Genomic characterization and virulence gene profiling of Erysipelothrix rhusiopathiae isolated from widespread muskox mortalities in the Canadian Arctic Archipelago

BACKGROUND

Muskoxen are important ecosystem components and provide food, economic opportunities, and cultural well-being for Indigenous communities in the Canadian Arctic. Between 2010 and 2021, Erysipelothrix rhusiopathiae was isolated from carcasses of muskoxen, caribou, a seal, and an Arctic fox during multiple large scale mortality events in the Canadian Arctic Archipelago. A single strain ('Arctic clone') of E. rhusiopathiae was associated with the mortalities on Banks, Victoria and Prince Patrick Islands, Northwest Territories and Nunavut, Canada (2010-2017). The objectives of this study were to (i) characterize the genomes of E. rhusiopathiae isolates obtained from more recent muskox mortalities in the Canadian Arctic in 2019 and 2021; (ii) identify and compare common virulence traits associated with the core genome and mobile genetic elements (i.e. pathogenicity islands and prophages) among Arctic clone versus other E. rhusiopathiae genomes; and iii) use pan-genome wide association studies (GWAS) to determine unique genetic contents of the Arctic clone that may encode virulence traits and that could be used for diagnostic purposes.

RESULTS

Phylogenetic analyses revealed that the newly sequenced E. rhusiopathiae isolates from Ellesmere Island, Nunavut (2021) also belong to the Arctic clone. Of 17 virulence genes analysed among 28 Arctic clone isolates, four genes - adhesin, rhusiopathiae surface protein-A (rspA), choline binding protein-B (cbpB) and CDP-glycerol glycerophosphotransferase (tagF) - had amino acid sequence variants unique to this clone when compared to 31 other E. rhusiopathiae genomes. These genes encode proteins that facilitate E. rhusiopathiae to attach to the host endothelial cells and form biofilms. GWAS analyses using Scoary found several unique genes to be overrepresented in the Arctic clone.

CONCLUSIONS

The Arctic clone of E. rhusiopathiae was associated with multiple muskox mortalities spanning over a decade and multiple Arctic islands with distances over 1000 km, highlighting the extent of its spatiotemporal spread. This clone possesses unique gene content, as well as amino acid variants in multiple virulence genes that are distinct from the other closely related E. rhusiopathiae isolates. This study establishes an essential foundation on which to investigate whether these differences are correlated with the apparent virulence of this specific clone through in vitro and in vivo studies.

Abortion and fetal death in sows

Abortion in sows or the expulsion of foetuses between days 35 and 109 of gestation results in major financial losses. Abortion is the result of maternal failure due to factors interfering with either the endocrine control of pregnancy or causing endometrial damage. In addition, causes of fetal origin, due to infections with a special affinity for the fetus, can also lead to abortion. Many different non-infectious and infectious factors may be involved. Non-infectious risk factors include inappropriate ambient temperature, seasonal effects, different stress factors, and toxic substances. Microorganisms that may cause abortion can be classified as facultative pathogenic and specific pathogenic microorganisms. The first category includes mostly bacteria that are endemic in many pig farms and that are normally harmless commensals. They can cause abortion only in case of decreased immunity or other predisposing factors. Different specific pathogenic microorganisms, especially viruses and bacteria, can cause fetal death and abortion. Some may have a special affinity for the reproductive tract and the foetuses (e.g. Aujeszky's disease virus, parvovirus, Leptospira sp.), while others may cause clinical disease or fever in sows (e.g. swine influenza viruses, Erysipelothrix rhusiopathiae), subsequently leading to abortion. Diagnosis of fetal death and abortion is challenging due to the broad array of processes that may be involved, and the fact that the inciting cause may happen well in advance of the abortion. The diagnostic process should start with a thorough evaluation of the clinical problem and the farm. In case an infectious cause is suspected, proper samples should be collected, preferably from different sows and foetuses, for the detection of specific pathogens. Prevention of abortion mainly relies on the implementation of good management practices, hygiene and biosecurity measures, and for some pathogens also on vaccination.

Streptococcus gallolyticus and Bacterial Endocarditis in Swine, United States, 2015-2020

To evaluate trends in bacterial causes of valvular endocarditis in swine, we retrospectively analyzed 321 cases diagnosed at Iowa State University Veterinary Diagnostic Laboratory (Ames, IA, USA) during May 2015--April 2020. Streptococcus gallolyticus was the causative agent for 7.59% of cases. This emerging infection in swine could aid study of endocarditis in humans.

Use of Commercial Swine Live Attenuated Vaccine to Control an Erysipelothrix rhusiopathiae Outbreak in Commercial Cage-Free Layer Chickens

Erysipelothrix rhusiopathiae septicemia was diagnosed in three cage-free commercial layer flocks from Washington State that experienced an increase in mortality and slight drop in egg production. Erysipelothrix rhusiopathiae was isolated from multiple organs and from environmental samples. An agar gel diffusion test of several E. rhusiopathiae isolates confirmed the presence of serotype 1b, and multiplex real-time PCR of the surface protective antigen (Spa) gene confirmed presence of SpaA. Bacitracin administered via the water reduced mortality minimally and only for a short period of time. Mortality was finally controlled by vaccination with a live attenuated swine E. rhusiopathiae vaccine delivered via the drinking water. This is the first report describing the use of an attenuated vaccine to control an E. rhusiopathiae outbreak in a chicken flock.

Bacterial Diseases

Common marmosets are susceptible to a number of bacterial infections, which may be enzootic, causing sporadic but occasionally severe disease, or which may result in epizootics associated with more severe colony morbidity and mortality. The spectrum of these diseases often differs from those observed in macaque species, and veterinarians caring for common marmosets need to be aware of these unique susceptibilities. In formulating differential diagnoses for sick or diseased animals, it should be recognized that diseases once common in imported animals in the 1960s and 1970s are now rare. It is also important to recognize that housing and sanitation conditions can influence exposure to potentially pathogenic bacteria. In a zoological setting where mixed- or free-ranging exhibits are utilized, animals may be exposed to many more potential pathogens than would be the case in animals raised in a barrier facility.

Bacterial Genomics Reveal the Complex Epidemiology of an Emerging Pathogen in Arctic and Boreal Ungulates

Northern ecosystems are currently experiencing unprecedented ecological change, largely driven by a rapidly changing climate. Pathogen range expansion, and emergence and altered patterns of infectious disease, are increasingly reported in wildlife at high latitudes. Understanding the causes and consequences of shifting pathogen diversity and host-pathogen interactions in these ecosystems is important for wildlife conservation, and for indigenous populations that depend on wildlife. Among the key questions are whether disease events are associated with endemic or recently introduced pathogens, and whether emerging strains are spreading throughout the region. In this study, we used a phylogenomic approach to address these questions of pathogen endemicity and spread for Erysipelothrix rhusiopathiae, an opportunistic multi-host bacterial pathogen associated with recent mortalities in arctic and boreal ungulate populations in North America. We isolated E. rhusiopathiae from carcasses associated with large-scale die-offs of muskoxen in the Canadian Arctic Archipelago, and from contemporaneous mortality events and/or population declines among muskoxen in northwestern Alaska and caribou and moose in western Canada. Bacterial genomic diversity differed markedly among these locations; minimal divergence was present among isolates from muskoxen in the Canadian Arctic, while in caribou and moose populations, strains from highly divergent clades were isolated from the same location, or even from within a single carcass. These results indicate that mortalities among northern ungulates are not associated with a single emerging strain of E. rhusiopathiae, and that alternate hypotheses need to be explored. Our study illustrates the value and limitations of bacterial genomic data for discriminating between ecological hypotheses of disease emergence, and highlights the importance of studying emerging pathogens within the broader context of environmental and host factors.

Shaggy Lame Fox Syndrome in Pribilof Island Arctic Foxes ( Alopex lagopus pribilofensis), Alaska

A previously unrecognized condition is described in wild free-ranging Pribilof arctic foxes ( Alopex lagopus pribilofensis) from the Pribilof Islands, Alaska, USA. This condition is called shaggy lame fox syndrome (SLFS) denoting the primary clinical signs first observed. Criteria used to suspect SLFS on gross examination included emaciation, failure to shed winter pelage and moderate to severe polyarthritis. Criteria used to confirm SLFS histologically included polyarthritis (characterized by lymphoplasmacytic synovitis, tenosynovitis, bursitis, periosteal bony proliferation, and periarticular lymphoplasmacytic vasculitis) and systemic leukocytoclastic vasculitis. Other histological lesions often found included renal cortical infarcts, myocarditis with myocardial infarcts, lymphoplasmacytic meningitis, lymphoplasmacytic cuffing of meningeal and a few cerebral vessels, and cavitating infarcts of the brainstem and thalamus. The cause of SLFS is not known at this time; however, the gross and histological lesions suggest that the cause of SLFS may be a bacterial polyarthritis with a secondary immune-mediated vasculitis. These lesions are consistent with changes described with Erysipelothrix rhusiopathiae in domestic dogs; E. rhusiopathiae was identified from the synovial membrane of a swollen stifle joint and the kidney from one fox using real-time polymerase chain reaction and with culture from a fox that had gross and histological lesions of SLFS. Therefore, E. rhusiopathiae is a possible etiological agent for SLFS.

Genomic analysis of the multi-host pathogen Erysipelothrix rhusiopathiae reveals extensive recombination as well as the existence of three generalist clades with wide geographic distribution

Background

Knowledge about how bacterial populations are structured is an important prerequisite for studying their ecology and evolutionary history and facilitates inquiry into host specificity, pathogenicity, geographic dispersal and molecular epidemiology. Erysipelothrix rhusiopathiae is an opportunistic pathogen that is currently reemerging in both the swine and poultry industries globally. This bacterium sporadically causes mortalities in captive marine mammals, and has recently been implicated in large-scale wildlife die-offs. However, despite its economic relevance and broad geographic and host distribution, including zoonotic potential, the global diversity, recombination rates, and population structure of this bacterium remain poorly characterized. In this study, we conducted a broad-scale genomic comparison of E. rhusiopathiae based on a diverse collection of isolates in order to address these knowledge gaps.

Results

Eighty-three E. rhusiopathiae isolates from a range of host species and geographic origins, isolated between 1958 and 2014, were sequenced and assembled using both reference-based mapping and de novo assembly. We found that a high proportion of the core genome (58 %) had undergone recombination. Therefore, we used three independent methods robust to the presence of recombination to define the population structure of this species: a phylogenetic tree based on a set of conserved protein sequences, in silico chromosome painting, and network analysis. All three methods were broadly concordant and supported the existence of three distinct clades within the species E. rhusiopathiae. Although we found some evidence of host and geographical clustering, each clade included isolates from diverse host species and from multiple continents.

Conclusions

Using whole genome sequence data, we confirm recent suggestions that E. rhusiopathiae is a weakly clonal species that has been shaped extensively by homologous recombination. Despite frequent recombination, we can reliably identify three distinct clades that do not clearly segregate by host species or geographic origin. Our results provide an essential baseline for future molecular epidemiological, ecological and evolutionary studies of E. rhusiopathiae and facilitate comparisons to other recombinogenic, multi-host bacteria.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2643-0) contains supplementary material, which is available to authorized users.

Improving ante mortem diagnosis of Erysipelothrix rhusiopathiae infection by use of oral fluids for bacterial, nucleic acid, and antibody detection

Swine erysipelas is an economically important disease caused by Erysipelothrix rhusiopathiae. Pen-based collection of oral fluids has recently been utilized for monitoring infection dynamics in swine operations. The diagnostic performance of bacterial isolation, real-time PCR, and antibody detection by enzyme-linked immunosorbent assay (ELISA) and fluorescent microbead-based immunoassay (FMIA) methods were evaluated on pen-based oral fluid samples from pigs experimentally infected with E. rhusiopathiae (n=112) and from negative controls (n=32). While real-time PCR was a sensitive method with an overall detection rate of 100% (7/7 pens) one day post inoculation (dpi), E. rhusiopathiae was successfully isolated in only 28.6% (2/7 pens). Anti-Erysipelothrix IgM and IgG antibodies in pen-based oral fluids were detected at 4 to 5 dpi by FMIA and at 5 and 8 dpi by ELISA. The number of infected animals per pen, and in particular the timing of antimicrobial treatment administration impacted bacterial isolation and ELISA results. In oral fluid field samples, E. rhusiopathiae DNA was found in 23.3% of the samples while anti-E. rhusiopathiae IgG and IgM antibodies were found in 59.6% and 5.5% of the samples, respectively. The results suggest that an algorithm integrating oral fluids as specimen and real-time PCR and FMIA as detection methods is effective for earlier detection of an erysipelas outbreak thereby allowing for a more effective treatment outcome.

Development and evaluation of an enzyme-linked immunosorbent assay based on a recombinant SpaA protein (rSpaA415) for detection of anti-Erysipelothrix spp. IgG antibodies in pigs

The aim of this study was to develop an enzyme-linked immunosorbent assay (ELISA) for detection of anti-Erysipelothrix spp. IgG in pig sera by utilizing recombinant polypeptide SpaA415 (rSpaA415) based on surface protective antigen (Spa) A (SpaA) of Erysipelothrix spp. The sensitivity of the rSpaA415 ELISA was evaluated on sera from pigs experimentally infected with E. rhusiopathiae serotype 1a (n=72), serotype 19 (n=12), or experimentally vaccinated with a commercial attenuated-live vaccine based on serotype 1a (n=12), a commercial bacterin based on serotype 2 (n=12), or an experimental bacterin based on serotype 2 (n=300). Specificity was tested using 221 negative control samples. The earliest antibody response was detected at 7 days post-inoculation (dpi) and 14 days post-vaccination (dpv). At the cutoff of 0.9 sample optical density, the sensitivity was 96.5% and the specificity was 100%. In experimentally infected pigs, the sensitivity of the rSpaA415 ELISA ranged from 5.5 to 100% which improved as dpi increased. Antimicrobial treatment, administered prior to appearance of clinical signs, decreased assay sensitivity. In vaccinated pigs, the rSpaA415 ELISA had a sensitivity of 48.3-100%. Serum samples from rabbits each hyperimmunized with one of the 28 Erysipelothrix spp. serotypes were used to determine cross-reactivity with strains expressing SpaB, SpaC or no currently recognized Spa protein and antibodies against E. tonsillarum were not detected. These data suggest that the novel rSpaA415 ELISA test is a useful tool to detect anti-IgG antibodies against different serotypes of E. rhusiopathiae in infected or vaccinated pigs without cross-reacting with the economically less important E. tonsillarum strains.

The in vivo extracellular life of facultative intracellular bacterial parasites: role in pathogenesis

Classically labeled facultative intracellular pathogens are characterized by the ability to have an intracellular phase in the host, which is required for pathogenicity, while capable of extracellular growth in vitro. The ability of these bacteria to replicate in cell-free conditions is usually assessed by culture in artificial bacteriological media. However, the extracellular growth ability of these pathogens may also be expressed by a phase of extracellular infection in the natural setting of the host with pathologic consequences, an ability that adds to the pathogenic potential of the infectious agent. This infective capability to grow in the extracellular sites of the host represents an additional virulence attribute of those pathogens which may lead to severe outcomes. Here we discuss examples of infectious diseases where the in vivo infective extracellular life is well documented, including infections by Francisella tularensis, Yersinia pestis, Burkholderia pseudomallei, Burkholderia cenocepacia, Salmonella enterica serovar Typhimurium and Edwardsiella tarda. The occurrence of a phase of systemic dissemination with extracellular multiplication during progressive infections by facultative intracellular bacterial pathogens has been underappreciated, with most studies exclusively centered on the intracellular phase of the infections. The investigation of the occurrence of a dual lifestyle in the host among bacterial pathogens in general should be extended and likely will reveal more cases of infectious diseases with a dual infective intracellular/extracellular pattern.

Pig-shed air polluted by α-haemolytic cocci and ammonia causes subclinical disease and production losses

There is mounting evidence that bacteria originating from pigs degrade the environment of the pig shed and adversely affect the health of the animals and the pig-shed workers. α-haemolytic cocci (AHC) occur in pig-shed environments, but are regarded as commensals. Ammonia is also a component of the pig-shed environment, and is known to damage upper respiratory tract epithelia. The aim of this study was to determine whether polluted air in pig sheds adversely affected performance indicators in pigs. Modelling revealed a direct effect of AHC on voluntary feed intake and hence AHC are not commensal. No direct effect of ammonia on the pigs was detected, but the combination of AHC and ammonia stimulated the immune system in a progressive manner, and there were direct effects of immune stimulation on food intake and growth resulting in poorer feed-conversion efficiency, even though the effects remained subclinical. The authors conclude that exposure of the respiratory epithelia of pigs to viable AHC in the presence of ammonia redirects nutrients away from production and towards the immune system, explaining the impact of poor pig-shed hygiene on production parameters.

Classical labeling of bacterial pathogens according to their lifestyle in the host: inconsistencies and alternatives

An ample understanding of the complex interactions between host and pathogen will improve our ability to develop new prophylactic and therapeutic measures against infection. Precise classification of infectious agents in regards to their infective lifestyles in the host and corresponding pathogenic implications are required because clear concepts are essential to plan fruitful research. Classically, pathogenic bacteria are classified as extracellular, facultative intracellular, and obligate intracellular. In my opinion, this classification is inadequate because, as concluded from data here discussed, it is based on inconsistencies and hyper-valorizes the capacity of the infectious agent replicate in vitro in cell-free media. For a microbial pathogen, what matters is whether intra- or extracellularity is in the context of the in vivo life and in association with pathogenicity. When living as a pathogen in association with its host, what is relevant in microbiological terms is not the ability to grow in artificial cell-free bacteriological media or in environmental niches but whether the intracellular infectious agent, besides the phase of intracellular growth which is behind its label, also is able to live extracellularly in the natural settings of the extracellular territories of their hosts. To eliminate the inconsistencies associated with the classical labeling of bacterial pathogens, I propose that bacterial pathogens be labeled exclusive extracellular, dual intracellular/extracellular and exclusive intracellular based on their infective lifestyle in the host, not in the ability to grow in artificial bacteriological media.

Erysipelothrix Spp. Genotypes, Serotypes, and Surface Protective Antigen Types Associated with Abattoir Condemnations

The objective of the current study was to investigate characteristics of Erysipelothrix spp. from slaughter condemnations. Specimens from 70 carcasses with lesions suspect for swine erysipelas were collected at an abattoir in Iowa from October 2007 to February 2009. Erysipelothrix spp. were isolated from 59 of 70 carcasses (84.3%). Abattoir inspectors classified lesions as acute, subacute, or chronic; 8 of 8 (100%) were acute cases, 31 of 32 (96.9%) were subacute cases, and 20 of 30 (66.6%) were chronic cases that were isolation positive. The following serotypes were identified: 1a (40.7%; 24/59), 2 (49.2%; 29/59), 7 (1/59), 10 (1/59), 11 (1/59), and untypeable (5.1%; 3/59). Serotypes 1a and 2 were identified in pigs with acute, subacute, or chronic clinical manifestations, whereas serotypes 7, 10, and 11 were only present in chronic cases. Fifty-seven of the 59 isolates were determined to belong to E. rhusiopathiae, and 2 of 59 of the isolates were determined to be E. tonsillarum by multiplex real-time polymerase chain reaction. Surface protective antigen (spa) A was detected in all E. rhusiopathiae isolates but not in E. tonsillarum serotypes 7 and 10. The results of the present study indicate that E. rhusiopathiae serotypes 1a and 2 continue to be commonly isolated from condemned pig carcasses and that spaA is the exclusive spa type in U.S. abattoir isolates. Interestingly, E. tonsillarum, thought to be avirulent for swine, was isolated from systemic sites from 3.4% of the carcasses that were negative for E. rhusiopathiae, indicating the potential importance of this genotype in erysipelas pathogenesis.

Identification of surface protective antigen (spa) types in Erysipelothrix reference strains and diagnostic samples by spa multiplex real-time and conventional PCR assays

AIM

To develop spa multiplex real-time and conventional PCR assays to detect and differentiate between spaA, spaB and spaC genes within Erysipelothrix spp.

METHODS AND RESULTS

For evaluation of the assays, 28 Erysipelothrix spp. reference strains, 25 tissues from pigs inoculated with reference strains of serotypes 1, 2, 5, 10 or 18, and 15 diagnostic samples were used. SpaA was found to be present in Erysipelothrix rhusiopathiae serotypes 1a, 1b, 2, 5, 9, 12, 15, 16, 17, 23 and N; spaB was detected in E. rhusiopathiae serotypes 4, 6, 8, 11, 19 and 21 and spaC was detected in E. sp. strain 2 serotype 18. Spa-related genes were not detected in E. tonsillarum strains (serotypes 3, 7, 10, 14, 20, 22, 24, 25, 26) or E. sp. strain 1 (serotype 13). With the spa multiplex real-time PCR assay, it was also possible to further differentiate spaB into spaB1 (serotypes 4, 6, 8, 19 and 21) and spaB2 (serotype 11). Overall, spaA was detected in seven experimental tissue samples and six diagnostic tissue samples, and spaC in two experimental tissue samples. The detection limits were determined to be five colony-forming units (CFU) per reaction for the spa multiplex real-time PCR assay and 4000 CFU per reaction for the conventional PCR assay.

CONCLUSIONS

Both spa PCR assays were specific and reproducible in the identification of spa types in Erysipelothrix spp.

SIGNIFICANCE AND IMPACT OF THE STUDY

The described spa PCR assays may be useful tools for investigating spa prevalence among strains isolated from field tissues and to determine the role of the Spa proteins in vaccine protection and pathogenesis.

Characterization of Erysipelothrix species isolates from clinically affected pigs, environmental samples, and vaccine strains from six recent swine erysipelas outbreaks in the United States

The aim of this study was to characterize Erysipelothrix sp. isolates from clinically affected pigs and their environment and compare them to the Erysipelothrix sp. vaccines used at the sites. Samples were collected during swine erysipelas outbreaks in vaccinated pigs in six Midwest United States swine operations from 2007 to 2009. Pig tissue samples were collected from 1 to 3 pigs from each site. Environmental samples (manure, feed, central-line water, oral fluids, and swabs collected from walls, feed lines, air inlets, exhaust fans, and nipple drinkers) and live vaccine samples were collected following the isolation of Erysipelothrix spp. from clinically affected pigs. All Erysipelothrix sp. isolates obtained were further characterized by serotyping. Selected isolates were further characterized by PCR assays for genotype (E. rhusiopathiae, E. tonsillarum, Erysipelothrix sp. strain 1, and Erysipelothrix sp. strain 2) and surface protective antigen (spa) type (A, B1, B2, and C). All 26 isolates obtained from affected pigs were E. rhusiopathiae, specifically, serotypes 1a, 1b, 2, and 21. From environmental samples, 56 isolates were obtained and 52/56 were E. rhusiopathiae (serotypes 1a, 1b, 2, 6, 9, 12, and 21), 3/56 were Erysipelothrix sp. strain 1 (serotypes 13 and untypeable), and one was a novel species designated Erysipelothrix sp. strain 3 (serotype untypeable). Four of six vaccines used at the sites were commercially available products and contained live E. rhusiopathiae serotype 1a. Of the remaining two vaccines, one was an autogenous live vaccine and contained live E. rhusiopathiae serotype 2 and one was a commercially produced inactivated vaccine and was described by the manufacturer to contain serotype 2 antigen. All E. rhusiopathiae isolates were positive for spaA. All Erysipelothrix sp. strain 1 isolates and the novel Erysipelothrix sp. strain 3 isolate were negative for all currently known spa types (A, B1, B2, and C). These results indicate that Erysipelothrix spp. can be isolated from the environment of clinically affected pigs; however, the identified serotypes in pigs differ from those in the environment at the selected sites. At one of the six affected sites, the vaccine strain and the isolates from clinically affected pigs were of homologous serotype; however, vaccinal and clinical isolates were of heterologous serotype at the remaining five sites, suggesting that reevaluation of vaccine efficacy using recent field strains may be warranted.

Rapid detection and differentiation of Erysipelothrix spp. by a novel multiplex real-time PCR assay

AIM

The aim of this study was to develop a multiplex real-time PCR assay for the identification and discrimination of Erysipelothrix rhusiopathiae, tonsillarum and Erysipelothrix sp. strain 2 for direct detection of Erysipelothrix spp. from animal specimens.

METHODS AND RESULTS

A primer set and three species-specific probes with different end labelling were designed from the noncoding region downstream of the 5S rRNA coding region. The sensitivity, specificity and repeatability of the assay were validated by analysing 27 Erysipelothrix spp. reference serotype strains and ten septicemia-associated non-Erysipelothrix spp. bacterial isolates. Cross-reactivity with Erysipelothrix sp. strain 1 was not observed with any of the primer probe combinations. The detection limit was determined to be <10 colony forming units and as low as one genome equivalent per PCR . Further evaluation of the Erysipelothrix spp. multiplex PCR was performed by comparing an enrichment isolation culture method and a conventional differential PCR on 15 samples from pigs experimentally inoculated with Erysipelothrix spp. and 22 samples from pigs with suspected natural infection.

CONCLUSION

The multiplex real-time PCR assay was found to be simple, rapid, reliable, specific and highly sensitive.

SIGNIFICANCE AND IMPACT OF THE STUDY

The developed real-time multiplex PCR assay does not require cumbersome and lengthy cultivation steps prior to DNA extraction, obtained comparable results to enrichment isolation, and will be useful in diagnostic laboratories for rapid detection of Erysipelothrix spp.