“…Serum was either heat inactivated (open symbols) or active (closed Moreover, the definitions of serum resistance and susceptibility depend upon the techniques chosen to monitor the reaction (1, 3, 4, 6, 9, 12, 16, 21, 24-28, 36-38, 40). Most of these methods are based on viable counts (1,4,6,16,28,32,(34)(35)(36); on the measurement of metabolic pertubations (22,34), cell respiration (18,33), or the release of various cell products, such as enzymes (20,32,33), DNA (2), radiolabeled thymidine (21,27), labeled ions (34), or 51Cr (13,30,34); or on photometric growth assays (24,32,39). It has been previously demonstrated that bacteriolysis represents the conversion of spheroplasts to ghost cells (8).…”