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C H Pai

Publications and source records attributed to C H Pai.

At least 73 records · Page 4Linked to original sources
PubMed1979

Efficacy of cold enrichment techniques for recovery of Yersinia enterocolitica from human stools.

Stool specimens from children with gastroenteritis and their household contacts were cultured for Yersinia enterocolitica by direct plating onto routine laboratory media. These stools were also inoculated into phosphate-buffered saline and subcultured to the same media after 1 day or 3 weeks of incubation at 4 degrees C. Y. enterocolitica was isolated from 174 index cases and 34 household contacts. One hundred eighty-one isolates were of serotype O:3, and the remaining 21 belonged to other serotypes. Eighty-one percent (147/181) of O:3 isolates were recovered by direct plating, and 6.1% (11/181) and 13% (23/181) were recovered by 1-day and 3-week cold enrichment, respectively. For other serotypes, 26% (7/27), 0%, and 74% (20/27) were isolated by direct plating, 1-day cold enrichment, and 3-week cold enrichment, respectively. The efficacy of the cold enrichment for the patients were still symptomatic, 94 and 6% of Y. enterocolitica were identified by direct plating and cold enrichment, respectively. Isolation rates were 66% by direct plating and 34% by cold enrichment when stools were obtained from asymptomatic carriers or from those convalescing from Y. enterocolitica gastroenteritis. These results indicate that the cold enrichment methods increase the sensitivity of Y. entercolitica culture methods considerably in convalescent and asymptomatic subjects but only minimally in patients with diarrhea caused by serotype O:3.

Bacteriological Techniques↗
PubMed1979

Yersinia enterocolitica infection in children: 4 years experience in the Montreal urban community.

From 1973 to 1976, a total of 146 strains of Yersinia enterocolitica was isolated from children at the Ste. Justine Hospital and Montreal Children's Hospital. All strains tested were of serotype 0:3, biotype 4. The majority (80%) of children from whom Y. enterocolitica was isolated were under 5 years of age and in 74 of 93 cases reviewed diarrhea was the predominant symptom. Case reports on 2 patients with unusual clinical features are also presented.

Abdomen↗
PubMed1978

In vitro susceptibility of Haemophilus influenzae to sulfamethoxazole-trimethoprim and cefaclor, cephalexin, and cephradine.

Sulfamethoxazole-trimethoprim and three oral cephalosporins, cefaclor, cephalexin, and cephradine, were evaluated in vitro as possible alternatives to chloramphenicol in the treatment of non-central nervous system infections due to ampicillin-resistant Haemophilus influenzae. Sixty-four isolates of H. influenzae, including 31 beta-lactamase-positive strains, were tested by the agar dilution method. All strains were inhibited by 0.78/0.039 mug sulfamethoxazole-trimethoprim per ml and by 0.78 mug of chloramphenicol per ml. At 6.25 mug/ml, 100, 11, and 3% of all strains were inhibited by cefaclor, cephalexin, and cephradine, respectively. Thus, on the basis of drug concentrations presumably achievable in serum, 100% of strains were susceptible to sulfamethoxazole-trimethoprim, chloramphenicol, and cefaclor. However, a considerable inoculum effect was noted with both beta-lactamase-positive and -negative strains, when tested with sulfamethoxazole-trimethoprim; the minimal inhibitory concentrations of cefaclor were only slightly affected. Also, synergistic effects of sulfamethoxazole-trimethoprim, sulfamethoxazole-erythromycin, and sulfamethoxazole-cefaclor were seen when combinations were tested against both beta-lactamase-positive and -negative strains, as determined by minimal inhibitory concentrations measured by the broth dilution method and by killing curve analyses. These results support further evaluation of these combinations and of cefaclor alone for the treatment of non-central nervous system infections due to H. influenzae.

Cephalosporins↗
PubMed1978

Production of enterotoxin by Yersinia enterocolitica.

Forty-three strains of Yersinia enterocolitica isolated from children with gastroenteritis and 18 laboratory strains were examined for enterotoxin production by using the infant mouse, Y1 adrenal cell, and rabbit ileal loop assay systems. All clinical isolates and seven laboratory strains were found enterotoxigenic in the infant mouse model, but none of the strains produced toxin in the Y1 adrenal cell system. One enterotoxin-producing strain was also tested by the rabbit ileal loop assay, confirming the results of the infant mouse assay. The enterotoxin was heat-stable and as active in the 6-h rabbit ileal loop as in the 18-h assay, suggesting a similarity to the heat-stable enterotoxin of Escherichia coli.

Animals↗
PubMed1978

Prevalence of enterotoxigenicity in human and nonhuman isolates of Yersinia enterocolitica.

A total of 414 cultures of Yersinia enterocolitica isolated from human and nonhuman sources were examined for heat-stable enterotoxin (ST) production to determine whether enterotoxigenicity was related to the source of isolation, serotype, or biochemical characteristics of the organism. A total of 65% of all cultures were found to produce ST. Enterotoxin production was much more prevalent in strains isolated from humans (218/232) than in those isolated from animals (17/34), water (9/49), raw milk (14/44), and food (10/55). Strains belonging to the serotypes O:3; 8; 5,27; 6,30; 9, often isolated from human infections, were almost always enterotoxigenic (191/196), although ST production was also highly prevalent among a few other serotypes. The most significant difference was observed between the groups that differed in the ability to ferment rhamnose; only 13 of 130 rhamnose-positive isolates produced ST (10%) compared to 255 of 284 rhamnose-negative cultures (90%). These results suggest that ST production is ubiquitous in Y. enterocolitica, with the highest prevalence among strains associated with human infections.

Animals↗
PubMed1975

Genetics of biotin biosynthesis in Bacillus subtilis.

Biotin auxotrophs of Bacillus subtilis were isolated and classified into three groups according to growth requirements, cross-feeding pattern, and biotin precursors excreted into culture supernatant fluids. Mutant genes were mapped by transduction using phage PBS1. All presently identified bio genes were linked to aroG with an order of bio-aroG-argA-leu-1. No linked markers were found to the left of the bio loci.

Arginine↗
PubMed1972

Mutant of Escherichia coli with derepressed levels of the biotin biosynthetic enzymes.

A cross-feeding technique was used to isolate a mutant of Escherichia coli K-12 that excretes 1,000 times more biotin into the growth medium than the parent strain. The mutant has high levels of the biotin biosynthetic enzymes even when grown in the presence of biotin. Desthiobiotin synthetase, the level of which was used as a measure of the biosynthetic activity of the biotin pathway, is not repressed by biotin at the concentration 250,000 times that sufficient to repress the enzyme in the wild type. The mutant gene is cotransducible with argC located at 77 min on the E. coli chromosome.

Acetates↗
PubMed1971

Biosynthesis of biotin: synthesis of 7,8-diaminopelargonic acid in cell-free extracts of Escherichia coli.

Cell-free extracts prepared from a biotin auxotroph of Escherichia coli were active in catalyzing the synthesis of 7,8-diaminopelargonic acid, an intermediate of the biotin pathway, from 7-oxo-8-aminopelargonic acid. The product was identified on the basis of its chromatographic characteristics and its biotin activities for biotin auxotrophs of E. coli. Enzyme activity was determined in a reaction coupled with the desthiobiotin synthetase system, which is required for the conversion of 7,8-diaminopelargonic acid to desthiobiotin, and by measuring the amount of desthiobiotin formed by microbiological assay. The reaction was stimulated by l-methionine and pyridoxal-5'-phosphate. l-Methionine could not be replaced by any other amino acids tested. Pyridoxamine and pyridoxamine-5'-phosphate were as active as pyridoxal phosphate. The enzyme, presumably an aminotransferase, was demonstrable in the parent strain of E. coli and all mutant strains tested with the exception of a strain which is able to grow on diaminopelargonic acid but not on 7-oxo-8-aminopelargonic acid. Furthermore, the enzyme was repressible by biotin. The results were consistent with the hypothesis that the biosynthesis of 7,8-diaminopelargonic acid from 7-oxo-8-aminopelargonic acid is an obligatory step in the biosynthetic pathway of biotin in E. coli.

Amines↗
PubMed1970

Partial purification and properties of D-desthiobiotin synthetase from Escherichia coli.

d-Desthiobiotin synthetase, an enzyme that catalyzes the synthesis of d-desthiobiotin from dl-7,8-diaminopelargonic acid and HCO(3) (-), was purified 100-fold from cells of a biotin mutant strain of Escherichia coli. Adenosine triphosphate and Mg(2+) were shown, especially in purified extracts, to be obligatory for enzyme activity, although concentrations higher than 5 mm caused severe inhibition of the reaction with unpurified cell-free extracts. Adenosine diphosphate and adenosine monophosphate were shown to inhibit the reaction, but fluoride (up to 50 mm) had no detectable effect. The product of the enzyme reaction was identical to d-desthiobiotin on the basis of biological activity and chromatography. Furthermore, when H(14)CO(3) (-) was used as a substrate, the radioactive product was shown to be (14)C-desthiobiotin labeled exclusively in the ureido carbon.

Adenine Nucleotides↗
PubMed1969

Biosynthesis of desthiobiotin in cell-free extracts of Escherichia coli.

Cell-free extracts of Escherichia coli were active in catalyzing the synthesis of a biotin vitamer from 7,8-diaminopelargonic acid. The vitamer was identified as desthiobiotin on the basis of its chromatographic and electrophoretic characteristics and its biotin activities for a variety of microorganisms. The reaction was stimulated five-fold by bicarbonate, suggesting that an "active CO(2)" was incorporated into the carbonyl carbon of desthiobiotin. The enzyme was demonstrable in a wild-type (K-12) and in all biotin mutants of E. coli that were tested, with the exception of a strain which was able to grow on desthiobiotin but not on diaminopelargonic acid. Furthermore, the enzyme was repressible by biotin in all of the strains tested. These results are consistent with the hypothesis that the biosynthesis of desthiobiotin from 7,8-diaminopelargonic acid is an obligatory step in the biosynthetic pathway of biotin in E. coli.

Bicarbonates↗
PubMed1967

Biosynthesis of biotin in microorganisms. V. Control of vitamer production.

Use of a yeast-lactobacillus differential microbiological assay permitted investigation into the synthesis of biotin vitamers by a variety of bacteria. A major portion of the biotin activity was found extracellularly. The level of total biotin (assayable with yeast) greatly exceeded the level of true biotin (assayed with lactobacillus). Values for intracellular biotin generally showed good agreement between the assays, suggesting the presence of only true biotin within the cells. Bioautographic analysis of the medium after growth of each organism revealed the presence of large amounts of a vitamer which corresponded to dl-desthiobiotin on the basis of Rf value and biological activity. Biotin, when detected at all, was at very low concentrations. Also, an avidin-uncombinable vitamer was synthesized by a majority of the bacteria. Addition of d-biotin to the growth medium prevented completely the synthesis of both vitamers of biotin. d-Biotin-d-sulfoxide had no effect on the synthesis of desthiobiotin or the avidin-uncombinable vitamer. Addition of dl-desthiobiotin did not prevent its own synthesis nor that of the other vitamer. Control of vitamer synthesis is therefore highly specific for d-biotin. The avidin-uncombinable vitamer was produced only at repressed levels in the presence of high concentrations of both d-biotin and dl-desthiobiotin, which suggested that it is not a degradation product of these substances. A possible mechanism for the overproduction of the biosynthetic precursors of biotin is presented.

Bacillus cereus↗