Isolation of exfoliative toxin from Staphylococcus hyicus subsp. hyicus and its exfoliative activity in the piglet

Virulence Mechanisms of Staphylococcal Animal Pathogens

Staphylococci are major causes of infections in mammals. Mammals are colonized by diverse staphylococcal species, often with moderate to strong host specificity, and colonization is a common source of infection. Staphylococcal infections of animals not only are of major importance for animal well-being but have considerable economic consequences, such as in the case of staphylococcal mastitis, which costs billions of dollars annually. Furthermore, pet animals can be temporary carriers of strains infectious to humans. Moreover, antimicrobial resistance is a great concern in livestock infections, as there is considerable antibiotic overuse, and resistant strains can be transferred to humans. With the number of working antibiotics continuously becoming smaller due to the concomitant spread of resistant strains, alternative approaches, such as anti-virulence, are increasingly being investigated to treat staphylococcal infections. For this, understanding the virulence mechanisms of animal staphylococcal pathogens is crucial. While many virulence factors have similar functions in humans as animals, there are increasingly frequent reports of host-specific virulence factors and mechanisms. Furthermore, we are only beginning to understand virulence mechanisms in animal-specific staphylococcal pathogens. This review gives an overview of animal infections caused by staphylococci and our knowledge about the virulence mechanisms involved.

[Increased piglet losses upon exudative epidermitis - a case report]

A massive outbreak of exudative epidermitis (EE) occurred on a Western German piglet producing farm with 350 productive sows. Gilts are produced on site. In one group of piglets, more than 50% of suckling and nursery piglets were clinically affected; furthermore, gilts as well as sows showed localized blackish-squamous skin lesions in the neck area. Generalized infection in suckling and nursery piglets resulted in mortality rates of up to 10% per weaning group. Swabs of moist, affected areas of skin taken on the farm in addition to swab and organ samples collected during necropsy were examined via bacterial cultivation. Both Staphylococcus (St.) hyicus and St. chromogenes strains were detected in affected skin lesions, with St. hyicus also present in systemic localizations. Further characterization of the St. hyicus strains identified ExhA and SHETA as toxins involved, and isolates showed resistance to penicillin and aminopenicillin. In the short term, antibiotic treatment with trimethoprim-sulfadiazine of the whole age group combined with individual treatment of severely affected animals as well as washing with an iodine-containing solution improved the clinical signs. In order to reduce the antibiotic use, an autogenous vaccine against the isolated St. hyicus and St. chromogenes strains for gilts and sows was produced and applied as a basic immunization twice before farrowing. In addition, external and internal biosecurity was evaluated and adjusted using an objective questionnaire (Bio-check.UGentTM). The combination of taken measures resulted in a long-term improvement of the overall health status. Several months after the severe EE outbreak, the sporadic occurrence of new EE cases in individual piglets could be controlled by the adjustment of the autogenous vaccine with an additional St. hyicus isolate. The case report illustrates how the combination of continuous monitoring, individual and group antibiotic treatment, biosecurity evaluation, and the use of appropriate immune prophylaxis can improve the clinical picture of EE.

Exudative Epidermitis in Combination with Staphylococcal Pyoderma in Suckling Piglets

A case of generalized exudative epidermitis (EE) is described, which occurred in a very small piglet producing farm in Austria. The antimicrobial treatment prescribed by the herd veterinarian did not improve the clinical problem. Therefore, the University Clinic for Swine intervened in the case. Lab investigations were initiated in which Staphylococcus hyicus (SH) and Staphylococcus aureus (SA), both methicillin-resistant and susceptible strains, could be isolated from the skin of affected piglets. Poor hygiene and management practices were identified as predisposing factors on site. Adaptation of antimicrobial treatment according to results of the in vitro susceptibility testing and the implementation of proper hygiene measures resolved the clinical problem. Here, we describe a fatal coinfection of SH and SA in suckling piglets.

Virulence Plasmids of Nonsporulating Gram-Positive Pathogens

Gram-positive bacteria are leading causes of many types of human infection, including pneumonia, skin and nasopharyngeal infections, as well as urinary tract and surgical wound infections among hospitalized patients. These infections have become particularly problematic because many of the species causing them have become highly resistant to antibiotics. The role of mobile genetic elements, such as plasmids, in the dissemination of antibiotic resistance among Gram-positive bacteria has been well studied; less well understood is the role of mobile elements in the evolution and spread of virulence traits among these pathogens. While these organisms are leading agents of infection, they are also prominent members of the human commensal ecology. It appears that these bacteria are able to take advantage of the intimate association between host and commensal, via virulence traits that exacerbate infection and cause disease. However, evolution into an obligate pathogen has not occurred, presumably because it would lead to rejection of pathogenic organisms from the host ecology. Instead, in organisms that exist as both commensal and pathogen, selection has favored the development of mechanisms for variability. As a result, many virulence traits are localized on mobile genetic elements, such as virulence plasmids and pathogenicity islands. Virulence traits may occur within a minority of isolates of a given species, but these minority populations have nonetheless emerged as a leading problem in infectious disease. This chapter reviews virulence plasmids in nonsporulating Gram-positive bacteria, and examines their contribution to disease pathogenesis.

Staphylococcus sciuri exfoliative toxin C (ExhC) is a necrosis-inducer for mammalian cells

Staphylococcus sciuri (S. sciuri) is a rare pathogen in humans, but it can cause a wide array of human infections. Recently a S. sciuri isolate (HBXX06) was reported to cause fatal exudative epidermitis (EE) in piglets and thus considered as a potential zoonotic agent. To investigate the pathogenicity of this bacterium, we cloned exfoliative toxin C (ExhC), a major toxin of the S. sciuri isolate and performed functional analysis of the recombinant ExhC-his (rExhC) protein using in vitro cell cultures and newborn mice as models. We found that rExhC could induce necrosis in multiple cell lines and peritoneal macrophages as well as skin lesions in newborn mice, and that the rExhC-induced necrosis in cells or skin lesions in newborn mice could be completely abolished if amino acids 79-128 of rExhC were deleted or blocked with a monoclonal antibody (3E4), indicating aa 79-128 portion as an essential necrosis-inducing domain. This information contributes to further understandings of the mechanisms underlying S. sciuri infection.

Development of a high-expression system for staphylococcal exfoliative toxin genes

We constructed a new expression system for staphylococcal exfoliative toxin (ET). The expression vector, pETA-exp2, was constructed based on Bacillus-Escherichia shuttle vector pHY300PLK. The pETA-exp2 vector includes the regulator of the ETA gene (eta), the promoter and Shine-Dalgarno (SD) sequences of eta, a SalI sequence at the end of the signal sequence of eta, a nucleotide sequence encoding mature ETA, an XhoI site, a 6x His sequence just before the stop codon and the end of the transcription sequence of eta. The nucleotide sequences coding for the mature proteins of ETB, ExhA, ExhB, ExhC, ExhD and SHETB were amplified by polymerase chain reaction (PCR) and inserted into pETA-exp2. These recombinant plasmids were transformed into Bacillus megaterium. The major protein in the culture supernatant of the transformant was recombinant ET (rET). The yields of all rETs were high, and all of them showed exfoliative activity in susceptible animals. The antigenicities of rETs and ETs were not distinguishable from each other.

Exfoliative toxins of Staphylococcus aureus

Staphylococcus aureus is an important pathogen of humans and livestock. It causes a diverse array of diseases, ranging from relatively harmless localized skin infections to life-threatening systemic conditions. Among multiple virulence factors, staphylococci secrete several exotoxins directly associated with particular disease symptoms. These include toxic shock syndrome toxin 1 (TSST-1), enterotoxins, and exfoliative toxins (ETs). The latter are particularly interesting as the sole agents responsible for staphylococcal scalded skin syndrome (SSSS), a disease predominantly affecting infants and characterized by the loss of superficial skin layers, dehydration, and secondary infections. The molecular basis of the clinical symptoms of SSSS is well understood. ETs are serine proteases with high substrate specificity, which selectively recognize and hydrolyze desmosomal proteins in the skin. The fascinating road leading to the discovery of ETs as the agents responsible for SSSS and the characterization of the molecular mechanism of their action, including recent advances in the field, are reviewed in this article.

Staphylococcal exfoliative toxins: “Molecular scissors” of bacteria that attack the cutaneous defense barrier in mammals

Bullous impetigo and its generalized form, staphylococcal scalded-skin syndrome (SSSS), are highly contagious, blistering skin diseases caused by Staphylococcus aureus infection. Virulent strains of the bacteria produce exfoliative toxins (ETs) that cause the loss of keratinocyte cell-cell adhesion in the superficial epidermis. Recent studies have indicated that the three isoforms of ETs, i.e., ETA, ETB, and ETD, are glutamate-specific serine proteases that specifically and efficiently cleave a single peptide bond in the extracellular region of human and mouse desmoglein 1 (Dsg1), a desmosomal intercellular adhesion molecule. In addition, four isoforms of S. hyicus exfoliative toxin, ExhA, ExhB, ExhC, and ExhD, cleave swine Dsg1, resulting in skin exfoliation similar to that observed in pigs with exudative epidermitis. In this review, we describe recent advances in our knowledge of the mechanisms of action of staphylococcal exfoliative toxins, which act as "molecular scissors" to facilitate percutaneous bacterial invasion of mammalian skin by cleavage of keratinocyte cell-cell adhesion molecules. The species-specificity of staphylococcal exfoliative toxins to cleave Dsg1 in certain mammalian species is discussed.

Cloning of swine desmoglein 1 and its direct proteolysis by Staphylococcus hyicus exfoliative toxins isolated from pigs with exudative epidermitis

Exudative epidermitis (EE) is an acute, often fatal skin disease of piglets caused by Staphylococcus hyicus. Clinical and histopathological manifestations of EE are similar to those of staphylococcal scalded skin syndrome (SSSS), a human blistering skin disease, in which exfoliative toxins produced by Staphylococcus aureus digest the extracellular domains of desmoglein (Dsg) 1 and cause loss of epidermal cell-cell adhesion. The aims of this study were to isolate and characterize cDNA for full length of swine Dsg1, and to determine whether the extracellular domains of swine Dsg1 produced by baculovirus (sDsg1-His) could be digested by four isoforms of exfoliative toxin produced by S. hyicus (ExhA, ExhB, ExhC and ExhD). Nucleotide sequencing revealed that swine Dsg1 cDNA consisted of an open reading frame of 3138 bp, encoding a precursor protein of 1045 amino acids. Deduced amino acid sequence of the swine Dsg1 precursor were highly homologous to corresponding bovine, canine, human and murine sequences. Immunoadsorption assay with a secreted form of sDsg1-His revealed that sDsg1-His specifically absorbs the immunoreactivity of 10 human pemphigus foliaceus sera against swine keratinocyte cell surfaces, suggesting its proper conformation. When sDsg1-His was incubated in vitro with Exhs, all four isoforms of Exh directly digested sDsg1-His into smaller peptides, whereas removal of calcium from sDsg1-His completely inhibited its proteolysis by these four Exhs. Recognition and digestion of calcium-stabilized structure on the extracellular domains of swine Dsg1 by Exhs indicated that EE shares similar molecular pathophysiological mechanisms of intra-epidermal splitting with SSSS in humans.

Staphylococcus hyicus exfoliative toxins selectively digest porcine desmoglein 1

Virulent strains of Staphylococcus hyicus can cause exudative epidermitis in pigs. The major symptom of this disease is exfoliation of the skin in the upper stratum spinosum. Exfoliation of the skin is strongly associated with exfoliative toxin including ExhA, ExhB, ExhC, ExhD, SHETA, and SHETB. Recently, genes for ExhA, ExhB, ExhC and ExhD were cloned. Exfoliative toxins produced by S. aureus have been shown to selectively cleave human or mouse desmoglein 1, a desmosomal adhesion molecule, that when inactivated results in blisters. In this study, we attempted to identify the molecular target of Exhs in porcine skin. Each of recombinant Exhs injected in the skin of pigs caused superficial epidermal blisters or crust formation. Cell surface staining of desmoglein 1, but not that of desmoglein 3, was abolished when cryosections of normal porcine skin were incubated with one of Exhs suggesting that Exh selectively degrade porcine desmoglein 1. In vitro incubation of the recombinant extracellular domains of desmoglein 1 and desmoglein 3 of human, mouse or canine origin demonstrated that only mouse desmogleins 1alpha and 1beta were cleaved by ExhA and ExhC at high concentration. Furthermore, injection of ExhA and ExhC at high concentration caused superficial blisters in neonatal mice. These findings strongly suggest that Exhs cause blister formation of porcine skin by digesting porcine desmoglein 1 in a similar fashion to exfoliative toxins from S. aureus.

Treatment of staphylococcal scalded skin syndrome

Humans are a natural reservoir for Staphylococcal aureus. Colonization begins soon after birth and predisposes to infection. S. aureus is one of the most common causes of skin infection, giving rise to folliculitis, furunculosis, carbuncles, ecthyma, impetigo, cellulitis and abscesses. In addition, S. aureus may cause a number of toxin-mediated life-threatening diseases, including staphylococcal scalded skin syndrome (SSSS). Epidermolytic toxins released by certain S. aureus strains cause SSSS by cleaving the epidermal cell adhesion molecule, desmogelin-1, resulting in superficial skin erosion. Recent experiments have revealed similarities in the pathophysiology of SSSS and pemphigus foliaceus, an autoimmune disorder that is characterized by antibodies targeting the same epidermal attachment protein. SSSS typically affects neonates and infants but may also occur in predisposed adults. It is painful and distressing for the patient and parents, although most cases respond to antibiotic treatment. Mortality is low in infants but can be as high as 67% in adults, and is dependent on the extent of skin involvement and the comorbid state. Thus, the management of adults who develop SSSS remains a major therapeutic challenge. The antibody response against the toxins neutralizes their effect and prevents recurrence or limits the effects to the area of infection, which is known as bullous impetigo.

Cloning and sequence analysis of genes encoding Staphylococcus hyicus exfoliative toxin types A, B, C, and D

Exfoliative toxins produced by certain strains of Staphylococcus hyicus mediate exudative epidermitis in pigs. In this study the genes coding for four different exfoliative toxin from S. hyicus (ExhA, ExhB, ExhC, and ExhD) were cloned and sequenced. The coding sequence of the four toxin genes ranged from 816 to 834 bp. The amino acid sequences of these four toxins were homologous to the earlier described exfoliative toxins SHETB from S. hyicus and ETA, ETB, and ETD from Staphylococcus aureus. The homology between the S. hyicus toxins was at the same level as the homology to the exfoliative toxins from S. aureus. The toxins showed similarity to serine proteases, including preservation of the catalytic tract in ExhA, ExhB, and ExhC. However, in ExhD, Asp in the putative catalytic tract was replaced with Glu. The recombinant toxins could be expressed in Escherichia coli, and three of the four toxins were recognized by monoclonal antibodies raised against native exfoliative toxins.

Detection of cell detachment activity induced by Moraxella bovis

OBJECTIVE

To characterize the effect that filtrate obtained from cultures of Moraxella bovis has on cultured corneal epithelial cells and other types of cultured mammalian cells.

SAMPLE POPULATION

Cultured hamster corneal epithelial cells, bovine epithelial cells, and several transformed cell lines exposed to culture filtrate from a pathogenic isolate of M bovis.

PROCEDURE

Moraxella bovis was cultured, and bacteria were removed by filtration. The resulting bacterial culture filtrate was incubated with various types of cultured cells, and effects of the filtrate on detachment of various mammalian cell types was quantified by the use of neutral red dye. Additionally, bacterial culture filtrate was treated with protease inhibitors as well as trypsin and heat prior to incubation with cultured mammalian cells.

RESULTS

Bacterial culture filtrate of M bovis caused all types of cultured cells to detach from each other and from the substrate, with the maximal effect evident 2 hours after initiating incubation. Detached cells were alive, and detachment was reversible. Serine protease inhibitors (phenylmethylsulfonylfluoride and alpha2-macroglobulin) inhibited cell detachment attributable to bacterial culture filtrate. Heating and treatment with trypsin also inhibited cell detachment.

CONCLUSIONS AND CLINICAL RELEVANCE

Moraxella bovis produces a soluble factor that causes reversible detachment of cultured cells. This activity may play a role in the pathogenesis of infectious bovine keratoconjunctivitis.

Cloning of the gene coding for Staphylococcus hyicus exfoliative toxin B and its expression in Escherichia coli

The Staphylococcus hyicus exfoliative toxin B (SHETB) gene was cloned into pUC118 and expressed in Escherichia coli. The nucleotide sequence of the SHETB gene consists of a coding region of 804 bp specifying a polypeptide of 268 amino acid residues, which included a putative 20-residue signal sequence.

Chromosomal and extrachromosomal synthesis of exfoliative toxin from Staphylococcus hyicus

Evidence for the existence of two molecular species of exfoliative toxin (ET) synthesized by Staphylococcus hyicus (SHET) under chromosomal and plasmid control is presented. Serological evidence that these molecular species of toxins are distinct from each other is given. The molecular weights of SHET from plasmidless strain P-1 (SHETA) and from plasmid-carrying strains P-10 and P-23 (SHETB) were almost equal. Both of the serotypes of SHET exhibited exfoliation in 1-day-old chickens. The plasmid-cured (P(-)) substrains (P-23C1 and P-23C2) of S. hyicus P-23 did not cause exfoliation in 1-day-old chickens, whereas P(-) substrains (P-10C1 and P-10C2) of strain P-10 caused exfoliation, but they decreased their exfoliative activity. These findings suggest that SHETB was synthesized along with SHETA by strain P-10, whereas the P-23 strain synthesized SHETB alone. The plasmid-carrying strain (P-23) as well as the plasmidless strain (P-1) exhibited the typical clinical signs of exudative epidermitis in pigs. However, plasmid-cured (P(-)) substrains of P-23 (P23C1 and P23C2) did not exhibit the typical clinical signs of exudative epidermitis. These findings suggest that SHETA is synthesized under chromosomal control and SHETB is synthesized under plasmid control and that SHET-producing strains can be divided into three groups: SHETA-producing strains, SHETB-producing strains, and strains producing both toxins.

New exfoliative toxin produced by a plasmid-carrying strain of Staphylococcus hyicus

A new serotype of Staphylococcus hyicus exfoliative toxin (SHET), serotype B, was isolated from the culture filtrate of a plasmid-carrying strain of S. hyicus. The new SHET was purified by precipitation with 70% saturated ammonium sulfate, gel filtration on a Sephadex G-75 column, column chromatography on DEAE-Cellulofine A-500, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The new SHET caused exfoliation of the epidermis as determined by the so-called Nikolsky sign when inoculated into 1-day-old chickens. The new SHET was serologically different from Staphylococcus aureus exfoliative toxins (ETs) (ETA, ETB, and ETC) and from the SHET from the plasmidless strain but showed the same molecular weight as the other serotypes of toxins on SDS-PAGE. It was thermolabile and lost its toxicity after being heated at 60 degrees C for 30 min. We propose that the new SHET be designated SHETB and that the SHET produced by the plasmidless strain be designated SHETA.

Studies on the effect of divalent metal ions on exfoliative toxins from Staphylococcus hyicus: indications of ExhA and ExhB being metalloproteins

The exfoliative toxins ExhA and ExhB produced by Staphylococcus hyicus strains NCTC10350 and 1289D-88, respectively, were investigated with regard to the effect of divalent metal ions on toxin production as measured in indirect enzyme-linked immunosorbent assay (ELISA) using monoclonal antibodies. Data were obtained as endpoint titer values and used as semiquantitative measures for the amount of exfoliative toxin detected in culture supernatants. It was shown that the endpoint titers of ExhA in supernatants from cultures of strain NCTC10350 grown in the presence of 0.5 mM CaCl2, Cu(NO3)2 or ZnSO4 were higher compared to titers obtained by growth in medium supplemented with a number of other divalent metal salts. The titer of ExhB as determined in the indirect ELISA was increased by addition of 0.5 mM CoCl2, Cu(NO3)2 or CuSO4 to the growth medium. When ExhA or ExhB, prepared without addition of metal salt to the liquid growth medium, was subsequently incubated with 25 mM of Co2+, Cu2+ or Zn2+, the endpoint titers of the toxins were increased. Dialysis of ExhA and ExhB prepared with Zn2+ and Co2+, respectively, against certain metal chelators, resulted in a reduction of the titer determined in ELISA. Other metal chelators had varied effect in the detection of the toxins in ELISA. It was, however, not possible to restore the recognition of toxins by the monoclonal antibodies by incubation of EDDHA-dialyzed toxin preparations with Co2+, Cu2+ or Zn2+. The results of this study suggest that ExhA and ExhB are metalloproteins.

Clinical, microbial, and biochemical aspects of the exfoliative toxins causing staphylococcal scalded-skin syndrome

The exfoliative (epidermolytic) toxins of Staphylococcus aureus are the causative agents of the staphylococcal scalded-skin syndrome (SSSS), a blistering skin disorder that predominantly affects children. Clinical features of SSSS vary along a spectrum, ranging from a few localized blisters to generalized exfoliation covering almost the entire body. The toxins act specifically at the zona granulosa of the epidermis to produce the characteristic exfoliation, although the mechanism by which this is achieved is still poorly understood. Despite the availability of antibiotics, SSSS carries a significant mortality rate, particularly among neonates with secondary complications of epidermal loss and among adults with underlying diseases. The aim of this article is to provide a comprehensive review of the literature spanning more than a century and to cover all aspects of the disease. The epidemiology, clinical features, potential complications, risk factors, susceptibility, diagnosis, differential diagnoses, investigations currently available, treatment options, and preventive measures are all discussed in detail. Recent crystallographic data on the toxins has provided us with a clearer and more defined approach to studying the disease. Understanding their mode of action has important implications in future treatment and prevention of SSSS and other diseases, and knowledge of their specific site of action may provide a useful tool for physiologists, dermatologists, and pharmacologists.

The structure of Staphylococcus aureus epidermolytic toxin A, an atypic serine protease, at 1.7 A resolution

BACKGROUND

Staphylococcal epidermolytic toxins A and B (ETA and ETB) are responsible for the staphylococcal scalded skin syndrome of newborn and young infants; this condition can appear just a few hours after birth. These toxins cause the disorganization and disruption of the region between the stratum spinosum and the stratum granulosum--two of the three cellular layers constituting the epidermis. The physiological substrate of ETA is not known and, consequently, its mode of action in vivo remains an unanswered question. Determination of the structure of ETA and its comparison with other serine proteases may reveal insights into ETA's catalytic mechanism.

RESULTS

The crystal structure of staphylococcal ETA has been determined by multiple isomorphous replacement and refined at 1.7 A resolution with a crystallographic R factor of 0.184. The structure of ETA reveals it to be a new and unique member of the trypsin-like serine protease family. In contrast to other serine protease folds, ETA can be characterized by ETA-specific surface loops, a lack of cysteine bridges, an oxyanion hole which is not preformed, an S1 specific pocket designed for a negatively charged amino acid and an ETA-specific specific N-terminal helix which is shown to be crucial for substrate hydrolysis.

CONCLUSIONS

Despite very low sequence homology between ETA and other trypsin-like serine proteases, the ETA crystal structure, together with biochemical data and site-directed mutagenesis studies, strongly confirms the classification of ETA in the Glu-endopeptidase family. Direct links can be made between the protease architecture of ETA and its biological activity.

Pulsed-field gel electrophoresis of Staphylococcus hyicus and Staphylococcus chromogenes genomic DNA and its taxonomic, epidemiologic and ecologic applications in veterinary medicine

One hundred and thirty-eight strains of Staphylococcus hyicus and 21 strains of S. chromogenes isolated from animals were analyzed by pulsed-field gel electrophoresis (PFGE) after restriction endonuclease Smal digestion of chromosomal DNA. Eighty-eight strains of S. hyicus from pigs with or without exudative epidermitis (EE) generated 16 to 26 fragments in the size range of < 1 to 485 kb, and yielded 39 different patterns. With regard to the strains from pigs with EE, PFGE patterns differed according to the country of origin. Outbreaks of EE occurring on four separate pig farms in Japan involved S. hyicus with different PFGE patterns. The PFGE patterns shown by S. hyicus strains from 4 kinds of animals were compared. Strains from pigs differed from those isolated from chickens (n = 45; 18 to 24 fragments of < 1 to 425 kb), cows (n = 3; 17 to 19 fragments of < 1 to 475 kb), and goats (n = 2; 16 or 17 fragments of < 1 to 1,125 kb). Also, each of the chicken, cow and goat strains had a host-specific fragment. The results suggest that PFGE analysis might be a useful marker for distinguishing ecovars within S. hyicus. In contrast, strains of S. chromogenes from pigs and cows generated 17 to 24 fragments ranging from < 1 to 545 kb. The PFGE patterns of S. chromogenes strains were more highly conserved than those of S. hyicus. S. chromogenes strains could be distinguished from S. hyicus strains by fragments within the range of 305 to 545 kb. The results indicate that PFGE analysis could be used to distinguish between S. hyicus and S. chromogenes. We conclude that PFGE analysis is a useful tool not only for species or strain identification but also for epidemiologic or ecologic studies of S. hyicus and S. chromogenes.

Importance of Staphylococcus hyicus ssp hyicus as a cause of arthritis in pigs up to 12 weeks of age

Lame pigs, up to 12 weeks of age, were necropsied to establish a diagnosis. Of 175 pigs examined, 165 were confirmed to have arthritis by histopathological examination of joint tissues. Lesions were most common in the elbow and tarsal joints and least common in the joints of the feet. Typically, there was severe fibrinopurulent inflammation of synovial membranes regardless of the bacteria isolated. A bacterial aetiology was found in 114 (69%) of the 165 pigs. In arthritic pigs in which an aetiology was established the causative agents were Staphylococcus hyicus ssp hyicus (24.6%), Streptococcus equisimilis (26.3%), Actinomyces pyogenes (13.2%), Staphylococcus aureus (7.9%) and Haemophilus parasuis (7.9%). While gender did not affect the prevalence of arthritis, there was an age influence, most of the pigs culled for arthritis being under 6 weeks of age.

Correlation between occurrence of exudative epidermitis and exfoliative toxin-producing ability of Staphylococcus hyicus

Staphylococcus hyicus was isolated from healthy pigs and pigs affected with exudative epidermitis (EE). Thirty seven strains (P-7 to P-43) were isolated from pigs affected with EE on 8 farms while 131 strains were isolated from healthy pigs bred on 2 farms in Japan. Isolation rate for pigs affected with EE was 100% while that for healthy pigs was 35.4%. The biochemical and cultural characteristics of the isolates from healthy and diseased pigs were identical except for the Voges-Proskauer reaction. The culture supernatant of many isolates caused skin exfoliation in 1-day-old chickens. Therefore, many isolates were considered to produce S. hyicus exfoliative toxin (shET). The rate of shET production by the isolates from piglets affected with EE was 87.5%, while that of the isolates from healthy pigs was 76.1%. shETs were divided in two serotypes by immunodiffusion. Piglets experimentally infected with shET-producing and nonproducing strains were observed. Local skin erythema at the inoculation site was observed with nonproducing strains and disappeared within 48 h, while the skin erythema at the sites inoculated with shET-producing strains did not disappear until 7 days after inoculation. Typical clinical signs, such as exfoliation, exudation and crusting were observed only in the piglets inoculated with shET-producing strains.

Optimum culture conditions for production of exfoliative toxin by Staphylococcus hyicus

Optimum culture conditions for the production of exfoliative toxin by Staphylococcus hyicus (shET) were examined. High shET activity was obtained from the culture filtrate of HI and TY broth inoculated with S. hyicus. The pH in these two media ranged from 7 to 8.5 during bacterial culture, while the lowest pH in TS and BHI broth was less than 6. shET activity in the culture filtrate from TY broth inoculated with 10(7) CFU of S. hyicus per ml was higher than that in TY broth inoculated with 10(6) and 10(8) CFU of bacteria per ml. When shET activity in the culture filtrate was measured under various shaking conditions, the culture filtrate shaken at 75 oscillations per min had the highest shET activity of the five shaking conditions. shET activity of the culture filtrate of TY broth to which protease inhibitor had been added was the same as that of TY broth without inhibitor. shET activity in a shaking culture in an Erlenmeyer flask was also the same as that in sac culture and that in shaking culture using a shaking (Sakaguchi) flask. shET activity in TY broth supplemented with 100 mM glucose was significantly lower than that in TY broth without glucose. Based on the above results, the optimum culture conditions for the production of shET were as follows: inoculation of 3 x 10(9) CFU of S. hyicus strain P-1 into 300 ml of TY broth in a 2,000-ml Erlenmeyer flask, and incubation at 37 C with shaking at 75 oscillations per min.(ABSTRACT TRUNCATED AT 250 WORDS)

Possible receptor for exfoliative toxins produced by Staphylococcus hyicus and Staphylococcus aureus

Exfoliative toxin produced by Staphylococcus hyicus bound to the GM4-like glycolipid extracted from the skin of 1-day-old chickens but did not bind to glycolipid from adult chickens or suckling mice. Exfoliative toxin produced by Staphylococcus aureus bound to the GM4-like glycolipid extracted from the skin of suckling mice but not to glycolipid from 1-day-old or adult chickens. S. hyicus and S. aureus exfoliative toxins lost their toxicity by preincubation with GM4-like glycolipid from 1-day-old chickens and suckling mice, respectively.

A new type of staphylococcal exfoliative toxin from a Staphylococcus aureus strain isolated from a horse with phlegmon

A new type of staphylococcal exfoliative toxin (sET) was isolated from the culture filtrate of a Staphylococcus aureus strain isolated from a horse with skin infection including phlegmon. The new sET was purified by precipitation with 80% saturated ammonium sulfate, column chromatography on DEAE-cellulofine A-500, gel filtration on a Sephadex G-75 column, and polyacrylamide gel electrophoresis (7.5% polyacrylamide). The new sET elicited general exfoliation of the epidermis with the so-called Nikolsky sign when inoculated into both 3-day-old mice and 1-day-old chicks, whereas sETA and sETB from human strains of S. aureus caused exfoliation in a 3-day-old mouse alone and shET from a porcine strain of Staphylococcus hyicus caused exfoliation in 1-day-old chicks alone. Intraepidermal splitting was observed at the granular layer of the epidermis of mice inoculated with the new sET as well as those inoculated with sETA. Exfoliation at the germinative layer of the epidermis was also observed in the chicks inoculated with the new sET as well as those inoculated with shET. The new sET was serologically different from sETA, sETB, and shET and showed the same molecular weight on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. It was thermolabile and lost its toxicity after being heated at 60 degrees C for 15 min. We propose that the new sET be designated as sETC.

Susceptibility of various animals and cultured cells to exfoliative toxin produced by Staphylococcus hyicus subsp. hyicus

In piglets inoculated with partially purified exfoliative toxin (pp-shET) produced by Staphylococcus hyicus subsp. hyicus, exfoliation was observed at 12 h after injection. Chickens inoculated with the same dose of pp-shET also showed exfoliation within 30 min of injection. However, exfoliation was not demonstrated in mouse, rat, guinea pig, hamster, dog or cat inoculated with pp-shET until 24 h after injection. In cultured cell lines, especially L-929 and Hep-2, the rounding effect occurred after incubation with pp-shET for 1 h. The rounding effect was also seen in five other cultured cells (NCTC 2544, HeLa/S3, HmLu-1, CHO and BHK-21) 6-24 h after exposure to pp-shET. These round cells survived for 72 h after inoculation and formed a monolayer 24 h after changeover to a toxin-free medium. The rounding effect was observed in cells after the formation of the monolayer, but not before. It was suggested that the rounding effect was not caused by the increase in cyclic AMP in cells inoculated with pp-shET but by the cleavage of intracellular contacts.