Avoiding artifacts in the infant rat model for bacterial meningitis: use of Sangur test strips for the rapid quantification of blood contamination in cerebrospinal fluid.

The infant rat model is widely used to study the pathogenesis of meningitis caused by a variety of gram-positive and gram-negative bacteria. However, the interpretation of published results concerning meningitis is difficult in many records because the fact that blood contamination of the cerebrospinal fluid (CSF) cannot be avoided during the traumatic puncture procedure has not been taken into consideration. Since bacterial invasion of the central nervous system develops following bacteremia in this model, blood contamination of the CSF leads to a falsification of the CSF bacterial counts. Here we present an evaluation of a rapid and quantitative test for CSF blood contamination using Sangur test strips. The procedure requires minimal amounts of CSF and allows direct calculation of the CSF bacterial load due to blood contamination and, thus, provides refined criteria for the presence of bacterial meningitis in the infant rat model. It is superior to the detection of erythrocytes using a hemocytometer since it is less time consuming. Furthermore, we demonstrate the value of this method for the experimental infection of rats with Neisseria meningitis.