Exudative epidermitis of piglets caused by non-toxigenic Staphylococcus sciuri.

Infections with strains of Staphylococcus sciuri are a potential threat to animal and public health, and a cause for considerable concern. We isolated and identified S. sciuri as a pathogen from an acute outbreak of exudative epidermitis in piglets for further genetic identification using experimental infections. The results of this study showed that S. sciuri strain NJ1306 reproduced exudative epidermitis in experimentally infected 5-day-old piglets. The isolated bacteria also caused sudden death in BALB/c mice following intraperitoneal injection with 5×108 CFU of the isolate. The data indicated that strain NJ1306 of S. sciuri was pathogenic to piglets and mice, and the study provided the first known report of clinical lung lesions and endocarditis in piglets due to S. sciuri.

A highly pathogenic strain of Staphylococcus sciuri caused fatal exudative epidermitis in piglets.

Staphylococcus sciuri are important human pathogens responsible for endocarditis, peritonitis, septic shock, urinary tract infection, pelvic inflammatory disease and wound infections. However, little information is known regarding the pathogenicity of S. sciuri to animals. From the pericardial fluid of a diseased piglet with exudative epidermitis (EE), we isolated a strain of Staphylococcus in pure culture. Surprisingly, this isolate was a member of S. sciuri rather than S. hyicus as identified by its biochemical traits and also by analysis of 23S ribosomal DNA using Internal Transcribed Spacer PCR. In addition, inoculation of newborn piglets with 1x10(10) CFU of the isolate by oral feeding or intra-muscular injection successfully reproduced EE in piglets, which suggested that the oral intake of the pathogen by the animals is one of the major routes of exposure. These unexpected findings prioritized S. sciuri as important zoonotic agents, which may have ramifications for human medicine.

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.

Exudative epidermitis in pigs caused by toxigenic Staphylococcus chromogenes.

Staphylococcus chromogenes is closely related to Staphylococcus hyicus, which is recognised as the causative agent of exudative epidermitis (EE) in pigs. S. chromogenes is part of the normal skin flora of pigs, cattle and poultry and has so far been considered non-pathogenic to pigs. A strain of S. chromogenes producing exfoliative toxin type B, ExhB, was identified by the use of a multiplex PCR specific for the exfoliative toxins from S. hyicus. The exfoliative toxin from S. chromogenes reacted in immunoblot analysis with polyclonal and monoclonal antibodies specific to ExhB from S. hyicus and had an apparent molecular weight of 30 kDa. Sequencing the gene encoding the exfoliative toxin from S. chromogenes revealed that the molecular weight of the toxin with the signal peptide and the mature toxin was 30,553 and 26,694 Da, respectively. Comparison of the exhB genes from S. chromogenes strain VA654 and S. hyicus strain 1289D-88 showed differences in seven base pairs of the DNA sequences and in two amino acid residues in the deduced amino acid sequences. Pigs were experimentally inoculated with S. chromogenes strain VA654. By clinical observations and histopathological evaluation of the skin alterations, all pigs revealed development of generalized exudative epidermitis. No toxin producing S. hyicus was isolated from the pigs and all ExhB-positive bacterial isolates were identified as S. chromogenes. This confirmed that the disease-causing agent was the inoculated S. chromogenes strain VA654. The results of this study show that S. chromogenes may cause exudative epidermitis in pigs.

Isolation of Staphylococcus hyicus subsp. hyicus from pigs affected with exudative epidermitis and experimental infection of piglets with isolates.

Five strains of Staphylococcus hyicus subsp. hyicus were isolated: three strains (P-1, P-2 and P-3) from the crust on the body surface of 6-month-old pigs on a farm in Aomori prefecture, and two (P-5 and P-6) from both the crust on the body surface and the joint of a 1-month-old piglet with exudative epidermitis (EE) on another farm. The characterization of the isolates and the experimental infection of the piglets with strain P-1 were carried out. Subcutaneous inoculation with the bacterial suspension (10(10) CFU) produced EE to all nine piglets. Eight of them had exudation and exfoliation within 24 hr of infection. Histopathologically, disappearance of stratum corneum and necrosis with vacuolar degeneration of prickle cells were remarkable in the epidermis. Infiltration of neutrophils and lymphocytes were observed in the dermis. The results clearly indicate that S. hyicus is responsible for incrustation of the body surface of weanling pigs and exudative epidermitis in young piglets.

Ulcerative glossitis and stomatitis associated with exudative epidermitis in suckling swine.

Thirty piglets 1 to 4 weeks old from five herds had epidermal, foot, conjunctival and renal lesions typical of exudative epidermitis. Ten piglets had a large central ulceration of the dorsum of the tongue. Three piglets had multiple erosions of the hard palate and one had mucoid degeneration of the urinary bladder epithelium and a thick viscous material in the renal pelvis, ureters and urinary bladder.