Comparison of Sheep and Human Blood Agar for Bacterial Growth and Hemolytic Pattern Expression
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Keywords
Bacterial Growth, Hemolysis, Culture Media, Pathogenic Bacteria, Blood Agar
Abstract
Objective: To comparatively evaluate the effectiveness of sheep blood agar and human blood agar for bacterial growth, visualization of hemolytic patterns, and colony morphological characteristics. Methods: Base agar media supplemented with 5% defibrinated sheep blood and human blood were prepared. Parallel inoculations were performed using eight clinical strains and four ATCC reference strains representing alpha, beta, and gamma hemolysis. Agreement between both culture media in hemolytic expression was assessed using the Kappa index, and statistical association was analyzed using Pearson’s chi-square test. Results: Sheep blood showed a higher erythrocyte count (10.31 million/mm³) compared with human blood (4.36 million/mm³), although it had lower hemoglobin concentration (11.5 g/dL vs. 12.8 g/dL) and hematocrit (33.61% vs. 38.57%). On sheep blood agar, bacterial colonies generally appeared larger, except for Escherichia coli. Hemolysis was more clearly expressed on sheep blood agar, with a moderate level of agreement between both media regarding hemolysis type (Kappa = 0.60; p = 0.010). Conclusions: Both culture media supported adequate bacterial growth. However, sheep blood agar demonstrated more uniform growth, larger colony size, and clearer visualization of hemolytic patterns, supporting its preferential use in routine microbiological analysis.
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