Enumeration of Viable Chlamydia from Infected Animals Using Immunofluorescent Microscopy

An appropriate means of quantitating infectious Chlamydia from infected animals is essential for the evaluation of vaccines. However, unlike methods involving culture, nonculture methods, including detection of antigen or DNA, are not able to differentiate between viable and nonviable organisms. As an obligate intracellular bacterium, Chlamydia replicates inside host cells by forming unique organelles called inclusions. Here, we describe the enumeration of viable C. trachomatis from infected mice by culturing vaginal swabs on McCoy cells and counting inclusions via immunofluorescent microscopy.