Toxigenic strains of Clostridium difficile have been reported to produce both toxins A and B nearly always, and nontoxigenic strains have been reported to produce neither of these toxins. Recent studies indicate that it is not always true. We established a PCR assay to differentiate toxin A-negative, toxin B-positive (toxin A−, toxin B+) strains from both toxin-positive (toxin A+, toxin B+) strains and both toxin-negative (toxin A−, toxin B−) strains as an alternative to cell culture assay and enzyme-linked immunosorbent assay (ELISA). By using the PCR primer set NK11 and NK9 derived from the repeating sequences of the toxin A gene, a shorter segment (ca. 700 bp) was amplified from toxin A−, toxin B+ strains compared to the size of the segment amplified from toxin A+, toxin B+ strains (ca. 1,200 bp), and no product was amplified from toxin A−, toxin B− strains. We examined a total of 421 C. difficile isolates by PCR. Of these, 48 strains showed a shorter segment by the PCR, were negative by ELISAs for the detection of toxin A, and were positive by cell culture assay. Although the cytotoxin produced by the toxin A−, toxin B+ strains was neutralized by anti-toxin B serum, the appearance of the cytotoxic effects on Vero cell monolayers was distinguishable from that of toxin A+, toxin B+ strains. By immunoblotting, the 44 toxin A−, toxin B+ strains were typed to serogroup F and the remaining four strains were serogroup X. Pulsed-field gel electrophoresis separated the 48 strains into 19 types. The PCR assay for the detection of the repeating sequences combined with PCR amplification of the nonrepeating sequences of either the toxin A or the toxin B gene is indicated to be useful for differentiating toxin A−, toxin B+ strains from toxin A+, toxin B+ and toxin A−, toxin B− strains and will contribute to elucidation of the precise role of toxin A−, toxin B+ strains in intestinal diseases.

No abstract

We have developed a method to improve the transformation efficiency in genome-sequenced bacteria, using ‘Plasmid Artificial Modification’ (PAM), using the host's own restriction system. In this method, a shuttle vector was pre-methylated in Escherichia coli cells, which carry all the putative genes encoding the DNA modification enzymes of the target microorganism, before electroporation was performed. In the case of Bifidobacterium adolescentis ATCC15703 and pKKT427 (3.9 kb E. coli-Bifidobacterium shuttle vector), introducing two Type II DNA methyltransferase genes lead to an enhancement in the transformation efficiency by five orders of magnitude. This concept was also applicable to a Type I restriction system. In the case of Lactococcus lactis IO-1, by using PAM with a putative Type I methyltransferase system, hsdMS1, the transformation efficiency was improved by a factor of seven over that without PAM.

No abstract

We examined the species of bacteria aerobically and anaerobically isolated from 30 acne lesions and determined antimicrobial susceptibilities of Propionibacterium acnes (P. acnes) and Staphylococcus epidermidis (S. epidermidis) using nine antimicrobial agents. Among the bacteria isolated, S. epidermidis was most dominant. Both P. acnes and S. epidermidis were isolated from half of the acne lesions. The MIC of seven antimicrobials (ampicillin, erythromycin, roxithromycin, clindamycin, tetracycline, minocycline, nadifloxacin) against P. acnes was under 3.13 micrograms/ml. There were very few resistant strains of P. acnes, but many of S. epidermidis. More than 30% of the S. epidermidis isolates were resistant to erythromycin, roxithromycin, and clindamycin. After long-term systemic antibiotic therapy, the resistant strains of S. epidermidis increased, but P. acnes resistance was still limited. When we use antimicrobial agents for the treatment of acne, it should be noticed that not only P. acnes but also S. epidermidis in the acne lesions may acquire resistance to antimicrobials.

We identified Lactobacillus isolates from Japanese women and newborn infants by a DNA-DNA hybridization method. The predominating lactobacilli were Lactobacillus crispatus andLactobacillus gasseri in the women’s vaginas and the newborns’ intestines and L. gasseri andLactobacillus fermentum in the women’s intestines. AllL. crispatus strains were exclusively strong H2O2 producers.

Clostridium difficile isolates recovered from patients with C. difficile-associated diarrhea (CDAD) at three hospitals located in diverse areas of Japan were analyzed by three typing systems, PCR ribotyping, pulsed-field gel electrophoresis (PFGE), and Western immunoblotting. At the three hospitals examined, a single PCR ribotype strain (type smz) was predominant and accounted for 22 (65%) of 34, 18 (64%) of 28, and 11 (44%) of 25 isolates, respectively. All of the 51 isolates that represented PCR ribotype smz were nontypeable by PFGE because of DNA degradation. Since the type smz strain did not react with any of the antisera against 10 different serogroups (A, B, C, D, F, G, H, I, K, and X), we prepared a new antiserum against a type smz isolate. All 51 type smz isolates presented identical banding patterns, reacting with the newly prepared antiserum (designated subserogroup JP-0 of serogroup JP). These results were compared with those of a strain from a hospital outbreak that occurred in New York, which has been identified as type J9 by restriction enzyme analysis and type 01/A by arbitrarily primed PCR but was nontypeable by PFGE because of DNA degradation. This strain was reported to be epidemic at multiple hospitals in the United States. The J9 strain represented a PCR ribotype pattern different from that of a type smz strain and was typed as subserogroup G-1 of serogroup G by immunoblot analysis. A single outbreak type causing nosocomial CDAD in Japan was found to be different from the strain causing multiple outbreaks in the United States, even though the outbreak strains from the two countries were nontypeable by PFGE because of DNA degradation.Clostridium difficile is the most frequently identified cause of nosocomial diarrhea. Numerous systems for the typing of C. difficile strains have been evaluated and employed for epidemiological studies of outbreaks of C. difficile-associated diarrhea (CDAD) (1,4,7,12,17). Recently obtained data suggest that strain differences play some role in the pathogenicity of this organism. Multicenter studies in the United States (16) and the United Kingdom (3) indicate that a single type may be responsible for outbreaks at geographically widely separated hospitals. In Belgium, strains belonging to serogroup C were reported to be the most frequently implicated in outbreaks (20). These studies indicate that particular types of C. difficile are associated with active disease and nosocomial outbreaks. Little is known about the significance of C. difficile types in the epidemiology and etiology of CDAD in Japan.In the present study, we analyzed C. difficile strains isolated from three geographically widely separated hospitals in Japan by three typing systems, PCR amplification of rRNA intergenic spacer regions (PCR ribotyping), pulsed-field gel electrophoresis (PFGE), and Western immunoblotting, and identified a single type that was predominant at these three different hospitals. MATERIALS AND METHODSBacterial strains. Eighty-seven isolates recovered at three hospitals geograph...

The flavone 4′,5,7-trihydroxy-3′,5′-dimethoxyflavone (tricin) present in rice, oats, barley, and wheat exhibits antigrowth activity in several human cancer cell lines and anti-inflammatory potential. However, the chemopreventive activity has not yet been elucidated in preclinical animal models of colorectal cancer. This study was designed to determine whether dietary tricin exerts inflammation-associated colon carcinogenesis induced by azoxymethane and dextran sulfate sodium in mice. Male Crj: CD-1 mice were initiated with a single i.p. injection of azoxymethane (10 mg/kg body weight) and followed by a 1-week exposure to dextran sulfate sodium (1.5%, w/v) in drinking water to induce colonic neoplasms. They were then given the experimental diet containing 50 or 250 ppm tricin. The experiment was terminated at week 18 to determine the chemopreventive efficacy of tricin. In addition, the effects of dietary tricin on the expression of several inflammatory cytokines, including tumor necrosis factor (TNF)-α, were assayed. The development of colonic adenomas and adenocarcinomas was significantly reduced by feeding with 50 and 250 ppm tricin, respectively. Dietary tricin also significantly reduced the proliferation of adenocarcinoma cells as well as the numbers of mitoses/ anaphase bridging in adenocarcinoma cells. The dietary administration with tricin significantly inhibited the expression of TNF-α in the nonlesional cypts. Our findings that dietary tricin inhibits inflammation-related mouse colon carcinogenesis by suppressing the expression of TNF-α in the nonlesional cyrpts and the proliferation of adenocarcinomas suggest a potential use of tricin for clinical trials of colorectal cancer chemoprevention.