THE NEW MICROBIOLOGICA, 28, 215-221, 2005 Treponema denticola infection is not a cause of false positive Treponema pallidum serology Antonella Marangoni 1 , Vittorio Sambri 1 , Francesca Cavrini 1,2 , Alessia Frabetti 1 , Elisa Storni 1,2 , Silvia Accardo 1 , Dora Servidio 3 , Federico Foschi 3 , Lucio Montebugnoli 3 , Carlo Prati 3 , Roberto Cevenini 1 1 Section of Microbiology, DMCSS, University of Bologna, St. Orsola Hospital, Bologna, Italy; 2 Centro Regionale di Riferimento per le Emergenze Microbiologiche, Bologna, Italy; 3 Department of Oral Sciences, University of Bologna, Bologna, Italy It has long been assumed that parodontal disease can be a cause of false positive results in syphilis serology, but so far there are no definitive data supporting this hypothesis. In this study we tested 250 serum samples obtained from blood donors all of which were negative when routinely screened for antibodies against Treponema pallidum. Then, all these samples were tested by immunoenzymatic (ELISA) and Western Blot (WB) assays to investigate reactivities against T. denticola. Thirteen samples showed a strong positivity when tested by both methods. When tested by WB against T. pallidum no sample met the positivity criteria. Nevertheless, bands with molecolar weights of about 30-35 KDa (endoflagellar core antigens) were recognized. All the 13 subjects serologically T. denticola pos- itive underwent oral clinical and radiological observation: all showed a very poor parodontal status (CPSS>103). Eleven crevicular fluid samples out of the total of 13 patients were T. denticola positive by Real Time PCR carried out using a LightCycler system. In this study we demonstrated that the presence of T. denticola in the crevicular fluid samples obtained from patients with a severe periodontal status and/or a positive serology against T. denti- cola is not a cause of false positive results in syphilis serology. KEY WORDS: Treponema denticola, syphilis, serology SUMMARY Received April 14, 2005 Accepted June 10, 2005 INTRODUCTION The laboratory diagnosis of syphilis is still a cru- cial point in the epidemiological and diagnostic evaluation of the disease (Larsen et al., 1995). Available serologic tests for syphilis are divided into nontreponemal and treponemal assays. Nontreponemal tests include the Venereal Disease Research Laboratory (VDRL) and the Rapid Plasma Reagin (RPR) card test. Treponemal tests include the serum fluorescent treponemal antibody absorption test (FTA-ABS), the T. pallidum hemagglutination test (TPHA), the immunoenzymatic assay (ELISA) and the Western Blot (WB) assay; both ELISA and WB tests can be based on either whole-cell lysate (Farshi et al., 1985; Halling et al., 1999) or recom- binant (Castro et al., 2003; Sambri et al., 2001a; Sambri et al., 2001b) treponemal antigens. A small percentage of false positive results (about 1%) still exits when treponemal tests are used as screening procedures (Norris et al., 2003). Oral spirochetes are certainly involved in the etiolo- gy of periodontitis (Riviere et al., 1997; Loesche and Grossman, 2001). It has been previously reported that patients with necrotizing ulcera- Corresponding author Vittorio Sambri, MD, PhD Section of Microbiology, DMCSS St. Orsola Hospital, University of Bologna Via Massarenti 9, 40138 Bologna, Italy e-mail: vsambri@med.unibo.it