Macrophages with Typhoid Bacteria (IMAGE) University of Washington Caption These cultured human immune cells (macrophages) contain <i>Salmonella typhi</i> bacteria, which cause typhoid fever. The bacteria are carrying a red fluorescent protein so that they can be readily visualized. Credit Larissa Singletary Usage Restrictions For use only by news media, educational institutions, and museums. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.