Junko Isobe

Clinical significance of Escherichia albertii.

Discriminating Escherichia albertii from other Enterobacteriaceae is difficult. Systematic analyses showed that E. albertii represents a substantial portion of strains currently identified as eae-positive Escherichia coli and includes Shiga toxin 2f–producing strains. Because E. albertii possesses the eae gene, many strains might have been misidentified as enterohemorrhagic or enteropathogenic E. coli.

Surveillance of severe invasive group-G streptococcal infections and molecular typing of the isolates in Japan

The number of patients with severe invasive group-G streptococcal (Streptococcus dysgalactiae subsp. equisimilis) infections has been increasing in Japan. The emm genotypes and SmaI-digested pulsed-field gel electrophoresis DNA profiles were variable among the strains isolated, suggesting there has not been clonal expansion of a specific subpopulation of strains. However, all strains carried scpA, ska, slo and sag genes, some of which may be involved in the pathogenesis of the disease.

Rapid Categorization of Pathogenic Escherichia coli by Multiplex PCR

A one‐shot multiplex polymerase chain reaction (PCR) was developed for detecting 12 virulence genes of diarrheagenic Escherichia coli. In order to differentiate between the five categories of diarrheagenic E. coli, we selected the target genes: stx1, stx2, and eaeA for enterohemorrhagic E. coli (EHEC); eaeA, bfpA, and EAF for enteropathogenic E. coli (EPEC); invE for enteroinvasive E. coli (EIEC); elt, estp, and esth for enterotoxigenic E. coli (ETEC); CVD432 and aggR for enteroaggregative E. coli (EAggEC); and astA distributed over the categories of diarrheagenic E. coli. In our multiplex PCR system, all 12 targeted genes (stx1, stx2, eaeA, invE, elt, estp, astA, esth, bfpA, aggR, EAF, and CVD432) were amplified in a single PCR reaction in one tube and detected by electrophoresis. Using our multiplex PCR, the 208 clinically isolated strains of diarrheagenic E. coli in our laboratory were successfully categorized and easily analyzed for the presence of virulence plasmids.

Characterization of Legionella pneumophila isolates from patients in Japan according to serogroups, monoclonal antibody subgroups and sequence types

We collected 86 unrelated clinical Legionella pneumophila strains that were isolated in Japan during the period 1980-2008. Most (80.2%) belonged to serogroup 1, followed by serogroups 5, 3 and 2. Interestingly, the patients with L. pneumophila serogroup 1 had a significantly higher male-to-female ratio (12.4) than the patients with other L. pneumophila serogroups (2.0) (OR, 10.5; 95% CI, 2.5-44.5). When the serogroup 1 strains were analysed by monoclonal antibody (mAb) typing, the most prevalent subgroup was Benidorm (34.9% of all isolates). Moreover, 79.7% of the serogroup 1 isolates were bound by mAb 3/1, which recognizes the virulence-associated epitope. When all 86 isolates were subjected to sequence-based typing (SBT) using seven loci, they could be divided into 53 sequence types (STs). The ST with the most isolates (seven) was ST1, to which most isolates from patients and environments around the world belong. However, six of the seven ST1 isolates were isolated before 1994. Other major STs were ST306 (n=6), ST120 (n=5) and ST138 (n=5). All ST306 and ST138 isolates, except for one isolate (ST306), were suspected or confirmed to be derived from bath water, which suggests that these strains prefer bath habitats. The sources of all ST1 and ST120 isolates remain unclear. By combining the SBT and mAb data, the 86 isolates could be divided into 59 types (discrimination index, 0.984). This confirms the usefulness of this combination in epidemiological studies.

Distribution of emm genotypes among group A streptococcus isolates from patients with severe invasive streptococcal infections in Japan, 2001–2005

We surveyed emm genotypes of group A streptococcus (GAS) isolates from patients with severe invasive streptococcal infections during 2001-2005 and compared their prevalence with that of the preceding 5 years. Genotype emm1 remained dominant throughout 2001 to 2005, but the frequency rate of this type decreased compared with the earlier period. Various other emm types have appeared in recent years indicating alterations in the prevalent strains causing severe invasive streptococcal infections. The cover of the new 26-valent GAS vaccine fell from 93.5% for genotypes of isolates from 1996-2000 to 81.8% in 2001-2005.

Antimicrobial Susceptibility Survey of Streptococcus pyogenes Isolated in Japan from Patients with Severe Invasive Group A Streptococcal Infections

ABSTRACT We assessed antimicrobial susceptibility against 211 Streptococcus pyogenes strains isolated from patients with severe invasive group A streptococcal infections. Overall, 3.8, 1.4, 1.4, and 0.5% of the isolates were resistant to erythromycin, clindamycin, telithromycin, and ciprofloxacin, respectively, and 10.4% had intermediate resistance to ciprofloxacin. All isolates were susceptible to ampicillin and cefotaxime.

Genetic Features of Clinical Isolates of Streptococcus dysgalactiae subsp. equisimilis Possessing Lancefield's Group A Antigen

ABSTRACT Thirteen Streptococcus dysgalactiae subsp. equisimilis isolates possessing Lancefields group A antigen recovered from people in Japan during 2000 to 2004 were genotyped. The results indicate that a conserved clone has persisted and spread within Japan, and two different emm types were observed within members of this clone.

emm Typing of Group A Streptococcus Clinical Isolates: Identification of Dominant Types for Throat and Skin Isolates

T and emm types were determined for group A streptococci isolated from patients with various infections during 1990–1999 in Toyama Prefecture, Japan. Out of 906 isolates, 872 isolates were divided into 20 T serotypes, and 34 isoltes were T nontypeable (TNT). T12, T1, and T4 were dominant among 699 throat isolates; on the other hand, T11, T28, TB3264, and TNT were dominant among 80 skin isolates. The emm types of 190 isolates were determined following specific PCR amplification and sequencing of the products. Twenty T serotypes were divided into 34 T type/emm type combinations. Thirty‐four TNT isolates were divided into 14 emm types, in which emm58 was the most common (38%). Among 82 throat isolates randomly selected, predominant T types T12, T1, and T4 isolates were of the respective same numbers in emm type. T11/emm89, T28/emm28, TB3264/emm 13w, and TNT/emm58 were predominant among 80 skin isolates. emm‐type distribution observed in the present study was that usually reported in the western world. To our knowledge, 3 T/emm is a novel combination. These results show that emm typing allows the characterization of group A streptococci from various sources.

Virulence Gene Profiles and Population Genetic Analysis for Exploration of Pathogenic Serogroups of Shiga Toxin-Producing Escherichia coli

ABSTRACT Infection with Shiga toxin (Stx)-producing Escherichia coli (STEC) is a serious public health concern, causing severe diarrhea and hemolytic-uremic syndrome. Patient symptoms are varied among STEC strains, possibly implying the presence of markers for STEC virulence other than Stx. To reveal the genotypic traits responsible for STEC virulence, we investigated 282 strains of various serogroups for the presence of 17 major virulence genes, i.e., stx 1, stx 2a, stx 2c, stx 2d, stx 2e, stx 2f, eae, tir, espB, espD, iha, saa, subA, ehxA, espP, katP, and stcE. Next, we examined the prevalence of virulence genes according to the seropathotypes in which serotypes were classified (seropathotypes A through E) based on the reported frequencies in human illness, as well as known associations with outbreaks and with severe disease. Our results demonstrate that the presence of both katP and stcE in STEC, in addition to the genes located in the locus of enterocyte effacement (LEE), including eae, tir, espB, and espD, may indicate the most pathogenic genotype of STEC. A population structure analysis of the profiles of virulence genes statistically supported the pathogenic genotype and, furthermore, revealed that there are serogroups with potentially higher pathogenicity than previously thought. Some strains in serogroups O26, O145, and O165 may have high virulence equivalent to that of serogroup O157. Several serogroups, including O14, O16, O45, O63, O74, 119, O128, and O untypeable, also may be potentially pathogenic, although rarely in humans.

Characterization of Enterohemorrhagic Escherichia coli O111 and O157 Strains Isolated from Outbreak Patients in Japan

ABSTRACT In April and May 2011, there was a serious food-poisoning outbreak in Japan caused by enterohemorrhagic Escherichia coli (EHEC) strains O111:H8 and O157:H7 from raw beef dishes at branches of a barbecue restaurant. This outbreak involved 181 infected patients, including 34 hemolytic-uremic syndrome (HUS) cases (19%). Among the 34 HUS patients, 21 developed acute encephalopathy (AE) and 5 died. Patient stool specimens yielded E. coli O111 and O157 strains. We also detected both EHEC O111 stx 2 and stx-negative E. coli O111 strains in a stock of meat block from the restaurant. Pulsed-field gel electrophoresis (PFGE) and multilocus variable-number tandem-repeat analysis (MLVA) showed that the stx-negative E. coli O111 isolates were closely related to EHEC O111 stx 2 isolates. Although the EHEC O157 strains had diverse stx gene profiles (stx 1, stx 2, and stx 1 stx 2), the PFGE and MLVA analyses indicated that these isolates originated from a single clone. Deletion of the Stx2-converting prophage from the EHEC O111 stx 2 isolates was frequently observed during in vitro growth, suggesting that strain conversion from an EHEC O111 stx 2 to an stx-negative strain may have occurred during infection.