Medical Microbiology and Infection

at a Glance

Fourth EditionStephen Gillespie and Kathleen Bamford

Case Studies

Case 7

A 42-year-old woman presents with a 2 day history of sweats, back ache, loin pain and fever. A dipstick test on her urine shows the presence of blood, pus and nitrites.

  • 1. What is the likely diagnosis??

    She probably has acute pyelonephritis. This can be investigated by taking blood and urine for culture and assessing a full blood count and C-reactive protein. Her blood pressure and pulse should be monitored and intravenous antibiotics given. Fluid intake should be encouraged.

  • 2. What might predispose her to this infection?

    Women are more susceptible than men to urinary tract infection, presumably because of the shorter urethra. Any abnormality of the urinary tract, such as obstruction, the presence of stones or stasis for any reason, and catheterization will predispose to infection. People who express the P blood group antigen on epithelium are particularly susceptible to pyelonephritis.

  • 3. What organisms are most likely to cause pyelonephritis?

    E. coli is the commonest cause of pyelonephritis. P fimbriae-positive E. coli are a particular problem for those who express the P blood group antigen. Other agents include Proteus species – especially if stones are present – and other Enterobacteriaceae.

  • 4. What microbiology laboratory findings would you expect?

    It is possible that blood cultures will be positive and there may be pus cells and >105 bacteria/mL in a freshly collected midstream sample of urine. A blood culture may also be positive as the infection progresses.

  • 5. How do symptoms of lower urinary tract infection differ from this case?

    In lower urinary tract infection, fever may be absent and the patient is usually well. Symptoms are dominated by dysuria (pain on micturition) that is often described as ‘burning on passing water’. Patients complain of frequency (the feeling of needing to pass water more often than normal).

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