remarkable diversity. None of the sequences here analyzed provided evidence of a genetic differentiation of Cff and Cfv in bovine isolates. Comparison of bovine and human isolates with Cft strains showed a striking divergence. Inter-host differences raise the possibility of determining the original host of human infections using CRISPR sequences. CRISPRs are the most variable sequences analyzed in C. fetus so far, and constitute excellent representatives of a dynamic fraction of the genome. CRISPR typing is a promising tool to characterize isolates and to track the source and transmission route of C. fetus infections.

A novel real-time PCR assay for quantitative detection of Campylobacter fetus based on ribosomal sequences.

BACKGROUND: Campylobacter fetus is a pathogen of major concern for animal and human health. The species shows a great intraspecific variation, with three subspecies: C. fetus subsp. fetus, C. fetus subsp. venerealis, and C. fetus subsp. testudinum. Campylobacter fetus fetus affects a broad range of hosts and induces abortion in sheep and cows. Campylobacter fetus venerealis is restricted to cattle and causes the endemic disease bovine genital campylobacteriosis, which triggers reproductive problems and is responsible for major economic losses. Campylobacter fetus testudinum has been proposed recently based on genetically divergent strains isolated from reptiles and humans. Both C. fetus fetus and C. fetus testudinum are opportunistic pathogens for immune-compromised humans. Biochemical tests remain as the gold standard for identifying C. fetus but the fastidious growing requirements and the lack of reliability and reproducibility of some biochemical tests motivated the development of molecular diagnostic tools. These methods have been successfully tested on bovine isolates but fail to detect some genetically divergent strains isolated from other hosts. The aim of the present study was to develop a highly specific molecular assay to identify and quantify C. fetus strains. RESULTS: We developed a highly sensitive real-time PCR assay that targets a unique region of the 16S rRNA gene. This assay successfully detected all C. fetus strains, including those that were negative for the cstA gene-based assay used as a standard for molecular C. fetus identification. The assay showed high specificity and absence of cross-reactivity with other bacterial species. The analytical testing of the assay was determined using a standard curve. The assay demonstrated a wide dynamic range between 102 and 107 genome copies per reaction, and a good reproducibility with small intra- and inter-assay variability. CONCLUSIONS: The possibility to characterize samples in a rapid, sensitive and reproducible way makes this assay a good option to establish a new standard in molecular identification and quantification of C. fetus species.

Mycobacterium paratuberculosis detection in cow's milk in Argentina by immunomagnetic separation-PCR

Abstract The aim of this study was to standardize a diagnosis procedure to detect Mycobacterium avium subsp. paratuberculosis (Map) DNA in raw cow milk samples under field conditions. A procedure that combines both immunomagnetic separation and IS900 -PCR detection (IMS-IS1 PCR) was employed on milk samples from 265 lactating Holstein cows from Map infected and uninfected herds in Argentina. IMS-IS1 PCR results were analyzed and compared with those obtained from milk and fecal culture and serum ELISA. The extent of agreement between both tests was determined by the Kappa test. IMS-IS1 PCR showed a detection limit of 101 CFU of Map/mL of milk, when 50:50 mix of monoclonal and polyclonal antibodies were used to coat magnetic beads. All of the 118 samples from the Map uninfected herds were negative for the set of the tests. In Map infected herds, 80 out of 147 cows tested positive by milk IMS-IS1 PCR (55%), of which 2 (1.4%) were also positive by milk culture, 15 (10%) by fecal culture, and 20 (14%) by serum ELISA. Kappa statistics (95% CI) showed a slight agreement between the different tests (<0.20), and the proportions of agreement were ≤0.55. The IMS-IS1 PCR method detected Map in milk of the cows that were not positive in other techniques. This is the first report dealing with the application of IMS-IS1 PCR in the detection of Map in raw milk samples under field conditions in Argentina.

Mycobacterium paratuberculosis detection in cow's milk in Argentina by immunomagnetic separation-PCR.

The aim of this study was to standardize a diagnosis procedure to detect Mycobacterium avium subsp. paratuberculosis (Map) DNA in raw cow milk samples under field conditions. A procedure that combines both immunomagnetic separation and IS900-PCR detection (IMS-IS1 PCR) was employed on milk samples from 265 lactating Holstein cows from Map infected and uninfected herds in Argentina. IMS-IS1 PCR results were analyzed and compared with those obtained from milk and fecal culture and serum ELISA. The extent of agreement between both tests was determined by the Kappa test. IMS-IS1 PCR showed a detection limit of 10(1) CFU of Map/mL of milk, when 50:50 mix of monoclonal and polyclonal antibodies were used to coat magnetic beads. All of the 118 samples from the Map uninfected herds were negative for the set of the tests. In Map infected herds, 80 out of 147 cows tested positive by milk IMS-IS1 PCR (55%), of which 2 (1.4%) were also positive by milk culture, 15 (10%) by fecal culture, and 20 (14%) by serum ELISA. Kappa statistics (95% CI) showed a slight agreement between the different tests (<0.20), and the proportions of agreement were ≤0.55. The IMS-IS1 PCR method detected Map in milk of the cows that were not positive in other techniques. This is the first report dealing with the application of IMS-IS1 PCR in the detection of Map in raw milk samples under field conditions in Argentina.

Identification and evaluation of new Mycobacterium bovis antigens in the in vitro interferon gamma release assay for bovine tuberculosis diagnosis.

Bovine tuberculosis (bTB) is a common zoonotic disease, caused by Mycobacterium bovis (M. bovis), responsible for significant economic losses worldwide. Its diagnosis is based on the detection of cell mediated immunity under the exposure to protein purified derivative tuberculin (PPD), a complex and poorly characterized reagent. The cross-reactivity to non-tuberculous mycobacterium species (false-positive results) has been crucial to develop a more proper antigen. In the present study, we selected six M. bovis Open Reading Frames (Mb1992, Mb2031c, Mb2319, Mb2843c, Mb2845c and Mb3212c) by in-silico analysis and evaluated them in experimental and natural infection; none of these antigens had been previously assessed as diagnostic antigens for bTB. The reactivity performance was tested in animals with both positive and negative Tuberculin Skin Test (TST) results as well as in cattle infected with Mycobacterium avium subesp. paratuberculosis (MAP). The six recombinant antigens individually induced an IFN-γ response, with overall responder frequency ranging from 18.3 to 31%. Mb2845c was the most valuable antigen with the potential to discriminate TST-positive cattle from either TST-negative or MAP infected animals. Mb2845c showed similar performance to that observed with ESAT-6 and PPD-B among TST and MTC specific-PCR positive animals, although this result needs to be proven in further studies with a higher sample size. Our data confirm the feacibility to implement bioinformatic screening tools and suggest Mb2845c as a potential diagnostic antigen to be tested in protein cocktails to evaluate their contribution to bTB diagnosis.

Eficiencia del cultivo bacteriológico y de la inmunofluorescencia en la detección de Campylobacter fetus en fluidos genitales bovinos / Efficiency of bacteriological culture and the immunofluorescent assay to detect Campylobacter fetus in bovine genital fluids

La campilobacteriosis genital bovina es una enfermedad reproductiva que afecta la producción bovina. Es causada por las subespecies de Campylobacter fetus, C. fetus fetus (Cff) y C. fetus venerealis (Cfv). El objetivo de este estudio fue identificar la presencia de C. fetus en fluidos genitales mediante cultivo bacteriológico e inmunofluorescencia directa (IFD) y comparar los resultados. Se conformaron 2 grupos de 6 vaquillonas y 5 toros cada uno. Uno se infectó con Cff (grupo Cff) y el otro con Cfv (grupo Cfv). Dos vaquillonas y 2 toros sin infectar conformaron el grupo control. Periódicamente se tomaron muestras de mucus cervicovaginal y fluido prepucial, las que se procesaron por cultivo e IFD. En el grupo Cff se infectó el 100 % de las vaquillonas y el 80 % de los toros, mientras que en el grupo Cfv se infectó el 50 y el 60 %, respectivamente. Los valores de concordancia (Kappa) obtenidos al comparar las técnicas diagnósticas fueron de 0,57 para las vaquillonas del grupo Cff y 0,52 para las del grupo Cfv, y para los toros fueron de 0,17 y 0,27, respectivamente. En las vaquillonas, la IFD arrojó más resultados positivos que el cultivo, un 5,6 % más para el grupo Cff y un 7,4 % más para el grupo Cfv. El menor porcentaje de resultados positivos por IFD en los toros, un 40 % menos que por cultivo para el grupo Cff y un 5,3 % menos para el grupo Cfv, podría deberse a un muestreo incorrecto. Los valores de Kappa indican una concordancia moderada en las vaquillonas y baja en los toros.

Bovine genital campylobacteriosis is a reproductive disease that affects cattle production. It is caused by Campylobacter fetus subspecies, C. fetus fetus (Cff) and C. fetus venerealis (Cfv). The aim of this study was to identify the presence of C. fetus in genital fluids by bacteriological culture and direct immunofluorescence (DIF) and to compare the results. Two groups of 6 heifers and 5 bulls, one infected with Cff (Cff group) and the other with Cfv (Cfv group) were formed. Two heifers and 2 bulls, all of them uninfected, made up the control group. Samples of cervicovaginal mucus and preputial fluid were processed by culture and DIF. In the Cff group, 100 % of the heifers and 80 % of the bulls were infected, while in the Cfv group, 50 % of the heifers and 60 % of the bulls were infected. The degree of agreement (Kappa values) from benchmarking diagnostic techniques were 0.57 for heifers in the Cff group and 0.52 for heifers in the Cfv group, whereas the values for bulls were 0.17 and 0.27, respectively. Heifers yielded more positive results in the DIF assay than in the culture, exhibiting 5.6 % increase in the Cff group and 7.4 % in the Cfv group. The lowest percentage of positive results for DIF in bulls, 40 % less for the Cff group and 5.2 % for the Cfv group, could be due to improper sampling. Kappa values showed moderate agreement for the heifers and low for the bulls.

Molecular typing of Argentinian Mycobacterium avium subsp. paratuberculosis isolates by multiple-locus variable number-tandem repeat analysis.

Multiple-locus variable number-tandem repeat analysis (MLVA) of Mycobacterium avium subspecies paratuberculosis (MAP) isolates may contribute to the knowledge of strain diversity in Argentina. Although the diversity of MAP has been previously investigated in Argentina using IS900-RFLP, a small number of isolates were employed, and a low discriminative power was reached. The aim of the present study was to test the genetic diversity among MAP isolates using an MLVA approach based on 8 repetitive loci. We studied 97 isolates from cattle, goat and sheep and could describe 7 different patterns: INMV1, INMV2, INMV11, INMV13, INMV16, INMV33 and one incomplete pattern. INMV1 and INMV2 were the most frequent patterns, grouping 76.3% of the isolates. We were also able to demonstrate the coexistence of genotypes in herds and co-infection at the organism level. This study shows that all the patterns described are common to those described in Europe, suggesting an epidemiological link between the continents.