Kikuyo Ogata

Commercially Distributed Meat as a Potential Vehicle for Community-Acquired Methicillin-Resistant Staphylococcus aureus

ABSTRACT The incidence of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infection has been increasing; however, the sources of infection remain unclear. Therefore, we investigated the involvement of meat as a possible mediator of CA-MRSA infection. We examined the distribution of MRSA strains in commercially distributed raw meat samples (n = 197) and diarrheal stool samples of outpatients (n = 1,287) that were collected in Oita Prefecture, Japan, between 2003 and 2009 for routine legal inspections. Fourteen MRSA strains were isolated from three meat and 11 stool samples. Among these, seven isolates from three meat and four stool samples exhibited the same epidemiological marker profiles [coagulase type III, staphylococcal enterotoxin C, staphylococcal chromosomal cassette mec (SCCmec) type IV, ST8, spa type 606 (t1767), and toxic shock syndrome toxin-1 (TSST-1) producing type]. Furthermore, of the seven strains, three isolates from two meat samples and one stool sample collected in 2007 exhibited completely identical characteristics with respect to phage open reading frame (ORF) typing, pulsed-field gel electrophoresis, and drug susceptibility profiles. The results suggest that commercially distributed meat could play a role in the prevalence of CA-MRSA in the community.

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.

Pathogenesis of Vibrio parahaemolyticus: Intraperitoneal and Orogastric Challenge Experiments in Mice

It has been noted that V. parahaemolyticus isolated from patients with food poisoning are almost always thermostable direct hemolysin (TDH)‐positive, whereas, isolates from foods or environmental sources are usually TDH‐negative. The virulence of V. parahaemolyticus in mice was examined by using intraperitoneal and orogastric challenge models, where the strains used were those isolated from patients and foods with food poisoning and included TDH‐positive and ‐negative. The LD50 in mice was estimated to be approximately 107 in the former and 108 in the latter challenge model. In the mice killed by challenge, either intraperitoneal or orogastric, the following pathological changes were almost always observed: swelling, redness and fluid accumulation in the small intestine, particularly the upper part of it. Histologically, congestion, edema, and vacuolation were observed in mucosal and submucosal tissues; furthermore, ulceration at tips of some villi was noticed. The lethality and pathological finding in mice due to V. parahaemolyticus were demonstrated similarly in both challenge models and irrespective of the TDH phenotype of the strain used. It will be suggested that the findings in challenged mice may be. attributed to enteropathogenic factor(s) other than TDH of V. par ahaemolyticus.

Distribution of Non-Locus of Enterocyte Effacement Pathogenic Island-Related Genes in Escherichia coli carrying eae from Patients with Diarrhea and Healthy Individuals in Japan

ABSTRACT The relationship to diarrhea of genes located on the pathogenicity islands (PAI) other than the locus of enterocyte effacement (LEE) was investigated. Enteropathogenic Escherichia coli (EPEC), the retention of espC on the EspC PAI, the OI-122 genes (efa1/lifA, nleB), the phylogenetic marker gene yjaA, and the bundle-forming pilus gene bfpA on the EPEC adherence factor (EAF) plasmid were studied. E. coli strains carrying the intimin gene (eae) without the Shiga toxin gene, isolated from patients with diarrhea (n = 83) and healthy individuals (n = 38) in Japan, were evaluated using PCR. The genotypes of eae and espC were identified by heteroduplex mobility assay (HMA). The proportions of strains isolated from individuals with and without diarrhea that carried these genes were as follows: bfpA, 13.3 and 7.9%, respectively; espC, 25.3 and 36.8%; efa1/lifA, 32.5 and 13.2%; nleB, 63.9 and 60.5%; yjaA, 42.2 and 55.3%. Statistical significance (P < 0.05) was achieved only for efa1/lifA. The proportion of strains lacking espC and carrying efa1/lifA was higher for patient-derived strains (30.1%) than for strains from healthy individuals (13.2%), but the difference was not significant. Strains carrying both espC and efa1/lifA were rare (2 strains from patients). Statistical analyses revealed significant relationships between espC and yjaA and between efa1/lifA and nleB, as well as significant inverse relationships between espC and efa1/lifA and between efa1/lifA and yjaA. espC was found in eae HMA types a1, a2, and c2, whereas efa1/lifA was found in types b1, b2, and c1. In addition, 6 polymorphisms of espC were found. The espC, yjaA, efa1/lifA, and nleB genes were mutually dependent, and their distributions were related to eae type, findings that should be considered in future epidemiological studies.

Evaluation of streptococcal toxic shock-like syndrome caused by group B streptococcus in adults in Japan between 2009 and 2013

Infection with Streptococcus agalactiae has long been recognized in infants. In recent years, S. agalactiae is an important cause of morbidity and mortality among adults and among those with underlying medical condition. Several cases of GBS infection and more fulminant disease similar to streptococcal toxic shock syndrome have recently been reported. We report here that 19 S. agalactiae strains were isolated from streptococcal toxic shock-like syndrome cases involving adult patients in Japan between 2009 and 2013. The average age of the patients was 66.3 years. At least one underlying disease was present in 47.4% (9/19) of the patients. The most prevalent serotype among these strains was Ib. All serotype Ib strains belonged to clonal complex 10 and were ciprofloxacin resistant. In contrast, all strains were susceptible to penicillin G, ampicillin, cefazolin, cefotaxime, imipenem, panipenem, and linezolid. The characteristic type distributions of streptococcal toxic shock-like syndrome isolates differed between isolates obtained from vaginal swabs of women and infants with invasive infections.

Differences in the stress tolerances of Vibrio parahaemolyticus strains due to their source and harboring of virulence genes.

To investigate the diversity of stress tolerance levels in Vibrio parahaemolyticus, 200 V. parahaemolyticus strains isolated from various coastal environments, seafood, and human clinical cases were exposed to acid, low-osmolality, freezing-thawing, and heat stresses. Tolerance against acid stress was higher in the virulent (tdh- and/or trh-positive) strains than in the avirulent (tdh- and trh-negative) strains. Tolerance against low-osmolality, freezing-thawing, and heat stresses was higher in the clinical strains of tdh- and/or trh-positive V. parahaemolyticus than in the coastal environment- and seafood-originated strains of tdh and/or trh-positive V. parahaemolyticus. Tolerance against acid stress was higher in the strains isolated from coastal seawater at ≤15°C than in the strains isolated at ≥20°C. Tolerance against heat stress was higher in the avirulent strains than the virulent strains, and in the strains isolated from coastal seawater at ≥20°C than the strains isolated from coastal seawater at ≤15°C. Therefore, this study demonstrated that the diversity of stress tolerance levels in V. parahaemolyticus strains depended on their source and whether they harbored virulence genes. In particular, there was significantly greater tolerance against acid in the virulence gene-harboring strains and strains isolated from low-temperature seawater. Because the stress tolerances of V. parahaemolyticus have direct influences for the survival in environment and food, it is important for the prevention of foodborne infection to control the stress-tolerant strains.

Bacteriological Studies on the Drinking Hot Spring Waters in Oita Prefecture

1995年7月から1998年10月にかけて大分県内で採水された温泉90検体を用いて, 細菌学的検査を中心に飲用泉の衛生状況を検討した.飲用利用の衛生管理基準の細菌検査による不適率は33.3%で, これにKMnO4消費量の結果をあわせたときの不適率は43.3%であった.項目別の不適率は一般細菌数で25.6%, 大腸菌群で10.0%, KMnO4消費量で13.3%を示した.衛生管理基準と温泉分類との関係から, 細菌検査による不適は泉温が低く, 中性～ 弱アルカリ性の温泉に多い傾向がみられた.泉質との関係では, アルカリ性単純温泉には大腸菌群による不適がなかった.外観との関係では着色や混濁のある温泉で細菌検査による不適が多い傾向がみられ, 化学成分との関係では大腸菌群を検出した温泉はヒ素およびフッ素の平均濃度が低かった.他方, KMnO4消費量は泉温やpHが高い温泉ほど, また着色した温泉やフッ素濃度の高い温泉で, 高値を示す傾向がみられた.衛生管理基準に適合した温泉のうち, 実際に飲用泉の利用施設に登録されたのは約半数であった.本調査結果から, 大分県内の飲用泉施設について微生物学的衛生管理をさらに徹底するとともに, 利用者には飲用に当たっての適正な指導と衛生知識の啓発が重要と考えられた.