Bacteria may be able to attach to cells in the urinary tract more easily in those with certain blood factors. But more research is needed to determine whether an association exists and whether it could be useful in identifying people at risk of recurrent UTIs. Bacteria or yeast are most often the culprits of Sarah Summer otitis externa. Other causes include an accumulation of wax, thick or matted hair in the ear canal, debris, a foreign body, a tumor or impaired drainage of the ear. Bacteria that have infected the bladder may travel up the ureters to the kidneys. This can cause pyelonephritis, a kidney infection.