Quantitation of bacterial adherence by image analysis

In studies of the adherence of pathogenic bacteria to host eukaryotic cells in vitro, the counting of the bacteria is often challenging, especially if many experiments are involved. We developed a method to use digital imaging and computer-aided recognition for the quantitation of bacteria attached to cultured cells. We employed an immunocytochemical method to stain the bacteria and leave the hosts cells relatively unstained. We describe this method for use with five species of bacteria, Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, Staphylococcus aureus, and Chlamydia pneumoniae. To demonstrate an application of this method, we studied the attachment of H. influenzae and S. pneumoniae to target epithelial cell lines derived from the respiratory tract.