Significance of serum bactericidal activity in gram-negative bacillary bacteremia in patients with and without granulocytopenia.

Serum bactericidal activity was determined routinely in 89 patients with gram-negative bacillary bacteremia, 79 of whom were analyzed because they had granulocyte counts either below 100/mm3 or above 1,000/mm3. A peak (one hour after the administration of the antibiotics) serum bactericidal titer of 1:8 or more in non-granulocytopenic patients or 1:16 or more in severely granulocytopenic patients could be correlated with a favorable clinical response, in 98 percent (44 of 45) (p less than 0.0001) and 87 percent (20 of 23), (p less than 0.001) respectively. Granulocytopenic patients required a statistically significantly higher serum bactericidal activity for a favorable response. Serum bactericidal activity appears to be a useful and simple method to monitor antibiotic treatment in gram-negative bacillary bacteremia, especially when combination therapy is used.