The causative organisms of catheter-associated urinary tract infections are mainly:Escherichia coli, Klebsiella, Proteus, enterococcus, Pseudomonas, Enterobacter, Serratia, and Candida. Many of these microorganisms are part of the patient's endogenous bowel flora, but they can also be acquired by cross-contamination from other patients or hospital personnel or by exposure to contaminated solutions or non-sterile equipment .