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It is well known that methicillin-resistantVancomycin (VCM) has been the standard treatment for MRSA infections for over 50 years. The area under the concentration-time curve [AUC/minimum inhibitory concentration (MIC) ratio] is a representative parameter of the pharmacokinetics-pharmacodynamics (PK-PD) of VCM.3) The Infectious Diseases Society of America recommends a target AUC/ MIC>400 for the treatment of severe MRSA infections. 4)However, this is often difficult to achieve for MRSA strains with high VCM MICs, thus increasing the risk of insufficient therapeutic response. Previous meta-analyses have attempted to address the association between MIC and clinical outcomes. [5][6][7] In contrast to these studies, a recent meta-analysis examining 8291 episodes reported no differences in the risk of death between patients with S. aureus high and low VCM MICs. 8) These results highlight the current lack of consensus regarding the relationship between VCM MICs and the prognosis of patients with MRSA infections.Our previous study measured MICs at 0.25 µg/mL intervals using the broth microdilution method and found that VCM MICs≥1.5 µg/mL affected the prognosis for MRSA bacteremia. 9) However, there were no significant differences in VCM AUC/MIC and clinical prognosis between the groups.The pathological mechanism of S. aureus infections includes infectious pathogenicity such as pneumonia, cellulitis, osteomyelitis, and infective endocarditis as well as toxic pathogenicity such as food poisoning and toxic shock syndrome.10,11) Several virulence factors have been reported to be associated with the clinical outcomes of MRSA infections. The expression of major virulence factors, such as Panton-Valentine leukocidin (PVL), is known to be correlated with higher mortality in community-associated MRSA infections. 12,13) We believe that toxic pathogenicity is closely associated with patient prognosis. S. aureus is known to produce various virulence factors, 14) such as toxic shock syndrome toxin-1 (TSST-1) and staphylococcal enterotoxins (SEs), which are superantigenic toxins (SAgT) associated with severe infections. 11,15,16) A previous study reported that TSST-1 and SEC1 caused shock when intravenously injected into an animal model. 17) In addition, recent experimental study showed that SAgT play a critical role in the development and progression of S. aureus infective endocarditis and sepsis.18) However, the association between SAgT and the prognosis of patients with MRSA bacteremia has not been sufficiently studied. Therefore, here we aimed to examine the effects of staphylococcal virulence factors on the prognosis of patients with MRSA bacteremia.

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Objective The objective of this study was to assess whether the distribution of pneumococcal capsular types has been changed, while also providing basic data on changes in the distribution after the introduction of Pneumococcal conjugated vaccine (PCV)13 in adult medical practice. Methods We analyzed 431 Streptococcus pneumoniae strains (200 in 2006 and 231 in 2012) that had been isolated from respiratory infection specimens from adult patients. Capsular typing was performed by the Quellung reaction and multiplex polymerase chain reaction. Results A comparison of the 2006 and 2012 strains revealed that the number and proportion of strains by serotype increased from 30 (15%) to 46 (20%) for serotype 3, from 4 (2%) to 14 (6%) for serotype 6A, and from 4 (2%) to 13 (6%) for serotype 6C, whereas the number and proportion of strains by serotype decreased from 8 (4%) to 0 (0%) for serotype 4 and from 24 (12%) to 17 (7%) for serotype 6B. From 2006 to 2012, the coverage rate significantly decreased from 39 to 28.1% for PCV7 (p=0.017). Conclusion Our study showed a decrease in the vaccine coverage of PCV7. However, PCV13 covered serotypes 3 and 6A, which are prevalent, as well as penicillin-resistant S. pneumoniae strains. At present, PCV 13 in adult clinical practice seems to be highly significant. However, there is a possibility that the distribution has changed, and careful screening should be continued in the future.

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