Yutaka Midorikawa

Diarrheal and Environmental Isolates of Aeromonas spp. Produce a Toxin Similar to Shiga-Like Toxin 1

Abstract. Diarrheal and environmental isolates of 39 strains of Aeromonas spp. were studied for detection of virulence factors. Although these 39 strains did not produce either heat-labile or heat-stable enterotoxins, culture filtrates of 31 strains produced cytopathic effects on Vero cells. Among these, culture filtrates of three strains of Aeromonas hydrophila and one strain of Aeromonas caviae could be neutralized by Escherichia coli O157:H7 Shiga-like toxin 1 antiserum. A single band of plasmid DNA of 2.14 kbp was isolated from these strains of Aeromonas spp. and E. coli O157:H7, which could be amplified by the polymerase chain reaction (PCR), employing oligonucleotide primers from the Shiga-like toxin 1 (SLT1) gene of E. coli O157:H7. E. coli HB 101 cells when transformed with the same plasmid showed cytopathic effects on Vero cells, which indicates that the SLT 1 homolog gene(s) of Aeromonas spp. is plasmid encoded. These results suggest that Aeromonas spp. may also produce Shiga-like toxin 1, or at least a cytotoxin with some homology with the Shiga-like toxin 1 of E. coli O157:H7.

Inhibition of Malaria-Infected Erythrocytes by Deoxyspergualin: Effect on in vitro Growth of Malarial Cultures

The effect of deoxyspergualin (DSG) on the K1 strain of human malarial parasite Plasmodium falciparum in vitro was studied to test a possible new antimalarial chemotherapy. Hypoxanthine labeled with tritium (3H) was used to assess macromolecular synthesis. The inhibitory effects of DSG on the parasite peaked after 72 h of incubation. Parasitemia without DSG treatment was 9%, whereas at a DSG concentration of more than 156 µg/ml it was less than 1%. The amount of [3H]hypoxanthine taken up decreased with increasing DSG concentration. DNA synthesis of malarial activity decreased with increasing DSG concentration. These findings provide more evidence for the effects of DSG on this malarial parasite. As in previous in vivo studies done with DSG, the in vitro findings showed that DSG may be a new antimalarial drug.

15-Deoxyspergualin, an Immunosuppressive Agent, Used in Organ Transplantation Showed Suppressive Effects on Malarial Parasites

Deoxyspergualin (DSG), which was discovered to be an immunosuppressive agent, was examined for its in vivo effect on parasites of rodent malaria. Although the mice that were not treated by DSG had an increased parasite percentage (% parasitemia) until they died, those that were treated with DSG had a decreased parasitemia and finally had 0% parasites. The spleens of infected mice became small by DSG treatment. Parasitemia of mice increased again after DSG treatment was stopped. However, DSG was a polyamine inhibitor. The two other types of polyamine inhibitors used in this study were not effective for decreasing the % parasitemia of Plasmodium berghei. Only DSG was available and the survival time of mice increased. The antiprotozoal effects shown by DSG-even this chemical is an immunosuppressive agent-suggest that there is a relation between the inhibition of the polyamine synthetic pathway or immunosuppression of DSG and the suppressive effect of malarial parasites.

Bactericidal Effect of 15-Deoxyspergualin on Staphylococcus aureus

15-Deoxyspergualin (DSG), an immunosuppressive agent used in organ transplantation, exerts metabolic and antiproliferative effects on methicillin- and gentamicin-resistant Staphylococcus aureus and other bacteria (e.g. Sarcina lutea, Bacillus subtilis, Shigella sonnei, Salmonella typhi and Citrobacter freundii). DSG, at the concentration of 20 mg/l, depleted intracellular putrescine and spermidine in S. aureus to 43 and 40% of the controls, respectively. In these polyamine-depleted S. aureus cells, the synthesis of protein, DNA and RNA was decreased to 20, 85, 78% of the controls. The minimal inhibitory concentrations (MIC) of DSG for growth of S. aureus, S. lutea, B. subtilis, S. sonnei, S. typhi and C. freundii were 17, 13, 7, 15, 4, and 29 mg/l, respectively.

Detection of non-typhoid Salmonella infection by citrus and citrus extracts in Lao PDR.

Abstract Objective To know the current state of non-typhoid Salmonella infection in Laos. To examine the usefulness of new screening methods for Salmonella using citrus. Methods Non-typhoid Salmonella infection of person in Lao PDR was studied in this research (2004-2009). The site was Vientiane capital city in 2004. Research from rural villages locating suburb of Vientiane during 2005-2008 was carried out. Rural villages in Attapu province where ethnic minorities were living was searched for this study in 2009. During this research, to detect Salmonella strain, a new method using citrus and citrus extract named MY phenomenon that observing black ring (MIDO ring) on DHL agar was tried. The slice lemon and lime were used for this trial in 2004. After 2005, disk of ascorbic acid and citric acid were used for the device instead of citrus fruits itself. Results During this research, 65 of 272 human samples (23.9%) were infected with non-typhoid Salmonella . Conclusions During this study, the method using citrus and citrus extracts was accepted for the detection of Salmonella . This study shows that with citrus and citrus extract, detection of Salmonella is possible using only DHL media. Results suggest that infectious rate of non-typhoid Salmonella was high.

Epidemiological Study on Contamination of Water and Diarrheal Diseases in a Rural Community in Northeast Thailand

An epidemiological and bacteriological study of diarrheal diseases as well as the relation between domestic-use water and passage of enteric pathogens with stools of the villagers was performed in the northeastern rural area of Thailand on 4 different occasions during the 3 years from 1992–1994. The questionnaire study indicated that 93% of the residents used rain water stored in containers for drinking and other domestic uses, and that 28% of them filtrated and/or boiled the water before drinking it. About 90% of drinking water samples collected from the same residents showed positive responses for the preliminary test ofEscherichia coli contamination. Furthermore, a precise bacteriological survey indicated that more than half of the drinking water samples collected from containers storing rain water were contaminated with various enteropathogenic bacteria, includingE. coli, Vibrio spp. andShigella spp. The new serotype ofV. cholerae O139, synonym ‘Bengal cholerae,’ which could be isolated from different specimens, is replacing the traditional species ofVibrio. Forty-one per cent of the villagers carried enteropathogenic bacteria in their stools. Most of them were asymptomatic carriers and only a few of them showed clinical features of diarrhea. A few concrete propositions were discussed to supply safe water in these areas where drinkable underground water is not available.

An Alkaloid, Cepharanthine, Potentiates the Bactericidal Effect of Methylglyoxal bis(Cyclopentylamidinohydrazone) on Staphylococcus aureus

Antiproliferative effects of combined treatment with methylglyoxal bis(cyclopentylamidinohydrazone) (MGBCP), a polyamine biosynthesis inhibitor, and cepharanthine, a biscoclaurine alkaloid, on methicillin- and gentamicin-resistant Staphylococcus aureus were investigated. The bactericidal effect of MGBCP on S. aureus was potentiated by the cepharanthine treatment. Cellular polyamine levels of the bacteria treated with both MGBCP and cepharanthine were much lower than those of the bacteria treated with MGBCP alone. On the contrary, the cellular MGBCP concentration was much higher in the cepharanthine-treated bacteria. Thus, cepharanthine was considered to enhance the incorporation of MGBCP into the bacteria. The combination of MGBCP and cepharanthine resulted in greater suppression of macromolecular synthesis in the bacteria that might have caused greater suppression of bacterial growth.