Two biotypes of Corynebacterium pseudotuberculosis

Corynebacterium pseudotuberculosis: Whole genome sequencing reveals unforeseen and relevant genetic diversity in this pathogen

Corynebacterium pseudotuberculosis (CPS) is an important bacterial animal pathogen. CPS causes chronic, debilitating and currently incurable infectious diseases affecting a wide range of livestock and wild herbivores including camelids worldwide. Belonging to the Corynebacterium diphtheriae complex, this pathogen can also infect humans. The classical characterization of CPS is typically based on the testing of nitrate reductase activity, separating the two biovars Equi and Ovis. However, more refined resolutions are required to unravel routes of infection. This was realized in our study by generating and analyzing whole genome sequencing (WGS) data. Using newly created core genome multilocus sequence typing (cgMLST) profiles we were the first to discover isolates grouping in a cluster adjacent to clusters formed by CPS biovar Equi isolates. This novel cluster includes CPS isolates from alpacas, llamas, camels and dromedaries, which are characterized by a lack of nitrate reductase activity as encountered in biovar Ovis. This is of special interest for molecular epidemiology. Nevertheless, these isolates bear the genes of the nitrate locus, which are characteristic of biovar Equi isolates. However, sequence analysis of the genes narG and narH of the nitrate locus revealed indels leading to frameshifts and inactivity of the enzymes involved in nitrate reduction. Interestingly, one CPS isolate originating from another lama with an insertion in the MFS transporter (narT) is adjacent to a cluster formed by ovine CPS isolates biovar Equi. Based on this knowledge, the combination of biochemical and PCR based molecular biological nitrate reductase detection can be used for a fast and uncomplicated classification of isolates in routine diagnostics in order to check the origin of camelid CPS isolates. Further analysis revealed that partial sequencing of the ABC transporter substrate binding protein (CP258_RS07935) is a powerful tool to assign the biovars and the novel genomovar.

Ovine and Caprine Strains of Corynebacterium pseudotuberculosis on Czech Farms-A Comparative Study

Caseous lymphadenitis (CLA) is a worldwide disease of small ruminants caused by Corynebacterium pseudotuberculosis, a facultative intracellular pathogen that is able to survive and multiply in certain white blood cells of the host. In this study, 33 strains of C. pseudotuberculosis were isolated from sheep and goats suffering from CLA on nine farms in the Czech Republic. All these strains were tested for their antibiotic susceptibility, ability to form a biofilm and resistance to the effects of commonly used disinfectant agents. To better understand the virulence of C. pseudotuberculosis, the genomes of strains were sequenced and comparative genomic analysis was performed with another 123 genomes of the same species, including ovis and equi biovars, downloaded from the NCBI. The genetic determinants for the virulence factors responsible for adherence and virulence factors specialized for iron uptake and exotoxin phospholipase D were revealed in every analyzed genome. Carbohydrate-Active Enzymes were compared, revealing the presence of genetic determinants encoding exo-α-sialidase (GH33) and the CP40 protein in most of the analyzed genomes. Thirty-three Czech strains of C. pseudotuberculosis were identified as the biovar ovis on the basis of comparative genome analysis. All the compared genomes of the biovar ovis strains were highly similar regardless of their country of origin or host, reflecting their clonal behavior.

Surveillance of diphtheria in the Netherlands between 2000-2021: cutaneous diphtheria supersedes the respiratory form

BACKGROUND

Diphtheria is a severe respiratory or cutaneous infectious disease, caused by exotoxin producing Corynebacterium diphtheriae, C. ulcerans and C. pseudotuberculosis. Diphtheria is once again prevalent due to breakdown of immunisation programmes, social disruption and unrest.

AIM

This study describes the notified diphtheria cases in the Netherlands between 2000-2021 and isolates that were sent to the National Institute for Public Health and the Environment (RIVM).

METHODS

File investigation was performed including all notified cases and isolates of C. diphtheriae, C. ulcerans and C. pseudotuberculosis that were tested for toxin production using a toxin-PCR and Elek test. An exploratory review was performed to understand transmission in populations with a high vaccination uptake.

RESULTS

Eighteen diphtheria notifications were made with confirmed toxigenic C. diphtheriae (n = 9) or ulcerans (n = 9) between 2000 and 2021. Seventeen (94.4%) presented with a cutaneous infection. All cases with a suspected source abroad (n = 8) concerned infection with C. diphtheriae. In contrast, 9/10 cases infected in the Netherlands were caused by C. ulcerans, a zoonosis. Secondary transmission was not reported. Isolates of C. ulcerans sent to the RIVM produced more often the diphtheria exotoxin (11/31; 35%) than C. diphtheriae (7/89; 7.9%).

CONCLUSION

Both human-to-human transmission of C. diphtheriae and animal-to-human transmission of C. ulcerans rarely occurs in the Netherlands. Cases mainly present with a cutaneous infection. Travel-related cases remain a risk for transmission to populations with low vaccination coverage, highlighting the importance of immunization and diphtheria control measures.

Exploring the MALDI Biotyper for the Identification of Corynebacterium pseudotuberculosis biovar Ovis and Equi

Biochemical, serological, and molecular methods have been developed for the laboratory diagnosis of diseases caused by C. pseudotuberculosis (CP), but the identification of the pathogen and biovars differentiation may be time-consuming, expensive, and confusing compared with other bacteria. This study aimed to evaluate MALDI Biotyper and Overall Genome Relatedness Index (OGRI) analysis to optimize the identification and differentiation of biovars of C. pseudotuberculosis. Out of 230 strains isolated from several hosts and countries, 202 (87.8%) were precisely classified using MALDI Biotyper and the BioNumerics platform. The classification accuracies for the Ovis and Equi biovars were 80 (88.75%) and 82 (92.68%), respectively. When analyzing a sampling of these strains by Average Nucleotide Identity based on BLAST and TETRA analyses using genomic sequence data, it was possible to differentiate 100% of the strains in Equi and Ovis. Our data show that MALDI Biotyper and OGRI analysis help identify C. pseudotuberculosis at the species and biovar levels.

A journey through the Corynebacterium pseudotuberculosis proteome promotes insights into its functional genome

Background

Corynebacterium pseudotuberculosis is a Gram-positive facultative intracellular pathogen and the etiologic agent of illnesses like caseous lymphadenitis in small ruminants, mastitis in dairy cattle, ulcerative lymphangitis in equines, and oedematous skin disease in buffalos. With the growing advance in high-throughput technologies, genomic studies have been carried out to explore the molecular basis of its virulence and pathogenicity. However, data large-scale functional genomics studies are necessary to complement genomics data and better understating the molecular basis of a given organism. Here we summarize, MS-based proteomics techniques and bioinformatics tools incorporated in genomic functional studies of C. pseudotuberculosis to discover the different patterns of protein modulation under distinct environmental conditions, and antigenic and drugs targets.

Methodology

In this study we performed an extensive search in Web of Science of original and relevant articles related to methods, strategy, technology, approaches, and bioinformatics tools focused on the functional study of the genome of C. pseudotuberculosis at the protein level.

Results

Here, we highlight the use of proteomics for understating several aspects of the physiology and pathogenesis of C. pseudotuberculosis at the protein level. The implementation and use of protocols, strategies, and proteomics approach to characterize the different subcellular fractions of the proteome of this pathogen. In addition, we have discussed the immunoproteomics, immunoinformatics and genetic tools employed to identify targets for immunoassays, drugs, and vaccines against C. pseudotuberculosis infection.

Conclusion

In this review, we showed that the combination of proteomics and bioinformatics studies is a suitable strategy to elucidate the functional aspects of the C. pseudotuberculosis genome. Together, all information generated from these proteomics studies allowed expanding our knowledge about factors related to the pathophysiology of this pathogen.

Molecular Characterization of Corynebacterium pseudotuberculosis Isolated over a 15-Year Period in Switzerland

Corynebacterium pseudotuberculosis biovar Ovis is the etiological agent of the contagious and chronic disease caseous lymphadenitis (CLA) in sheep and goats. The economic impact of CLA in Switzerland remains largely unknown, and the transmission modalities, as well as the genetic diversity of circulating strains, are poorly understood. This work presents further characterization data for 215 C. pseudotuberculosis isolates from sheep, goats and a dromedary originating from Switzerland and the Principality of Liechtenstein, collected over a 15-year period. The isolates were classified into the two biovars Ovis and Equi, analyzed for the presence of the diphtheria-like toxin gene and characterized using MLSA. All sheep and goat isolates were classified as C. pseudotuberculosis biovar Ovis. The isolate from a dromedary was classified as biovar Equi. No isolates harboring the diphtheria-like toxin gene were detected. Phylogenetic analysis of the concatenated sequences of four genes revealed the existence of 24 clusters. There was no correlation between MLSA sequence types, year of isolation and the geographical origin of the isolates. These findings confirm the presence of several MLSA sequence types in the study area and over a 15-year period. Moreover, no sheep- and goat-specific MLSA sequence types were found.

Microbiological assessment of sheep lymph nodes with lymphadenitis found during post-mortem examination of slaughtered sheep: implications for veterinary-sanitary meat control

Background

Microbiological examination of lesions found in slaughtered animals during meat inspection is an important part of public health protection as such lesions may be due to zoonotic agents that can be transmitted by meat. Examination of inflamed lymph nodes also plays a particular important role, as lymphadenitis may reflect a more widespread infection. Such lesions in sheep are mainly caused by pyogenic bacteria but also mycobacteria are occasionally found. Meat inspection data from 2017 to 2018 from southern Poland, especially from the Małopolska region, indicate that purulent or caseous lymphadenitis involving the mediastinal and tracheobronchial lymph nodes (MTLNs) is a common finding. The primary aim of the current study was to determine the aetiology of these lesions. Furthermore, it was investigated how presence of lesions was correlated with age and grazing strategy of affected sheep.

Results

Post-mortem examination revealed purulent or caseous lymphadenitis in the MTLNs of 49 out of 284 animals (17.3%). Subsequent microbiological examination revealed the presence of Corynebacterium pseudotuberculosis (34.7%), Streptococcus dysgalactiae subsp. equisimilis (34.7%), Staphylococcus aureus (8.2%), Enterococcus spp. (2.0%), Trueperella pyogenes (2.0%), and β-haemolytic strains of Escherichia coli (2.0%). Mycobacterium spp. and Rhodococcus equi were not detected. In older sheep, the probability of the presence of purulent or caseous lymphadenitis was higher than in younger, and the risk was increasing by 1.5% with each month of life. Sheep grazing locally had 4.5-times greater risk of having purulent or caseous lymphadenitis than individuals summer grazing in the mountains.

Conclusion

The most common aetiological agents of purulent or caseous lymphadenitis in the MTLNs of sheep in the Małopolska region were C. pseudotuberculosis and S. dysgalactiae subsp. equisimilis. Particular attention during post-mortem examination should be paid to the carcasses of older sheep and sheep grazing on permanent pastures, as they seem more prone to develop purulent or caseous lymphadenitis.

A comparative pan-genomic analysis of 53 C. pseudotuberculosis strains based on functional domains

Corynebacterium pseudotuberculosis is a pathogenic bacterium with great veterinary and economic importance. It is classified into two biovars: ovis, nitrate-negative, that causes lymphadenitis in small ruminants and equi, nitrate-positive, causing ulcerative lymphangitis in equines. With the explosive growth of available genomes of several strains, pan-genome analysis has opened new opportunities for understanding the dynamics and evolution of C. pseudotuberculosis. However, few pan-genomic studies have compared biovars equi and ovis. Such studies have considered a reduced number of strains and compared entire genomes. Here we conducted an original pan-genome analysis based on protein sequences and their functional domains. We considered 53 C. pseudotuberculosis strains from both biovars isolated from different hosts and countries. We have analysed conserved domains, common domains more frequently found in each biovar and biovar-specific (unique) domains. Our results demonstrated that biovar equi is more variable; there is a significant difference in the number of proteins per strains, probably indicating the occurrence of more gene loss/gain events. Moreover, strains of biovar equi presented a higher number of biovar-specific domains, 77 against only eight in biovar ovis, most of them are associated with virulence mechanisms. With this domain analysis, we have identified functional differences among strains of biovars ovis and equi that could be related to niche-adaptation and probably help to better understanding mechanisms of virulence and pathogenesis. The distribution patterns of functional domains identified in this work might have impacts on bacterial physiology and lifestyle, encouraging the development of new diagnoses, vaccines, and treatments for C. pseudotuberculosis diseases.Communicated by Ramaswamy H. Sarma.

Atypical Multibacterial Granulomatous Myositis in a Horse: First Report in Italy

Infectious causes of myositis are reported relatively uncommonly in horses. Among them, bacterial causes include Streptococcus equi subsp. zooepidemicus, Actinobacillus equuli, Fusobacterium spp. Staphylococcus spp, and Corynebacterium pseudotuberculosis. Infection can be spread to muscles via haematogenous or extension from skin lesions. Parasitic myositis has also been documented. In this report, a 12 year-old Italian Quarter Horse mare presented with diffuse subcutaneous nodules and masses ranging from 2 × 3 to 5 × 20 cm in size, and adherent to subcutis and muscles that were first macroscopically and cytologically diagnosed as pyogranulomas. Subsequently, histological, molecular, bacteriological, and biochemical investigations were performed. All the data obtained allowed to diagnose a severe and diffuse multibacterial granulomatous myositis caused by Corynebacterium pseudotuberculosis and Corynebacterium amycolatum. Following the therapy and an initial disappearance of most of the lesions together with a general improvement of the mare, the clinical condition deteriorated, and new nodules appeared. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and PCR techniques revealed the presence of bacteria as Glutamicibacter creatinolyticus and Dietzia spp. To the authors’ knowledge, this case report represents the first description of multibacterial granulomatous myositis due to Corynebacterium pseudotuberculosis, Corynebacterium amycolatum, Glutamicibacter creatinolyticus, and Dietzia spp. in a horse reared in Italy.

Rapidly evolving changes and gene loss associated with host switching in Corynebacterium pseudotuberculosis

Phylogenomics and genome scale positive selection analyses were performed on 29 Corynebacterium pseudotuberculosis genomes that were isolated from different hosts, including representatives of the Ovis and Equi biovars. A total of 27 genes were identified as undergoing adaptive changes. An analysis of the clades within this species and these biovars, the genes specific to each branch, and the genes responding to selective pressure show clear differences, indicating that adaptation and specialization is occurring in different clades. These changes are often correlated with the isolation host but could indicate responses to some undetermined factor in the respective niches. The fact that some of these more-rapidly evolving genes have homology to known virulence factors, antimicrobial resistance genes and drug targets shows that this type of analysis could be used to identify novel targets, and that these could be used as a way to control this pathogen.

First genome sequencing and comparative analyses of Corynebacterium pseudotuberculosis strains from Mexico

Corynebacterium pseudotuberculosis is a pathogenic bacterium which has been rapidly spreading all over the world, causing economic losses in the agricultural sector and sporadically infecting humans. Six C. pseudotuberculosis strains were isolated from goats, sheep, and horses with distinct abscess locations. For the first time, Mexican genomes of this bacterium were sequenced and studied in silico. All strains were sequenced using Ion Personal Genome Machine sequencer, assembled using Newbler and SPAdes software. The automatic genome annotation was done using the software RAST and in-house scripts for transference, followed by manual curation using Artemis software and BLAST against NCBI and UniProt databases. The six genomes are publicly available in NCBI database. The analysis of nucleotide sequence similarity and the generated phylogenetic tree led to the observation that the Mexican strains are more similar between strains from the same host, but the genetic structure is probably more influenced by transportation of animals between farms than host preference. Also, a putative drug target was predicted and in silico analysis of 46 strains showed two gene clusters capable of differentiating the biovars equi and ovis: Restriction Modification system and CRISPR-Cas cluster.

Multilocus Sequencing of Corynebacterium pseudotuberculosis Biotype Ovis Strains

Thirteen Corynebacterium pseudotuberculosis biotype ovis strains isolated from clinical cases of caseous lymphadenitis in Hungary were characterised using multilocus sequencing and their phylogenetic comparison was carried out on the basis of four housekeeping genes (groEL1, infB, dnaK, and leuA). The in silico analysis of the 16 frequently studied housekeeping genes showed that C. pseudotuberculosis strains could be readily distinguished from C. diphtheriae and C. ulcerans strains; however, sequences of the same genes in the two biotypes of the C. pseudotuberculosis were highly similar; the heterogeneity values were low. Genes dnaK, infB, groEL1, and leuA showed marked genetic variation within C. pseudotuberculosis, and strains of the two biotypes of C. pseudotuberculosis could be differentiated. Analysis of the individual genes showed a fairly conservative nature of C. pseudotuberculosis biotype ovis strains. The greatest genetic differentiation was seen in the dnaK and infB genes and concatenations of these two genes were very useful in the genetic separation of the studied strains.

Quadruplex PCR assay for identification of Corynebacterium pseudotuberculosis differentiating biovar Ovis and Equi

BACKGROUND

Corynebacterium pseudotuberculosis is classified into two biovars, nitrate-negative biovar Ovis which is the etiologic agent of caseous lymphadenitis in small ruminants and nitrate-positive biovar Equi, which causes abscesses and ulcerative lymphangitis in equines. The aim of this study was to develop a quadruplex PCR assay that would allow simultaneous detection and biovar-typing of C. pseudotuberculosis.

METHODS

In the present study, genomes of C. pseudotuberculosis strains were used to identify the genes involved in the nitrate reduction pathway to improve a species identification three-primer multiplex PCR assay. The nitrate reductase gene (narG) was included in the PCR assay along with the 16S, rpoB and pld genes to enhance the diagnosis of the multiplex PCR at biovar level.

RESULTS

A novel quadruplex PCR assay for C. pseudotuberculosis species and biovar identification was developed. The results of the quadruplex PCR of 348 strains, 346 previously well-characterized clinical isolates of C. pseudotuberculosis from different hosts (goats, sheep, horse, cattle, buffalo, llamas and humans), the vaccine strain 1002 and the type strain ATCC 19410T, were compared to the results of nitrate reductase identification by biochemical test. The McNemar's Chi-squared test used to compare the two methods used for C. pseudotuberculosis biovar identification showed no significant difference (P = 0.75) [95% CI for odds ratio (0.16-6.14)] between the quadruplex PCR and the nitrate biochemical test. Concordant results were observed for 97.13% (338 / 348) of the tested strains and the kappa value was 0.94 [95% CI (0.90-0.98)].

CONCLUSIONS

The ability of the quadruplex assay to discriminate between C. pseudotuberculosis biovar Ovis and Equi strains enhances its usefulness in the clinical microbiology laboratory.

Comparative genomic analysis between Corynebacterium pseudotuberculosis strains isolated from buffalo

Corynebacterium pseudotuberculosis is a Gram-positive, pleomorphic, facultative intracellular pathogen that causes Oedematous Skin Disease (OSD) in buffalo. To better understand the pathogenic mechanisms of OSD, we performed a comparative genomic analysis of 11 strains of C. pseudotuberculosis isolated from different buffalo found to be infected in Egypt during an outbreak that occurred in 2008. Sixteen previously described pathogenicity islands (PiCp) were present in all of the new buffalo strains, but one of them, PiCp12, had an insertion that contained both a corynephage and a diphtheria toxin gene, both of which may play a role in the adaptation of C. pseudotuberculosis to this new host. Synteny analysis showed variations in the site of insertion of the corynephage during the same outbreak. A gene functional comparison showed the presence of a nitrate reductase operon that included genes involved in molybdenum cofactor biosynthesis, which is necessary for a positive nitrate reductase phenotype and is a possible adaptation for intracellular survival. Genomes from the buffalo strains also had fusions in minor pilin genes in the spaA and spaD gene cluster (spaCX and spaYEF), which could suggest either an adaptation to this particular host, or mutation events in the immediate ancestor before this particular epidemic. A phylogenomic analysis confirmed a clear separation between the Ovis and Equi biovars, but also showed what appears to be a clustering by host species within the Equi strains.

Genomic analysis of four strains of Corynebacterium pseudotuberculosis bv. Equi isolated from horses showing distinct signs of infection

The genomes of four strains (MB11, MB14, MB30, and MB66) of the species Corynebacterium pseudotuberculosis biovar equi were sequenced on the Ion Torrent PGM platform, completely assembled, and their gene content and structure were analyzed. The strains were isolated from horses with distinct signs of infection, including ulcerative lymphangitis, external abscesses on the chest, or internal abscesses on the liver, kidneys, and lungs. The average size of the genomes was 2.3 Mbp, with 2169 (Strain MB11) to 2235 (Strain MB14) predicted coding sequences (CDSs). An optical map of the MB11 strain generated using the KpnI restriction enzyme showed that the approach used to assemble the genome was satisfactory, producing good alignment between the sequence observed in vitro and that obtained in silico. In the resulting Neighbor-Joining dendrogram, the C. pseudotuberculosis strains sequenced in this study were clustered into a single clade supported by a high bootstrap value. The structural analysis showed that the genomes of the MB11 and MB14 strains were very similar, while the MB30 and MB66 strains had several inverted regions. The observed genomic characteristics were similar to those described for other strains of the same species, despite the number of inversions found. These genomes will serve as a basis for determining the relationship between the genotype of the pathogen and the type of infection that it causes.

Assessing the Genotypic Differences between Strains of Corynebacterium pseudotuberculosis biovar equi through Comparative Genomics

Seven genomes of Corynebacterium pseudotuberculosis biovar equi were sequenced on the Ion Torrent PGM platform, generating high-quality scaffolds over 2.35 Mbp. This bacterium is the causative agent of disease known as "pigeon fever" which commonly affects horses worldwide. The pangenome of biovar equi was calculated and two phylogenomic approaches were used to identify clustering patterns within Corynebacterium genus. Furthermore, other comparative analyses were performed including the prediction of genomic islands and prophages, and SNP-based phylogeny. In the phylogenomic tree, C. pseudotuberculosis was divided into two distinct clades, one formed by nitrate non-reducing species (biovar ovis) and another formed by nitrate-reducing species (biovar equi). In the latter group, the strains isolated from California were more related to each other, while the strains CIP 52.97 and 1/06-A formed the outermost clade of the biovar equi. A total of 1,355 core genes were identified, corresponding to 42.5% of the pangenome. This pangenome has one of the smallest core genomes described in the literature, suggesting a high genetic variability of biovar equi of C. pseudotuberculosis. The analysis of the similarity between the resistance islands identified a higher proximity between the strains that caused more severe infectious conditions (infection in the internal organs). Pathogenicity islands were largely conserved between strains. Several genes that modulate the pathogenicity of C. pseudotuberculosis were described including peptidases, recombination enzymes, micoside synthesis enzymes, bacteriocins with antimicrobial activity and several others. Finally, no genotypic differences were observed between the strains that caused the three different types of infection (external abscess formation, infection with abscess formation in the internal organs, and ulcerative lymphangitis). Instead, it was noted that there is a higher phenetic correlation between strains isolated at California compared to the other strains. Additionally, high variability of resistance islands suggests gene acquisition through several events of horizontal gene transfer.

Molecular epidemiology of Corynebacterium pseudotuberculosis isolated from horses in California

Corynebacterium pseudotuberculosis biovar Equi is an important pathogen of horses. It is increasing in frequency in the United States, and is responsible for various clinical forms of infection, including external abscesses, internal abscesses of the abdominal or thoracic cavities, and ulcerative lymphangitis. The host/pathogen factors dictating the form or severity of infection are currently unknown. Our recent investigations have shown that genotyping C. pseudotuberculosis isolates using enterobacterial repetitive intergenic consensus (ERIC)-PCR is useful for understanding the evolutionary genetics of the species as well for molecular epidemiology studies. The aims of the present study were to assess (i) the genetic diversity of C. pseudotuberculosis strains isolated from horses in California, United States and (ii) the epidemiologic relationships among isolates. One hundred and seven C. pseudotuberculosis biovar Equi isolates from ninety-five horses, and two C. pseudotuberculosis biovar Ovis strains, C. pseudotuberculosis ATCC 19410^T type strain and C. pseudotuberculosis 1002 vaccine strain, were fingerprinted using the ERIC 1+2-PCR. C. pseudotuberculosis isolated from horses showed a high genetic diversity, clustering in twenty-seven genotypes with a diversity index of 0.91. Minimal spanning tree showed four major clonal complexes with a pattern of temporal clustering. Strains isolated from the same horse showed identical ERIC 1+2-PCR genotype, with the exception of two strains isolated from the same animal that showed distinct genotypes, suggesting a co-infection. We found no strong genetic signals related to clinical form (including internal versus external infections). However, temporal clustering of genotypes was observed.

Experimental transmission of Corynebacterium pseudotuberculosis biovar equi in horses by house flies

BACKGROUND

The route of Corynebacterium pseudotuberculosis infection in horses remains undetermined, but transmission by insects is suspected.

OBJECTIVES

To investigate house flies (Musca domestica L.) as vectors of C. pseudotuberculosis transmission in horses.

ANIMALS

Eight healthy, adult ponies.

METHODS

Randomized, controlled, blinded prospective study. Ten wounds were created in the pectoral region where cages for flies were attached. Three ponies were directly inoculated with C. pseudotuberculosis. Four ponies were exposed for 24 hours to 20 hours C. pseudotuberculosis-inoculated flies. One negative control pony was exposed to noninoculated flies. Ponies were examined daily for swelling, heat, pain, and drainage at the inoculation site. Blood was collected weekly for CBC and biochemical analysis, and twice weekly for synergistic hemolysis inhibition titers.

RESULTS

Clinical signs of local infection and positive cultures were observed in 7/7 exposed ponies and were absent in the negative control. In exposed ponies, peak serologic titers (1:512 to 1:2,048) were obtained between days 17 and 21. Seroconversion was not observed in the negative control. Neutrophil counts were higher in the positive and fly-exposed groups than in the negative control (P = .002 and P = .005) on day 3 postinoculation. Serum amyloid A concentrations were higher in the positive control than in the negative control and fly-exposed ponies on days 3 (P < .0001) and 7 (P = .0004 and P = .0001). No differences were detected for other biochemical variables.

CONCLUSIONS AND CLINICAL IMPORTANCE

House flies can serve as mechanical vectors of C. pseudotuberculosis and can transmit the bacterium to ponies.

The relationship between Corynebacterium pseudotuberculosis biovar equi phenotype with location and extent of lesions in horses

Equine infection with Corynebacterium pseudotuberculosis can manifest in several forms, including external or internal abscesses. The objective of this study was to phenotype clinical isolates of C. pseudotuberculosis and to investigate the relationship between lesion location and extent of lesions in the animals from which they were collected. One hundred and seventy-one C. pseudotuberculosis biovar equi isolates were collected from horses presenting to the University of California Veterinary Medical Teaching Hospital and two other sources in the period between September 1996 and December 2011. Bacterial isolates were grouped on the bases of biochemical characteristics and growth on brain heart infusion agar. Six phenotypes were identified: (1) large colonies that metabolized sucrose (n = 81); (2) large sucrose-negative colonies (n = 47); (3) medium sucrose-positive (n = 20); (4) medium sucrose-negative (n = 11); (5) small sucrose-positive (n = 7), and (6) small sucrose-negative (n = 5). Medical records corresponding to each isolate were accessed from the University's administrative computer system or from the submitting source in order to determine the anatomical site from which the isolate was collected (n = 171), as well as the extent of lesions (n = 164) in the patient. The relationship between phenotype, lesion location and extent of lesions was then investigated statistically. No significant relationship between strain and lesion location or extent of lesions was found. This suggests that phenotypic differences during in vitro culture does not account for external versus internal disease in horses. Further work to characterize strains genotypically and to identify determinants for bacterial virulence should be performed. Importantly, host and environmental factors should also be further investigated.

Ion Torrent-based transcriptional assessment of a Corynebacterium pseudotuberculosis equi strain reveals denaturing high-performance liquid chromatography a promising rRNA depletion method

Corynebacterium pseudotuberculosis equi is a Gram-positive pathogenic bacterium which affects a variety of hosts. Besides the great economic losses it causes to horse-breeders, this organism is also known to be an important infectious agent to cattle and buffaloes. As an outcome of the efforts in characterizing the molecular basis of its virulence, several complete genome sequences were made available in recent years, enabling the large-scale assessment of genes throughout distinct isolates. Meanwhile, the RNA-seq stood out as the technology of choice for comprehensive transcriptome studies, which may bring valuable information regarding active genomic regions, despite of the still impeditive associated costs. In an attempt to increase the use of generated reads per instrument run, by effectively eliminating unwanted rRNAs from total RNA samples without relying on any commercially available kits, we applied denaturing high-performance liquid chromatography (DHPLC) as an alternative method to assess the transcriptional profile of C. pseudotuberculosis. We have found that the DHPLC depletion method, allied to Ion Torrent sequencing, allows mapping of transcripts in a comprehensive way and identifying novel transcripts when a de novo approach is used. These data encourage us to use DHPLC in future transcriptional evaluations in C. pseudotuberculosis.

The pan-genome of the animal pathogen Corynebacterium pseudotuberculosis reveals differences in genome plasticity between the biovar ovis and equi strains

Corynebacterium pseudotuberculosis is a facultative intracellular pathogen and the causative agent of several infectious and contagious chronic diseases, including caseous lymphadenitis, ulcerative lymphangitis, mastitis, and edematous skin disease, in a broad spectrum of hosts. In addition, Corynebacterium pseudotuberculosis infections pose a rising worldwide economic problem in ruminants. The complete genome sequences of 15 C. pseudotuberculosis strains isolated from different hosts and countries were comparatively analyzed using a pan-genomic strategy. Phylogenomic, pan-genomic, core genomic, and singleton analyses revealed close relationships among pathogenic corynebacteria, the clonal-like behavior of C. pseudotuberculosis and slow increases in the sizes of pan-genomes. According to extrapolations based on the pan-genomes, core genomes and singletons, the C. pseudotuberculosis biovar ovis shows a more clonal-like behavior than the C. pseudotuberculosis biovar equi. Most of the variable genes of the biovar ovis strains were acquired in a block through horizontal gene transfer and are highly conserved, whereas the biovar equi strains contain great variability, both intra- and inter-biovar, in the 16 detected pathogenicity islands (PAIs). With respect to the gene content of the PAIs, the most interesting finding is the high similarity of the pilus genes in the biovar ovis strains compared with the great variability of these genes in the biovar equi strains. Concluding, the polymerization of complete pilus structures in biovar ovis could be responsible for a remarkable ability of these strains to spread throughout host tissues and penetrate cells to live intracellularly, in contrast with the biovar equi, which rarely attacks visceral organs. Intracellularly, the biovar ovis strains are expected to have less contact with other organisms than the biovar equi strains, thereby explaining the significant clonal-like behavior of the biovar ovis strains.

Use of antibody titers measured via serum synergistic hemolysis inhibition testing to predict internal Corynebacterium pseudotuberculosis infection in horses

OBJECTIVE

To estimate likelihood ratios (LRs) of correctly identifying internal Corynebacterium pseudotuberculosis infection in horses by measurement of antibody titers via serum synergistic hemolysis inhibition (SHI) testing.

DESIGN

Retrospective case-control study.

ANIMALS

170 horses (171 records; 92 cases of C pseudotuberculosis infection and 79 controls).

PROCEDURES

Medical records were reviewed, and horses were grouped on the basis of evidence of internal or external C pseudotuberculosis infection. The LRs and 95% confidence intervals for identification of internal C pseudotuberculosis infection by use of SHI test results were estimated.

RESULTS

LRs for C pseudotuberculosis infection increased as antibody titers increased when all horses were included in analyses; LRs for detecting internal infection were significantly > 1 (null value) for reciprocal antibody titers ≥ 1,280 overall and > 160 when horses with external abscesses were excluded. Likelihood ratios for detecting internal infection did not differ from 1 (indicating no change in pretest-to-posttest odds of internal infection) when only horses with external C pseudotuberculosis infection (horses with external and internal abscesses vs those with external abscesses only) were included. The LR for detecting internal infection was 2.98 (95% confidence interval, 2.19 to 4.05) for horses with titers ≥ 512.

CONCLUSIONS AND CLINICAL RELEVANCE

In the study population, higher titers were typically more indicative of active external or internal C pseudotuberculosis infection than of internal disease specifically. The SHI test was not a useful predictor of internal C pseudotuberculosis infection in horses with external abscesses but was useful in the absence of external disease.

Complete genome sequence of Corynebacterium pseudotuberculosis biovar ovis strain P54B96 isolated from antelope in South Africa obtained by rapid next generation sequencing technology

The Actinobacteria, Corynebacterium pseudotuberculosis strain P54B96, a nonmotile, non-sporulating and a mesophile bacterium, was isolated from liver, lung and mediastinal lymph node lesions in an antelope from South Africa. This strain is interesting in the sense that it has been found together with non-tuberculous mycobacteria (NTMs) which could nevertheless play a role in the lesion formation. In this work, we describe a set of features of C. pseudotuberculosis P54B96, together with the details of the complete genome sequence and annotation. The genome comprises of 2.34 Mbp long, single circular genome with 2,084 protein-coding genes, 12 rRNA, 49 tRNA and 62 pseudogenes and a G+C content of 52.19%. The analysis of the genome sequence provides means to better understanding the molecular and genetic basis of virulence of this bacterium, enabling a detailed investigation of its pathogenesis.

Genome sequence of Corynebacterium pseudotuberculosis biovar equi strain 258 and prediction of antigenic targets to improve biotechnological vaccine production

Corynebacterium pseudotuberculosis is the causative agent of several veterinary diseases in a broad range of economically important hosts, which can vary from caseous lymphadenitis in sheep and goats (biovar ovis) to ulcerative lymphangitis in cattle and horses (biovar equi). Existing vaccines against C. pseudotuberculosis are mainly intended for small ruminants and, even in these hosts, they still present remarkable limitations. In this study, we present the complete genome sequence of C. pseudotuberculosis biovar equi strain 258, isolated from a horse with ulcerative lymphangitis. The genome has a total size of 2,314,404 bp and contains 2088 predicted protein-coding regions. Using in silico analysis, eleven pathogenicity islands were detected in the genome sequence of C. pseudotuberculosis 258. The application of a reverse vaccinology strategy identified 49 putative antigenic proteins, which can be used as candidate vaccine targets in future works.

Corynebacterium pseudotuberculosis and its role in ovine caseous lymphadenitis

Caseous lymphadenitis (CLA) of sheep, caused by Corynebacterium pseudotuberculosis, has been a significant disease in the majority of sheep-rearing regions for over a century. Because of the chronic and often sub-clinical nature of the infection, it has proved difficult to control and prevalence is high in many parts of the world, which in turn leads to significant economic losses for farmers. This review describes the important characteristics of C. pseudotuberculosis and examines the pathogenesis and epidemiology of the infection in sheep. The review also discusses the immune response to infection and describes the methods that have been developed to control CLA, with particular emphasis on the use of vaccination and serological testing.

Molecular genotyping of multinational ovine and caprine Corynebacterium pseudotuberculosis isolates using pulsed-field gel electrophoresis

Caseous lymphadenitis (CLA) is a chronic, suppurative disease, with a worldwide distribution, caused by Corynebacterium pseudotuberculosis. The clinical manifestation of CLA is known to vary between different countries, and has been postulated to be due to differences in the strains present in these countries. Forty-two sheep and goat isolates of C. pseudotuberculosis from Australia, Canada, Eire, The Netherlands and Northern Ireland were characterized by pulsed-field gel electrophoresis (PFGE), biotyping, antimicrobial susceptibility, and production of phospholipase D. The PFGE-determined genotypes of this multicentric collection were then compared with representative ovine and caprine isolates from a previously published panel of PFGE profiles of United Kingdom isolates. Digestion with SfiI generated 16-18 bands in the 48.5 and 290 kb range, and differentiated four distinct pulsotypes amongst the 36 ovine and 6 caprine strains which displayed remarkable homogeneity. Based on these results, it would appear that the genome of C. pseudotuberculosis is highly conserved, irrespective of the country of strain origin.

Multiplex PCR assay for identification of Corynebacterium pseudotuberculosis from pure cultures and for rapid detection of this pathogen in clinical samples

Corynebacterium pseudotuberculosis is the aetiological agent of caseous lymphadenitis (CLA), a debilitating disease of sheep and goats. Accurate diagnosis of CLA primarily relies on microbiological examination, followed by biochemical identification of isolates. In an effort to facilitate C. pseudotuberculosis detection, a multiplex PCR (mPCR) assay was developed targeting three genes of this bacterium: the 16S rRNA gene, rpoB and pld. This method allowed efficient identification of 40 isolates of this bacterium that had been identified previously by biochemical testing. Analysis of taxonomically related species did not generate the C. pseudotuberculosis mPCR amplification profile, thereby demonstrating the assay's specificity. As little as 1 pg of C. pseudotuberculosis genomic DNA was detected by this mPCR assay, demonstrating the sensitivity of the method. The detection limit in clinical samples was estimated to be 10(3) c.f.u. C. pseudotuberculosis could be detected directly in pus samples from infected sheep and goats (n=56) with a high diagnostic sensitivity (94.6 %). The developed assay significantly improves rapid C. pseudotuberculosis detection and could supersede bacteriological culture for microbiological and epidemiological diagnosis of CLA.

A herd level analysis of a Corynebacterium pseudotuberculosis outbreak in a dairy cattle herd

Corynebacterium pseudotuberculosis infection in an Israeli dairy cattle herd is described. The disease was characterized by ulcerative granulomatous lesions, which occurred in an epidemic form. Thirty-two cows and two heifers were affected, the ratio of the number affected to number at risk being 17.5 : 1 and 9.5 : 1, respectively. The culling rate was 50% of the affected animals. Most of the affected animals were cows (91.2%), with one first-calving cow (2.9%) and two heifers (5.9%) also affected. The infection occurred during the summer to autumn months (August-December), and lasted 118 days. The incubation period is about 2 months. The disease appeared in two clinical forms - cutaneous and mastitic - or as a mixed form. C. pseudotuberculosis organisms that were isolated from the ulcerative granulomatous lesions and from milk samples failed to reduce nitrate. A decrease in milk production (4%) and an increase in the bulk-milk somatic cell count from a herd mean of 240 x 10(3) mL(-1) to 460 x 10(3) mL(-1) were noted during the morbidity period. The organism was isolated from milk samples of eight animals (25%). Clinical, epizootiological and microbiological aspects of the infection are described.

Molecular epidemiologic features of Corynebacterium pseudotuberculosis isolated from horses

OBJECTIVE

To characterize isolates of Corynebacterium pseudotuberculosis from horses, cattle, and sheep in Colorado, Kentucky, Utah, and California in samples collected during perceived epidemics of infection (increased numbers of cases identified) in 2002 and 2003, and determine how closely isolates were related and their possible source.

SAMPLE POPULATION

54 isolates of C pseudotuberculosis from 49 horses, 4 cattle, and 1 sheep.

PROCEDURES

Random amplified polymorphic DNA (RAPD) polymerase chain reaction (PCR) assay, PCR assay for the gene encoding the phospholipase D (PLD) toxin, biochemical analyses, and tests for susceptibility to 17 antimicrobial drugs were performed.

RESULTS

All isolates reduced nitrate to nitrite, most yielded positive results for the PLD toxin gene, and all were susceptible to antimicrobial drugs. Ten genetic types were detected by use of RAPD PCR assay; types III to X were isolated from horses, cattle, or both in 1 or more states. Types III and IX were isolated from both horses and cattle. Types VII and VIII were isolated in only 1 state, but the number of isolates in these groups was small. In contrast, all other types were isolated in 2 or more states. All isolates from Utah were type III, but the other 3 states had isolates from more than 1 type.

CONCLUSIONS AND CLINICAL RELEVANCE

These data are consistent with a clonally expanding epidemic of infection in Utah and an increase in number of infections caused by multiple strains of C pseudotuberculosis not derived from a single source in the other states. The increase in number of infections could be the result of reporting bias, environmental factors facilitating infection, or host factors such as greater herd susceptibility.

Use of a real-time polymerase chain reaction-based fluorogenic 5' nuclease assay to evaluate insect vectors of Corynebacterium pseudotuberculosis infections in horses

OBJECTIVE

To develop and use a sensitive molecular assay for detecting the phospholipase D (PLD) exotoxin gene of Corynebacterium pseudotuberculosis in an attempt to identify insect vectors that may be important in transmission of clinical disease in horses.

SAMPLE POPULATION

2,621 flies of various species.

PROCEDURE

A real-time polymerase chain reaction (PCR)-based fluorogenic 5' nuclease (TaqMan) system (ie, TaqMan PCR assay) was developed for the detection of the PLD gene in insects. Flies were collected monthly (May to November 2002) from 5 farms in northern California where C. pseudotuberculosis infection in horses is endemic. Three of the 5 farms (which housed a total of 358 horses) had diseased horses during the study period. A total of 2,621 flies of various species were tested for the PLD gene of C. pseudotuberculosis.

RESULTS

Evidence of bacterial DNA for the PLD gene was detected in skin biopsy specimens from clinically affected horses and from 3 fly species collected from farms where affected horses were housed. Farms with a high incidence of diseased horses had a high proportion of insects carrying the organism. High percentages of flies with positive results for the PLD gene were observed in October, when most clinically affected horses were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

Our results are consistent with the hypothesis that C. pseudotuberculosis may be vectored to horses by flies. Three potential vectors were identified, including Haematobia irritans, Stomoxys calcitrans, and Musca domestica. The organism can be identified in up to 20% of house flies (Musca domestica) in the vicinity of diseased horses.

Oedematous skin disease of buffalo in Egypt

This review covers a historical view and etiology of oedematous skin disease which affects buffalo in Egypt, the microbiology of Corynebacterium pseudotuberculosis causing the disease: its virulence; clinical signs; mechanism of pathogenesis; histopathology; mode of transmission; immunological aspects; treatment and control. It is concluded that C. pseudotuberculosis serotype II is the main cause of OSD and exotoxin phospholipase D and its lipid contents of the cell wall are the major causes of pathogenesis. After declaring the role of Hippobosca equina in transmission of the causative agent among buffaloes, control of OSD is now available.

Characterization of United Kingdom isolates of Corynebacterium pseudotuberculosis using pulsed-field gel electrophoresis

Caseous lymphadenitis is a chronic suppurative disease caused by Corynebacterium pseudotuberculosis and is responsible for serious economic losses to the sheep and goat industry. Caseous lymphadenitis was first reported for goats in the United Kingdom in 1990 and for sheep in 1991. Recent evidence suggests that the prevalence of the disease within the national flock is increasing. Fifty isolates of C. pseudotuberculosis from the United Kingdom comprising sheep and horse isolates, the original goat outbreak strain, and the type strain were characterized by biotyping, antimicrobial susceptibility, production of phospholipase D, and genotyping by pulsed-field gel electrophoresis using SfiI and SmaI. All of the isolates were confirmed as C. pseudotuberculosis, and all produced phospholipase D but none reduced nitrate. Restriction with SfiI generated 16 to 18 bands between 48.5 and 290 kb and differentiated six pulsotypes. We conclude that 80% of the strains tested were epidemiologically related to the outbreak strain and that the equine profile was distinct both phenotypically and genotypically.

Tumor necrosis factor alpha and gamma interferon are required for the development of protective immunity to secondary Corynebacterium pseudotuberculosis infection in mice

The production and role of endogenous cytokines during the course of secondary Corynebacterium (C.) pseudotuberculosis infection were investigated in mice. When immunized mice were challenged on day 28 after primary infection, tumor necrosis factor alpha (TNF-alpha) and interferon gamma (IFN-gamma) were found to appear at 3 hr and to reach the maximum at 24 hr after challenge. Spleen cells of mice primarily infected from 2 to 8 weeks before produced a significant amount of TNF-alpha and IFN-gamma when stimulated with formalin-killed bacteria. However, they could not produce detectable amounts of IL-4. The administration of anti-TNF-alpha monoclonal antibody (MAb) and IFN-gamma MAb increased bacterial proliferation in the organs of immune mice and exacerbated the secondary infection. Injection of anti-CD4 MAb alone or anti-CD4 plus anti-CD8 MAbs resulted in significantly increased mortality and a marked suppression of bacterial elimination as well as cytokine production of secondarily infected mice, while the treatment with anti-CD8 MAb alone showed no effect on either the resistance or cytokine production of mice. These results suggest that CD4, probably Th1 T cells, play an important role for establishment of protective immunity against secondary C. pseudotuberculosis infection by secreting TNF-alpha and IFN-gamma.

Identification of nonlipophilic corynebacteria isolated from dairy cows with mastitis

Nonlipophilic corynebacteria associated with clinical and subclinical mastitis in dairy cows were found to belong to four species: Corynebacterium amycolatum, Corynebacterium ulcerans, Corynebacterium pseudotuberculosis, and Corynebacterium minutissimum. These species may easily be confused. However, clear-cut differences between C. ulcerans and C. pseudotuberculosis were found in their acid production from maltotriose and ethylene glycol, susceptibility to vibriostatic agent O129, and alkaline phosphatase. Absence of growth at 20 degrees C and lack of alpha-glucosidase and 4MU-alpha-D-glycoside hydrolysis activity differentiated C. amycolatum from C. pseudotuberculosis and C. ulcerans. The mastitis C. pseudotuberculosis strains differed from the biovar equi and ovis reference strains and from caprine field strains in their colony morphologies and in their reduced inhibitory activity on staphylococcal beta-hemolysin. C. amycolatum was the most frequently isolated nonlipophilic corynebacterium.

Role of endogenous tumor necrosis factor alpha and gamma interferon in resistance to Corynebacterium pseudotuberculosis infection in mice

The production and roles of endogenous tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) in the infection of Corynebacterium (C.) pseudotuberculosis were investigated in mice. The maximum levels of TNF-alpha and IFN-gamma were detected on day 4 after infection. The administration of anti-TNF-alpha monoclonal antibody (mAb) as well as anti-IFN-gamma mAb increased bacterial proliferation in the organs, leading to the death of infected mice, but anti-IFN-gamma mAb showed a less marked effect than anti-TNF-alpha mAb. The suppressive effect of anti-TNF-alpha and anti-IFN-gamma mAbs on anticorynebacterial resistance was augmented by the simultaneous administration of these antibodies. Anti-TNF-alpha mAb was found to be highly effective when administered on day 0 and day 4, suggesting that TNF-alpha produced during the early stage of infection is critical for the generation of resistance. Histologically, many microabscesses, severe follicular swelling and lymphocyte destruction were observed in mice treated with anti-TNF-alpha or anti-IFN-gamma mAb. Injection of anti-CD4 or anti-CD8 mAb also resulted in significantly increased mortality and a marked suppression of IFN-gamma production, but had no effect on TNF-alpha production. Carrageenan also showed a marked effect on the exacerbation of infection. Taken together, these results suggest that endogenously produced TNF-alpha and IFN-gamma are both essential to the host defense against C. pseudotuberculosis infection and that these cytokines may have an additive effect.

Comparative molecular characterization of Corynebacterium pseudotuberculosis of different origin

Ribotyping and susceptibility to 17 antimicrobial agents were used to compare 37 isolates of Corynebacterium pseudotuberculosis (28 from horses, 1 from cattle, 3 from sheep and 5 from goats) derived from various types of lesions, and different geographic locations. According to the presence of nitrate reductase, all but one isolate from horses reduced nitrate (nitrate-positive), whereas all isolates from sheep and goats were unable to reduce nitrate (nitrate-negative). The ribotype of the nitrate-negative isolate from a horse with ulcerative lymphangitis was identical to all the other isolates from horses, and different than the ribotype of nitrate-negative isolates from sheep and goats. Ribotyping with one of the restriction endonucleases, Apa 1, revealed differences between, but not within, the two biotypes. However, ribotyping with Pst 1 endonuclease revealed one variant within the equine biotype and one variant within the ovine biotype. The minimum inhibitory concentration (MIC; microgram/ml) of antimicrobial agents against isolates from nitrate-negative and nitrate-positive groups was very similar, with the exception of isolates from sheep and goats which had a higher MIC for amikacin than isolates from horses and cattle.

Phylogenetic positions and assignment of swine and ovine corynebacterial isolates based on the 16S rDNA sequence

The nucleotide sequences of the 16S ribosomal RNA gene (rDNA) of swine and ovine corynebacterial strains were determined. The sequences of the strains that identified as Corynebacterium pseudotuberculosis by their biochemical characteristics were homologous with each other. The phylogenetic position of C. pseudotuberculosis strains was closet to C. ulcerans and next closet to C. diphtheriae. The nucleotide sequence of another swine isolate, SC8, was similar to that of a recently proposed species, C. seminale, and a non-validated species, "C. glucuronolyticum," with about 0.01 to 0.02 evolutionary distances. Analysis of the predicted secondary structure of the 16S rRNA molecule agreed with the close phylogenetic relationships between C. pseudotuberculosis and C. ulcerans and between C. seminale and strain SC8.

Corynebacterium pseudotuberculosis infection in Israeli cattle: clinical and epidemiological studies

Morbidity due to Corynebacterium pseudotuberculosis infection occurred in 29 dairy herds in Israel during 1989 to 1995. The disease occurred sporadically in 17 of the herds with a morbidity of up to 5 per cent, and was epidemic in 12, with a morbidity of 5 to 35 per cent. Cutaneous abscesses were diagnosed in 609 animals. Young cattle appeared to be less susceptible to the disease than older cows. Beef cattle herds were not affected. The disease appeared in the cutaneous form in 92.5 per cent of cases, the cutaneous and mastitic form in 5.9 per cent and the cutaneous and visceral form in 1.6 per cent. The cutaneous form appeared as deep subcutaneous abscesses on various parts of the body, with granulating ulcers exuding pus and blood. In 10 of the herds, C pseudotuberculosis was isolated from 33 mastitic cows which also had cutaneous lesions. The visceral form of the disease was detected when severely affected animals were slaughtered. In 23 of the herds, the disease occurred during the spring and summer dry season, from March to October; the highest prevalence was in the semi-arid Negev region. In 25 herds, the infection lasted for up to five months. The skin lesions on individual cows healed on average in 23.4 days, after either local or parenteral treatment. No significant difference was observed between the effect of systemic antibiotic treatment and local antiseptic treatment. One hundred and two (16.7 per cent) severely affected animals were culled. There was a decrease in milk production and large increases in somatic cell counts in the 12 herds in which the disease was epidemic. None of the strains of isolated C pseudotuberculosis reduced nitrate.

Mastitis in dairy cattle caused by Corynebacterium pseudotuberculosis and the feasibility of transmission by houseflies. I

Morbidity due to Corynebacterium pseudotuberculosis infection occurred in 29 dairy herds. The disease appeared basically in three clinical forms: cutaneous, mastitic, and visceral. The appearance of the disease showed a marked seasonality: in 23 herds it occurred during the spring and summer months (dry season) (March-October). The mastitic form occurred in only 10 herds and the causative bacterium was isolated from 33 cows (5.8%). All the strains of C. pseudotuberculosis isolated from the milk samples were found not to be nitrate reducers. The bacterium was excreted in the milk of six cows from herd B during a period of 11 months. In the mastitic cows, a decrease in milk production and considerable increases in the somatic cell count were noted. C. pseudotuberculosis was isolated from houseflies collected over a cow lesion. Laboratory-reared houseflies were successfully infected with C. pseudotuberculosis-contaminated milk, broth and sugar cubes. Flies infected with the bacterium from contaminated milk excreted the bacterium in their droppings for up to 4 h and from their saliva for up to 3 h post infection. The bacterium survived on the external organs of houseflies for no longer than 10 min post infection, after the flies had been dipped in contaminated broth.