An improved phagocytic plaque method using gram-negative bacilli.

The phagocytic plaque method developed for evaluation of the phagocytic function of leukocytes is not only very useful but convenient for both basic and clinical investigations. So far, only Staphylococcus aureus has been demonstrated to give clear phagocytic plaques. In this study, we successfully obtained clear phagocytic plaques with gram-negative bacilli (Pseudomonas aeruginosa and Escherichia coli). The plaques given by E. coli were morphologically nearly the same as those by S. aureus, whereas those of P. aeruginosa were elongated.