Brucella species, and Mycoplasma species.89 Urinary antigen tests are available for L pneumophila serogroup 1. When one examines surgical materials (vegetations, valves, grafts) for potential bacterial or fungal pathogens, it is important to note that conventional culture techniques yield very high rates of false-positive results (13% 55%) compared with prior blood cultures or NAAT-based testing of surgical materials.91,92 It is best that culture-based methods be supplemented by molecu- lar methods or histological examination of tissues for greater Histology of surgical materials contributes a major criterion to the Duke classification scheme and remains positive for months after antibiotic drugs are started.93 NAAT- based testing of surgical materials is more sensitive than culture testing but may still yield false-positive results, and this is particularly obvious when multiple agents are iden- NAAT-based testing of surgical materials may also detect organisms associated with previous episodes of IE that were treated up to 12 years before surgery and are unrelated to the current episode.95,96 There is little loss of sensitivity by NAAT when surgical specimens are obtained within 5 days of initiation of antibiotic therapy; treatment for several weeks before surgery will increase the false-negative rate.93,97 Investigational approaches to the pathogenesis of CNE include tissue-culture based growth for propagation of intra- cellular pathogens and autoimmunohistochemistry on surgi- In fact, it has been proposed that molecular techniques be added to the pathological criteria of the Duke (Treatment of CNE is discussed later, in Antibiotic Treatment, where recommendations for empirical antibi- otic treatment of patients diagnosed with CNE are contained in Table 8. Epidemiological clues that may help in narrow- ing empirical antibiotic coverage for patients diagnosed with CNE are contained in Table 9.) Recommendations 1. 