[Molecular epidemiology of methicillin-resistant Staphylococcus aureus isolates with toxic shock syndrome toxin and staphylococcal enterotoxin C genes]

Comparative Genomic Analysis of Staphylococcal Cassette Chromosome mec Type V Staphylococcus aureus Strains and Estimation of the Emergence of SCCmec V Clinical Isolates in Korea

Background

Staphylococcal cassette chromosome mec type V (SCCmec V) methicillin-resistant Staphylococcus aureus (MRSA) has been recovered from patients and livestock. Using comparative genomic analyses, we evaluated the phylogenetic emergence of SCCmec V after transmission from overseas donor strains to Korean recipient strains.

Methods

Sixty-three complete MRSA SCCmec V genomes (including six Korean clinical isolates) were used to construct a phylogenetic tree. Single-nucleotide polymorphisms were identified using Snippy, and a maximum-likelihood-based phylogenetic tree was constructed using RAxML. The possible emergence of the most common ancestor was estimated using BactDating. To estimate mecA horizontal gene transfer (HGT) events, Ranger-dtl was applied to 818 SCCmec V strains using publicly available whole-genome data.

Results

The phylogenetic tree showed five major clades. German strains formed a major clade; their possible origin was traced to the 1980s. The emergence of Korean SCCmec V clinical isolates was traced to 2000-2010. mecA HGT events in Staphylococcus spp. were identified in seven strains. P7 (Hong Kong outbreak strain) served as the donor strain for two Korean sequence type (ST) 59 strains, whereas the other five recipient strains emerged from different SCCmec V donors.

Conclusions

Most Korean SCCmec V strains may have emerged during 2000-2010. A unique MRSA SCCmec V strain, ST72 (a Korean common type of community-associated MRSA), was also identified. The genomic dynamics of this clone with a zoonotic background should be monitored to accurately understand MRSA evolution.

Acute heart failure associated with toxic shock syndrome due to methicillin-susceptible Staphylococcus aureus during the postpartum period: case report and systematic literature review

BACKGROUND

Toxic shock syndrome (TSS) caused by Staphylococcus aureus in the postpartum period is a rare but life-threatening disease. We present a case of acute heart failure as the initial presentation of TSS due to methicillin-susceptible Staphylococcus aureus (MSSA) and describe its clinical characteristics with a systematic literature review.

CASE PRESENTATION

A 34-year-old woman, 8 days after a normal vaginal delivery presented to our hospital with dyspnea and fever. She had jugular venous distension, bilateral leg edema, and erythema. Laboratory examinations revealed elevated NT-pro-BNP level of 3,233 pg/mL. Transthoracic echocardiography showed elevated tricuspid regurgitation peak gradient, with decreased respiratory variability of the inferior vena cava diameter and bilateral pleural effusions. The patient was hospitalized with suspicion of congestive heart failure. MSSA positive for toxic shock syndrome exotoxin-1 was detected in the culture of the perineal incision wound, and we diagnosed TSS caused by MSSA. Intravenous diuretics were administered, along with eventual cefazolin plus clindamycin. After 2 weeks of antimicrobial therapy, the patient showed improvement and was discharged. No recurrence was observed at the 24-month follow-up.

CONCLUSION

This is a rare case report of acute heart failure being the initial manifestation of TSS due to MSSA in the postpartum period. Clinicians should consider TSS as a possibility in postpartum patients with acute heart failure. This systematic review provides insights into its clinical features, treatment regimens, and prognosis of TSS by S. aureus in the postpartum period. TSS requires an appropriate, prompt diagnosis, because delayed treatment can be fatal.

Staphylococcal and streptococcal superantigen exotoxins

SUMMARY This review begins with a discussion of the large family of Staphylococcus aureus and beta-hemolytic streptococcal pyrogenic toxin T lymphocyte superantigens from structural and immunobiological perspectives. With this as background, the review then discusses the major known and possible human disease associations with superantigens, including associations with toxic shock syndromes, atopic dermatitis, pneumonia, infective endocarditis, and autoimmune sequelae to streptococcal illnesses. Finally, the review addresses current and possible novel strategies to prevent superantigen production and passive and active immunization strategies.

[Production and characterization of anti-staphylococcal toxic shock syndrome toxin-1 monoclonal antibody]

BACKGROUND

Recently the association between the virulence factors of Staphylococcus aureus and the outcome of the patients infected with the organism appears to be the subject of active investigation. Toxic shock syndrome toxin-1 (TSST-1) is thought to be a clinically more significant virulence factor than other staphylococcal toxins. We attempted to produce and characterize monoclonal antibodies to staphylococcal TSST-1.

METHODS

An important epitope of TSST-1, amino acids 1-15 region, was synthesized into a peptide antigen, and Balb/c mice were immunized by intraperitoneal injection of the synthetic antigen. Hybridomas were produced by fusing immunized murine splenocytes with immortal myeloma cells. Hybridomas were cloned through a limiting dilution method. Stable cultured hybridoma was injected into the peritoneal cavity of Balb/c mice, and peritoneal fluid containing the monoclonal antibody was produced.

RESULTS

One IgG(2b) type monoclonal antibody and two IgM type monoclonal antibodies were obtained. The IgG(2b) type monoclonal antibody was able to detect 5 microg of TSST-1 with Western blot analysis and showed a strong reactivity to TSST-1 with ELISA.

CONCLUSIONS

Highly immunoreactive anti-TSST-1 monoclonal antibody was produced by the use of synthesized peptide antigen. Diagnostic and protective capacity of this monoclonal antibody should be evaluated in the future.