Usefulness of phage open-reading frame typing method in an epidemiological study of an outbreak of methicillin-resistant Staphylococcus aureus infections.

A novel genotyping method for methicillin-resistant Staphylococcus aureus (MRSA), the phage open-reading frames typing (POT) method, was evaluated using 92 MRSA isolates collected from blood cultures between 1991 and 2003 at Nagoya University Hospital. These strains were divided into 64 distinct POT types, classified into 21 genotypes by pulsed-field gel electrophoresis (PFGE) using SmaI, and analyzed with the DICE coefficient of 80% in dendrogram analysis, with 48 subtypes analyzed with the DICE coefficient of 100%. The discriminatory indices of these three methods were 0.988, 0.719, and 0.953, respectively. The first and second prevalent PFGE subtypes A1 and A2, which comprised 16 and 13 isolates recovered serially during the study period, were both divided into 11 distinct POT types. Six isolates belonging to PFGE subtype A1 were indistinguishable with POT. The six isolates were probably involved in an outbreak. Phenotypic analysis suggested that these isolates were the siblings of the New York/Japan clone which are prevalent in many Japanese hospitals. In conclusion, in the strain population studied, POT is a more rapid and discriminatory method than PFGE, and is a useful epidemiological tool for evaluating the available clinical information.

First case of bloodstream infection caused by Rhodococcus erythropolis.

We describe the first case of bloodstream infection caused by Rhodococcus erythropolis. The identification was performed using 16S rRNA sequencing. This case illustrates that non-equi Rhodococcus infections may be underdiagnosed due to difficulties in identification in the routine clinical microbiology laboratory.

Characterization of group C and G streptococcal strains that cause streptococcal toxic shock syndrome.

Twelve strains (the largest number ever reported) of group C and G(1) streptococci (GCS and GGS, respectively) that caused streptococcal toxic shock syndrome (STSS) were collected and characterized. Eleven strains were identified as Streptococcus dysgalactiae subsp. equisimilis, and one strain was identified as Streptococcus equi subsp. zooepidemicus. We found that it was the first reported case of STSS caused by S. equi subsp. zooepidemicus. Cluster analysis according to the 16S rRNA gene (rDNA) sequences revealed that the S. dysgalactiae strains belonged to clusters I and II, both of which were closely related. The emm types and the restriction patterns of chromosomal DNA measured by pulsed-field gel electrophoresis were highly variable in these strains except BL2719 and N1434. The 16S rDNA sequences and other characteristics of these two strains were indistinguishable, suggesting the clonal dissemination of this particular S. dysgalactiae strain in Japan. As the involvement of superantigens in the pathogenesis of group A streptococcus-related STSS has been suggested, we tried to detect known streptococcal superantigens in GCS and GGS strains. However, only the spegg gene was detected in seven S. dysgalactiae strains, with none of the other superantigen genes being detected in any of the strains. However, the sagA gene was detected in all of the strains except Tokyo1291. In the present study no apparent factor(s) responsible for the pathogenesis of STSS was identified, although close genetic relationships of GCS and GGS strains involved in this disease were suggested.

A novel apoptosis-inducing protein from Helicobacter pylori.

Helicobacter pylori infection induces apoptosis in gastric epithelial cells. Here, we report a novel apoptosis-inducing protein that functions as a leading factor in H. pylori-mediated apoptosis induction. We purified the protein from H. pylori by separating fractions that showed apoptosis-inducing activity. This protein induced apoptosis of AGS cells in a dose-dependent manner. The purified protein consisted of two protein fragments with molecular masses of about 40 and 22 kDa, which combined to constitute a single complex in their natural form. N-terminal sequencing indicated that both these protein fragments were encoded by the HP1118 gene. The purified protein exhibited gamma-glutamyl transpeptidase activity, the inhibition of which by 6-diazo-5-oxo-l-norleucine resulted in a complete loss of apoptosis-inducing activity. To the best of our knowledge, the apoptosis-inducing function is a newly identified physiological role for bacterial gamma-glutamyl transpeptidase. The apoptosis-inducing activity of the isogenic mutant gamma-glutamyl transpeptidase-deficient strain was significantly lower compared with that of the parent strain, demonstrating that gamma-glutamyl transpeptidase plays a significant role in H. pylori-mediated apoptosis. Our findings provide new insights into H. pylori pathogenicity and reveal a novel aspect of the bacterial gamma-glutamyl transpeptidase function.