Identification of Campylobacter fetus subspecies by phenotypic differentiation and PCR

Uncovering the boundaries of Campylobacter species through large-scale phylogenetic and nucleotide identity analyses

Campylobacter species are typically helical shaped, Gram-negative, and non-spore-forming bacteria. Species in this genus include established foodborne and animal pathogens as well as emerging pathogens. The accumulation of genomic data from the Campylobacter genus has increased exponentially in recent years, accompanied by the discovery of putative new species. At present, the lack of a standardized species boundary complicates distinguishing established and novel species. We defined the Campylobacter genus core genome (500 loci) using publicly available Campylobacter complete genomes (n = 498) and constructed a core genome phylogeny using 2,193 publicly available Campylobacter genomes to examine inter-species diversity and species boundaries. Utilizing 8,440 Campylobacter genomes representing 33 species and 8 subspecies, we found species delineation based on an average nucleotide identity (ANI) cutoff of 94.2% is consistent with the core genome phylogeny. We identified 60 ANI genomic species that delineated Campylobacter species in concordance with previous comparative genetic studies. All pairwise ANI genomic species pairs had in silico DNA-DNA hybridization scores of less than 70%, supporting their delineation as separate species. We provide the tool Campylobacter Genomic Species typer (CampyGStyper) that assigns ANI genomic species to query genomes based on ANI similarities to medoid genomes from each ANI genomic species with an accuracy of 99.96%. The ANI genomic species definitions proposed here allow consistent species definition in the Campylobacter genus and will facilitate the detection of novel species in the future.IMPORTANCEIn recent years, Campylobacter has gained recognition as the leading cause of bacterial gastroenteritis worldwide, leading to a substantial rise in the collection of genomic data of the Campylobacter genus in public databases. Currently, a standardized Campylobacter species boundary at the genomic level is absent, leading to challenges in detecting emerging pathogens and defining putative novel species within this genus. We used a comprehensive representation of genomes of the Campylobacter genus to construct a core genome phylogenetic tree. Furthermore, we found an average nucleotide identity (ANI) of 94.2% as the optimal cutoff to define the Campylobacter species. Using this cutoff, we identified 60 ANI genomic species which provided a standardized species definition and nomenclature. Importantly, we have developed Campylobacter Genomic Species typer (CampyGStyper), which can robustly and accurately assign these ANI genomic species to Campylobacter genomes, thereby aiding pathogen surveillance and facilitating evolutionary and epidemiological studies of existing and emerging pathogens in the genus Campylobacter.

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.

The History of Bovine Genital Campylobacteriosis in the Face of Political Turmoil and Structural Change in Cattle Farming in Germany

Contagious bovine genital campylobacteriosis (BGC), also known as bovine venereal campylobacteriosis, is a disease relevant to international trade listed by the World Organization for Animal Health (WOAH). It is caused by Campylobacter fetus subsp. venerealis (Cfv), one of three subspecies of Campylobacter fetus. Bulls are the reservoir but BGC may also be spread by artificial insemination (AI). BGC is characterized by severe reproductive losses such as infertility, early embryonic death and abortion with considerable economic losses. This significant economic impact has prompted several countries to adopt stringent eradication and surveillance measures to contain the disease. While there are commercial and autologous vaccines available, scientific evidence for the effectiveness of vaccination is still lacking. In Germany, BCG was already found to be endemic in the 1920s, shortly after the agent and the disease had been described for the first time. It can be assumed that BCG had already circulated uncontrolled for a long time in the predecessor states of Germany, influenced only by the political situation and trading networks of the time. After WW II, BCG was eradicated in the German Democratic Republic due to industrialized cattle production based on AI but it was still endemic at low levels in the Federal Republic of Germany with its diverse cattle production. There has been a steady decline in BGC incidence in re-unified Germany over the past 28 years. A single genetic Cfv lineage was identified which probably emerged in the 19th century and diversified over time. Interestingly, no recurrent cross-border introduction became evident. This review gives insight into the history of bovine genital campylobacteriosis considering the structural change in cattle farming in Germany and reflecting on the political background of the time.

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.

Genomic epidemiology of Campylobacter fetus subsp. venerealis from Germany

Campylobacter fetus subsp. venerealis (Cfv) causes bovine genital campylobacteriosis (BGC), a World Organization for Animal Health (WOAH)-listed trade-relevant disease characterized by severe reproductive losses, such as infertility, early embryonic death and abortion in cattle. BGC has significant economic implications that have prompted several countries to adopt stringent eradication and surveillance measures to contain the disease. In Germany, there has been a low incidence of BGC cases over the past 28 years. This study aimed to illustrate the genomic diversity of German Cfv strains isolated from different federal states in Germany. This study analyzed 63 Cfv strains, collected between 1985 and 2015, by whole-genome sequencing and compared them with genome data of 91 international Cfv isolates. The phylogenetic analysis showed that the Cfv population is genetically conserved and has geographic clusters. In Germany, one phylogenetic lineage comprising all strains was identified. This German lineage was part of a subclade that probably emerged in the nineteenth century and diversified over time. The results of this study point to a non-recurrent cross-border introduction of Cfv in Germany. The BGC control interventions in Germany can be considered successful as no outbreaks were reported since 2015.

Current methodologies and future direction of Campylobacter isolation and detection from food matrices, clinical samples, and the agricultural environment

Campylobacter spp. are the leading cause of bacterial foodborne infections in both developed and developing countries. The food commodities primarily attributed to campylobacteriosis include raw milk, poultry, seafood, and fresh produce. Furthermore, insects, animal/bird fecal material, and agricultural water have been shown to be the sources of Campylobacter contamination in these commodities. Both established and emerging species of Campylobacter have been recovered from food and environmental sources. Therefore, optimal detection and isolation of Campylobacter spp., including the emerging species, is critical for improved surveillance, prevention, and traceback of Campylobacter outbreaks. This review focuses on the existing variability in Campylobacter enrichment and isolation procedures used by researchers and regulatory agencies worldwide, for various matrices. Additionally, the challenges associated with developing and validating new culture, molecular, and immunological methods for rapid and sensitive Campylobacter detection are discussed.

A survey of food-borne and antimicrobial resistance-harbouring bacteria in meat by-products from knackeries and associated equipment and kennels

Background

In Ireland, meat by-products (MBP) harvested at knackeries from farmed animals that have not died of an infectious or systemic disease are legally permitted to be fed to dogs in kennels and packs of hounds. There is limited information available on the risks of spreading foodborne bacteria or antimicrobial resistant (AMR) determinants to dogs, their handlers or the associated environment. The aim of this study was to investigate the distribution of Salmonella serovars, Listeria monocytogenes, Campylobacter species, enterococci, their associated AMR determinants and the level of Escherichia coli in samples of MBP from knackeries and associated equipment and kennels. For this purpose, 313 fresh and 208 frozen MBP samples from 22 knackeries, 16 swabs of mincing equipment from two of the knackeries and 138 swabs from kennels adjacent to seven of the knackeries were collected and processed over a 12-month period.

Results

From the 521 MBP samples analysed, a total of 77 Salmonella (14.8%), 101 L. monocytogenes (19.4%), 12 Campylobacter (2.3%), 271 Enterococcus faecalis (52.0%) and 127 Enterococcus faecium (24.4%) strains were recovered. The 154 analysed environmental samples from kennels and mincing equipment yielded 194 isolates (3 Salmonella, 85 E. coli, 76 E. faecalis and 30 E. faecium.). E. coli was quantifiable in 423 of the 521 MBP samples with log counts per gram ranging between 1 and 6. AMR characterisation of 168 E. coli, enterococci and Salmonella isolates from MBP and environmental samples showed high levels of AMR including multi-drug resistance (MDR) with 63.6%, 9.1%, 29% and 45.8% of E. coli, Salmonella, E. faecalis and E. faecium isolates, respectively showing resistance to three or more antimicrobials (MDR)

Conclusions

The findings of this survey confirm that MBP from fallen animals contain high levels of zoonotic and AMR-harbouring bacteria that pose a risk of transmission to dogs, their handlers, and the environment.

Evaluation of PCR assays for Campylobacter fetus detection and discrimination between C. fetus subspecies in bovine preputial wash samples

Campylobacter fetus is a zoonotic pathogen found in cattle, in which it is one of the main causes of infectious infertility. Most diagnostic laboratories use PCR as quick easy tool for C. fetus identification. However, there is no standardized PCR assay for C. fetus detection and subspecies differentiation, hindering the comparison of results. In this study, we evaluated selected PCR assays targeting the 16S rRNA, gyrB, cpn60, cstA, cdtB and nahE genes for C. fetus identification and ISCfe1, sapB2, parA and virB11 for subspecies differentiation. Analytical sensitivity and specificity were assessed for each PCR assay, and the assays were then tested on 289 bull preputial samples that had also been analysed by 16S rRNA barcode metagenomics. In total, 41 C. fetus-positive samples were included. The P12 PCR assay targeting the gyrB gene performed best, detecting the pathogen in 95.1% of positive samples. For the discrimination of C. fetus subspecies, we were able to identify a proportion (85.4%) of the C. fetus-positive samples correctly as C. fetus venerealis with at least one subspecies-specific PCR, but C. fetus fetus was not detected in any of the samples tested. Remarkably, C. fetus subspecies amplification was observed following PCR on some samples (33.1%) considered C. fetus-negative, highlighting the need for rigorous criteria for discriminating between C. fetus subspecies, to improve understanding of the role of the two C. fetus subspecies in the epidemiology and pathogenesis of bovine infectious infertility.

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.

Phylogenomic Analysis of Campylobacter fetus Reveals a Clonal Structure of Insertion Element ISCfe1 Positive Genomes

Subspecies of the species Campylobacter fetus are associated with specific host niches including mammals and reptiles. Campylobacter fetus subsp. fetus is a zoonotic pathogen infecting humans. Infections can vary from an acute intestinal illness to severe systemic infections, with sheep and cattle as major reservoirs. In contrast, Campylobacter fetus subsp. venerealis causes bovine genital campylobacteriosis, which leads to abortion in cattle and a high economic burden for the farmers. Therefore, high-quality molecular subtyping is indispensable for interventional epidemiology. We used whole-genome sequencing (WGS) data of 283 Campylobacter fetus strains from 18 countries and compared several methods for Campylobacter fetus subtyping, including WGS, multilocus sequence typing, PCR assays, and the presence of the insertion element ISCfe1. We identified a highly clonal clade (designated as clade 1) that harbors the insertion sequence ISCfe1. The presence of this insertion sequence is an essential diagnostic tool for the identification of the subspecies Campylobacter fetus subsp. venerealis, serving as a target for several PCR assays. However, we have found a high sequence variability for the ISCfe1 besides the presence of ISCfe1-paralogues in certain other genomes (n = 7) which may cause incorrect diagnostic results. Clade 1 seems to be the cattle-specific clade of this species. We propose that only this clade might be designated as Campylobacter fetus subsp. venerealis as it harbors the ISCfe1 marker sequence, which is a major target for molecular methods currently used for Campylobacter fetus subspecies identification. Fostering this proposal, we defined eleven stable nucleotide markers specific for this clade. Additionally, we developed a bioinformatics toolbox for the fast identification of this clade based on WGS data. In conclusion, our results demonstrate that WGS can be used for Campylobacter fetus subtyping overcoming limitations of current PCR and MLST protocols.

Genome Sequence of Campylobacter fetus subsp. venerealis NW_ED23, Isolated from Bovine Sheath Wash

Campylobacter fetus subsp. venerealis is the causative agent of bovine genital campylobacteriosis, which is mostly characterized by reproduction problems. The strain reported in this study was isolated from bull sheath wash in South Africa.

Campylobacter fetus subsp. venerealis is the causative agent of bovine genital campylobacteriosis, which is mostly characterized by reproduction problems. The strain reported in this study was isolated from bull sheath wash in South Africa.

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.

Infection, colonization and shedding of Campylobacter and Salmonella in animals and their contribution to human disease: A review

Livestock meat and offal contribute significantly to human nutrition as sources of high-quality protein and micronutrients. Livestock products are increasingly in demand, particularly in low- and middle-income settings where economies are growing and meat is increasingly seen as an affordable and desirable food item. Demand is also driving intensification of livestock keeping and processing. An unintended consequence of intensification is increased exposure to zoonotic agents, and a contemporary emerging problem is infection with Campylobacter and Salmonella spp. from livestock (avian and mammalian), which can lead to disease, malabsorption and undernutrition through acute and chronic diarrhoea. This can occur at the farm, in households or through the food chain. Direct infection occurs when handling livestock and through bacteria shed into the environment, on food preparation surfaces or around the house and surroundings. This manuscript critically reviews Campylobacter and Salmonella infections in animals, examines the factors affecting colonization and faecal shedding of bacteria of these two genera as well as risk factors for human acquisition of the infection from infected animals or environment and analyses priority areas for preventive actions with a focus on resource-poor settings.

First reported detection of biofilm formation by Campylobacter fetus during investigation of a case of prosthetic valve endocarditis

AIMS

Campylobacter fetus subsp fetus (CFF) can cause intestinal illness, particularly in immunocompromised humans, with the potential to cause severe systemic infections. CFF is a zoonotic pathogen with a broad host range among farm animals and humans, inducing abortion in sheep and cows. The current paper describes a strain of CFF isolated from a patient with prosthetic valve endocarditis in Mercy University Hospital, Cork, Ireland, during 2017. Only five cases of C. fetus as a cause of prosthetic valve endocarditis have been reported in the literature, with no reports of biofilm formation within the species.

METHODS

The aetiological strain was speciated and subspeciated by the VITEK 2 NH card and matrix-assisted laser desorption ionisation time-of-flight mass spectrometry. CFF biofilm formation was analysed using a crystal violet staining method. C. jejuni National Collection of Type Cultures (NCTC) 11168 was used as a positive control organism. Strains were incubated statically in Mueller-Hinton broth and Mueller-Hinton broth supplemented with 0.025% sodium deoxycholate for 3 and 7 days at 37°C, microaerobically.

RESULTS

The CFF strain formed stronger attached biofilms on polystyrene plates on day 3 (72 hours) than the C. jejuni NCTC 11168 control strain, but were weaker than the control strain on day 7 in Mueller-Hinton broth. Monoculture of this C. fetus isolate was found to exist in three defined forms of biofilms (attached, air-liquid interface and floccules).

CONCLUSIONS

This clinically significant C. fetus isolate showed considerable biofilm-forming capability, which we suggest conferred a survivalist advantage, contributing to the genesis of infective prosthetic valve endocarditis.

Current trends in bovine abortion in Argentina

ABSTRACT: Bovine abortion is an important cause of significant economic losses in beef and dairy herds. This syndrome is usually difficult to diagnose. The aim of this study was to characterize bovine abortion causes in Argentina by standard diagnosis procedures (histology, bacterial and viral isolation) and other diagnostic tests like direct fluorescent antibody test (DFAT), fetal serology, immunohistochemistry (IHC), and PCR, showing their specific advantages and limitations. Necropsies were performed in 150 aborted bovine fetuses submitted to the diagnostic laboratories of Instituto Nacional de Tecnología Agropecuaria (INTA) Balcarce, Argentina. Etiological diagnosis was confirmed in 78 fetuses (52% of the cases). Most causes of abortion were of infectious origin, being Neospora caninum (14.67%), Campylobacter fetus sp. (9.33%), Leptospira spp. (7.33%) and Brucella abortus (6.65%) the main microorganisms identified. Bovine viral diarrhea virus (BVDV) and bovine herpes virus (BHV) were diagnosed in 2 (1.33%) and 3 (2%) cases, respectively. This study showed a better characterization of bovine abortion compared with previous researches done on this topic.

Evaluation of Targeted Next-Generation Sequencing for Detection of Bovine Pathogens in Clinical Samples

The laboratory diagnosis of infectious diseases, especially those caused by mixed infections, is challenging. Routinely, it requires submission of multiple samples to separate laboratories. Advances in next-generation sequencing (NGS) have provided the opportunity for development of a comprehensive method to identify infectious agents. This study describes the use of target-specific primers for PCR-mediated amplification with the NGS technology in which pathogen genomic regions of interest are enriched and selectively sequenced from clinical samples. In the study, 198 primers were designed to target 43 common bovine and small-ruminant bacterial, fungal, viral, and parasitic pathogens, and a bioinformatics tool was specifically constructed for the detection of targeted pathogens. The primers were confirmed to detect the intended pathogens by testing reference strains and isolates. The method was then validated using 60 clinical samples (including tissues, feces, and milk) that were also tested with other routine diagnostic techniques. The detection limits of the targeted NGS method were evaluated using 10 representative pathogens that were also tested by quantitative PCR (qPCR), and the NGS method was able to detect the organisms from samples with qPCR threshold cycle (C_T) values in the 30s. The method was successful for the detection of multiple pathogens in the clinical samples, including some additional pathogens missed by the routine techniques because the specific tests needed for the particular organisms were not performed. The results demonstrate the feasibility of the approach and indicate that it is possible to incorporate NGS as a diagnostic tool in a cost-effective manner into a veterinary diagnostic laboratory.

Campylobacter fetus meningitis associated with eating habits of raw meat and raw liver in a healthy patient: A case report and literature review

Meningitis caused by the zoonotic pathogen Campylobacter fetus in immunocompetent adults is rare. We report a 48-year-old Japanese woman with no underlying disease who was found to have meningitis caused by C. fetus. Both C. fetus subsp. fetus and C. fetus subsp. venerealis were isolated from the cerebrospinal fluid culture. The mode of infection in our patient was considered to be associated with the consumption of raw beef and raw cattle liver on a regular basis. Public awareness and education to avoid the consumption of raw or undercooked meat might help prevent C. fetus meningitis.

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.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0913-3) contains supplementary material, which is available to authorized users.

Campylobacter-Associated Diseases in Animals

Campylobacter includes a group of genetically diverse species causing a range of diseases in animals and humans. The bacterium is frequently associated with two economically important and epidemiologically distinct reproductive diseases in ruminants: enzootic infectious infertility in cattle owing to Campylobacter fetus subsp. venerealis and abortions in sheep, goats, and cattle. Septic abortion, usually epizootic in sheep, has been historically associated with C. fetus subsp. fetus and to a lesser extent with Campylobacter jejuni. However, there has been a dramatic species shift in the etiology of Campylobacter abortions in recent years: C. jejuni has now replaced C. fetus subsp. fetus as the predominant cause of sheep abortion in the United States, which appears to be driven primarily by clonal expansion of a hypervirulent tetracycline-resistant C. jejuni clone. Here we provide a review on the recent advances in understanding the pathobiology of Campylobacter infections in animals, with an emphasis on the diseases in ruminants, covering epidemiology, pathogenesis, genomics, and control measures.

Prevalence and risk factors associated with bovine genital campylobacteriosis and bovine trichomonosis in the state of Pernambuco, Brazil

The aim of the present study was to determine the prevalence and risk factors associated with Campylobacter fetus subsp. venerealis and Tritrichomonas foetus infection in cows from dairy herds in the state of Pernambuco, Brazil. In total, 383 samples of cervico-vaginal mucus were collected from cows on 21 herds in 19 districts. Genomic DNA was extracted from the samples and submitted for polymerase chain reaction analysis. An investigative questionnaire was used to analyze the risk factors, using questions related to reproductive and hygiene/sanitation management. A prevalence of 1.8% (0.8-3.9%; confidence interval (CI) 95%) and 33.4% (28.7-38.4%; CI 95%) was found for C. fetus subsp. venerealis and T. foetus, respectively. In terms of the number of foci, 28.6% of the herds contained at least one animal that was positive for C. fetus subsp. venerealis and 90.5% for T. foetus. The present study identified herds larger than 100 animals as a risk factor for bovine genital campylobacteriosis (OR = 7.2; CI 1.3-38.4%; p = 0.020) and the use of natural breeding as a risk factor for bovine trichomonosis (OR = 2.4; CI 1.1-5.9%; p = 0.041). In conclusion, C. fetus subsp. venerealis and T. foetus infections occurred in the region studied and high numbers of foci were found. Thus, prophylaxis and control measures, such as diagnosis, separation, and sexual rest for infected females, are suggested. An artificial insemination program with early rigorous sanitary care should be implemented on the properties in order to avoid the spread of agents in the herds.

Infective Internal Iliac Artery Aneurysm Caused by Campylobacter fetus

A 67-year-old man with a persistent high fever was diagnosed to have an infective aneurysm in his left internal iliac artery. A blood culture detected a gram-negative spiral rod that was first identified as Campylobacter fetus subsp. venerealis based on a matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) analysis. However, the strain was finally confirmed to be Campylobacter fetus subsp. fetus based on a genetic analysis. The infection was successfully treated with emergency resection of the aneurysm, followed by 4 weeks of antibiotic therapy. Involvement of the peripheral artery is uncommon in cases of C. fetus-infective aneurysm. To figure out the epidemiology and pathogenicity of C. fetus infection, the accurate identification of the responsible organisms is essential.

Meningitis and endocarditis caused by Campylobacter fetus after raw-liver ingestion

We report Campylobacter fetus meningitis associated with endocarditis in a 75-year-old diabetic man after he consumed raw liver. C. fetus was isolated from blood samples and cerebrospinal fluid. Cure was obtained with combined intravenous imipenem-gentamicin for 4 weeks; no relapse occurred after 6 months of follow-up.

Real Time PCR to detect and differentiate Campylobacter fetus subspecies fetus and Campylobacter fetus subspecies venerealis

Bovine venereal campylobacter infection, caused by Campylobacter fetus venerealis, is of significant economic importance to the livestock industry. Unfortunately, the successful detection and discrimination of C. fetus venerealis from C. fetus fetus continue to be a limitation throughout the world. There are several publications warning of the problem with biotyping methods as well as with recent molecular based assays. In this study, assessed on 1071 isolates, we report on the successful development of two Real Time SYBR® Green PCR assays that will allow for the detection and discrimination of C. fetus fetus and C. fetus venerealis. The sensitivity reported here for the C. fetus (CampF4/R4) and the C. fetus venerealis (CampF7/R7) specific PCR assays are 100% and 98.7% respectively. The specificity for these same PCR assays are 99.6% and 99.8% respectively.

Application of a multiplex PCR assay for Campylobacter fetus detection and subspecies differentiation in uncultured samples of aborted bovine fetuses

Campylobacter (C.) fetus (epsilonproteobacteria) is an important veterinary pathogen. This species is currently divided into C. fetus subspecies (subsp.) fetus (Cff) and C. fetus subsp. venerealis (Cfv). Cfv is the causative agent of bovine genital Campylobacteriosis, an infectious disease that leads to severe reproductive problems in cattle worldwide. Cff is a more general pathogen that causes reproductive problems mainly in sheep although cattle can also be affected. Here we describe a multiplex PCR method to detect C. fetus and differentiate between subspecies in a single step. The assay was standardized using cultured strains and successfully used to analyze the abomasal liquid of aborted bovine fetuses without any pre-enrichment step. Results of our assay were completely consistent with those of traditional bacteriological diagnostic methods. Furthermore, the multiplex PCR technique we developed may be easily adopted by any molecular diagnostic laboratory as a complementary tool for detecting C. fetus subspecies and obtaining epidemiological information about abortion events in cattle.

Application of a new diagnostic approach to a bovine genital campylobacteriosis outbreak in a Saskatchewan beef herd

A new real-time quantitative polymerase chain reaction (qPCR) test was used to diagnose Campylobacter fetus subsp. venerealis infection associated with dramatic reproductive losses in a commercial cow-calf herd. The results were verified with repeated culture, phenotypic characterization of the organism and DNA sequencing. This case demonstrates the need for a practical field test for C. fetus subsp. venerealis and the importance of considering this organism as a potential cause of pregnancy failure in beef herds.

PCR detection of Campylobacter fetus subspecies venerealis in smegma samples collected from dairy cattle in Fars, Iran

Bovine venereal campylobacteriosis, caused by Campylobacter fetus subsp. venerealis (Cfv), is regarded as one of the major threats to the cattle industry around the world. Abortion and infertility are two important reproductive problems in cows infected with C. fetus subsp. venerealis. Reports on the presence of Cfv are scarce in the cattle, in Iran. Therefore, the present study was designed to examine the presence of Cfv in the reproductive tract of dairy cattle either slaughtered in Shiraz abattoir or dairy herds with a history of infertility and abortion, and further to identify and differentiate this micro-organism in dairy cattle in Fars, south of Iran. A total of 95 smegma samples from the preputial cavity and the fornix of the cervical opening were collected using scraping method from bulls (n = 34) and cows (n = 61) in addition to eight samples of commercially bull frozen semen. Smegma samples were then cultured for isolation of Cfv and then the extracted DNA was examined for the presence of Cfv using an optimized multiplex PCR assay. None of the frozen semen samples examined were positive for Cfv. However, out of 95 smegma samples, thirteen animals (12.6%) were found positive for Cfv consisting of 3 males and 10 females. In conclusion, the results of the current study clearly confirmed the presence of Cfv using PCR in the slaughtered cattle and dairy farms with a history of poor fertility and abortion in Fars, Iran.

So close and yet so far - Molecular Microbiology of Campylobacter fetus subspecies

Campylobacter fetus comprises two subspecies, C. fetus subsp. fetus and C. fetus subsp. venerealis, which are considered emerging pathogens in humans and animals. Comparisons at the genome level have revealed modest subspecies-specific variation; nevertheless, these two subspecies show distinct host and niche preferences. C. fetus subsp. fetus is a commensal and pathogen of domesticated animals that can be transmitted to humans via contaminated food. The clinical features of human infection can be severe, especially in impaired hosts. In contrast, C. fetus subsp. venerealis is a sexually transmitted pathogen essentially restricted to cattle. Infections leading to bovine venereal campylobacteriosis cause substantial economic losses due to abortion and infertility. Recent genome sequencing of the two subspecies has advanced our understanding of C. fetus adaptations through comparative genomics and the identification of subspecies-specific gene regions predicted to be involved in pathogenesis. The most striking difference between the subspecies is the highly subspecies-specific association of a pathogenicity island in the C. fetus subsp. venerealis chromosome. The inserted region encodes a Type 4 secretion system, which contributes to virulence properties of this organism in vitro. This review describes the main differences in epidemiological, phenotypic, and molecular characteristics of the two subspecies and summarizes recent advances towards understanding the molecular mechanisms of C. fetus pathogenesis.

The clinical importance of emerging Campylobacter species

A growing number of Campylobacter species other than C. jejuni and C. coli have been recognized as emerging human and animal pathogens. Although C. jejuni continues to be the leading cause of bacterial gastroenteritis in humans worldwide, advances in molecular biology and development of innovative culture methodologies have led to the detection and isolation of a range of under-recognized and nutritionally fastidious Campylobacter spp., including C. concisus, C. upsaliensis and C. ureolyticus. These emerging Campylobacter spp. have been associated with a range of gastrointestinal diseases, particularly gastroenteritis, IBD and periodontitis. In some instances, infection of the gastrointestinal tract by these bacteria can progress to life-threatening extragastrointestinal diseases. Studies have shown that several emerging Campylobacter spp. have the ability to attach to and invade human intestinal epithelial cells and macrophages, damage intestinal barrier integrity, secrete toxins and strategically evade host immune responses. Members of the Campylobacter genus naturally colonize a wide range of hosts (including pets, farm animals and wild animals) and are frequently found in contaminated food products, which indicates that these bacteria are at risk of zoonotic transmission to humans. This Review presents the latest information on the role and clinical importance of emerging Campylobacter spp. in gastrointestinal health and disease.

Epidemiology of bovine venereal campylobacteriosis: geographic distribution and recent advances in molecular diagnostic techniques

Bovine venereal campylobacteriosis (BVC) is a major cause of economic loss to the cattle industries in different parts of the world. Camplylobacter fetus subsp. venerealis (Cfv), the main causative agent of BVC, is highly adapted to the genital tract of cattle and is transmitted by carrier bulls. However, infertility and abortions can also be caused by the intestinal pathogens C. fetus subsp. fetus (Cff), and C. jenuni, which are not venereally transmitted. Bovine venereal campylobacteriosis, caused by Cfv associated with lowered fertility, embryo mortality and abortion, repeated returns to service, reduced pregnancy rates and extended calving intervals, has the highest prevalence in developing countries where natural breeding in cattle is widely practised. The epidemiology, pathogenesis and diagnosis of the disease have been the subject of previous reviews. The main focus of this review is to highlight the epidemiology of this disease with particular reference to geographical distribution and recent advances in molecular diagnostic techniques. It is hoped that further research interest of scientists will be stimulated with a view to finding lasting solutions to the reproductive problems associated with the disease for better livestock productivity, particularly in developing endemic countries.

Campylobacter fetus subspecies fetus spondylodiscitis

Campylobacter spp. are common causes of gastrointestinal infections. Campylobacter fetus is a much rarer pathogen in humans, and usually causes bacteraemia and systemic complications in patients with predisposing conditions. We report a case of spondylodiscitis caused by C. fetus subsp. fetus as revealed by vertebral biopsy culture. This identification was confirmed by sequencing the 16S rRNA gene and by phylogenetic analysis. Treatment consisted of 6 weeks antimicrobial therapy combined with a strict initial immobilization, followed by a re-education program. The patient's recovery was uneventful.

Genomic analysis of Campylobacter fetus subspecies: identification of candidate virulence determinants and diagnostic assay targets

Background

Campylobacter fetus subspecies venerealis is the causative agent of bovine genital campylobacteriosis, asymptomatic in bulls the disease is spread to female cattle causing extensive reproductive loss. The microbiological and molecular differentiation of C. fetus subsp. venerealis from C. fetus subsp. fetus is extremely difficult. This study describes the analysis of the available C. fetus subsp. venerealis AZUL-94 strain genome (~75–80%) to identify elements exclusively found in C. fetus subsp. venerealis strains as potential diagnostic targets and the characterisation of subspecies virulence genes.

Results

Eighty Kb of genomic sequence (22 contigs) was identified as unique to C. fetus subsp. venerealis AZUL-94 and consisted of type IV secretory pathway components, putative plasmid genes and hypothetical proteins. Of the 9 PCR assays developed to target C. fetus subsp. venerealis type IV secretion system genes, 4 of these were specific for C. fetus subsp. venerealis biovar venerealis and did not detect C. fetus subsp. venerealis biovar intermedius. Two assays were specific for C. fetus subsp. venerealis AZUL-94 strain, with a further single assay specific for the AZUL-94 strain and C. fetus subsp. venerealis biovar intermedius (and not the remaining C. fetus subsp. venerealis biovar venerealis strains tested). C. fetus subsp. fetus and C. fetus subsp. venerealis were found to share most common Campylobacter virulence factors such as SAP, chemotaxis, flagellar biosynthesis, 2-component systems and cytolethal distending toxin subunits (A, B, C). We did not however, identify in C. fetus the full complement of bacterial adherence candidates commonly found in other Campylobacter spp.

Conclusion

The comparison of the available C. fetus subsp. venerealis genome sequence with the C. fetus subsp. fetus genome identified 80 kb of unique C. fetus subsp. venerealis AZUL94 sequence, with subsequent PCR confirmation demonstrating inconsistent amplification of these targets in all other C. fetus subsp. venerealis strains and biovars tested. The assays developed here highlight the complexity of targeting strain specific virulence genes for field studies for the molecular identification and epidemiology of C. fetus.

Influence of Campylobacter fetus subsp. fetus on ram sperm cell quality

Campylobacter fetus subsp. fetus infection can occur in female sheep, causing infertility or abortion. Despite extensive research on the effect of these bacteria on female fertility, little research has been done on the influence of C. fetus subsp. fetus on the male factor. Our objective was to examine the influence of C. fetus subsp. fetus on ram sperm. Motility index, percentage of live spermatozoa, mean αt value (an indication of the chromatin stability of the sperm cell) and percentage of sperm cells expressing the FAS receptor were measured in sperm incubated in the presence or absence of C. fetus subsp. fetus. The motility index and viability of sperm incubated with the bacteria were lower than those of untreated sperm samples after 5 h. In bacteria-incubated sperm cells, the percentage expressing FAS receptor was already significantly elevated at 15 min. Bacteria-incubated sperm showed a greater prevalence of morphological damage. The bacteria were attached to tail and acrosome regions, and the sperm damage was concentrated in both the motility and chromatin regions. Bacteria-infected sperm cells showed a decrease in motility, increase in early acrosome reaction and chromatin damage. Similar effects were induced by incubation of the sperm with supernatants from C. fetus subsp. fetus cultures. Thus this study demonstrates that C. fetus subsp. fetus has a detrimental effect on the quality of ram sperm.

Discovery of insertion element ISCfe1: a new tool for Campylobacter fetus subspecies differentiation

The species Campylobacter fetus is divided into the subspecies C. fetus subsp. venerealis (CFV) and C. fetus subsp. fetus (CFF). CFV is the causative agent of bovine genital campylobacteriosis, a highly contagious venereal disease that may lead to serious reproductive problems, including sterility and abortion. In contrast, CFF can be isolated from the gastrointestinal tract of a wide range of host species, is associated with abortion in sheep and cattle, and can also be isolated from local and systemic infections in humans. Despite differences in host and niche preferences, microbiological differentiation of the two subspecies of C. fetus is extremely difficult. This study describes the identification of a new insertion element, ISCfe1, which is present exclusively in CFV strains, with highly conserved specific ISCfe1 insertion sites. The results are useful for identification and differentiation of the two C. fetus subspecies and will help in understanding the evolution and pathogenesis of C. fetus.

Fatal relapse of a purulent pleurisy caused by Campylobacter fetus subsp. fetus

Campylobacter fetus is associated with invasive disease, while other Campylobacter species, such as C. coli and C. jejuni, are a common cause of bacterial diarrhea. Bacteremia has been well described, but pleurisy remains very uncommon. We report the recurrent isolation of a C. fetus subsp. fetus strain during two episodes of pleural effusion with a fatal outcome.