Comparison of the virulence of methicillin-resistant and methicillin- sensitive Staphylococcus aureus

S. Mizobuchi, J. Minami, F. Jin, Osamu Matsushita, A. Okabe

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36 Citations (Scopus)

Abstract

The virulence of methicillin-resistant Staphylococcus aureus (MRSA) was compared with that of methicillin-sensitive S. aureus (MSSA), using 13 MRSA and 7 MSSA strains isolated from clinical specimens. The infectivity and lethality of the two groups were examined as to the inoculum required to infect 50% of guinea pigs (ID50) and to kill 50% of mice (LD50), respectively. The mean ID50 [log10 colony forming units (CFU)] for MRSA strains was 7.1 ± 0.60 standard deviation, which was 1.5 higher than that for MSSA strains (P <0.001). The mean LD50 (log10 CFU) for MRSA strains was 9.0 ± 0.42, being 1.1 higher than that for MSSA strains (P = 0.001). Pretreatment of mice with cyclophosphamide decreased the mean LD50 for MRSA strains more than that for MSSA strains, resulting in the difference in the mean LD50 being insignificant (P = 0.502). These results indicate that MRSA is less virulent than MSSA in normal hosts, but that they are equally virulent in immunocompromised hosts. The growth of MRSA strains was much slower than that of MSSA strains in the lag phase, although their growth rates were almost the same in the exponential growth phase, suggesting that the difference in virulence between them may be at least partly due to such a difference in growth.

Original languageEnglish
Pages (from-to)599-605
Number of pages7
JournalMicrobiology and Immunology
Volume38
Issue number8
Publication statusPublished - 1994
Externally publishedYes

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Methicillin Resistance
Methicillin
Methicillin-Resistant Staphylococcus aureus
Virulence
Staphylococcus aureus
Lethal Dose 50
Growth
Stem Cells
Immunocompromised Host
Cyclophosphamide
Guinea Pigs

ASJC Scopus subject areas

  • Immunology and Microbiology(all)
  • Microbiology
  • Microbiology (medical)

Cite this

Comparison of the virulence of methicillin-resistant and methicillin- sensitive Staphylococcus aureus. / Mizobuchi, S.; Minami, J.; Jin, F.; Matsushita, Osamu; Okabe, A.

In: Microbiology and Immunology, Vol. 38, No. 8, 1994, p. 599-605.

Research output: Contribution to journalArticle

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