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Biomedical subjects

M Sasatsu

Publications and source records attributed to M Sasatsu.

At least 37 records · Page 2Linked to original sources
PubMed1997

Antibacterial activity of (+/-) 6-benzyl-1-(3-carboxypropyl) indane; a possible way to identify leading novel anti-H. pylori agents.

Magainin 2, isolated from the skin of the Xenopus laevis, is an antimicrobial peptide which reacts directly with the biological membrane to lyse various bacteria from negative and positive microorganisms. In a previous report, we showed that (+/-)1-(4-aminobutyl)-6-benzylindane (PM2), which mimicked the conformation of the side-chains of a complementary unit on the amino acid sequence of magainin 2 analogs, expressed the in vitro antibacterial activity not only against Helicobacter, pylori (ATCC43526, ATCC43579), but also against Escherichia coli (ATCC25922) and Staphylococcus aureus (ATCC25923). In addition, PM2 caused human blood red cells (RBCs) to lyse at the minimum inhibitory concentration (MIC) value. Based on the antibacterial activities of 9-phenylnonanoic acid (pC9c), we further synthesized (+/-)-6-benzyl-1-(3-carboxypropyl) indane (PM2c), which replaced a positive charge of PM2 with a negative one, and tested the biological activities. PM2c had the ability to inhibit the growth of H. pylori strains, but its activity to inhibit the growth of E. coli and S. aureus was not detected and weak, respectively. Moreover, PM2c showed non-hemolytic activity against RBCs at the MIC value. These results indicate the possibility that PM2c may be more useful than PM2 either alone or in combination with well-known therapeutic agents for the treatment of H. pylori infection.

Animals↗
PubMed1997

Antibacterial activity of two alkylamines integrated an indane scaffold: mimicry of a complementary unit on magainin 2.

Based on the antibacterial activity of 9-phenylnonylamine (pC9a) against Escherichia coli (ATCC29522) and Staphylococcus aureus (ATCC25923), we have further tested the inhibitory ability of the growth of the bacteria by (+/-)1-(4-aminobutyl)-6-benzylindane (PM2) and (+/-)1-benzyl-6-(4-aminobutyl) indane (PM3), that is, two kinds of 1,6-disubstituted indanes. In an in vitro assay, they showed almost the same antibacterial activities against the bacteria as pC9a, as well as that of magainin 2 analogs (i.e., the peptides MSI-78 and 87-ISM), except in the case of 87-ISM against S. aureus. At the MIC (minimum inhibitory concentration) values, however, their killing rate of E. coli is actually quicker than pC9a. This indicates that an indane scaffold, used as a template to mimic a part of the alpha-helical structure of magainin 2, can accelerate the killing rate. At present, however, it is unknown whether either the hydrophobicity or the alpha-helical structure, or both, of the indane scaffold is involved in accelerating the rate. Moreover, these two indanes also showed stronger antibacterial activity against two strains of Helicobacter pylori (ATCC43526, ATCC43579) than either pC9a or magainin 2 related peptides.

Anti-Bacterial Agents↗
PubMed1997

On the antibacterial activity of normal and reversed magainin 2 analogs against Helicobacter pylori.

Magainin 2 is an antimicrobial peptide isolated from the skin of Xenopus laevis. We have tested the antibacterial activities of normal and reversed magainin 2 analogs against two strains of Helicobacter pylori (ATCC 43526, ATCC 43579), compared with those against Escherichia coli (ATCC 25922) and Staphylococcus aureus (ATCC 25923). Among these analogs, MSI-78A showed the strongest activity against H. pylori. The MIC (minimum inhibitory concentration) values were almost the same as those against E. coli and S. aureus. No or lesser activity was observed in all the reversed peptides compared to the corresponding normal magainin 2 analogs. Based on the CD (circular dichroism) measurement, the more active peptide tends to show a higher alpha-content. The positively-charged five amino acids (KILKK) positioned at the C terminus on the amphipathical alpha-helical structure play important roles in exerting the strong activity against H. pylori. This indicates that the net charge of the cell surface in H. pylori may be more negative than that of E. coli, though both strains belong to the same genus.

Amino Acid Sequence↗
PubMed1996

A new gene, aadA2b, encoding an aminoglycoside adenylyltransferase, AAD(3")(9), isolated from integron InC in Pseudomonas aeruginosa.

A gene, designated aadA2 and encoding an aminoglycoside-adenylyltransferase, was located on integron InC, isolated from the R-plasmid of Pseudomonas aeruginosa, as a gene cassette. The aadA2 gene of InC was identical to those of pSa and R1033 with the exception of one base in each case. This single-base substitution did not influence the expression of streptomycin resistance. It is proposed that the aadA2 genes isolated from pSa and from R1033, and the aadA2 gene from InC, be designated aadA2a and aadA2b, respectively.

Anti-Bacterial Agents↗
PubMed1995

Isolation and structure of a new integron that includes a streptomycin resistance gene from the R plasmid of Pseudomonas aeruginosa.

A new integron, located on the R plasmid of Pseudomonas aeruginosa, was isolated in Japan. This integron was made up of two conserved segments (5'-and 3'-conserved segments) and a single streptomycin resistance gene as a gene cassette. The structure of this integron resembles that of integron InC, the existence of which was postulated by Bissonnette and Roy (J. Bacteriol. 174, 1248-1257, 1992).

Biological Evolution↗
PubMed1995

The tetracycline efflux protein encoded by the tet(K) gene from Staphylococcus aureus is a metal-tetracycline/H+ antiporter.

The tet(K) gene from Staphylococcus aureus was highly expressed in Escherichia coli by an alteration of its initiation codon from TTG to ATG and its ribosome-binding sequence from GAGG to GGAGG [Noguchi, N. et al. (1994) Biol. Pharm. Bull. 17, 352-355]. The inverted membrane vesicles prepared from the tet(K)-expressing cells showed respiration-dependent [3H]tetracycline transport comparable to the vesicles from the tet(B)-expressing cells. The affinity of Tet(K) vesicles to tetracycline was the same as that of Tet(B) vesicles, whereas the former Vmax value was about 60% of the latter one. Contrary to Tet(B) vesicles, Tet(K) vesicles showed no significant minocycline uptake, which was consistent with the low minocycline resistance of the Tet(K)-producing cells. The tetracycline transport mediated by Tet(K) vesicles was coupled with proton transport and the translocation of 60Co2+ ions as well as in Tet(B) vesicles. This observation indicates that the class K tetracycline resistance determinant from Gram-positive bacteria also encodes a metal-tetracycline/H+ antiporter that is functionally similar to that encoded by tet(B), although there is a considerable difference in the primary sequences and the putative topologies of these Tet proteins.

Antiporters↗
PubMed1995

Nucleotide sequence and characterization of erythromycin resistance determinant that encodes macrolide 2'-phosphotransferase I in Escherichia coli.

The DNA fragment (3.3 kb) containing the erythromycin resistance determinant was cloned from Escherichia coli Tf481A and sequenced. Deletion and complementation analyses indicated that the expression of high-level resistance to erythromycin requires two genes, mphA and mrx, which encode macrolide 2'-phosphotransferase I and an unidentified hydrophobic protein, respectively.

Amino Acid Sequence↗
PubMed1995

The origin of the antiseptic-resistance gene ebr in Staphylococcus aureus.

The antiseptic-resistance gene ebr was detected not only in resistant strains of Staphylococcus aureus but also in sensitive strains of S. aureus, in coagulase-negative staphylococcal strains and in enterococcal strains by means of the polymerase chain reaction. The nucleotide sequence of the amplified DNA fragment of the ebr gene from a sensitive strain and that of the previously reported ebr gene were identical. It seems likely that antiseptic-resistant cells result from an increase in the copy number of a gene whose normal function is to remove toxic substances from normal sensitive cells of staphylococci and enterococci.

Anti-Infective Agents, Local↗
PubMed1994

Evaluation of antiseptics by the modified phenol coefficient method: sensitivity of methicillin-resistant Staphylococcus aureus.

The relationship between an effective concentration and the duration of exposure to antiseptics was evaluated in strains of Staphylococcus aureus with a known genetic background, which include methicillin-resistant strains, using a modified version of the phenol coefficient method as part of an effort to investigate the antiseptic resistance of S. aureus. Chlorhexidine digluconate killed an antiseptic-sensitive strain within 1.5 min at 22 degrees C at a standard concentration (0.1%), whereas resistant strains still survived after 1.5 min. Povidone-iodine killed the sensitive strain within 1.5 min at a concentration of 0.1%, whereas it took this agent 3.0 and 4.5 min to kill low- and high-level resistant strains, respectively, at a concentration of 0.8%. These results indicate that the modified phenol coefficient method used is suitable for the evaluation of the sensitivity of microorganisms to antiseptics. An antiseptic-resistant chain that was associated with the ebr gene exhibited cross-resistance to povidone-iodine.

Anti-Infective Agents, Local↗
PubMed1994

Substrates and inhibitors of antiseptic resistance in Staphylococcus aureus.

The range of substrates of antiseptic resistance associated with the ebr gene is very wide and includes antiseptics, DNA-intercalating drugs and preservatives which have no quaternary ammonium group in methicillin-resistant Staphylococcus aureus. Antiseptic resistance was inhibited by calcium channel blockers and calmodulin inhibitors similarly to the resistance to multiple antitumor agents encoded by the mdr gene in human cells. These results show that the common properties of the mdr gene and the ebr gene may be shared by the mechanisms that are involved in the removal of toxic substances from the cell.

Anti-Infective Agents, Local↗
PubMed1994

Expression in Escherichia coli of a TetK determinant from Staphylococcus aureus.

The expression in Escherichia coli of a tet(K) gene, which originated in Staphylococcus aureus, was studied. The minimum inhibitory concentration (MIC) of tetracycline (TC) for E. coli cells that carried the tet(K) gene was only slightly higher than that for the recipient cells. This result indicated that the level of expression of the tet(K) gene in E. coli was very low. Insertion of a lac promoter into the upstream region of the tet(K) gene resulted in a slight increase in the MIC, from 12.5 to 50 micrograms/ml in the presence of isopropyl-beta-D-thiogalactopyronoside. An altered tet(K) gene, in which the initiation codon and the ribosome-binding site (RBS) were changed from TTG to ATG and from GAGG to GGAGG, respectively, and in which the distance between the RBS and the initiation codon was increased from 4 to 11 bases, was associated with high-level resistance to TC, with a MIC of 200 micrograms/ml. The MIC resembles that associated with expression of the tetA(B) gene of E. coli. These results indicate that the barrier to expression of the tet(K) gene in E. coli is located at the initiation of translation.

Base Sequence↗
PubMed1994

Effect of beta-lactamase on minimum inhibitory concentrations of methicillin in methicillin-resistant Staphylococcus aureus.

A study was undertaken to determine whether the production of penicillin-binding protein-2' (PBP-2') and the production of beta-lactamase were related to the minimum inhibitory concentrations of methicillin (DMPPC) in various strains of methicillin-resistant Staphylococcus aureus. The amount of PBP-2' produced by the low-level resistant strain L20A was small and the strain became resistant to DMPPC as a result of inactivation of DMPPC by beta-lactamase. The largest amount of PBP-2' produced was in a moderately resistant strain L21A but the MIC was not high since the strain was not capable of producing beta-lactamase and the population of cells was heterogeneous. The amount of PBP-2' produced in the high-level resistant strain L457A was lower than that in strain L21A but the MIC was high as a result of the production of beta-lactamase. Production of PBP-2' was essential for resistance to methicillin but production of beta-lactamase had a major effect on the MIC.

Bacterial Proteins↗
PubMed1993

Genetic mapping in Bacillus subtilis 168 of the aadK gene which encodes aminoglycoside 6-adenylyltransferase.

Bacillus subtilis 168 has an aadK gene, which encodes aminoglycoside 6-adenylyltransferase, a streptomycin-modifying enzyme, on its chromosome. To characterize the aadK gene, we constructed a B. subtilis 168 strain that carried the chloramphenicol resistance gene near the aadK on the chromosome and an aadK deletion mutant using an integration technique. The aadK gene was mapped between azlB and pheA on the chromosome of B. subtilis 168. The aadK deletion mutant was slightly more susceptible to streptomycin than the original strain. The result indicates that the aadK gene contributes low-level resistance to streptomycin in B. subtilis 168.

Bacillus subtilis↗
PubMed1993

Detection of plasmid DNA in Erysipelothrix rhusiopathiae isolated from pigs with chronic swine erysipelas.

Forty-three strains of Erysipelothrix rhusiopathiae, isolated from pigs with chronic swine erysipelas, were examined for the presence of plasmid DNA by agarose gel electrophoresis and electron microscopy. Seven of these strains were found to contain plasmids of which number were varied from 1 to 6. The plasmids ranged from 1.4 to 86 kb in size. This is the first reported evidence for plasmid DNA in E. rhusiopathiae. The functions of the plasmids are unknown at present.

Animals↗
PubMed1993

Survival ability of clinical isolates of methicillin-resistant Staphylococcus aureus.

The survival abilities of methicillin-resistant strains of Staphylococcus aureus were compared with those of sensitive strains. Absorbent cotton was inoculated with 10(8) cells of each strain tested and stored at 30% humidity at 25 degrees C. The numbers of cells of sensitive strains decreased significantly to well below those of resistant strains after 4 weeks, while cells of resistant strains remained above 10(3) after 14 weeks.

Anti-Bacterial Agents↗