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Biomedical subjects

R Nakaya

Publications and source records attributed to R Nakaya.

At least 37 records · Page 2Linked to original sources
PubMed1989

[Serovars, antimicrobial resistance and conjugative R plasmids of Salmonella isolated from human during the period of 1966-1986 in Tokyo. Research Group for Infectious Enteric Diseases].

We examined 4,739 isolates of Salmonella isolated from patients with gastroenteritis during the period of 1966-1986 in Tokyo for the incidences of serovars, antibiotic resistance and conjugative R plasmids. The period of study was divided into three: 1966-73 (early period), 1974-79 (middle period), and 1980-86 (late period). The predominant serovars were S. typhimurium (34.3%), Infantis (5.6%), Panama (4.9%) in the middle period, S. typhimurium (31.7%), Paratyphi B (9.4%), Litchfield (7.3%) in the late period. These results were consistent with serovars of isolates from healthy citizens. The frequency of resistant isolates was as high as 86.9% in the early period, mostly streptomycin (SM)- and tetracycline (TC)-resistant isolates, but decreased significantly in the middle and the late periods, to 53.3 and 39.4%, respectively. The percentages of ampicillin (ABPC)-, chloramphenicol (CP)-, and kanamycin (KM)-resistant isolates increased in the late period. Strains carrying conjugative R plasmids were isolated as frequently as 57.8% of the total isolates in 1973, but as less frequently as 6.7% in 1981 indicating that the rate was roughly proportional to the incidence of the drug resistant isolates. The rate, however, increased gradually after 1981. The predominant resistance pattern of the R plasmids was TC-resistance in the early period, gradually changed into multiple and finally to AP-, CP-, KM-, SM-, TC- and sulfonamides-resistance in the late period.

Conjugation, Genetic↗
PubMed1988

Differences among Shigella spp. in susceptibility to the bactericidal activity of human serum.

Clinical isolates of Shigella spp. were examined for their susceptibility to human serum. The susceptibility of the strains to immune and nonimmune human serum was dependent upon the size of the bacterial inoculum and the concentration of serum. There were differences among Shigella spp. in susceptibility to human serum: S. sonnei strains were the least susceptible, strains of S. boydii and S. flexneri serotype 6 were intermediate, and those of S. flexneri other than serotype 6 and S. dysenteriae were the most susceptible. Experiments in which heat-treated (56 degrees C for 30 min, or 50 degrees C for 20 min) serum was used, and analysis of activation of complement by lipopolysaccharides (LPS) from each Shigella sp., suggested that LPS composition, especially the O antigen polysaccharide chains, contributes to the differences among Shigella spp. in susceptibility to human serum.

Blood Bactericidal Activity↗
PubMed1987

Overproduction of gene products by the super-high-copy-number plasmid pNR333.

The plasmid pNR333 is a kanamycin-resistant, deletion derivative of pNR113 with an extremely high copy number in Escherichia coli and in Proteus mirabilis. In order to determine the usefulness of pNR333 as a replication gene of vector, the genes encoding chloramphenicol acetyl-transferase (CAT) and beta-galactosidase (beta-gal) were cloned individually into both pNR333 and other low-copy-number plasmids. The expression of the cloned genes was compared by measuring the specific activity of each enzyme and the amounts of the proteins produced. A hybrid plasmid pNR333-cat expressed 53 times as much activity of CAT as the low-copy plasmid S-a which had a copy number of four. The lacZ gene cloned in pNR333 produced 17 times as much beta-gal as in the low-copy-number plasmid pNR1150. These results suggest that pNR333 is a useful vector plasmid for producing a large amount of polypeptides in E. coli hosts.

Acetyltransferases↗
PubMed1987

Antimicrobial resistance of Campylobacter jejuni and Campylobacter coli with special reference to plasmid profiles of Japanese clinical isolates.

A total of 111 clinical isolates of Campylobacter jejuni and 10 clinical isolates of Campylobacter coli were characterized by their susceptibility to nine antimicrobial agents and by their plasmid profiles on agarose gel electrophoresis. All of the C. jejuni isolates were susceptible to chloramphenicol, ciprofloxacin, erythromycin, kanamycin, and nalidixic acid, but 55% were tetracycline resistant. In the 10 C. coli isolates, a high prevalence of multiple-antibiotic resistance was noted. Plasmids were found in 82% of the tetracycline-resistant and 15% of the tetracycline-susceptible C. jejuni isolates. Tetracycline resistance in six randomly selected C. jejuni isolates, which contained 50- or 135-kilobase (kb) plasmids, was transferred by conjugation to a Campylobacter fetus subsp. fetus recipient with recovery of a 50- or a 45-kb plasmid from transconjugants. From one multiple-antibiotic-resistant C. coli isolate, resistance to tetracycline, kanamycin, and chloramphenicol was transferred concomitantly with a 58-kb plasmid, pNR9589. Nonconjugative 98-kb plasmids, pNR9131 and pNR9581, from C. coli isolates with resistance to tetracycline, kanamycin, and erythromycin were shown by cloning experiments to code for at least kanamycin resistance. Restriction digests revealed that 50-kb plasmids from tetracycline-resistant C. jejuni isolates were identical, although plasmids from multiple-antibiotic-resistant C. coli isolates shared partial DNA homology to each other. Cloning of the kanamycin and chloramphenicol resistance genes of pNR9589 into Escherichia coli showed that the two genes are closely linked or clustered. Double-digestion analysis of the fragments encoding the kanamycin resistance of pNR9131, pNR9581, and pNR9589 showed that these three plasmids contain a common fragment related to kanamycin resistance.

Anti-Bacterial Agents↗
PubMed1987

Identification of the DNA sequence required for transposition immunity of the gamma delta sequence.

A plasmid containing the transposon gamma delta sequence was immune to further insertion of gamma delta (transposition immunity). Plasmids carrying a fragment containing either 0.2 kilobase pairs of the gamma end or 0.4 kilobase pairs of the delta end of the gamma delta sequence were immune, and other parts of the gamma delta sequence did not confer immunity. The terminal 38-base-pair (bp) sequence of the delta end of the gamma delta was sufficient to confer immunity, the 38-bp sequence of the gamma end conferred only moderate immunity, and the terminal 35-bp sequence, which was completely identical at both the gamma and delta ends, was insufficient to confer immunity.

Base Sequence↗
PubMed1985

Bioluminescent assay as a potential method of rapid susceptibility testing.

A method of rapid susceptibility testing by bioluminescent assay was developed. Correlation between the 50% inhibition dose of antimicrobics for bacterial adenosine triphosphate measured by bioluminescent assay and the minimum inhibitory concentration obtained by the broth dilution method was satisfactory. In the bioluminescent assay the incubation time required was only 90 min.

Adenosine Triphosphate↗
PubMed1985

Serogrouping of Bacteroides vulgatus by the agglutination test.

The agglutination technique was used to establish a serological classification scheme for Bacteroides vulgatus strains isolated from normal human feces and clinical specimens, especially from ulcerative colitis patients. Absorbed antisera to 10 strains of B. vulgatus were prepared. These 10 absorbed antisera were species specific. Of 90 B. vulgatus strains tested, 55 (61%) were agglutinated by one or more of these 10 absorbed antisera. A total of 27 serological patterns were grouped into 18 serogroups; 10 of these serogroups contained only one group component, whereas the other 8 serogroups were composed of more than one component. This serological classification could be used to study the epidemiology of this organism.

Adult↗
PubMed1984

Conduction of nonconjugative plasmids by F' lac is not necessarily associated with transposition of the gamma delta sequence.

A nonconjugative kanamycin-resistant (Kmr) recombinant plasmid, pNR5311, transferred at a low frequency from an Hfr or F' lac Escherichia coli donor to an F- lac- recipient. Among the transconjugants, two types of Kmr plasmids were found: one was indistinguishable from pNR5311 (type A), and the other was a recombinant between pNR5311 and the gamma delta sequence (type B). When the F' lac strain was used as a donor, 5% of lactose-fermenting (Lac+) and 75% of lactose-nonfermenting (Lac-) transconjugants had type A plasmids. A kinetic study revealed that type A plasmids were transferred more readily in short mating periods than were type B plasmids. Involvement of Tn903, which is present in pNR5311, in transfer of type A plasmids was unlikely since there was no discernible change in the F' lac molecule coexisting with the type A plasmid in the transconjugant cells. The non-gamma delta-associated conduction of pNR5311 by F' lac did not require the recA+ function of the donor. Conduction of pBR322 by F' lac was also carried out, and two types of plasmids with and without gamma delta were found, as with pNR5311. These findings suggest that the transfer of nonconjugative plasmids is conducted by a novel pathway which is not associated with translocation of transposable elements into either plasmid.

Base Sequence↗
PubMed1984

[Studies on the method of susceptibility test of Campylobacter jejuni to fosfomycin].

Conditions for the susceptibility test of Campylobacter jejuni to fosfomycin (FOM) were studied and it was concluded that the following procedure is most appropriate for routine tests. The test organisms were subcultured in 0.5 ml of heart infusion broth (Difco) in test tubes for a microplanter (Sakuma Seisakusho) and incubated in a GasPak jar with a CampyPak and catalyst (BBL) at 37 degrees C for 44--48 hours. The cultures were then diluted 100-fold in the same broth and inoculated with a microplanter on test plates. The test plates were nutrient agar (Difco) supplemented with 0.2% MgCl2 and 5% defibrinated horse blood. The plates were then incubated under the condition as described above and the growth of the cells was examined. It should be noted that drying of plates for more than 1 hour caused significant loss of viability of the cells.

Anti-Bacterial Agents↗
PubMed1983

HeLa cell invasiveness and O antigen of Shigella flexneri as separate and prerequisite attributes of virulence to evoke keratoconjunctivitis in guinea pigs.

Many rough mutants selected from isogenic smooth virulent and avirulent strains of Shigella flexneri were examined for virulence, using tissue culture infection and Sereny tests. Many of the rough mutants isolated from a virulent smooth strain were capable of penetrating tissue culture cells but incapable of producing a positive Sereny test. In contrast, we could not obtain from smooth avirulent strains any rough mutants capable of penetrating HeLa cells. Chemical analysis of lipopolysaccharide of some representative rough strains showed several patterns of sugar composition with a range of from Ra to Re chemotypes. There was no correlation between HeLa cell invasiveness and chemotypes of lipopolysaccharides, thus indicating little significance of oligosaccharides of the rough core as well as O antigens in the ability of S. flexneri to penetrate HeLa cells. When these invasive rough strains were given O antigen genes from a smooth avirulent Shigella Hfr strain, most of the transconjugants that expressed O antigens regained the ability to evoke keratoconjunctivitis in guinea pigs. We also examined the chromosomal loci of HeLa cell invasion by transferring carbohydrate fermentation genes of Escherichia coli K-12 Hfr and found two chromosomal loci, the rha and lac-gal regions, which control the ability to penetrate HeLa cells. These results suggested that O antigens and ability to penetrate tissue culture cells are independent and prerequisite attributes of virulence in Shigella flexneri to evoke keratoconjunctivitis in guinea pigs.

Animals↗
PubMed1982

[The effect of new broad-spectrum cephamycin, cefotetan administered intravenously on human fecal flora (author's transl)].

The changes in the fecal flora and their correlation with the fecal drug concentrations were studied, employing 4 volunteers (healthy adult males) to whom 1 g of cefotetan was intravenously administered daily for 6 days. 1. In all of the subjects, the total counts of fecal organisms were slightly decreased 1 day after administration of cefotetan, then showed gradual increase, and recovered to the normal level on 8 days after the withdrawal of the drug. 2. Cefotetan caused drastic suppression of normal aerobic and anaerobic flora during the administration period, except streptococci that remained unchanged at all. The bacterial groups suppressed were bacteroidaceae, eubacteria, bifidobacteria, peptococcaceae, lactobacilli, enterobacteriaceae, lecithinase-positive clostridia, and staphylococci. Yeasts were found to increase during the administration period. 3. The changes in flora well correlated with the fecal level of the drug concentrations. This is in accordance with the in vitro antibacterial activity of the drug. 4. A period of more than 15 days was required after the withdrawal of cefotetan to recover the normal fecal flora. 5. Loss of body weight and diarrhoea were not observed in any of the subjects.

Adult↗