Most urinary tract infections are due to the colonization of the urogenital tract with rectal and perineal flora. The most common organisms include Escherichia coli, Enterococcus, Klebsiella, Pseudomonas, and other Enterococcus or Staphylococcus species. Of these, Escherichia coli is the most common, followed by Klebsiella. Residential care patients, diabetics, and those with indwelling catheters or any form of immunocompromise can also colonize with Candida.[10] E. coli and possibly Klebsiella overwhelmingly cause simple UTIs. Complicated UTIs tend to be caused by a much wider range of organisms which is significant because multidrug resistance is increasing, and therefore specific antibiotic regimens will vary.