ETBF Gram Stain (IMAGE) Johns Hopkins Medicine Caption This is a gram stain of Enterotoxigenic <i>B. fragilis</i> (ETBF) under oil immersion. 100x. Credit Courtesy of Shaoguang Wu Usage Restrictions None 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.