A quantitative study of the multiplication of Pseudomonas aeruginosa in vented and unvented blood-culture bottles.

A quantitative study of the growth of Pseudomonas aeruginosa in both vented and unvented vaccum blood-culture bottles revealed that these organisms multiply readily in the latter. After a 3- to 4-hour lag period they double at 33--34-minute intervals, reaching a maximum growth of 10(8) - 10(10) organisms by 18 hours. Multiplication then stops. The data indicate that blind sampling should invariably be successful in isolating organisms after 8 hours of incubation. The rate of recovery of these organisms is not increased by venting, but the maximum level of growth in unvented containers is at the borderline level of visibility, necessitating a blind subculture for definitive diagnosis, whereas vented containers show relatively unrestrained growth. A method for the use of single vacuum bottles for the detection of Ps. aeruginosa, and optionally, Candida species, is proposed.