Increased Occurrence of Treponema spp. and Double-species Infections in Patients with Alzheimer’s Disease

Objective Although the link between microbial infections and Alzheimer’s disease (AD) has been demonstrated in multiple studies, the involvement of pathogens in the development of AD remains unclear. Therefore, this theory beckons further systematic investigation. In this study, we have examined the association between the 10 most widely discussed viral and bacterial pathogens found in serum and cerebrospinal fluid (CSF) from patients with AD. Methods We have used an in-house developed multiplex PCR kit for simultaneous detection of five bacterial and five viral pathogens in serum and CSF from 50 AD patients and 53 healthy controls. Data analysis was performed with multiple statistical methods: Fisher’s exact test, chisquare goodness of fit test, and one-sample proportion test. Results We observed an increased frequency of AD patients tested positive for Treponema spp. (AD: 62.2%; CTRL: 30.3%; p -value = 0.007). Furthermore, we confirmed a significantly higher prevalence of cases with two and more simultaneous infections in AD patients compared to controls (AD: 24%; CTRL 7.5%; p -value = 0.029). The studied pathogens were widespread equally in serum and CSF. Borrelia burgdorferi , human herpesvirus 7, and human cytomegalovirus were not detected in any of the studied samples. Discussion An increased prevalence of Treponema spp. and double-species infections in AD patients compared to the healthy controls provides further evidence of the association between microbial infections and AD. Paralleled analysis of multiple sample specimens provides complementary information and is advisable for future studies. ### Competing Interest Statement The authors have declared no competing interest.