Effect of serum from different patient populations on the serum bactericidal test

We evaluated the effect of serum from normal and uraemic volunteers, neutropenic patients and burn patients on the serum bactericidal test. Serum samples were spiked with ceftazidime to mimic in vivo peak (75 mg/L) and trough (5 mg/L) concentrations. Serum inhibitory and bactericidal titres (SIT and SBT) were performed in triplicate using Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. For E. coli, the trough SIT and SBT were significantly higher in serum from burn patients compared with normal volunteers (P < or = 0.024). The trough SIT was significantly higher in serum from burn patients compared with neutropenic patients (P = 0.022) and in uraemic patients compared with normal volunteers (P = 0.04). No significant differences between subject populations were found for P. aeruginosa.