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PubMed1985

Production and biological properties of M-protein of Streptococcus equi.

The production of M-protein antigen of Streptococcus equi was studied during in vitro growth in equine blood and in various media. Of 11 S equi strains studied, seven which had initially possessed 0.04 mg or less M-protein per 10 mg of streptococcal cell extract showed an increase in M-protein content after successive culture in heparinised horse blood. Maximum proliferation occurred in Todd-Hewitt (TH) medium with added 0.2 per cent w/v glucose when compared with TH medium alone or TH medium with 2 per cent w/v sucrose, starch, neopeptone or normal horse serum. The M-protein of these strains did not change after the addition of either neopeptone or normal horse serum to TH medium but declined with the addition of sugars. In experiments involving phagocytosis of S equi by equine polymorphs, the percentage of polymorphs which engulfed cocci was higher with a capsule-deficient strain (69.0 +/- 11.6 per cent) than with five typical encapsulated strains (21.1 +/- 7.0 per cent to 30.9 +/- 13.3 per cent). Phagocytosis of five typical strains was greater after growth in a trypsin-containing medium than in medium devoid of trypsin. Trypsin-grown cells took longer to kill mice than did normal cells. It was concluded that M-protein was one of the factors involved in the virulence of S equi.

Animals↗
PubMed1996

Characterisation of murine monoclonal antibodies recognising opsonic, mouse-protective, chaining and mucosally relevant epitopes on the M protein of Streptococcus equi subspecies equi.

Six hybridomas secreting murine monoclonal antibodies (mAbs) specific for the M protein of Streptococcus equi subspecies equi were characterised. The mAbs recognised the major 41 and 46 kDa fragments of M protein in an acid extract of S equi and the 56 and 58 kDa dimer of the native molecule in a mutanolysin extract, but did not react with recombinant M-like protein of S equi subspecies zooepidemicus. One mAb (2A10) showed strong opsonic activity for S equi and protected mice against an experimental challenge with virulent S equi. Two other mAbs were mouse-protective but not opsonic. All the mAbs elicited a strong chaining response from S equi, but had only a weak chaining effect on a strain of S equi (19) that expressed only 4 per cent of the normal amount of M protein. Antibodies in nasopharyngeal mucus of horses recently recovered from strangles were inhibited to different extents by each mAb. These different functional behaviours and the result of inhibition ELISAs suggest that the M protein of S equi carries multiple epitopes.

Animals↗
PubMed1987

Complications associated with Streptococcus equi infection on a horse farm.

Complications associated with Streptococcus equi infection developed in 15 (20.3%) of 74 horses on one farm included death, guttural pouch empyema, purpura hemorrhagica, upper respiratory tract obstruction, pneumonia, pleuropneumonia, agalactia, mesenteric lymph node abscessation, and periorbital abscessation. Death was attributed to pneumonia in 3 horses and to upper respiratory tract obstruction in 2 horses. One horse was euthanatized because of severe purpura hemorrhagica.

Animals↗
PubMed2002

Functional characterization of domains found within a lytic enzyme produced by Streptococcus equi subsp. zooepidemicus.

Zoocin A is a lysostaphin-like streptococcolytic enzyme produced by Streptococcus equi subsp. zooepidemicus 4881 that specifically targets the cell walls of some closely related species. On the basis of sequence homology it was suggested that zoocin A was a domain-structured enzyme with the N-terminal domain responsible for catalysis (CAT) and the C-terminal domain for target recognition (SBD). Polypeptides corresponding to zoocin A (rZooA) and each of the putative domains (rCAT and rSBD) were prepared by use of recombinant technology. The biological activities of each was compared by use of a dye-release assay and a cell-binding assay. Cell wall hydrolysis was shown to be a function of CAT and target recognition a function of the SBD. Expression of the zoocin A immunity factor gene produced cell walls resistant to hydrolysis by either rZooA or its component domains, and with reduced capacity to bind rZooA and rSBD.

Bacterial Proteins↗
PubMed1983

Adherence of Streptococcus equi on tongue, cheek and nasal epithelial cells of ponies.

Streptococcus equi was found to adhere to tongue, cheek and nasal epithelial cells of ponies, in vitro. Maximum adherence was observed at pH 7.5 after one hour of incubation of bacteria with epithelial cells. This adherence was more on epithelial cells from adult animals than from foals. Streptococci exposed to heat (60 degrees C for 10 min) or treated with pepsin or trypsin showed a reduced adherence, whereas an increase occurred on treatment with hyaluronidase. Antibodies against whole S. equi cells or M-like protein blocked the adherence, whereas antibodies against group-specific carbohydrate or lipoteichoic acids did not. Pretreatment of epithelial cells with either the M-like protein or crude extract of S. equi lowered the adherence, whereas an extract of S. zooepidemicus did not. Adherence of S. equi to the epithelial cells was considered to be mediated by structures specific to S. equi.

Adhesiveness↗
PubMed2006

Sequence variation of the SeM gene of Streptococcus equi allows discrimination of the source of strangles outbreaks.

Improved understanding of the epidemiology of Streptococcus equi transmission requires sensitive and portable subtyping methods that can rationally discriminate between strains. S. equi is highly homogeneous and cannot be distinguished by multilocus enzyme electrophoretic or multilocus sequence-typing methods that utilize housekeeping genes. However, on sequence analysis of the N-terminal region of the SeM genes of 60 S. equi isolates from 27 strangles outbreaks, we identified 21 DNA codon changes. These resulted in the nonsynonymous substitution of 18 amino acids and allowed the assignment of S. equi strains to 15 distinct subtypes. Our data suggest the presence of multiple epitopes across this region that are subjected to selective immune pressure (nonsynonymous-synonymous substitution rate [d(N)/d(S)] ratio = 3.054), particularly during the establishment of long-term S. equi infection. We further report the application of SeM gene subtyping as a method to investigate potential cases of disease related to administration of a live attenuated S. equi vaccine. SeM gene subtyping successfully differentiated between the vaccine strain and field strains of S. equi responsible for concurrent disease. These results were confirmed by the development and application of a PCR diagnostic test, which identifies the aroA partial gene deletion present in the Equilis StrepE vaccine strain. Although the vaccine strain was found to be responsible for injection site lesions, all seven outbreaks of strangles investigated in recently vaccinated horses were found to be due to concurrent infection with wild-type S. equi and not due to reversion of the vaccine strain.

Amino Acid Sequence↗
PubMed1995

An assessment of mucosal immunisation in protection against Streptococcus equi ('Strangles') infections in horses.

The ability of mucosally administered antigen to provide protection against Streptococcus equi ('Strangles') infections in horses was examined. First, an enzyme linked immunosorbent assay (ELISA) was developed to detect the immune status of horses to S. equi. This assay was used to select Strangles-naive horses for the study and also to monitor their response to immunisation. Potential vaccine candidates were: (a) orally administered paraformaldehyde killed S. equi; (b) intraperitoneally (IP) administered paraformaldehyde killed S. equi in a non-inflammatory adjuvant; (c) orally administered live avirulent S. equi; (d) orally administered microencapsulated streptococcal M protein. The latter three preparations were first assessed in a rat model, using rate of lung bacterial clearance following intratracheal inoculation of live virulent bacteria as an indication of efficacy. Candidates (a) and (b) were then assessed in an equine model. IP immunisation of horses was shown to effectively induce production of specific antibody in mucosal and systemic sites. Four weeks after initial immunisation, horses were challenged intranasally with live virulent S. equi. Both groups of immunised horses demonstrated partial protection following vaccination. Of the IP immunised horses, only two out of four developed clinical signs of Strangles following live challenge. The orally immunised horses all developed submandibular abscesses containing S. equi. However, none of the immunised horses became as ill as the control horses in terms of fever, anorexia, loss of condition and general malaise.

Administration, Oral↗
PubMed2000

Neither the A- nor B-repeat regions of the fibrinogen-binding protein of Streptococcus equi subsp. equi are essential for fibrinogen binding.

The major cell wall-associated protein (FgBP) of Streptococcus equi subsp. equi possesses two internal blocks of repeated sequence (A and B) and binds horse fibrinogen (Fg) avidly through residues located in the N-terminal half of the molecule. In the present study, we investigated the roles of the two repeats blocks in Fg binding through construction of recombinant FgBP proteins containing defined internal deletions of sequence. Ligand binding experiments clearly showed that neither repeat is essential for Fg binding. However, residues within the B repeats seem to play a major role in the aberrant mobility observed for FgBP following sodium dodecyl sulfate polyacrylamide gel electrophoresis.

Animals↗
PubMed2005

Identification and molecular characterization of Streptococcus equi subsp. zooepidemicus isolated from camels (Camelus dromedarius) and camel milk in Kenya and Somalia.

Seventeen Streptococcus equi subsp. zooepidemicus strains isolated from camels and camel milk in Kenya and Somalia were identified by their cultural characteristics, by biochemical and serological reactions with the help of commercial identification systems and by molecular studies using a multiplex PCR. The isolates were further characterized by a PCR-mediated detection of size polymorphisms in the 16S-23S rDNA intergenic spacer region and the virulence gene szp and by amplification of the virulence gene cne. These molecular analysis are potentially useful in identifying and characterizing S. equi subsp. zooepidemicus strains of this origin and could possibly be valuable in epidemiological investigations.

Animals↗
PubMed2001

Peritonitis in a llama caused by Streptococcus equi subsp. zooepidemicus.

A 7-month-old, male llama was diagnosed with peritonitis caused by Streptococcus equi subsp. zooepidemicus. Clinical findings, medical treatment, and case outcome are described. Hematogenous dissemination from suspected pneumonia is proposed as the route of infection in this case. Possible transmission of the organism through contact with horses is discussed.

Animals↗
PubMed1997

Naturally occurring persistent and asymptomatic infection of the guttural pouches of horses with Streptococcus equi.

During an outbreak of strangles on a farm with approximately 1500 horses, the spread of Streptococcus equi infection was monitored by repeated nasopharyngeal swabbing and culture. In order to control the infection and prevent new introductions of strangles on to the premises, a system of quarantine and swabbing of cases and all incoming animals was instituted. Long-term carriage of the organism was detected in four clinically healthy convalescent animals, and in two of 350 new ponies; it persisted for between seven and 39 months, but it was detected only intermittently by the culture of swabs which was a much less sensitive method than the culture of guttural pouch lavages taken by endoscopy (45 per cent v 88 per cent sensitivity, respectively, for any single sample). Repeated swabs were often negative for several weeks between positive samples. Nonetheless, in all but one of the long-term carriers, S equi was detected by culture of repeated swabs taken over a period of less than two to three months. Infection was detected unilaterally in the guttural pouches of five of the carriers and was accompanied by large numbers of neutrophils in the lavage samples whether or not there was empyema. Abnormalities of the affected guttural pouches were detectable by radiography but only after the instillation of contrast medium. The study indicated that clinically healthy long-term carriers of S equi present a serious risk of spreading strangles, particularly because they may be detected only by repeated nasopharyngeal swabbing over two to three months.

Animals↗
PubMed1986

Passive transfer of mucosal antibody to Streptococcus equi in the foal.

Passive transfer of mucosal antibody to Streptococcus equi was studied in foals during the first 2 months of life. Immunoglobulin G (IgG) and IgA antibodies were found in sera and nasal secretions of foals shortly after colostrum intake. Titers were highest 2 days after birth; IgG predominated in sera, and IgA predominated in nasal washes. Intragastrically administered 99mTc-labeled IgA was transported from the bloodstream to the nasal mucosa of a newborn foal within a few hours of colostrum intake. Western blot analysis of the specificities of colostral and serum antibodies showed that selective transfer of immunoglobulins of defined specificity did not occur. Antibodies from milk samples taken a month or more into lactation had different specificities than those of colostrum or serum samples. Acid-extracted M protein fragments of S. equi recognized by milk antibodies were the same as those recognized by IgG and IgA from nasopharyngeal mucus of horses recently recovered from strangles. We postulate that passive antibody protection of the foal is derived both by secretion of colostral immunoglobulins onto the nasopharyngeal mucosa and by immunoglobulins ingested in milk that directly coat the upper respiratory and oral mucosa during the first months of life.

Age Factors↗
PubMed1982

A mild form of strangles caused by an atypical Streptococcus equi.

A mild form of strangles caused by an atypical Streptococcus equi was recognized on a large horse breeding farm. The organism differed from most S equi isolates by disappearance of the mucoid capsule by 24 hours of culture, leaving a matt-type colony. Typically, the clinical signs were a transient (24-48 hour) fever, profuse nasal discharge, and anorexia. In about half the affected animals, there was moderate mandibular lymph node enlargement, and these glands usually ruptured or were drained. The use of a passive hemagglutination antibody test showed that subclinical infection was widespread in horses on the farm.

Animals↗
PubMed2001

Surface immunolocalisation of HPr in the equine pathogen Streptococcus equi.

We have investigated the surface localisation of the phosphotransferase system protein HPr in the equine pathogen Streptococcus equi subsp. equi using immunogold localisation and transmission electron microscopy. Like the LppC acid phosphatase lipoprotein, a reference surface antigen, the S. equi HPR could be clearly detected on the surfaces of intact cells. This study is consistent with previous reports that some streptococcal HPr is cell surface associated and suggests that the extracytoplasmic mobilisation and transfer of phosphate groups by streptococci warrant further investigation.

Bacterial Proteins↗
PubMed2000

Streptococcus equi with truncated M-proteins isolated from outwardly healthy horses.

The M-protein genes of Streptococcus equi isolated from 17 outwardly healthy horses after 4 strangles outbreaks had ended, including a quarantined animal, were compared with those of S. equi isolates from 167 active cases of strangles across 4 countries. The healthy horses included 16 persistent S. equi carriers, at least one from each of the four outbreaks. These carriers, despite being outwardly healthy, had empyema of the guttural pouch(es), an enlargement of the equine Eustachian tube. A persistent carrier from two of these outbreaks, the quarantined animal and a healthy animal with normal guttural pouches, from which S. equi was isolated only once, were colonized by variant S. equi with truncated M-protein genes (24% of outwardly healthy animals with S. equi). The truncated M-protein genes had in-frame deletions in slightly different positions between the signal sequence and the central repeat region, equivalent to approximately 20% of the mature expressed protein. Immunoblotting with antibody to recombinant M-protein confirmed that the variants expressed a truncated form of the M-protein. In contrast to the outwardly healthy S. equi carriers, only 1/167 of S. equi isolates from strangles cases possessed a truncated M-protein gene (<1%; Fisher's exact test, P=0.0002). Compared with isolates from healthy horses with a truncated M-protein, much more of the N terminus of the truncated M-protein was retained in the variant S. equi from a strangles case. Variant S. equi from outwardly healthy animals were more susceptible to phagocytosis by neutrophils in vitro than typical isolates. This is the first report of detection of S. equi with a truncated M-protein. The distribution of the variants between strangles cases and carriers suggests that the 80% of the M-protein retained in the variants may contribute to colonization whilst the deleted portion of the gene may be needed for full virulence.

Amino Acid Sequence↗
PubMed2002

Characterization and immunogenicity of pyrogenic mitogens SePE-H and SePE-I of Streptococcus equi.

Two pyrogenic mitogens, SePE-H and SePE-I, were characterized in Streptococcus equi, the cause of equine strangles. SePE-H and SePE-I have molecular masses of 27.5 and 29.5 kDa, respectively, and each is almost identical to its counterpart in Streptococcus pyogenes M1. Both genes are adjacent to a gene encoding a phage muramidase of 49.7 kDa and are located immediately downstream from a phage genomic sequence almost identical to a similar phage sequence in S. pyogenes M1. Strong mitogenic responses were elicited by both proteins from horse peripheral blood mononuclear cells. However, although both were pyrogenic for rabbits, only SePE-I was pyrogenic in ponies. Convalescent sera contained antibody to each mitogen and horses recovered from strangles or immunized with SePE-I were resistant to the pyrogenic effect of SePE-I. The immunogenicity of SePE-I suggests that it should be included in new generation strangles vaccines. In isolates of S. equi sepe-I and sepe-H were consistently present but they were absent from the closely related Streptococcus zooepidemicus, suggesting that phage mediated transfer was an important event in the formation of the clonal, more virulent, S. equi from its putative S. zooepidemicus ancestor.

Amino Acid Sequence↗
PubMed2006

Outbreak of Streptococcus equi subsp. zooepidemicus infections on the island of Gran Canaria associated with the consumption of inadequately pasteurized cheese.

Streptococcus equi subsp. zooepidemicus infections are infrequent in humans. A clinical and epidemiological study of a milk-borne outbreak caused by this organism is described. Fifteen patients (5 females, 10 males) with a median age of 70 years (range 47-86) were infected. Twelve (80%) had underlying diseases. Infection with S. equi subsp. zooepidemicus presented as primary bacteremia in six cases, as bacteremia associated with aortic aneurism in four cases, as septic arthritis in two cases, as pneumonia in two cases, and as meningitis in one case. Five (33.3%) patients died. A case-control study proved that consumption of inadequately pasteurized cheese of a specific brand was associated with S. equi subsp. zooepidemicus disease (OR=4.5; 95% CI 1.57-19.27; p<0.001). This outbreak serves as a reminder that S. equi subsp. zooepidemicus causes serious infections that are usually zoonoses. Identification of beta-hemolytic streptococci to the species level to detect contaminated foods of animal origin is important for preventing new food-borne outbreaks. For a precise characterization of the isolates, the application of molecular markers is recommended.

Aged↗