Sulfonamide resistance mechanism in Escherichia coli: R plasmids can determine sulfonamide-resistant dihydropteroate synthases.
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Several natural isolate E. coli strains highly resistant to sulfonamides and antibiotics are shown to contain a sulfonamide-resistant dihydropteroate synthase (2-amino-4-hydroxy-6-hydroxymethyl-7,8-dihydropteridine-diphosphate:4-aminobenzoa te 2-amino-4-hydroxydihydropteridine-6-methenyltransferase, EC 2.5.1.15) in addition to the normal sensitive enzyme. The resistant dihydropteroate synthases examined are determined by an R plasmid and are smaller and less heat stable than the normal sulfonamide-sensitive enzyme. One synthase resistant to any sulfonamide tested, and to sulfanilic and arsanilic acids, was still inhibited by several non-sulfonamide analogs of p-aminobenzoate. Citrobacter and Klebsiella pneumoniae strains also show similar mechanisms of sulfonamide resistance. (+info)
Calcium influx in skeletal muscle at rest, during activity, and during potassium contracture.
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Calcium influx in the sartorius muscle of the frog (Rana pipiens) has been estimated from the rate of entry of Ca(45). In the unstimulated preparation it is about equal to what has been reported for squid giant axons, but that per impulse is at least 30 times greater than in nerve fibers. The enhanced twitch when NO(-) (2) replaces Cl(-) in Ringer's is associated with at least a 60 per cent increase in influx during activity, whereas this anion substitution does not affect the passive influx significantly. Calcium entry during potassium contracture is even more markedly augmented than during electrical stimulation, but only at the beginning of the contracture; thus, when a brief Ca(45) exposure precedes excess K(+) application, C(45) uptake is increased three- to fivefold over the controls not subjected to K(+), whereas when C(45) and K(+) are added together, no measurable increase in Ca(45) uptake occurs. These findings are in keeping with the brevity of potassium contracture in "fast (twitch)" fibers such as in sartorius muscle. (+info)
SURGICAL MANAGEMENT OF REGIONAL ENTERITIS.
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The present-day concepts concerning the surgical management of regional enteritis are reviewed and the multitude of problems that may arise in surgical treatment are discussed. The primary treatment of regional enteritis remains medical. Surgical intervention is necessary only for the complications of intractability, obstruction, fistula, abscess formation, anal and rectal complications, massive hemorrhage and perforation. To ensure the best possible results, medical treatment should continue after surgery. A perfect operation for this disease does not exist. Operations for regional enteritis can now be performed with a mortality rate of less than 2%, and although the recurrence rate following surgery averages approximately 30%, the disease is well controlled in the majority of patients with medical and/or surgical treatment. (+info)
PIGMENTATION VARIANTS OF PSEUDOMONAS AERUGINOSA.
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Howarth, S. (University of Otago, Dunedin, New Zealand), and M. D. Dedman. Pigmentation variants of Pseudomonas aeruginosa. J. Bacteriol. 88:273-278. 1964.-Pigmentation variants were isolated from Pseudomonas aeruginosa strain 1, including both FP(+) and FP(-) sublines, and strain 78 by growth with sulfathiazole. The changes were from the normal yellow-green color to brown and nonpigmented variants. Brown variants arising from strain 1 were studied in most detail, and were found to occur as spontaneous mutants in the normal population with a frequency of about 10(-7). These variants have other altered characteristics; notably, they show a change to a smooth colony morphology and resistance to the virulent bacteriophage E79. When grown in the presence of sulfathiazole, pigmentation variants have a selective growth advantage, which would account for their presence in unusually high numbers in populations surviving sulfathiazole treatment. (+info)
TRANSFER OF DRUG RESISTANCE BETWEEN ENTERIC BACTERIA INDUCED IN THE MOUSE INTESTINE.
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Kasuya, Morimasa (Nagoya University School of Medicine, Nagoya, Japan). Transfer of drug resistance between enteric bacteria induced in the mouse intestine. J. Bacteriol. 88:322-328. 1964.-Transfer of multiple drug resistance in the intestines of germ-free and conventional mice was studied with strains of Shigella, Escherichia, and Klebsiella. The transfer experiment was carried out under antibiotic-free conditions to eliminate the production of drug-resistant bacteria by antibiotics. All resistance factors (chloramphenicol, streptomycin, tetracycline, and sulfathiazole) were transferred with ease in the intestinal tracts of mice, when donors and recipients multiplied freely, and acquired resistance was further transferred to other sensitive enteric bacteria in the intestinal tract. Bacteria to which resistance factors were transferred showed, in most of the experiments, exactly the same level and pattern of resistance as the donors. Based on the above, a hypothesis that the same process may possibly occur in the human intestine is presented. (+info)
Catalysis and sulfa drug resistance in dihydropteroate synthase.
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Role of purine biosynthetic intermediates in response to folate stress in Escherichia coli.
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Folic acid plays a central role in anabolic metabolism by supplying single-carbon units at varied levels of oxidation for both nucleotide and amino acid biosyntheses. It has been proposed that 5-amino-4-imidazole carboxamide riboside 5'-triphosphate (ZTP), an intermediate in de novo purine biosynthesis, serves as a signal of cellular folate stress and mediates a physiologically beneficial response to folate stress in Salmonella typhimurium (B. R. Bochner, and B. N. Ames, Cell 29:929-937, 1982). We examined the physiological response of Escherichia coli to folate stress induced by the drugs psicofuranine, trimethoprim, and sodium sulfathiazole or by p-aminobenzoic acid (pABA) starvation. Analysis of nucleotide pools showed that psicofuranine or trimethoprim treatment of a prototrophic strain or growth of a pABA auxotroph on limiting pABA induced the production of the nucleotide ZTP, as previously observed in S. typhimurium by Bochner and Ames. Accumulation of ZTP and its precursor 5-amino-4-imidazole carboxamide riboside 5'-monophosphate (ZMP) did not correlate well with folate stress in E. coli, as measured by determination of the folate/protein ratios of extracts of treated cells. Treatment of cells with psicofuranine caused a marked accumulation of 5-amino-4-imidazole carboxamide ribonucleotides (Z-ribonucleotides) but a statistically insignificant drop in the folate/protein ratio of cell extracts. Sodium sulfathiazole treatment at a drug concentration that led to a threefold drop in the growth rate and in the folate/protein ratio of treated cells led to little accumulation of Z-ribonucleotides in E. coli A purF his+ strain which produces ZTP and ZMP when treated with trimethoprim was constructed. In this strain, histidine represses the synthesis of both ZMP and ZTP. Treatment of cells of this strain with trimethoprim resulted in a decrease in the folate/protein ratio of cell extracts, but a blockade of Z-ribonucleotide accumulation did not affect the extent of folate depletion seen in treated cells and had only a small effect on the resistance of this strain to growth inhibition by trimethoprim. The patterns of protein expression induced by treatment of this strain with trimethoprim or psicofuranine were examined by two-dimensional electrophoretic resolution of the total cellular proteins. No differences in protein expression were seen when the treatment were performed in media containing or lacking histidine. These studies failed to provide evidence in E. coli for a folate stress regulon controlled by ZTP. (+info)
Modification of the solid-state nature of sulfathiazole and sulfathiazole sodium by spray drying.
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