As populations of older Americans grow rapidly and live longer, so too will the number of individuals living with a neurodegenerative disorder. Neurodegenerative conditions, such as Alzheimer’s disease, are sporadic, often age-related, and hereditary conditions that manifest as progressive cognitive decline, behavioral disorders, and impaired daily functioning. Various factors, such as genetics, environmental triggers, metabolic disorders, and infectious agents, have been implicated in the development of these diseases. Recent studies have suggested a complex polymicrobial causality, wherein pathogens interact with genetic factors to initiate pathological processes in the brain, including the accumulation of beta-amyloid plaques, hyperphosphorylated tau protein, immunosuppression, and inflammation. However, the etiology of dementia-inducing disorders remains elusive. In this study, we aimed to investigate the presence of polymicrobial infections in post-mortem brain tissue samples from patients with Alzheimer's disease, utilizing a comprehensive molecular approach. Immunohistochemistry, highly sensitive polymerase chain reaction, and genomic sequencing were employed to analyze the samples. Control samples were initially examined to assess the ability of target pathogens to access the brain without causing dementia-associated neuropathology. Subsequently, autopsy samples from Alzheimer's disease patients and normal controls were tested for the presence of Borrelia burgdorferi, Bartonella henselae, Herpes simplex virus type 1, Treponema denticola, Candida albicans, and Chlamydia pneumoniae using the molecular methods mentioned. Our findings revealed the presence of Borrelia burgdorferi, Bartonella henselae, T. denticola, and Candida albicans in the brain tissue of patients with Alzheimer's disease as well as in 6 normal controls. However, no evidence of Chlamydia pneumoniae or HSV-1 infection was detected in any of the tested samples. Immunofluorescence assays were performed to visualize the organisms, but no positivity was observed in Alzheimer's disease brains, although Candida albicans was detected in a control case. While this study did not establish a direct causal link between Alzheimer's disease and microbial infection of the central nervous system, our results contribute to the understanding of the complex microbial landscape associated with neurodegenerative disorders. Further investigations are warranted to elucidate the role of these pathogens in disease progression and to explore potential therapeutic interventions targeting polymicrobial infections in Alzheimer's disease and related dementias.