Ikue Taneike

A Panton-Valentine Leucocidin (PVL)-Positive Community-Acquired Methicillin-Resistant Staphylococcus aureus (MRSA) Strain, Another Such Strain Carrying a Multiple-Drug Resistance Plasmid, and Other More-Typical PVL-Negative MRSA Strains Found in Japan

ABSTRACT Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) was collected from children with bullous impetigo in 2003 and 2004. One strain collected in 2003 was Panton-Valentine leucocidin (PVL) positive. In 2004, a multiple-drug-resistant PVL+ CA-MRSA strain was isolated from an athlete with a cutaneous abscess. These strains were analyzed by multilocus sequence typing, spa typing, agr typing, coagulase typing, staphylococcal cassette chromosome mec (SCCmec) typing, PCR assay for 30 virulence genes, drug susceptibility testing, pulsed-field gel electrophoresis, and for plasmids. The two Japanese PVL+ CA-MRSA strains belonged to the globally extant (“pandemic”) sequence type 30 (ST30) with SCCmec IV. A transmissible, multiple-drug resistance plasmid emerged in such ST30 strains. The PVL− CA-MRSA strains (“domestic” CA-MRSA) accumulated for bullous impetigo, exhibiting new genotypes. Hospital-acquired MRSA of ST91 (but not pandemic ST5) shared common features with the PVL− CA-MRSA strain.

A Novel Action of the Proton Pump Inhibitor Rabeprazole and Its Thioether Derivative against the Motility of Helicobacter pylori

ABSTRACT The motility of Helicobacter pylori was maximum at 37°C and at pH 6. A newly developed proton pump inhibitor, rabeprazole (RPZ), and its thioether derivative (RPZ-TH) markedly inhibited the motility of H. pylori. The concentrations of the drug necessary to inhibit 50% of the motility were 0.25, 16, 16, and >64 μg/ml for RPZ-TH, RPZ, lansoprazole, and omeprazole, respectively. No such inhibitory effects were observed with H2 blockers or anti-H. pylori agents. The motilities of Campylobacter jejuni and C. coli—but not those of Vibrio cholerae O1 and O139,Vibrio parahaemolyticus, Salmonella entericaserovar Typhimurium, and Proteus mirabilis—were also inhibited. Prolonged incubation with RPZ or RPZ-TH inhibited bacterial growth of only H. pylori, except for a turbid colony mutant. The results indicate that RPZ and RPZ-TH have a characteristic inhibitory effect against the motility of H. pylori(spiral-shaped bacteria), which is distinguished from that against bacterial growth.

Effects of Azithromycin on Shiga Toxin Production by Escherichia coli and Subsequent Host Inflammatory Response

ABSTRACT Shiga toxin (Stx)-producing Escherichia coli (STEC) colonizes the human intestinal mucosa, produces Stx from phage, and causes the development of hemolytic-uremic syndrome via Stx-induced inflammatory cytokine production. Azithromycin exhibited strong in vitro activity against STEC without inducing Stx-converting phage, in marked contrast to norfloxacin. Azithromycin decreased the tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), and IL-6 production from Stx-treated human peripheral mononuclear cells or monocytes to a greater extent than did clarithromycin. In Stx-injected mice, azithromycin significantly suppressed Stx-induced TNF-α, IL-1β, and IL-6 levels in serum and improved the outcome as assessed by survival rate. In the STEC oral infection experiment using immature mice immediately after weaning (weaned immature-mouse model), all mice died within 7 days postinfection. Azithromycin administration gave the mice 100% protection from killing, while ciprofloxacin administration gave them 67% protection. The data suggest that azithromycin (at least at higher concentrations) has a strong effect on Stx production by STEC and on the Stx-induced inflammatory host response and prevents death in mice. Azithromycin may have a beneficial effect on STEC-associated disease.

Molecular nature of methicillin‐resistant Staphylococcus aureus derived from explosive nosocomial outbreaks of the 1980s in Japan

Community‐acquired methicillin‐resistant Staphylococcus aureus (CA‐MRSA) with Panton‐Valentine leukocidin (PVL) genes is increasing worldwide. Nosocomial outbreak‐derived (hospital‐acquired) MRSA (HA‐MRSA) in Japan in the 1980s was also largely PVL+. PVL+ HA‐MRSA and CA‐MRSA shared the same multi‐locus sequence type (ST30) and methicillin resistance cassette (SCCmecIV), but were divergent in oxacillin resistance, spa typing, PFGE analysis or clfA gene analysis. PVL+ HA‐MRSA, which probably originated in PVL+ S. aureus ST30, was highly adhesive (carrying cna and bbp genes), highly‐toxic (carrying luk PV and sea genes) and highly drug‐resistant. PVL+ HA‐MRSA was once replaced by other PVL− HA‐MRSA (e.g., ST5), and is re‐emerging as CA‐MRSA.

Enterohemolysin operon of Shiga toxin-producing Escherichia coli: a virulence function of inflammatory cytokine production from human monocytes

Shiga toxin‐producing Escherichia coli (STEC) is associated with hemolytic uremic syndrome (HUS). Although most clinical isolates of STEC produce hemolysin (called enterohemolysin), the precise role of enterohemolysin in the pathogenesis of STEC infections is unknown. Here we demonstrated that E. coli carrying the cloned enterohemolysin operon (hlyC, A, B, D genes) from an STEC human strain induced the production of interleukin‐1β (IL‐1β) through its mRNA expression but not tumor necrosis factor‐α from human monocytes. No IL‐1β release was observed with an enterohemolysin (HlyA)‐negative, isogenic E. coli strain carrying a mutation in the hlyA gene. The data suggest that enterohemolysin, a pore‐forming toxin, induces the production of IL‐1β, which is one of serum risk markers for HUS.

The sequences of enterohemorrhagic Escherichia coli and Yersinia pestis that are homologous to the enteroaggregative E. coli heat-stable enterotoxin gene: cross-species transfer in evolution

The enteroaggregative Escherichia coli heat‐stable enterotoxin 1 (EAST1) gene is widely distributed among diarrheagenic E. coli. In this study, we examined the sequences of enterohemorrhagic E. coli (EHEC) strains by PCR and sequencing. All the EHEC strains possessed the EAST1 gene homologues but with two types of mutations. One of the mutation types was strongly associated with the large outbreak episodes in 1996 in Japan. Sequence comparison showed that the EHEC sequences are a branch of the EAST1 gene sequence family that showed the cross‐species transfer in evolution among E. coli and Yersinia pestis.

Inhibitory Action of a Novel Proton Pump Inhibitor, Rabeprazole, and its Thioether Derivative Against the Growth and Motility of Clarithromycin-Resistant Helicobacter pylori

Clarithromycin‐resistant Helicobacter pylori (CRHP) has increasingly been isolated from patients in Japan. The aim of our study was to test whether proton pump inhibitors (PPIs) and their thioether derivatives, which are secreted into the gastric mucosa, could inhibit the growth and motility (a factor in colonization) of CRHP.

Helicobacter pylori Intrafamilial Infections: Change in Source of Infection of a Child from Father to Mother after Eradication Therapy

ABSTRACT Biopsy specimens of the antrum and corpus were obtained from fourHelicobacter pylori-infected members of a family and from the same boy (son 1) in whom the infection reappeared after simultaneous successful eradication treatment of three family members, excluding the mother. A total of 18 to 60 H. pyloriisolates were obtained from each specimen and subjected to rRNA gene restriction pattern analysis. The fathers isolates and the initial isolates from son 1 showed the same HindIII type, which was divided into three HaeIII subtypes. Isolates from the mother and a brother (son 2) and posttreatment isolates from son 1 showed a distinct HindIII type (with one minor subtype), which was divided into six HaeIII subtypes. All subtypes of the initial isolates from son 1 were present in the fathers isolates, and all subtypes of the posttreatment isolates from son 1 were present in the mothers isolates but not in son 2s. Electron microscopic analysis of the biopsy specimens demonstrated extremely high levels ofH. pylori colonization in the fathers gastric mucosa.H. pylori adherence with a ruffle formation was also demonstrated. The findings suggest that son 1 was infected initially with the H. pylori strain of the father and son 2 was infected with the H. pylori strain of the mother and that after eradication therapy son 1 was reinfected with the H. pylori strain of the mother, who did not undergo eradication therapy.

Emergence of Clarithromycin-Resistant Helicobacter pylori (CRHP) with a High Prevalence in Children Compared with Their Parents

Background. Clarithromycin‐resistant Helicobacter pylori (CRHP) is increasing worldwide. Clarithromycin resistance in H. pylori from familial members has not been investigated.

60Co irradiation of Shiga toxin (Stx)‐producing Escherichia coli induces Stx phage

Shiga toxin (Stx)-producing Escherichia coli (STEC), an important cause of hemolytic uremic syndrome, was completely killed by (60)Co irradiation at 1 x l0(3) gray (1 kGy) or higher. However, a low dose of irradiation (0.1-0.3 kGy) markedly induced Stx phage from STEC. Stx production was observed in parallel to the phage induction. Inactivation of Stx phage required a higher irradiation dose than that for bacterial killing. Regarding Stx, cytotoxicity was susceptible to irradiation, but cytokine induction activity was more resistant than Stx phage. The findings suggest that (1). although (60)Co irradiation is an effective means to kill the bacteria, it does induce Stx phage at a lower irradiation dose, with a risk of Stx phage transfer and emergence of new Stx-producing strains, and (2). irradiation differentially inactivates some activities of Stx.