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

Outbreak of staphylococcal bullous impetigo in a maternity ward linked to an asymptomatic healthcare worker

An outbreak of staphylococcal bullous impetigo occurred over a period of five months in a maternity ward involving seven infected and two colonised neonates. The skin lesions were due to epidermolytic toxin A-producing Staphylococcus aureus. Infection control measures were implemented and a retrospective case-control study performed. Contact with an auxiliary nurse was the only risk factor for cases of bullous impetigo (P<0.01). The nurse cared for all seven cases and was an asymptomatic nasal carrier of the epidemic strain. Repeated courses of decontamination treatment failed to eradicate carriage. Nine months after the last case, another neonate developed a more severe form of bullous impetigo and the auxiliary nurse was reassigned to an adult ward.

Distribution of the exfoliative toxin D gene in clinical Staphylococcus aureus isolates in France

Exfoliative toxin D (ETD) was identified recently as a new exfoliative toxin serotype. Like other exfoliative toxins, ETD induces intra-epidermal cleavage through the granular layer of the epidermis of neonatal mice. The distribution of ETD production was investigated in Staphylococcus aureus isolates from infected and colonised patients in France. The etd gene was found in 55 (10.5%) of 522 isolates tested. Isolates responsible for bullous impetigo and generalised staphylococcal scalded skin syndrome did not harbour etd, but etd was significantly more frequent in isolates causing cutaneous abscesses and furuncles. Most etd- and Panton-Valentine leukocidin-positive strains belonged to the clone of community-acquired methicillin-resistant S. aureus spreading currently throughout France.

Transduction of the plasmid encoding antiseptic resistance gene qacB in Staphylococcus aureus

The plasmid-borne qacA and qacB genes encode a multidrug efflux protein. The proteins encoded by qacA and qacB mediate efflux of cationic antiseptic agents such as quaternary ammonium compounds. In methicillin-resistant Staphylococcus aureus (MRSA), qacA and qacB are widely prevalent and decrease antiseptic susceptibility. However, it is difficult to find the plasmids encoding qacA or qacB in community-associated MRSA (C-MRSA) isolated from patients with impetigo. Most MRSA, the strains causative of impetigo, carry the plasmid-borne exfoliative toxin-producing gene etb. To find the reason for the paucity of qacA or qacB in MRSA isolated from patients with impetigo, we performed transfer experiments of the plasmid pTZ2162qacB encoding qacB. The pTZ2162qacB was transferred to S. aureus strain RN4220 by transduction, although no pTZ2162qacB was transferred by conjugation. Additionally, pTZ2162qacB was transduced to MRSA carrying etb, and was coexistence with the plasmid encoding etb. Our results showed that pTZ2162qacB was horizontally transferred by transduction and was compatible with the plasmid encoding etb. Consequently, there will be risk of the emergence of C-MRSA with decreased antiseptic susceptibility among patients with impetigo.

Virulence determinants in community and hospital meticillin-resistant Staphylococcus aureus

Staphylococcus aureus produces many virulence factors, most of which act in a synergistic and coordinated fashion. Some appear to be specifically associated with certain severe infections and are produced by meticillin-resistant Staphylococcus aureus (MRSA) clones distributed worldwide. Superantigenic exotoxins appear to be major virulence factors in hospital MRSA clones (HA-MRSA), and staphylococcal enterotoxin A (SEA) may be involved in the physiopathology of septic shock. Panton Valentine Leucocidin (PVL) has emerged as a major virulence factor in community-acquired Staphylococcus aureus (CA-MRSA) infections. In particular, the leukotoxic action of PVL is responsible for the high mortality rate associated with necrotizing pneumonia. CA-MRSA can also harbour the toxic shock toxin 1 (TSST-1) and rarely the exfoliative toxin.

Characterization of oxacillin-susceptible mecA-positive Staphylococcus aureus: a new type of MRSA

Methicillin-resistant Staphylococcus aureus (MRSA) has been defined as S. aureus having the mecA gene or showing a minimum inhibitory concentration (MIC) of oxacillin higher than 4 mg/l. However, some clinical isolates are mecA-positive and oxacillin-susceptible. Therefore, we surveyed the occurrence of S. aureus having the mecA gene and an MIC of oxacillin of less than 2 mg/l (oxacillin-susceptible MRSA; OS-MRSA) in a total of 480 strains of S. aureus collected from 11 hospitals in different location in Japan isolated from 2003 through 2005. We found 6 strains matching the criteria for OS-MRSA. All 6 strains were staphylococcal cassette chromosome (SCC) mec-positive, without exception, and 4 strains showed the SCCmec type III-variant, which is unique in Japan. These OS-MRSAs were least resistant to oxacillin among the MRSAs tested and they were within the susceptible range to seven other beta-lactam antibiotics tested. Thus, OS-MRSA may become a high-resistant MRSA upon the treatment of patients with beta-lactam antibiotics. To characterize whether these OS-MRSAs were hospital-acquired or community-acquired MRSAs, we tested for the presence of the genes encoding toxins. Genes encoding hemolysin, exfoliative toxin, enterotoxin, toxic shock syndrome toxin-1, and Panton-Valentine leukocidin were found in 6, 4, 0, 0, and 0 strains, respectively. These results revealed that OS-MRSAs could be classified as a new type of MRSA that exhibits properties distinguishable from either hospital- or community-acquired MRSA. Coagulase typing of the OS-MRSAs supported the above conclusion. In this study, the occurrence of OS-MRSA at a certain frequency was noted; precautions are called for in the classification of oxacillin-resistant S. aureus and in the treatment of OS-MRSA infection.

Nationwide molecular surveillance of exfoliative toxigenic Staphylococcus hyicus on pig farms across Japan

We investigated the carriage of Staphylococcus hyicus and their exfoliative toxin genes (exhA, exhB, exhC, exhD, and shetb) among 424 pigs from 38 Japanese pig farms by PCR and characterized the isolates by 16S-23S intergenic spacer region polymorphism analysis. S. hyicus (n=207) were isolated from 17.9% of pigs and 72.5% of them were toxigenic. The isolation rate of toxigenic S. hyicus was four times higher in the pigs with exudative epidermitis than the healthy pigs (87.6% versus 19.6%; p<0.01). Among the toxins, exhA was the most prevalent, being detectable in 49.3% of toxin gene-positive strains. S. hyicus isolates were distributed into nine ITS-PCR types (a-i), with ITS-PCR types d, h, and e being predominant accounting for 70% (145/207) of total isolates or 76% (114/150) of toxin gene-positive strains. This study denotes high prevalence of toxigenic strains among S. hyicus circulating on pig farms in Japan.

Relatedness between the two-component lantibiotics lacticin 3147 and staphylococcin C55 based on structure, genetics and biological activity

Background

Two component lantibiotics, such as the plasmid-encoded lacticin 3147 produced by Lactococcus lactis DPC3147 and staphylococcin C55 produced by Staphylococcus aureus C55, represent an emerging subgroup of bacteriocins. These two bacteriocins are particularly closely related, exhibiting 86% (LtnA1 and C55α) and 55% (LtnA2 and C55β) identity in their component peptides. The aim of this study was to investigate, for the first time for any two component bacteriocins, the significance of the relatedness between these two systems.

Results

So close is this relatedness that the hybrid peptide pairs LtnA1:C55β and C55α:LtnA2 were found to have activities in the single nanomolar range, comparing well with the native pairings. To determine whether this flexibility extended to the associated post-translational modification/processing machinery, the staphylococcin C55 structural genes were directly substituted for their lacticin 3147 counterparts in the ltn operon on the large conjugative lactococcal plasmid pMRC01. It was established that the lacticin LtnA1 post-translational and processing machinery could produce functionally active C55α, but not C55β. In order to investigate in closer detail the significance of the differences between LtnA1 and C55α, three residues in LtnA1 were replaced with the equivalent residues in C55α. Surprisingly, one such mutant LtnA1-Leu21Ala was not produced. This may be significant given the positioning of this residue in a putative lipid II binding loop.

Conclusion

It is apparent, despite sharing striking similarities in terms of structure and activity, that these two complex bacteriocins display some highly dedicated features particular to either system.

Staphylococcal Scalded Skin Syndrome: Criteria for Differential Diagnosis from Lyell's Syndrome. Two Cases in Adult Patients

A review of the relative international literature of the last few years is followed by a description of two cases of staphylococcal scalded skin syndrome in adults. As in both cases the initial diagnosis was that of Lyell's syndrome, the main criteria for the differential diagnosis of the two pathologies are considered in order to permit specific and effective treatment.

Association between the methicillin resistance of clinical isolates of Staphylococcus aureus, their staphylococcal cassette chromosome mec (SCCmec) subtype classification, and their toxin gene profiles

Virulence and antimicrobial resistance are important determinators of the clinical manifestations and of the treatments of bacterial infections. Here, we studied the associations between the methicillin resistance of clinical Staphylococcus aureus isolates, their classifications as particular staphylococcal cassette chromosome mec (SCCmec) subtypes, and their toxin gene profiles. In total, 252 S. aureus isolates were collected from 13 healthcare facilities in 6 Korean provinces. The overall prevalence of methicillin-resistant S. aureus (MRSA) was 63%. SCCmec typing and toxin gene analysis were performed by multiplex polymerase chain reaction. One or more staphylococcal toxin genes were found in 190 (75.4%) strains. Methicillin-resistant S. aureus strains carried toxin genes more frequently than methicillin-susceptible S. aureus strains (85.5% versus 53.8%). SCCmec subtypes differed in terms of their frequencies of toxin gene carriage (95.9% in SCCmec II, 74.4% in SCCmec III, and 68.8% in SCCmec IV). Specific SCCmec subtypes frequently harbored particular toxin gene combinations: 77.3% of SCCmec II strains carried sec and tst genes, 48.8% of SCCmec III strains carried sea and see genes, and 46.9% of SCCmec IV carried sea and seb genes. Indeed, the most prevalent combination in MRSA strains, that of sec and tst, was only observed in SCCmec II strains, and these strains failed to show the coexistence of sea and see or sea and seb genes. Thus, the SCCmec subtypes of S. aureus revealed specific staphylococcal toxin profiles. We revealed that certain staphylococcal toxin gene profiles are associated not only with the methicillin resistance of S. aureus but also with their SCCmec subtypes.

Multiplex PCR for detection of three exfoliative toxin serotype genes in Staphylococcus aureus

Rapid and specific detection of exfoliative toxin (ET)-producing Staphylococcus aureus strains by multiplex polymerase chain reaction (PCR) was used for identification of exfoliative toxin genes in a diverse set of 115 clinical S. aureus strains isolated in 14 Czech cities between 1998 and 2004. Fifty-nine wild-type ET-positive isolates of which 40 strains were the causative agents of toxic epidermolysis in neonates were classified into 4 PCR types. The genes coding for ETA, ETB or ETD were not detected in any of non-ET-producing isolates. The PCR method using the multiplex and specific primer set was shown to be reliable in rapid identification of the exfoliative toxin producing S. aureus and can be used as a convenient tool for hospital epidermolytic infection control.

Antimicrobial agent of susceptibilities and antiseptic resistance gene distribution among methicillin-resistant Staphylococcus aureus isolates from patients with impetigo and staphylococcal scalded skin syndrome

The susceptibilities to antimicrobial agents of and distributions of antiseptic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA) strains isolated between 1999 and 2004 in Japan were examined. The data of MRSA strains that are causative agents of impetigo and staphylococcal scalded skin syndrome (SSSS) were compared with those of MRSA strains isolated from patients with other diseases. The susceptibilities to antiseptic agents in MRSA isolates from patients with impetigo and SSSS were higher than those in MRSA isolates from patients with other diseases. The distribution of the qacA/B genes in MRSA strains isolated from patients with impetigo and SSSS (1.3%, 1/76) was remarkably lower than that in MRSA strains isolated from patients with other diseases (45.9%, 95/207). Epidemiologic typings of staphylococcal cassette chromosome mec (SCCmec) and pulsed-field gel electrophoresis (PFGE) showed that MRSA strains isolated from patients with impetigo and SSSS had type IV SCCmec (75/76), except for one strain, and 64.5% (49/76) of the strains had different PFGE types. In addition, the patterns of restriction digestion of all tested qacA/B plasmid in MRSA isolates having different PFGE types were identical. The results showed that a specific MRSA clone carrying qacA/B was not prevalent, but qacA/B was spread among health care-associated MRSA strains. Therefore, it was concluded that the lower distribution rate of qacA/B resulted in higher susceptibilities to cationic antiseptic agents in MRSA isolated from patients with impetigo and SSSS.

Staphylococcal cutaneous infections: invasion, evasion and aggression

Staphylococcal infections cause a variety of cutaneous and systemic infections, including impetigo, furuncle, subcutaneous abscess, staphylococcal scalded skin syndrome (SSSS), toxic shock syndrome (TSS) and neonatal toxic shock syndrome-like exanthematous disease (NTED), in association with microbial virulence factors. The virulence factors produced by Staphylococcus aureus have a wide array of biological properties, including disruption of the epithelial barrier, inhibition of opsonization by antibody and complement, interference with neutrophil chemotaxis, cytolysis of neutrophils, and inactivation of antimicrobial peptides. Exfoliative toxins (ETs) induce the 'acantholytic' infection of S. aureus due to the disruption of cell-to-cell cohesion, which allows the pathogenic organisms to spread within the epithelium. Furthermore, S. aureus expresses exotoxins with biological properties of superantigens that induce T-cell activation with subsequent anergy and immunosuppression. Of the S. aureus leukotoxins, Panton-Valentine leukocidin (PVL) is involved in the development of multiple furuncles with more intense erythema, particularly in healthy young adults. TSS is an acute life-threatening illness caused by TSS toxin-1 (TSST-1) and is usually classified into two categories; menstrual TSS, originally described in association with tampon use, and nonmenstrual TSS with a variety of clinical settings. NTED is a neonatal disease induced by TSST-1 although clinical symptoms are much milder than those of TSS. In TSS and NTED, the expansion of TSST-1-reactive Vbeta2-positive T cells is observed. The production of pathogenic S. aureus exotoxins and biofilm formation is regulated by the accessory gene regulator (agr) locus in the quorum-sensing signaling pathway. There is no doubt that targeting the quorum-sensing signaling pathway or anti-toxin therapy is a promising therapeutic approach supportive of primary antibiotic therapy.

Staphylococcal skin infections in children: rational drug therapy recommendations

Staphylococcus aureus remains one of the most common and troublesome of bacteria causing disease in humans, despite the development of effective antibacterials and improvement in hygiene. The organism is responsible for over 70% of all skin and soft tissue infections in children and accounts for up to one-fifth of all visits to pediatric clinics. Skin and soft tissue infections that are predominantly caused by S. aureus include bullous and non-bullous impetigo, folliculitis, furunculosis, carbunculosis, cellulitis, surgical and traumatic wound infections, mastitis, and neonatal omphalitis. Other skin and soft tissue infections may also be caused by S. aureus but are often polymicrobial in origin and require special consideration. These include burns, decubitus ulcers (particularly in the perianal region), puncture wounds of the foot, as well as human and mammalian bites. Treatment of staphylococcal skin infections varies from topical antiseptics to prolonged intravenous antibacterials, depending on severity of the lesions and the health of the child. The treatment of choice for oral antibacterials remains the penicillinase-resistant penicillins such as flucloxacillin. Cefalexin and erythromycin are suitable cost-effective alternatives with broader cover, although care must be taken with the use of macrolides because of development of resistance to multiple families of antibacterials, particularly the lincosamides. Other cephalosporins such as cefadroxil and cefprozil are also effective, can be given once daily and have a better tolerability profile -- while azithromycin has a further advantage of a 3-day course. However, all of these agents are more expensive. Although the antibacterials have been given for 10 days in most clinical trials, there is no evidence that this duration is more effective than a 7-day course. In children requiring intravenous therapy, ceftriaxone has a major advantage over other antibacterials such as sulbactam/ampicillin and cefuroxime in that it can be given once daily and may, therefore, be suitable for outpatient treatment of moderate-to-severe skin infections. Newer-generation cephalosporins and loracarbef are also effective and have a broader spectrum of activity, but do not offer any added benefit and are significantly more expensive. Skin and soft tissue infections due to methicillin-resistant S. aureus (MRSA) are still relatively uncommon in children. Well children with community-acquired MRSA infections can be treated with clindamycin or trimethoprim-sulfamethoxazole (cotrimoxazole), but must be observed closely for potentially severe adverse effects. In severe infections, vancomycin remains the treatment of choice, while intravenous teicoplanin and clindamycin are suitable alternatives. Linezolid and quinupristin/dalfopristin are currently showing great promise for the treatment of multi-resistant Gram-positive infections. While the choice of antibacterial is important, supportive management, including removal of any infected foreign bodies, surgical drainage of walled-off lesions, and regular wound cleaning, play a vital role in ensuring cure.

Virulence determinants in Staphylococcus aureus and their involvement in clinical syndromes

Staphylococcus aureus is a major human pathogen responsible for a variety of toxin-mediated and suppurative diseases. About 50 staphylococcal virulence factors have been described to date. In this review, we examine the clinical implications of key staphylococcal virulence factors in toxin-mediated diseases, septic shock, and severe focal infections such as arthritis, infective endocarditis, pneumonia acquired during mechanical ventilation, and necrotizing pneumonia. Staphylococcal pathogenicity is sometimes due principally to a single virulence factor, as in toxic shock syndrome and necrotizing pneumonia. In contrast, several virulence factors are involved in other staphylococcal disease, such as septic shock. A better knowledge of the mechanism of action of each virulence factor involved in the different staphylococcal diseases could open the way to the use of specific inhibitors in the clinical setting.

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.

Molluscum contagiosum prevents progression of staphylococcal scalded skin syndrome

Prevention of progression of staphylococcal scalded skin syndrome by molluscum contagiosum indicated a possible interference by viral anti-cytokine molecule such as interleukin-18 binding protein.

Nosocomial outbreak of staphylococcal scalded skin syndrome in neonates: epidemiological investigation and control

Over a three-month period, 13 neonates developed staphylococcal scalded skin syndrome (SSSS) in a maternity unit, between four and 18 days after their birth. An epidemiological and descriptive study followed by a case-control study was performed. A case was defined as a neonate with blistering or peeling skin, and exfoliative toxin A Staphylococcus aureus positive cultures. Controls were selected at random from the asymptomatic, non-colonized neonates born on the same day as the cases. All staff members and all neonates born during the outbreak period were screened for carriage by nasal swabs and umbilical swabs, respectively. S. aureus isolates were polymerase chain reaction (PCR) screened for etA gene and genotyped by pulsed-field gel electrophoresis (PFGE). Two clusters of eight and five cases were identified. Receiving more than one early umbilical care procedure by the same ancillary nurse was the only risk factor identified in the case-control study (odds ratio=15, 95% confidence intervals 2-328). The ancillary nurse suffered from chronic dermatitis on her hands that favoured S. aureus carriage. Exfoliative-toxin-A-producing strains, as evidenced by PCR and indistinguishable by PFGE, were isolated from all but one of the SSSS cases, from four asymptomatic neonates, from two staff members and from the ancillary nurse's hands. Removal of the ancillary nurse from duty, infection control measures (isolation precautions, chlorhexidine handwashing and barrier protections), and treatment of the carriers (nasal mupirocin and chlorhexidine showers) led to control of the epidemic. In conclusion, this study emphasizes the need for tight surveillance of chronic dermatitis in healthcare workers.

A Panton-Valentine leucocidin (PVL)-positive community-acquired methicillin-resistant Staphylococcus aureus (MRSA) strain, another such strain carrying a multiple-drug resistance plasmid, and other more-typical PVL-negative MRSA strains found in Japan

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was collected from children with bullous impetigo in 2003 and 2004. One strain collected in 2003 was Panton-Valentine leucocidin (PVL) positive. In 2004, a multiple-drug-resistant PVL(+) CA-MRSA strain was isolated from an athlete with a cutaneous abscess. These strains were analyzed by multilocus sequence typing, spa typing, agr typing, coagulase typing, staphylococcal cassette chromosome mec (SCCmec) typing, PCR assay for 30 virulence genes, drug susceptibility testing, pulsed-field gel electrophoresis, and for plasmids. The two Japanese PVL(+) CA-MRSA strains belonged to the globally extant ("pandemic") sequence type 30 (ST30) with SCCmec IV. A transmissible, multiple-drug resistance plasmid emerged in such ST30 strains. The PVL(-) CA-MRSA strains ("domestic" CA-MRSA) accumulated for bullous impetigo, exhibiting new genotypes. Hospital-acquired MRSA of ST91 (but not pandemic ST5) shared common features with the PVL(-) CA-MRSA strain.

Clinical manifestations of staphylococcal scalded-skin syndrome depend on serotypes of exfoliative toxins

We sought a possible correlation between the clinical manifestations of staphylococcal scalded-skin syndrome (SSSS) and the serotype of exfoliative toxins (ET) by PCR screening of the eta and etb genes in Staphylococcus aureus strains isolated from 103 patients with generalized SSSS and 95 patients with bullous impetigo. The eta gene and the etb gene were detected in, respectively, 31 (30%) and 20 (19%) episodes of generalized SSSS and 57 (60%) and 5 (5%) episodes of bullous impetigo. Both genes were detected in 52 (50%) episodes of generalized SSS and 33 (35%) episodes of bullous impetigo. To explain this link between etb and generalized SSSS, we examined the distribution of ETA- and ETB-specific antibodies in the healthy population (n = 175) and found that the anti-ETB antibody titer was lower than the anti-ETA titer. Thus, ETA is associated with bullous impetigo and ETB is associated with generalized SSSS, possibly owing to a lower titer of anti-ETB neutralizing antibodies in the general population.

Sensitive and specific detection of staphylococcal epidermolysins A and B in broth cultures by flow cytometry-assisted multiplex immunoassay

Two of the most common bacterial skin infections of young infants and children are bullous impetigo due to Staphylococcus aureus and its more acute form, staphylococcal scalded skin syndrome. Epidermolysin A (ETA), ETB and, possibly, ETD are responsible for these diseases, which may appear as epidemics in pediatric patients. We tested the reliability of a flow cytometry-assisted multiplex immunoassay (Bio-Plex system) for the detection of ETA and ETB. The Bio-Plex system was found to be highly specific and highly sensitive for toxin concentrations of between 2 and 80,000 pg/ml. The results of this assay were 100% identical to the results of a PCR-based method. We demonstrated that this test did not generate any cross-reactions with ETD-producing isolates. The level of detection of ETB by this test differed according to culture conditions and from isolate to isolate; these results must be taken into account for diagnostic purposes.

Neonatal skin barrier: structure, function, and disorders

The development of the human skin from intrauterine to extrauterine life is a balletic interplay of maturing layers and interlocking structures. We discuss this transition and then branch out to touch on issues of premature infant as well as neonatal skin care. Disruption of the barrier function due to toxins and development errors are expounded upon. Staph scalded skin syndrome, collodion membrane, bullous congenital ichthyosiform erythroderma, autosomal recessive ichthyosis (lamellar and congenital ichthyosiform erythroderma), and harlequin fetus are used as examples of these disruptions. Discussion of therapy with the authors' experience highlights each disease.

Comparative genomics of Staphylococcus aureus musculoskeletal isolates

Much of the research aimed at defining the pathogenesis of Staphylococcus aureus has been done with a limited number of strains, most notably the 8325-4 derivative RN6390. Several lines of evidence indicate that this strain is unique by comparison to clinical isolates of S. aureus. Based on this, we have focused our efforts on two clinical isolates (UAMS-1 and UAMS-601), both of which are hypervirulent in our animal models of musculoskeletal infection. In this study, we used comparative genomic hybridization to assess the genome content of these two isolates relative to RN6390 and each of seven sequenced S. aureus isolates. Our comparisons were done by using an amplicon-based microarray from the Pathogen Functional Genomics Resource Center and an Affymetrix GeneChip that collectively represent the genomes of all seven sequenced strains. Our results confirmed that UAMS-1 and UAMS-601 share specific attributes that distinguish them from RN6390. Potentially important differences included the presence of cna and the absence of isaB, sarT, sarU, and sasG in the UAMS isolates. Among the sequenced strains, the UAMS isolates were most closely related to the dominant European clone EMRSA-16. In contrast, RN6390, NCTC 8325, and COL formed a distinct cluster that, by comparison to the other four sequenced strains (Mu50, N315, MW2, and SANGER-476), was the most distantly related to the UAMS isolates and EMRSA-16.

PCR-based Detection of Genes encoding Virulence Determinants in Staphylococcus aureus from Birds

The present study was designed to comparatively investigate 19 Staphylococcus aureus strains isolated from specimens of 19 different birds during routine microbiological diagnostics. The S. aureus strains were characterized genotypically by polymerase chain reaction (PCR) amplification using 62 different oligonucleotide primers amplifying genes encoding staphylococcal cell surface proteins, exoproteins and two classes of the accessory gene regulator agr. All 19 investigated S. aureus were positive for the gene segment encoding a S. aureus-specific part of the 23S rRNA, the genes encoding thermostable nuclease (nuc), clumping factor (clfA) and coagulase (coa) and the gene segments encoding the Xr-repetitive region and the immunoglobulin G (IgG)-binding region of protein A (spa). In addition, all tested strains were positive for the genes hla and fnbA and negative for the genes seb, sec, sed, see, sej, tst, eta and etb. The remaining genes, including sbi, hlb, fnbB, ebpS, cna (domains A and B), cap5, cap8, set1, agr class I, agr class II, sea, seg, seh and sei were detected in a variable number of isolates. The presented data give an overview on the distribution of virulence determinants of S. aureus strains isolated from birds. This might be useful to understand the role of these virulence determinants in bird infections.

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.

Defining the pathogenic involvement of desmoglein 4 in pemphigus and staphylococcal scalded skin syndrome

Desmogleins (Dsgs), cadherin-type cell adhesion molecules, are targeted in skin-blistering diseases such as pemphigus and staphylococcal scalded skin syndrome (SSSS). The role of Dsg4, a new isoform, was investigated in these diseases. Dsg4 was recognized by 30 (77%) of 39 pemphigus sera containing anti-Dsg1 IgG but not by 16 pemphigus sera containing no anti-Dsg1 IgG or by 34 normal control sera. The Dsg4 immunoreactivity of these sera was abolished by removal of anti-Dsg1 IgG. Conversely, the removal of anti-Dsg4 IgG from pemphigus sera reduced the immunoreactivity against Dsg1 only 13.8% +/- 8.8% (n = 23) and did not affect its ability to induce blisters in neonatal mice. IgG that was affinity-purified on Dsg4 recognized Dsg1 but failed to induce blisters, while IgG purified on Dsg1 from the same pemphigus foliaceus sera induced blisters. Thus, pemphigus sera show Dsg4 reactivity due to cross-reactivity of a subset of anti-Dsg1 IgG, and the Dsg4/Dsg1-cross-reacting IgG has no demonstrable pathogenic effect. In addition, Dsg4 was not cleaved by exfoliative toxins that induce blisters in SSSS. These findings suggest that Dsg4 may play a role other than adhesion and that the cross-reactivity of desmoglein autoantibodies should be factored into the framework of future studies of autoimmune mechanisms in pemphigus.

Staphyloccocal scalded skin syndrome in an adult

We report a case of staphyloccocal scalded skin syndrome due to an oxacillin-susceptible Staphylococcus aureus in an 81-year-old woman. The patient was admitted to the emergency room with arthritis of the left shoulder, ten days after an intra-articular injection of corticosteroids. The shoulder's puncture showed a purulent liquid and gram positive cocci in cluster suggesting the presence of Staphylococcus sp. on the Gram-stain. The culture confirmed the identification of an oxacillin-susceptible Staphylococcus aureus. Before administration of any dose of oxacillin, blisters appeared on the skin, that quickly ruptured, particulary in areas of friction. The exfoliated areas were extensive and resolution of all the lesions was reached after 3 weeks. The skin biopsy showed superficial epidermolysis confirming the diagnosis. Staphyloccocal scalded skin syndrome is usually described in neonates and young children, often in outbreaks. Few cases have been reported in adults, most often associated with severe underlying diseases. The mortality rate is low in children but can reach almost 60% in adults. The most important diagnosis to exclude is Lyell's syndrome which can be done by the skin biopsy.

Presence of staphylococcal exfoliative toxin A in sera of patients with atopic dermatitis

BACKGROUND

It has been reported that the toxins that Staphylococcus aureus produces are associated with the exacerbation of atopic dermatitis (AD). It has been shown in many studies that staphylococcal enterotoxin (SE) A and SEB contribute to AD by humoral immunity through IgE production as a superantigen. On the other hand, little attention has been paid to the relationship between AD and exfoliative toxin x (ETx).

OBJECTIVE

We investigated the toxins that are frequently detected from the skin of patients and how these toxins affect AD.

METHODS

S. aureus, isolated from the skin of 100 patients with mild to severe AD, were examined for the producibility of toxins by polymerase chain reaction. Serum samples were obtained from 21 patients with mild and moderate AD. The levels of SEB, ETA, total IgE, specific IgE, and specific IgG in sera were measured by ELISA.

RESULTS

SEB was most frequently detected from S. aureus on the skin of these patients as previously reported. And ETx, to which little attention has been paid so far, was frequently detected next to SEB. Furthermore, ETA was detected from the sera of almost all the AD patients. SEB was not detected at all. Although the level of ETA in the AD group was significantly higher than that of controls, ETA-specific IgE was not detected from their sera. High levels of ETA tended to be detected from infantile patients. Although there were no significant differences in the levels of ETA-IgG between AD and the controls, its prevalence was more than twice as high as the controls in AD.

CONCLUSION

These results suggest that many AD patients were exposed to ETx. We conclude that ETx may contribute to exacerbation of AD, particularly in infants, by a mechanism that is not through specific IgE production, unlike SEB.

A multiplex PCR for detection of genes encoding exfoliative toxins from Staphylococcus hyicus

AIMS

To develop a multiplex PCR for detection of genes encoding the exfoliative toxins ExhA, ExhB, ExhC and ExhD from Staphylococcus hyicus and to estimate the prevalence of exfoliative toxins among Staph. hyicus isolates from Danish pig herds with exudative epidermitis (EE).

METHODS AND RESULTS

A multiplex PCR employing specific primers for each of the genes encoding four different exfoliative toxins was developed and evaluated using a collection of Staph. hyicus with known toxin type and a number of other staphylococcal species. A total of 314 Staph. hyicus isolates from pigs with EE were screened by multiplex PCR and the combined results of the present and previous investigations showed that ExhA, ExhB, ExhC and ExhD was found in 20, 33, 18 and 22%, respectively, of 60 cases of EE investigated.

CONCLUSIONS

This study has provided a new tool for detection of toxigenic Staph. hyicus and a more comprehensive picture of the prevalence of the Staph. hyicus exfoliative toxins in Danish pig herds.

SIGNIFICANCE AND IMPACT OF THE STUDY

The multiplex PCR can be used in studies on the prevalence of toxigenic Staph. hyicus elucidating the epidemiology of EE in pigs. The multiplex PCR is currently being used for selection of Staph. hyicus isolates for production of autogenous vaccine.

Phages and the evolution of bacterial pathogens: from genomic rearrangements to lysogenic conversion

Comparative genomics demonstrated that the chromosomes from bacteria and their viruses (bacteriophages) are coevolving. This process is most evident for bacterial pathogens where the majority contain prophages or phage remnants integrated into the bacterial DNA. Many prophages from bacterial pathogens encode virulence factors. Two situations can be distinguished: Vibrio cholerae, Shiga toxin-producing Escherichia coli, Corynebacterium diphtheriae, and Clostridium botulinum depend on a specific prophage-encoded toxin for causing a specific disease, whereas Staphylococcus aureus, Streptococcus pyogenes, and Salmonella enterica serovar Typhimurium harbor a multitude of prophages and each phage-encoded virulence or fitness factor makes an incremental contribution to the fitness of the lysogen. These prophages behave like "swarms" of related prophages. Prophage diversification seems to be fueled by the frequent transfer of phage material by recombination with superinfecting phages, resident prophages, or occasional acquisition of other mobile DNA elements or bacterial chromosomal genes. Prophages also contribute to the diversification of the bacterial genome architecture. In many cases, they actually represent a large fraction of the strain-specific DNA sequences. In addition, they can serve as anchoring points for genome inversions. The current review presents the available genomics and biological data on prophages from bacterial pathogens in an evolutionary framework.

Enterotoxin B Is the Predominant Toxin Involved in Staphylococcal Scarlet Fever in Taiwan

This study retrospectively reviewed all pediatric cases of staphylococcal scarlet fever (SSF) that occurred during a 10-year period in a 1400-bed tertiary medical center in northern Taiwan. All 20 cases of SSF occurred in previously healthy individuals. Skin and soft-tissue infections predominated among children from whom Staphylococcus aureus was isolated. Polymerase chain reaction testing was used to detect known staphylococcal toxin genes, and of the isolates studied, most (18 [90%] of 20) contained only the staphylococcal enterotoxin B. One of the other strains was positive for staphylococcal enterotoxin A only, and the last strain was positive for both staphylococcal enterotoxin G and staphylococcal enterotoxin I. Pulsed-field gel electrophoresis identified a small cluster of isolates (6 [30%] of 20) that were genetically related, but these strains came from epidemiologically unrelated patients during a 3-year period.

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.

Enzymatic and Molecular Characteristics of the Efficiency and Specificity of Exfoliative Toxin Cleavage of Desmoglein 1

Exfoliative toxins (ETs) from Staphylococcus aureus blister the superficial epidermis by hydrolyzing a single peptide bond, Glu381-Gly382, located between extracellular domains 3 and 4 of desmoglein 1 (Dsg1). Enzyme activity is dependent on the calcium-stabilized structure of Dsg1. Here we further define the characteristics of this cleavage. Kinetic studies monitoring the cleavage of Dsg1 by ETA, ETB, and ETD demonstrated kcat/Km values of 2-6 x 10(4) m(-1) s(-1), suggesting very efficient proteolysis. Proteolysis by ETA was not efficiently inhibited by broad spectrum serine protease inhibitors, suggesting that the enzyme cleavage site may be inactive or inaccessible before specific binding to its substrate. Using truncated mutants of human Dsg1 and chimeric molecules between human Dsg1 and either human Dsg3 or canine Dsg1, we show that for cleavage, human-specific amino acids from Dsg1 are necessary in extracellular domain 3 upstream of the scissile bond. If these residues are canine rather than human, ETA binds, but does not cleave, canine Dsg1. These data suggest that the exquisite specificity and efficiency of ETA may depend on the enzyme's binding upstream of the cleavage site with a very specific fit, like a key in a lock.

Phage conversion of exfoliative toxin A in Staphylococcus aureus isolated from cows with mastitis

An exfoliative toxin produced by Staphylococcus aureus is the causative agent of staphylococcal scalded-skin syndrome (SSSS) in young children. Recently, we reported that only few isolates of S. aureus from bovine mastitis contained the eta gene encoding exfoliative toxin A (ETA) and produced ETA in vitro. In this study, we isolated temperate phages from two ETA-positive bovine isolates of S. aureus by treatment with mitomycin C. Polymerase chain reaction (PCR) assay of the phage genomes suggested that the temperate phages carried the structural gene for ETA. Moreover, the nucleotide sequence analysis of the PCR products revealed that the eta gene was located very close to an amidase gene on the phage genomes. The nucleotide sequence for the amidase gene of the bovine phage (bovine phi ETA) differed at nine positions from that of the amidase gene of phi ETA from a human isolate reported by Yamaguchi et al. [Mol. Microbiol. 38 (2000) 694], suggesting that eta-converting phages are heterogeneous. Bovine phi ETA had a head with a hexagonal outline and a non-contractile and flexible tail. Bovine phi ETA was able to lysogenize ETA-negative bovine isolates of S. aureus, and the lysogenized S. aureus isolates had the ability to produce ETA. These results suggest the possibility of horizontal transmission of the eta gene by temperate bacteriophages among bovine isolates of S. aureus.

Superantigens and nasal polyps

Nasal polyps represent an often severe T-cell-orchestrated eosinophilic upper airway disease with currently unknown pathogenesis, often associated with lower airway disease, such as asthma. Superantigens, predominantly derived from Staphylococcus aureus, are potent activators of T cells, induce the synthesis of IgE in B cells, and have direct effects on pro-inflammatory cells, such as eosinophils. IgE antibodies to S. aureus enterotoxins have been described in polyp tissue, linked to a local polyclonal IgE production and an aggravation of eosinophilic inflammation. Furthermore, such IgE antibodies have also been described in the sera of patients with asthma, and linked to severity of disease and steroid insensitivity. This review summarizes our current understanding of the possible role of S. aureus enterotoxins in chronic severe airway disease, such as nasal polyposis.

Understanding the mechanism of action of the exfoliative toxins of Staphylococcus aureus

The exfoliative toxins of Staphylococcus aureus are responsible for the staphylococcal scalded skin syndrome, a blistering skin disorder that particularly affects infants and young children, as well as adults with underlying disease. Their three-dimensional structure is similar to other glutamate-specific trypsin-like serine proteases with two substrate-binding domains and a serine-histidine-aspartate catalytic triad that forms the active site. However, unlike other serine proteases, the exfoliative toxins possess a highly charged N-terminal alpha-helix and a unique orientation of a critical peptide bond, which blocks the active site of the toxins so that, in their native state, they do not possess any significant enzymatic activity. The target for the toxins has recently been identified as desmoglein-1, a desmosomal glycoprotein which plays an important role in maintaining cell-to-cell adhesion in the superficial epidermis. It is speculated that binding of the N-terminal alpha-helix to desmoglein-1 results in a conformation change that opens the active site of the toxin to cleave the extracellular domain of desmoglein-1 between the third and fourth domains, resulting in disruption of intercellular adhesion and formation of superficial blisters. Elucidating the mechanism of action of the toxins and identifying desmoglein-1 as their specific epidermal substrate has not only given us an insight into the pathogenesis of the staphylococcal scalded skin syndrome, but also provided us with useful information on normal skin physiology and the pathogenesis of other toxin-mediated diseases. It is hoped that this knowledge will lead to development of rapid screening and diagnostic tests, and new antitoxin strategies for the treatment and prevention of the staphylococcal scalded skin syndrome in the near future.

Antibiotics and pharmacogenomics

The widespread use of antibiotics impacts both the bacterial ecology and the host at multiple levels, both advantageously and deleteriously. Since serious bacterial infection can lead to death in the absence of antibiotic therapy, antibiotics remain a necessary weapon in the clinician's arsenal for maintaining good health. It is thus critical that the placement and usage of these crucial antibiotics be constantly improved, and that emerging antibiotic resistance is vigorously assessed. To realize both these ends, it may be valuable to turn to the discipline of pharmacogenomics and develop it for use in a fairly novel way, that is, as the means by which to determine and analyze the impact of antibiotic therapy on both the pathogen and host.

Calcium-dependent conformation of desmoglein 1 is required for its cleavage by exfoliative toxin

In bullous impetigo, Staphylococcus aureus spreads under the stratum corneum of skin by elaboration of exfoliative toxin, which hydrolyzes only one peptide bond in a highly structured calcium-binding domain of desmoglein 1, resulting in loss of its function. We investigated the basis of this exquisite specificity. Exfoliative toxin cannot cleave desmoglein 1 pretreated at 56 degrees C or higher or at low or high pH, suggesting that the proper conformation of desmoglein 1 is critical for its cleavage. Because cleavage occurs in an area of desmoglein 1 stabilized by calcium, we determined if the conformation necessary for cleavage is calcium-dependent. Depletion of calcium from desmoglein 1 completely inhibited its cleavage by exfoliative toxin, even after calcium was added back. A change in conformation of desmoglein 1 by calcium depletion was shown, with immunofluorescence and enzyme-linked immunoassay, by loss of binding of PF sera, which recognize conformational epitopes. This change in conformation was confirmed by tryptophan fluorometry and circular dichroism, and was irreversible with repletion of calcium. These data suggest that the specificity of exfoliative toxin cleavage of desmoglein 1 resides not only in simple amino acid sequences but also in its calcium-dependent conformation.

Targetting of desmoglein 1 in inherited and acquired skin diseases

Desmoglein 1 is a member of the desmosomal cadherin family that comprise the desmogleins and desmocollins. The desmoglein 1 gene (DSG1) is centromeric to the desmoglein gene cluster and spans approximately 45 kb of 18q12, comprising 15 exons. The transcript encodes a precursor protein of 1049 amino acids that is cleaved to yield a mature protein of 1000 residues. This mature protein is expressed in certain specialized epithelia, and in the epidermis is expressed within the superficial layers. Within the desmosome the extracellular domain of the protein is essential for calcium dependent heterophilic binding to the desmocollins, whereas the intracellular domain is essential for binding to the desmosomal plaque protein, plakoglobin. Desmoglein 1 has been implicated in several human diseases. Mutations within the extracellular domain lead to autosomal dominant striate palmoplantar keratoderma, whereas autoantibodies and strains of Staphylococcus aureus target the extracellular domain in the acquired bullous disorders pemphigus foliaceus and staphylococcal scalded skin syndrome, respectively. Therefore, intact and functionally active desmoglein 1 is essential to epidermal integrity. Here, we review the expression, protein structure, genetics, and molecular interactions of desmoglein 1 and outline the role it plays within the desmosome and how it becomes defective in human disease.

Severe epidermal necrolysis after treatment with imatinib and consecutive allogeneic hematopoietic stem cell transplantation

Imatinib is a new promising therapeutic option for chronic myeloid leukemia (CML) with efficacy even in the blast phase of the disease. However, most patients treated with imatinib in the blast phase develop progressive disease rapidly. Thus, treatment with imatinib has to be followed by other treatment strategies. The normally mild to moderate side effects of imatinib including skin rashes might therefore be aggravated. Here, we describe a patient with severe epidermal necrolysis after treatment with imatinib and consecutive allogeneic hematopoietic stem cell transplantation. Prolonged inhibition of platelet-derived growth factor by imatinib may be an explanation for this observed skin toxicity.

Staphylococcal and streptococcal superantigens: molecular, biological and clinical aspects

Superantigens (SAgs) include a class of certain bacterial and viral proteins exhibiting highly potent lymphocyte-transforming (mitogenic) activity towards human and or other mammalian T lymphocytes. Unlike conventional antigens, SAgs bind to certain regions of major histocompatibility complex (MHC) class II molecules of antigen-presenting cells (APCs) outside the classical antigen-binding groove and concomitantly bind in their native form to T cells at specific motifs of the variable region of the beta chain (Vbeta) of the T cell receptor (TcR). This interaction triggers the activation (proliferation) of the targeted T lymphocytes and leads to the in vivo or in vitro release of high amounts of various cytokines and other effectors by immune cells. Each SAg interacts specifically with a characteristic set of Vbeta motifs. The review summarizes our current knowledge on S. aureus and S. pyogenes superantigen proteins. The repertoire of the staphylococcal and streptococcal SAgs comprises 24 and 8 proteins, respectively. The staphylococcal SAgs include (i) the classical enterotoxins A, B, C (and antigenic variants), D, E, and the recently discovered enterotoxins G to Q, (ii) toxic shock syndrome toxin-1, (iii) exfoliatins A and B. The streptococcal SAgs include the classical pyrogenic exotoxins A and C and the newly identified pyrogenic toxins, G, H, I, J, SMEZ, and SSA. The structural and genomic aspects of these toxins and their molecular relatedness are described as well as the available 3-D crystal structure of some of them and that of certain of their complexes with MHC class II molecules and the TcR, respectively. The pathophysiological properties and clinical disorders related to these SAgs are reviewed.

Molecular typing of exfoliative toxin-producing Staphylococcus aureus strains involved in epidermolytic infections

Genotyping of sixteen exfoliative toxin-producing (ET-positive) strains of Staphylococcus aureus isolated in maternity units of two distant hospitals was accomplished by PFGE, ribotyping, PCR ribotyping, and prophage carriage. Three strains secreted combined ETA + ETB, and the remaining produced ETA and enterotoxin C, or TSST-1. The comparison of various genomic profiles resulted in the identification of nine genotypes. The presence of one prevailing genotype was demonstrated in each hospital. Evidence was given that the outbreak-related ET-positive strains causing the skin disease pemphigus neonatorum disseminated in both the hospitals did not originate from a single source or a common ancestor.

Identification of the Staphylococcus aureus etd pathogenicity island which encodes a novel exfoliative toxin, ETD, and EDIN-B

We identified a novel pathogenicity island in Staphylococcus aureus which contains open reading frames (ORFs) similar to the exfoliative toxin (ET) gene, glutamyl endopeptidase gene, and edin-B gene in tandem and the phage resistance gene, flanked by hsdM, hsdS (restriction and modification system), and IS256. The protein encoded by the ET-like gene showed 40, 59, and 68% amino acid sequence identities with exfoliative toxin A (ETA), exfoliative toxin B (ETB), and Staphylococcus hyicus ETB (ShETB), respectively. When injected into neonatal mice, the recombinant protein derived from the ET-like gene induced exfoliation of the skin with loss of cell-to-cell adhesion in the upper part of the epidermis as observed in histological examinations, just as was found in neonatal mice injected with ETA or ETB. Western blot analysis indicated that the recombinant protein is serologically distinct from ETA and ETB. Therefore, the product encoded by this new ORF is a new ET member produced by S. aureus and is termed ETD. ETD did not induce blisters in 1-day-old chickens. In the skins of mice injected with ETD, cell surface staining of desmoglein 1 (Dsg1), a cadherin type cell-to-cell adhesion molecule in desmosomes, was abolished without affecting that of desmoglein 3 (Dsg3). Furthermore, in vitro incubation of the recombinant extracellular domains of Dsg1 and Dsg3 with the recombinant protein demonstrated that both mouse and human Dsg1, but not Dsg3, were directly cleaved in a dose-dependent manner. These results demonstrate that ETD and ETA induce blister formation by identical pathophysiological mechanisms. Clinical strains positive for edin-B were suggested to be clonally associated, and all edin-B-positive strains tested were positive for etd. Among 18 etd-positive strains, 12 produced ETD extracellularly. Interestingly, these strains are mainly isolated from other sources of infections and not from patients with bullous impetigo or staphylococcal scalded-skin syndrome. This strongly suggests that ETD might play a pathogenic role in a broader spectrum of bacterial infections than previously considered.

Staphylococcal and enterococcal infections in the neonatal intensive care unit

Along with the successes in improving the survival of preterm neonates have come changes in the epidemiology of pathogens that cause healthcare-associated infections. Although gram-negative bacilli and group B streptococci predominated in past years, gram-positive organisms such as staphylococci and enterococci have since taken on greater roles. This shift has been accompanied by difficulties in defining optimal treatments for these pathogens because of emerging resistance patterns.

Toxic epidermal necrolysis: differential diagnosis of an epidermolytic dermopathy in a hematopoietic stem cell transplant recipient

Toxic epidermal necrolysis (TEN) is an epidermolytic skin disorder associated with drug administration. It is associated with an erythematous rash with full thickness epidermal loss and characteristic histology. A 35-year-old woman underwent allogeneic hematopoietic stem cell transplantation (HSCT) for severe aplastic anemia (SAA). She developed an acute epidermolytic rash and TEN was diagnosed on the basis of skin biopsy. In the HSCT setting, TEN should be thought of as an important differential diagnosis of epidermolytic dermopathies. The most distinctive diagnostic test in the differential diagnosis of these disorders is skin biopsy