Wright method

Wright method (A. E. Wright) - method proportional counting the total number of bacterial phone Thoroughly mix certain volumes investigated suspension of bacteria and human blood. The mixture is evenly applied to the surface of the glass, dried, fix and paint in the usual way. Microscopic examination of the drug in some fields separately count the number of red blood cells and bacterial cells. Wright took the number of red blood cells in 1 ml of blood for 5 million and, based on the established microscopic examination of the drug for the numerical ratio of red blood cells and bacteria, counted the number of bacterial cells in the investigated volume of the suspension. The advantage of this method is proportional counting is its simplicity. Possible errors when using this method are due to: 1) significant fluctuations in the number of red blood cells in 1 ml of human blood, which Wright had always taken for 5 million; 2) by covering part of the bacterial cell erythrocytes; 3) uneven distribution of cells and erythrocytes on a slide; 4) partial washout of cells and erythrocytes in the painting process; 5) bacteriolytic action of fresh blood.
Subsequent modifications of other authors addressed some of the shortcomings of the method Wright is Necessary to conduct a preliminary counting the number of red blood cells in the accounts chamber or to prepare a standard suspension chicken erythrocytes that after fixing chloride mercury and canning formalin long retain their stability. Instead of the standard suspension chicken erythrocytes you can use the standard suspension of yeast. To prevent political action of blood it expedient to replace a suspension of erythrocytes in the same environment, which is used for cultivation of bacteria. It is recommended that before mixing the suspension of erythrocytes with bacteria to pre-coloring bacteria methylene blue. With these amendments counting the total number of bacteria method Wright gives the opportunity to get a sufficiently clear and stable results. Cm. also the Blood (research methods).