organisms in UTIs

Last reviewed 01/2018

In acute uncomplicated infection, the organisms are those normally colonising the perineum:

• E. coli - 65 to 80% of all UTIs
• Proteus
• Klebsiella
• Enterobacter
• Candida
• Enterococci
• Staphylococci - especially, Staph. saprophyticus in young, fit adults, especially women

In complicated UTI’s, more unusual organisms are found - such as:

• Pseudomonas aeruginosa
• Staphylococcus epidermidis
• Klebsiella
• Enterobacter
• Proteus
• Enterococcus (1)

Occasionally, organisms secondary to systemic disease arising elsewhere - such as:

• Tuberculosis
• Salmonellosis

Rarely, viruses:

• adenovirus types 2 and 11, in children
• Herpes simplex

In sexually active young men and women infection with Chlamydia trachomatis should be considered (2).

Reference:

• (1) Health Protection Agency (HPA) 2009. National standard method. Investigation of urine.  
• (2) Health Protection Agency (HPA) 2009. Diagnosis of UTI – Quick reference guide for primary care