Search PubMed⌕ Search

Biomedical subjects

S D Davis

Publications and source records attributed to S D Davis.

At least 109 records · Page 6Linked to original sources
PubMed1975

Activity of gentamicin, tobramycin, polymyxin B, and colistimethate in mouse protection tests with Pseudomonas aeruginosa.

Mouse protection tests were carried out with four antibiotics and six strains of Pseudomonas aeruginosa. All strains were susceptible to all four antibiotics by an in vitro test. A heavier bacterial inoculum increased the mean effective dose of gentamicin and tobramycin, but not polymyxin B. Second and third doses of gentamicin in the mouse protection test made little change in the mean effective dose. In the mouse protection tests, tobramycin was the most active antibiotic if the results were analyzed in terms of the therapeutic index or ratio of toxicity to efficacy. Colistimethate was poorly inactive in vivo. Polymyxin B was most active on an absolute basis but also was the most toxic. One strain of Pseudomonas was classified as resistant to gentamicin in vivo although it was susceptible in vitro. Strains of Pseudomonas that were uniformly susceptible to antibiotics in vitro were not uniformly susceptible in the mouse protection test to low doses of antibiotic.

Animals↗
PubMed1975

Experimental keratitis due to Pseudomonas aeruginosa: model for evaluation of antimicrobial drugs.

An improved method for experimental keratitis due to Pseudomonas aeruginosa is described. Essential features of the method are use of inbred guinea pigs, intracorneal injection of bacteria, subconjunctival injection of antibiotics, "blind" evaluation of results, and statistical analysis of data. Untreated ocular infections were most severe 5 to 7 days after infection. Sterilized bacterial suspensions caused no abnormalities on day 5. Tobramycin and polymyxin B were more active than gentamicin against two strains of Pseudomonas. This model is suitable for many types of quantitative studies on experimental keratitis.

Animals↗
PubMed1975

Structure and function of the gastrointestinal tract in primary immunodeficiency syndromes (IDS) and in granulocyte dysfunction.

Gastrointestinal (GI) disease is frequently encountered in patients with defective defense mechanisms. The incidence of GI disease and the structure and function of the GI tract have been studied systematically in 41 patients with immunodeficiency syndromes (IDS) and in 9 patients with chronic granulomatous diesase (CGD). Giardia lamblia was a major cause of GI disease in patients with IDS. Eradication of the parasite resulted in disappearance of symptoms and malabsorption, and normalization of the villus architecture. Six of 9 patients with CGD had either GI symptoms or malabsorption or both. Typical histologic changes were found in the small intestinal and rectal mucosa of all patients biopsied.

Carotenoids↗
PubMed1975

The recognition and classification of immunodeficiency diseases with bacteriophage phiChi 174.

A standard antigen to assess humoral responses is needed for the immunodeficiency syndromes. Bacteriophage phiChi 174 is the best available antigen. Large, standardized batches can be prepared, stored and distributed; samples for assay can be transported by mail. We have systematically studied the immune response to this antigen in over 200 persons, including 49 immunodeficiency patients. Phage provides consistent delineation of humoral responses in primary immunodeficiency diseases.

Antibodies, Viral↗
PubMed1974

Combined immunodeficiency and reticuloendotheliosis with eosinophilia.

A generalized erythematous scaly rash, alopecia, lympadenopathy, and hepatosplemonegaly developed in an infant girl during the first 6 weeks of life. Repeated bacterial and fungal infections, persistent diarrhea, and generalized wasting complicated the course of her illness, and death occurred at 5 1/2 months of age. Lymph node architecture was completely obliterated by histiocytes and eosinophils; no plasma cells or germinal centers were present. Both humoral and cellular immune systems were severely but not completely impaired. Familial reticuloendotheliosis with eosinophilia is, in some cases, associated with combined immune deficiency.

Antibody Formation↗
PubMed1974

Dissociation between results of in vitro and in vivo antibiotic susceptibility tests for some strains of Pseudomonas aeruginosa.

The relative efficacy in vivo of the polymyxin and aminoglycoside antibiotics in experimental Pseudomonas infection has apparently never been established. This study was designed to determine such efficacy in experimental infection of mice. Eleven strains of Pseudomonas aeruginosa were selected for the study, representing six of the seven recognized immunotypes. All strains were susceptible to colistin, gentamicin, and tobramycin in vitro, and all were virulent for mice. None was lethal because of preformed toxins. Infections were established in mice by intraperitoneal (i.p.) injection of 100 ID(50) of bacteria (infectious doses that would kill 50% of the mice). Graduated doses of antibiotics or saline were given subcutaneously 1 h later. Infections by three strains of P. aeruginosa were cured by low doses of all three antibiotics. Infections by two strains were relatively resistant in vivo to all three antibiotics. Infections by seven strains were relatively resistant in vivo to colistimethate. For most strains, colistimethate was less effective in vivo than gentamicin or tobramycin. To determine the influence of the size of the bacterial inoculum upon the results of chemotherapy, groups of mice were infected with serial dilutions of bacterial suspensions and treated with antibiotics. The antibiotics were more effective when a lighter bacterial inoculum was used. However, colistimethate at 30 mg/kg failed to cure some infections established with an inoculum of only 10 ID(50). To examine the possibility that death despite apparently adequate chemotherapy might be due to bacterial lysis and delayed release of toxins, numbers of viable bacteria in the peritoneal cavity of treated animals were determined by colony count. Antibiotic failure by colistimethate was associated with a steady rise in the number of i.p. bacteria. The findings support the conclusion that i.p. infections in mice with some strains of P. aeruginosa that are fully susceptible in vitro are relatively resistant to chemotherapy in vivo. The dissociation between in vitro and in vivo results was greatest for colistimethate.

Animals↗
PubMed1972

Antagonistic effect of calcium in serum on the activity of tobramycin against Pseudomonas.

Physiological concentrations of calcium in serum antagonize the activities of colistin, polymyxin B, and gentamicin against Pseudomonas aeruginosa. Studies were carried out to determine whether tobramycin, a new aminoglycoside antibiotic, is also antagonized by calcium. The activity of tobramycin in vitro was shown to be antagonized by human serum and by physiological concentrations of calcium. The addition of human serum in broth-dilution tests produced a fourfold rise in the minimal inhibitory concentrations of tobramycin for five strains of Pseudomonas. In disc diffusion tests, the addition of calcium to the agar significantly decreased the size of inhibition zones, and the addition of a chelating agent to the agar increased the zone sizes. In a limited comparative study, tobramycin and gentamicin were tested against both light and heavy bacterial inocula of two strains of Pseudomonas. Tobramycin appeared to be antagonized less by serum than was gentamicin at equal antibiotic concentrations.

Anti-Bacterial Agents↗