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S Iyobe

Publications and source records attributed to S Iyobe.

At least 55 records · Page 3Linked to original sources
PubMed1986

Differences in susceptibility to quinolones of outer membrane mutants of Salmonella typhimurium and Escherichia coli.

The mechanism of penetration of quinolones through the bacterial outer membrane was studied with lipopolysaccharide-deficient and porin-deficient mutants. The data indicated that the lipopolysaccharide layer might form a permeability barrier for hydrophobic quinolones such as nalidixic acid but not for hydrophilic quinolones such as norfloxacin and ciprofloxacin. The results also showed that quinolones with a low relative hydrophobicity appeared to permeate through OmpF porin, whereas quinolones with a low relative hydrophobicity appeared to permeate through OmpF porin, whereas quinolones with a high relative hydrophobicity appeared to permeate through both OmpF porin and phospholipid bilayers.

Cell Membrane↗
PubMed1986

Isolation and characterization of norfloxacin-resistant mutants of Escherichia coli K-12.

We isolated spontaneous mutants from Escherichia coli K-12 with low-level resistance to norfloxacin. These mutants were classified into the following three types on the basis of their properties: (i) NorA appeared to result for mutation in the gyrA locus for the A subunit of DNA gyrase; (ii) NorB showed low-level resistance to quinolones and other antimicrobial agents (e.g., cefoxitin, chloramphenicol, and tetracycline), and the norB gene was considered to map at about 34 min on the E. coli K-12 chromosome; (iii) NorC was less susceptible to norfloxacin and ciprofloxacin but was hypersusceptible to hydrophobic quinolones such as nalidixic acid and rosoxacin, hydrophobic antibiotics, dyes, and detergents. Susceptibility to bacteriophages and the hydrophobicity of the NorC cell surface also differed from that of the parent strain. The norC gene was located near the lac locus at 8 min on the E. coli K-12 chromosome. Both NorB and NorC mutants had a lower rate of norfloxacin uptake, and it was found that the NorB mutant was altered in OmpF porin and that the NorC mutant was altered in both OmpF porin and apparently in the lipopolysaccharide structure of the outer membrane.

Bacterial Outer Membrane Proteins↗
PubMed1983

Mapping of the gene specifying aminoglycoside 3'-phosphotransferase II on the Pseudomonas aeruginosa chromosome.

We examined the aminoglycoside inactivation enzymes in Pseudomonas aeruginosa strains, seven clinical isolates and seven laboratory strains without plasmids. All strains were found to possess the enzyme aminoglycoside 3'-phosphotransferase II [APH(3')-II]. We isolated an APH(3')-II-deficient mutant from a PAO strain by mutagenesis with N-methyl-N'-nitro-N-nitrosoguanidine. By plasmid (FP5 or R68.45)-mediated conjugation, we determined the locus of the gene specifying the APH(3')-II between trp-6 and pro-82 on the PAO chromosome and designated this gene aphA. It was concluded that the intrinsic resistance of P. aeruginosa to kanamycins, neomycins, paromomycins, ribostamycin, and butirosins was due to this newly determined gene.

Chromosome Mapping↗
PubMed1982

Plasmid-mediated gentamicin resistance of Pseudomonas aeruginosa and its lack of expression in Escherichia coli.

We isolated 11 nonconjugative plasmids mediating resistance to aminoglycoside antibiotics, including gentamicin, from Pseudomonas aeruginosa strains. Their genetic properties were investigated in both P. aeruginosa and Escherichia coli transformants. The plasmid molecular weights ranged from 11 x 10(6) to 24 x 10(6). A low level or complete absence of gentamicin resistance was observed when these plasmids were introduced into E. coli, but gentamicin resistance was restored when the plasmids were transferred back to P. aeruginosa from E. coli. Aminoglycoside-modifying enzyme activity was detected in P. aeruginosa harboring these plasmids, but was absent or greatly reduced in E. coli strains. This lack of expression may explain the observed decrease in aminoglycoside resistance.

Aminoglycosides↗
PubMed1982

Isolation and characterization of a streptomycin resistance plasmid from Pseudomonas cepacia.

A plasmid, Rms425, mediating resistance to streptomycin(Sm) and mercury(Hg) was isolated from Pseudomonas cepacia GN11131 of clinical origin. Rms425 was transferred to Pseudomonas cepacia, Pseudomonas aeruginosa and Escherichia coli strains by transformation with purified DNA and by conjugation between isogenic strains of P. aeruginosa or of E. coli by mixing on membrane filters. The molecular weight of Rms425 was estimated to be about 32 megadaltons by electron microscopy and it was classified as incompatibility group P. Examining the incorporation of [gamma-32P] or [8-14C] from isotope-labelled ATP into Sm using the cell-free extracts from P. cepacia or E. coli strains harboring Rms425, we found that the Sm resistance conferred by Rms425 was due to the phosphorylation of the drug.

Adenosine Triphosphate↗
PubMed1981

Tn2001, a transposon encoding chloramphenicol resistance in Pseudomonas aeruginosa.

We isolated a new transposon, Tn2001, from the group P-2 plasmid Rms159-1 in Pseudomonas aeruginosa. Tn2001-encoded chloramphenicol resistance did not result from the formation of chloramphenicol acetyltransferase. Tn2001 was transposable between temperate phages and conjugative and nonconjugative plasmids belonging to various incompatibility groups, including P-1, P-3, P-4, P-5, P-7, and P-8 in P. aeruginosa. Transposition occurred independently of the general recombination ability of the Pseudomonas host, and its frequency varied between 10(-1) and 10(-8), depending upon the donor and recipient replicons. Tn2001 transposition also occurred in a recombination-deficient strain of Escherichia coli. Agarose gel electrophoresis and electron microscopic observations revealed that Tn2001 could transpose to different sites in the RP4 replicon and that the transposed deoxyribonucleic acid fragment was 2.1 kilobases long.

Chloramphenicol↗
PubMed1981

Purification and properties of cephalosporinase from Pseudomonas aeruginosa.

Cephalosporin beat-lactamase (cephalosporinase, CSase) was purified from a strain of Pseudomonas aeruginosa resistant to beta-lactam antibiotics. The purified enzyme preparation gave a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and its molecular weight was about 34,000. The specific activity was 49.7 mumoles/minute/mg of protein of the purified enzyme for the hydrolysis of cephaloridine. The optimal pH and optimal temperature were about 8.0 and 40 degrees C, respectively. Its isoelectric point was 8.7. The enzyme activity was inhibited by iodine, some divalent ions, and some semisynthetic beta-lactam antibiotics, including cephamycin derivatives such as moxalactam and YM09330. Mouse antiserum obtained against the purified enzyme showed no cross-reaction with other types of beta-lactamase in neutralization test.

Anti-Bacterial Agents↗
PubMed1980

Purification and properties of a new beta-lactamase from Pseudomonas cepacia.

An inducible beta-lactamase was purified from a beta-lactam antibiotic-resistant strain (GN11164) of Pseudomonas cepacia. The purified enzyme preparation gave a single protein band on polyacrylamide gel electrophoresis. The specific enzyme activity for the hydrolysis of cephalothin as a substrate was 314.5 U/mg of protein. The optimal pH was about 8.0, and the optimal temperature was 45 degrees C. The isoelectric point was 9.3, and the molecular weight was estimated to be about 22,000 to 24,000 from gel filtration on a Sephadex G-200 column and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The enzyme activity was inhibited by iodine, p-chloromercuribenzoate, clavulanic acid, CP 45899, and cloxacillin. The beta-lactamase showed a unique substrate profile by hydrolyzing most of the cephalosporins, including cefuroxime, cefotaxime (HR 756), ampicillin, and penicillin G, at a high rate.

Cell-Free System↗
PubMed1980

Isolation of two types of Pseudomonas aeruginosa mutants highly sensitive to a specific group of beta-lactam antibiotics and with defect in penicillin-binding proteins.

Two types of mutants highly sensitive to beta-lactam antibiotics were obtained from Pseudomonas aeruginosa PAO 2142 by treatment with N-methyl-N'-nitro-N-nitrosoguanidine. One type of mutant showed over 30 times higher sensitivity to mecillinam, carbenicillin and sulbenicillin than did the parent, but not to most other beta-lactam antibiotics tested. In contrast, the other type mutant was about 30 times more sensitive to ampicillin, cephaloridine, cefoxitin and cefmetazole, but resistant to mecillinam, carbenicillin and sulbenicillin at the same level as the parent. Beta-lactamase activity of these mutants ws not different from that of the parent. Defect in either of penicillin-binding proteins 1A/1B or 5 was observed in some mutants of P. aeruginosa highly sensitive to beta-lactam antibiotics.

Bacterial Proteins↗
PubMed1977

Inducible high resistance to colistin in Proteus strains.

Wild-type Proteus strains are usually resistant to colistin. We have observed an increase in the level of colistin resistance in four clinical isolates of P. vulgaris, P. morganii, and P. rettgeri by prior treatment with subinhibitory concentrations of the drug. The enhanced resistance in these strains was lost after cultivating them in colistin-free medium, indicating that the enhanced resistance in the Proteus group is inducible.

Colistin↗
PubMed1976

Classification of R plasmids by incompatibility in Pseudomonas aeruginosa.

R plasmids identified in Pseudomonas aeruginosa strains isolated in our laboratories were classified by their incompatibility characters by using intraspecies conjugation in P. aeruginosa. The fertility factor, FP2, was compatible with R plasmids belonging to all groups, and was classified in a new group. From these data, the plasmids examined have been placed into seven or eight incompatibility groups.

Anti-Bacterial Agents↗
PubMed1976

Inhibition of conjugal transfer of R plasmids by pipemidic acid and related compounds.

It was found that pipemidic acid and related compounds have the common property of inhibiting the conjugal transfer of R plasmids carried by Escherichia coli and Pseudomonas aeruginosa. This inhibition was not due to bactericidal activity of the compounds against donors, recipients, or R(+) transconjugants. However, it was correlated inversely with their minimal inhibitory concentrations, depending especially upon sensitivity of donors to the compounds. The inhibition was generally observed in mating systems using various combinations of 14 R plasmids and 9 bacterial strains. The pretreatment of a donor or a recipient strain with pipemidic acid showed only a small inhibitory effect on the transfer of an R plasmid, whereas the presence of the compound during an active mating caused a marked inhibitory effect.

Anti-Bacterial Agents↗
PubMed1976

Plasmid-mediated penicillin beta-lactamases in Pseudomonas aeruginosa.

A penicillin beta-lactamase (PCase) was extracted from Pseudomonas aeruginosa Rms139(+) and purified by means of column chromatography. The isoelectric point of Rms139 PCase was 5.7 and its molecular weight was 22,500 +/- 1,000. The optimal pH for the hydrolysis of benzylpenicillin was 7.0 to 7.5 and the optimal temperature was 45 C, with the PCase also showing high activity against carbenicillin. It is concluded that this enzyme is a new type of penicillin beta-lactamase different from the type I, II, or III R plasmid-mediated PCases reported previously.

Bacterial Proteins↗
PubMed1975

R factor-mediated resistance to aminoglycoside antibiotics in Pseudomonas aeruginosa.

Conjugal transferability of drug resistance was examined, in eleven Pseudomonas aeruginosa strains which were isolated in Frankfurt. Four R factors were demonstrated from three strains using P. aeruginosa as recipients but they were nontransferable to Escherichia coli K12. Two R factors, i.e., Rms146 and Rms147, mediated resistances to tetracycline (TC), streptomycin (SM), sulfanilamide (SA), kanamycin (KM), lividomycin (LV), gentamicin C complex (GM) and 3', 4'-dideoxykanamycin B (DKB). They mediated the formation of aminoglycoside-inactivating enzymes, i.e., SM phosphotransferase, SM adenylyltransferase, KM and LV phosphotransferase l, and GM and DKB 6'-N-acetyltransferase. TC resistance conferred by these R factors was due to impermeability of the drug. P. aeruginosa Ps 142 carried two kinds of R factor in one cell, Rms148 (SM) and Rms149 (SM-SA-GM-CPC) (CPC, carbenicillin). Rms148 (SM) was transferable at a high frequency of 10-1 and mediated the formation of SM phosphotransferase. Rms149 mediated the formation of drug-inactivating enzymes, ie., GM 3-N-acetyltransferase and beta-lactamase, but did not inactivate SM. SM resistance was probably due to impermeability of the drug.

Acetyltransferases↗
PubMed1975

Gentic properties of an R factor carrying resistance to aminolgycoside antibiotics.

R factor Rms 151 is an fi+ R factor and belongs to a incompatibility group FII. It carries the genes governing resistance to various aminoglycoside antibiotics, i.e., kanamycin (KM), lividomycin (LV), gentamicin C complex (GM), and 3',4'-dideoxykanamycin B (DKB), in addition to those governing to tetracycline (TC), chloramphenicol (CM), sulfanilamide (SA), and ampicillin (APC). Electron microscopy observation disclosed that the Rms151 deoxyribonucleic acid was a circular form with length of 31.2 mum. A probable circular genetic map of Rms151 was proposed by genetic and biochemical studies, the genes being in the order of -tet-tra-amp-aad-sul-aph-cml-, in which aad and aph confer resistance to KM.GM.DKB by adenylytransferase or resistance to KM.LV by phosphotransferase, respectively.

Aminoglycosides↗