Determination of bacterial challenge dose.

<p>The association between the OD₆₀₀ of the bacterial culture and the number of CFUs/µl was determined for <i>Pseudomonas aeruginosa</i> (A) and <i>Klebsiella pneumoniae</i> (B) bacteria by plating dilutions of culture and quantitating colonies. The OD₆₀₀ quantitation of CFU/µl was then used to determine the amount of bacteria that untreated mice could control with minimal morbidity in ICR mice with <i>Pseudomonas aeruginosa</i> delivered IP (C) and <i>Klebsiella pneumoniae</i> delivered by inhalation (D). The numbers of CFUs of <i>Klebsiella pneumoniae</i> were found to be the same for Balb/c and C3H/HeN mice as for ICR mice. The maximal number of CFUs of <i>Pseudomonas aeruginosa</i> that resulted in the ability of Balb/c (E) and C3H/HeN (F) mice to control the infection with minimal morbidity was determined.