A Plaque Assay on Agar for Detection of Gram-Negative Bacilli Sensitive to Complement

Summary A screening method to detect serum (complement) sensitive Gram-negative bacilli is described. Normal serum, dropped on the surface of a T.S.A. plate inoculated with the test organism will inhibit the growth of serum sensitive bacteria. Gram-negative bacteria isolated from blood cultures were tested and only 9/120 were sensitive. Bacteria isolated from infections, other than urinary tract, were also usually serum resistant.