Antibacterial Activity in Serum and Urine as a Therapeutic Guide in Bacterial Infections

Abstract

The peak and trough levels of bacteriostatic and bactericidal activity of the serum and the urine of 317 patients with cancer and a bacteriologically proven infection were measured, using the patient's microorganism and the serum or urine containing the given antibiotics. When the peak titer of bacteriostatic activity in serum was ⩾ 1: 8, the infection was cured in ⩾ 80% of cases. The response to therapy of patients with urinary tract infections correlated best with the inhibitory level found in the urine; clinical cure was observed in at least 90% of the patients who had a titer of bacteriostatic activity in urine ⩾ 1:4. The antibacterial activity of serum was influenced by the in vitro sensitivity of the offending microorganism, and by the composition of the antimicrobial regimen; these two factors were shown to be related to the clinical outcome. It is suggested that the determination of the antimicrobial activity of the serum, early in the course of treated infection, might allow some adjustment of antibiotic therapy.