Showing papers in "American Journal of Clinical Pathology in 1966"

Antibiotic susceptibility testing by a standardized single disk method.

Abstract: In the words of the authors, the paper by A. W. Bauer et al., from the University of Washington in Seattle, on a standardized single-disk method for antibiotic susceptibility testing “. . . consolidate(s) and update(s) previous descriptions of the method and provide(s) a concise outline for its performance and interpretation.” Clinical microbiologists were relieved that finally a disk diffusion method had been standardized, could be used with ease, and provided reliable results as compared with minimum inhibitory concentration tests. The pivotal role of Hans Ericsson’s theoretical and practical studies (H. Ericsson and G. Svartz-Malmberg, Antibiot. Chemother. 6:41–74, 1959), as well as earlier reports by some of the authors of the publications cited, must be mentioned as a matter of fairness. Most of the recommendations given are still valid today even though some of the antimicrobial agents are obsolete, new ones have been added, some zone sizes had to be modified, and new media were designed for Haemophilus influenzae and Neisseria gonorrhoeae. Recommendations of the National Committee for Clinical Laboratory Standards continue to be based on this publication; the “Kirby-Bauer” method is, among the many disk methods used in other countries, still the one that has been researched most thoroughly and updated continuously. ALEXANDER VON GRAEVENITZ

Determination of serum calcium by means of orthocresolphthalein complexone.

Abstract: The use of orthocresolphthalein complexone (OCPC) as a reagent for the determination of calcium was introduced by Anderegg and associates and Schwarzenbach. Pollard and Martin and Stern and Lewis soon thereafter described manual spectrophotometric procedures using this dye. The procedure of Pollard and Martin is not applicable to the analysis of biologic materials. The method described by Stern and Lewis deals with the analysis of blood serum. Calcium is precipitated as the oxalate from 0.1 ml. of serum. The precipitate is washed and the oxalate ion, which in this procedure interferes with subsequent color development, is destroyed by heat (500 C. for 30 min). The calcium carbonate residue is dissolved in 0.1 ml. of N HC1, all traces of which must be removed by drying and heating before and residue is treated with a pH 8.5 borate-buffered OCPC color reagent. The absorbance is measured at 575 mju. Kessler and Wolfman have recently described an automated procedure adapted to the Autotechnicon. Our paper presents a greatly improved manual spectrophotometric method based upon release of the bound calcium by means of protein precipitation and the complete masking of the response of the dye to magnesium by means of 8-quinolinol (direct method). As a reference method, the calcium is precipitated as the oxalate. Without being washed, this is dissolved in 0.2 N HC1, an aliquot of which is reacted with the OCPC color reagent (alternate procedure).

Modification of the Brown and Brenn Gram Stain for the Differential Staining of Gram-Positive and Gram-Negative Bacteria in Tissue Sections.

Abstract: The Brown and Breiin method for differential staining of Gram-positive and Gram-negative organisms in tissue sections was introduced to histologic technic in 1931. The most frequent difficulty encountered in the Gram-staining technic is not in the staining of Gram-positive organisms, but the staining of Gram-negative organisms in tissue sections. In many instances the Gram-negative organisms are stained faintly pink or remain unstained. In the following modification, with explanation and points of changes in each step, we have had consistent and dependable results in staining Gram-negative organisms in tissue sections. When there is close correlation with the bacteriology laboratory, the value of the stain is greatly augmented.

Ethylene glycol toxicity.

Abstract: Renal tubular oxalosis is a striking and regular phenomenon following the ingestion of ethylene glycol by a variety of mammals, including man. Doubt exists, however, regarding the relation of renal oxalate crystal formation to the mechanism of ethylene glycol toxicity. It has been proposed that the toxicity of ethylene glycol may be related either to a direct effect of the unaltered compound or to the production of toxic intermediaries in the course of degradation. The identification of glycolaldehyde, glycolic, and glyoxylic acid as probable intermediaries by Gessner and associates prompted the following experiment, in which the genesis of renal tubular oxalosis following the administration of these compounds was sought as an indicator of the validity of their place in the sequential degradation of ethylene glycol.