It has been suggested that infection with Chlamydia may play a role in the initiation/progression of Alzheimer’s disease (AD). To evaluate this hypothesis APP/PS transgenic mice (genetically manipulated to express AD pathology) and wild type (Wt) mice were infected with C. muridarum, and magnetic resonance imaging (MRI) and histopathology were used to assess pathological changes. Congo red staining of tissue sections demonstrated no AD plaque pathology in Wt infected and non-infected mice, while clear pathology (neuritic plaques) was seen in transgenic mice, with a trend towards higher plaque counts in the brains in the infected transgenic mice. When MRI was used to evaluate the effects of infection in vivo, hyperintensities in T2 times were observed in APP/PS infected mice compared to APP/PS control mice both at month 5 and month 20. Together these results suggest that infection with Chlamydia may accelerate the development of AD.