A simple titration method for determining Chlamydia infectivity using an image analyzing system

In the biological study of Chlamydia, it is very important to determine the infectivity titer of the organism. For many years researchers used the ser ial dilution method to determine this titer. This method consists of diluti ng the material to be examined, inoculating suitable dilutions into suscept ible cell cultures and cultivating them. The number of inclusions formed in host cells can be calculated with the naked eye under a microscope. The pr ecision and accuracy of this method, however, depend on the number of inclu sions per field and the number of fields counted. In this report, we presen t a simple and rapid method for counting a large number of inclusions using an image analysis system and an appropriate number of samples, and propose a sampling method based on a statistical analysis of the data obtained wit h 84 microscopic fields. (C) 2001 Elsevier Science B.V. All rights reserved .