[Usefulness of micro-organism counts in positive haemocultures (author's transl)].

In patients with positive haemoculture counting the number of micro-organisms per ml of blood can be of interest for both diagnosis and prognosis. Contamination is practically excluded when values exceed 20 organisms/ml, and bacteraemia when they exceed 500 organisms/ml. Generally, the higher the count the greater the likelihood of septicaemia. Values lower than 2 organisms/ml correspond in most cases to Gram-negative infections. Excluding the latter, which carry a high lethal risk, the mortality rate in septicaemia increases with the number of micro-organisms in the blood.