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Molecular epidemiology of enteritis-causing methicillin-resistant Staphylococcus aureus
1Programmes for Applied Biomedicine, Division of Clinical Medical Science, Department of Surgery, Graduate School of Biomedical Science, Hiroshima University, 1-2-3, Kasumi, Hiroshima 734-8551, Japan. okii@hiroshima-u.ac.jp
The Journal of Hospital Infection
|October 12, 2005
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) enteritis decreased due to fewer enteritis-causing clones and altered bacterial phenotypes. This study compared early MRSA enteritis isolates with later non-enteritis strains to understand this decline.
Area of Science:
- Microbiology
- Infectious Diseases
- Epidemiology
Background:
- Severe enteritis caused by methicillin-resistant Staphylococcus aureus (MRSA enteritis) was common in Japan in the early 1990s.
- The incidence of MRSA enteritis has since declined significantly.
Purpose of the Study:
- To compare the genotypes and phenotypes of MRSA enteritis isolates from an earlier period with non-enteritis isolates from a later period.
- To investigate the reasons behind the decreased incidence of MRSA enteritis.
Main Methods:
- Genotyping using pulsed-field gel electrophoresis (PFGE) and coagulase typing.
- Phenotypic analysis including detection of staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 (TSST-1) production.
- Molecular detection of toxin genes (entA, entB, entC, entD, tst) using polymerase chain reaction (PCR).
Main Results:
- MRSA enteritis isolates (1990-1993) were distinct in genotype and phenotype from most later non-enteritis isolates (1998-2002).
- Enteritis isolates predominantly produced SE-A and TSST-1, while non-enteritis isolates mainly produced SE-C and TSST-1.
- A small group of non-enteritis isolates shared PFGE patterns with enteritis isolates but exhibited altered toxin production, suggesting phenotypic changes.
Conclusions:
- The decline in MRSA enteritis is likely due to a reduced prevalence of specific enteritis-associated MRSA clones.
- Phenotypic shifts in MRSA strains, potentially involving altered toxin production, may also contribute to the decreased incidence of enteritis.