Urinary tract infections Flashcards
What parts of the urinary tract are sterile in normal health?
Kidneys
Ureters
Bladder (usually, but my not always be the case)
What type of flora does the urethra contain?
Perineal flora
Skin/lower GI tract flora
What does skin flora consist of?
Predominantly coagulase-negative staphylococci
What does perianal flora consist of?
Skin flora
Lower GI tract flora
- Anaerobic bacteria
- Aerobic bacteria
- -Enterobacteriaceae (“enteric Gram-negative bacilli”, “coliforms”)
- Gram-positive cocci
- -Enterococcus spp.
What is cystitis?
Lower urinary tract infection syndrome
- Dysuria
- Urinary frequency
- Urgency
- Supra-pubic pain/tenderness
- Polyuria, nocturia, haematuria
What is pyelonephritis?
Upper urinary tract infection
- Infection of kidney and/or renal pelvis
What is the clinical presentation of pyelonephritis?
Symptoms of lower UTI
Loin/abdominal pain/tenderness
Fever
Other evidence of systemic infection
- Rigors, nausea, vomiting, diarrhoea
- Elevated CRP, WBC
What is ‘urethral syndrome’?
Controversial term
a.k.a. abacterial cystitis, frequency-dysuria syndrome
Mostly affects 30-50 yr old women
Symptoms of lower UTI without demonstrable infection
What criteria is used to define ‘significant bacteriuria’?
Kass criteria = 10^5 cfu/mL = “significant bacteriuria”
What are the limitations of the Kass criteria?
Bacterial count is on a normal curve
Many symptomatic females have bacterial counts of less
What is asymtomatic bacteriuria?
Significant bacteriuria
- With a single organism
No symptoms of urinary tract infection
What is sterile pyuria?
Pus cells in urine
No organisms grown
What are the risk factors for UTI?
Female sex - 10:1 female:male ratio
Urinary stasis - Pregnancy, prostatic hypertrophy, stones, strictures, neoplasia, residual urine
Instrumentation
Sexual intercourse - Associated with recent sexual intercourse and commoner in sexually active women
Fistulae - Recto-vesical, vesico-vaginal
Congenital abnormalities - Vesico-ureteric reflux (VUR)
What are the sources of infection in UTIs?
Perineum
- Movement of bacteria along a lumen
Fistulae
- Movement of bacteria from genital/GI tract to urinary tract
Haematogenous
- Seeding of infection from the blood (rare)
Which organisms commonly cause UTIs?
E. coli S. saprophyticus P.mirabilis Enterococcus spp. Klebsiella spp. Other coliforms P. aeruginosa
Which organism causes 70-80% of all GP UTIs and 50% of all hospital UTIs?
E.coli
What are the possible causes of sterile pyuria?
Inhibition of bacterial growth
- Unprescribed antibiotics
- Specimen contaminated with antiseptic
“Fastidious” (hard to grow) organisms
- e.g. Mycobacterium tuberculosis, Haemophilus spp., Neisseria gonorrhoeae
- Anaerobes
Urinary tract inflammation
- Renal or bladder stones
- Other renal disease
How do long-term indwelling catheters result in bacteriuria?
Biofilm colonisation (NB: colonisation does not equal infection)
At LTHT under what circumstances may antibiotic prophylaxis be used?
History of symptomatic urinary catheter-associated infection with previous catheter changes
Purulent urethral/suprapubic catheter exit site discharge
Catheter or meatal/suprapubic catheter exit site colonisation with Staphylococcus aureus (including MRSA).
What samples are taken for microbiological testing if a UTI is suspected?
Urine
- Mid-stream (MSU)
- Catheter urine (CSU)
- “Clean catch”
- Supra-pubic aspirate (SPA)
Blood
- Suspected pyelonephritis
- Microscopy, culture and sensitivity testing
Why would you perform an early morning urine (EMUx3) test?
For suspected urinary tuberculosis
What are the indications for further investigation?
Recurrent UTI
Any UTI in male patient
Any UTI in childhood
Pyelonephritis
What further investigations may be carried out?
Renal tract ultrasound scan
Specialised tests
- Isotope scans (DMSA, DTPA, MAG3)
- micturating cystourethrogram
What are the requirements for a UTI antibiotic?
Present in urine
Minimally toxic
Effective against likely organisms
Easily administered
Cheap
