Urinary Tract Infection

Very common

Significant cause of morbidity and mortality.

Occurs anywhere between the glomerulus and the external os of the urethra

– Upper UTI is above the bladder – Lower UTI is from the bladder down

Urinary Tract Infection

Stages of life :

• Infancy

• Preschool

• Honeymoon cystitis

• Pregnancy

• Prostatism

UTI - Who is susceptible?

Mostly females due to the (20cm) shorter urethra (30:1).

Exceptions are neonatal boys who are 4X more likely than neonatal girls to have an UTI – reasons not clear.

Elderly men become more susceptible due to prostatic hyperplasia but never overtake the females (2:1).

The one equalising factor is the urethral catheter.

UTI

• Urinary tract and bladder are normally sterile apart from the anterior urethra which may be colonised with skin flora

• Presence of microflora alone does not establish significance

• Pyuria may or may not, reflect a response to infection

Urinary Tract Infection

Sterile Pyuria:

• Renal TB Viral cystitis

• Glomerulonephritis Prostatitis

• Urethritis GU Fistula

• Pelvic Abscess Stones

• Schistosomiasis

UTI - Frequency and dysuria syndrome

• Bacterial CystitisCharacterised by significant bacteriuria, pyuria and sometimes haematuria.

• Abacterial cystitis. Previously known as ‘urethral syndrome’. No bacteria are cultured from urine and the cause is usually unknown. (Often gut and vaginal anaerobes)

UTI

Infections are described as ‘uncomplicated’ as in most OPD or GP patients.

Or ‘complicated’ eg. in patients with congenital or surgical abnormalities of the tract or those having urological procedures and / or the presence of a urethral catheter.

UTI – Urinary Catheter

Hospital-Acquired UTI

1. Urinary catheter for relief of retention

2. Intermittent catheterisation following head or spinal cord injury, may be required several times a day.

3. Indwelling catheters - continuous drainage may be needed following spinal cord lesion or shorter term post TUR.

4. Any instrumentation or surgery on the urinary tract increases the chances of HA-UTI.

Hospital-Acquired UTI

Care and insertion of Urethral Catheter :• Motives? • Choice of catheter (smallest bore and balloon)• Insertion• Sterile procedure but NO disinfectant.• Bag emptying - maintain closed system.• Catheter toilet• Urine collection• Limit washouts and antibiotics.

UTI

Almost all UTI’s are caused by organisms ascending the tract.

Few are caused by haematogenous transport of bacteria and other agents -especially M. tuberculosis and Salmonella spp. Also rarely Schisto. haematobium, Histoplasma and viruses such as CMV and Adenovirus

Recognised Urinary Pathogens

Mostly Gram-negative bacilli Enterobacteriaceae

• E. coli• Proteus spp• Klebsiella spp• Enterobacter spp

• Citrobacter spp• Serratia spp• Providencia spp

Recognised Urinary Pathogens

Other Gram negatives :

Pseudomonadaceae• Pseudomonas spp• Alcaligenes spp

Gram-negative coccobacilliAcinetobacter spp

Recognised Urinary Pathogens

Gram-positive cocci :Micrococcaceae :• Staph saprophyticus • Staph aureus• Staph. epidermidis

Streptococcaceae :• Strep faecalis and other enterococci• Strep. agalactiae (Lancefield group B)

Also yeasts (Candida species)

UTI – Asymptomatic Bacteriuria

A significant bacteriuria (>100,000/ml) without symptoms - not treated except for at risk patients:

• Pregnancy (To prevent acute Pyelonephritis)• Renal Disease diabetes or polycystic kidneys• The immunocompromised• Anatomical or neurological defects• Patients about to undergo urological examination• Children – require investigation for congenital reflux

abnormalities

UTI – Acute Pyelonephritis

Predisposing factors :• Prostatic enlargement• Pregnancy (3rd Trimester)• Children with congenital malformations• Obstruction, calculi, tumours• Urethral catheterisation.

Diagnosis as for UTI

UTI – Lab. Diagnosis

Specimens are frequently contaminated with normal flora from perineum or genitalia.

Contamination reduced by taking ‘midstream urine’ specimens (MSU) having cleaned the genitalia

UTI – Lab. Diagnosis

Collection methods :

• MSU/CSU

• Adhesive bags

• Suprapubic stimulation (Babies)

• Suprapubic aspiration

NEVER by catheterisation

UTI – Lab. Diagnosis

Must be transported rapidly to lab and refrigerated if delayed.

Use of transport kits have been recommended but often inhibitory to organisms

UTI – Lab. Diagnosis

Interpretation of results for MSU:

1. >100,000 bacteria/ml urine – UTI

2. 10,000 bacteria/ml urine - usually either contamination or prior antibiotics

3. 1,000 bacteria/ml urine – Usually contamination but may be significant with acute dysuria and frequency

4. More than one organism or mixed growth:

Contamination likely

UTI Factors affecting bacterial counts

• Stage of infection• Fluid intake/ frequency of micturition.• Presence of antibiotics and other

antibacterial substances (eg. Urea)• Underlying illness of the patient.• Whether patient is post-operative• The presence of a urinary catheter• Residual urine

UTI Factors affecting bacterial counts cont’d

• Probably the age and sex of the patient

• pH of urine

• The growth rates of the organisms

• The number of bacteria in a colony forming unit

• The site of infection

UTI – Lab. Diagnosis

White cell count in urine is normally less than 10 white cells / cubic mm of urine.

Figures above this suggest an infection.

Though the WCC may be raised for other reasons eg :

Interstitial neuropathies (diabetes and analgesics)• Acute glomerulonephritis• Renal failure• Neoplasms

UTI – Lab. Diagnosis

Reasons for raised WCC cont’d:

• Postoperative

• Catheterisation

• Fevers in children

• Spread of inflammation of neighbouring sites (eg appendix or bowel)

• White cells from preputial sac or vagina may contaminate the urine

UTI - Factors predisposing bladder to bacteruria

Factors which facilitate ascent of organisms up the urethra :

• Urethral, bladder or prostatic surgery

• Sexual intercourse

• Vaginal prolapse

UTI - Factors predisposing bladder to bacteruria

Factors which result in the stagnation of urine in the bladder :

• Infrequent micturition• Inadequate fluid intake (or urinary output)• Obstruction (Urethral valves, strictures, prostatic

hypertrophy, constipation, calculi and catheters)• Vesico-ureteric reflux• Impairment of neurogical control of bladder• Bladder diverticula

UTI Treatment

1. Increase fluid intake (= urine output)2. Acidify urine3. Antibiotics• Uncomplicated – 3 days• Pyelonephritis – 7 -14 days IV• Asymptomatic bacteriuria in pregnancy –

3-7 days