Introduction

The great majority of UTIs in hospitalised patients are associated with the use of urinary drainage devices, such as bladder catheters. Under normal circumstances urethral flora, which tends to migrate into the bladder, is constantly flushed out during urination. When a catheter is inserted, this flushing mechanism is circumvented and perineal and urethral flora (usually aerobic bowel organisms) can pass up into the bladder in the fluid layer between the outside of the catheter and the urethral mucosa. Because of this, bladder colonisation is almost inevitable if catheters are left in place for prolonged periods. In addition, bladder infection can be caused by bacterial reflux from contaminated urine in the drainage bag. It has been clearly demonstrated that the use of closed drainage systems significantly reduce urine contamination and thus infection rates, and open systems should be avoided if at all possible.

Where the use of bladder catheters is common, UTIs may be the most frequent nosocomial or hospital acquired infections encountered. Although most patients will have asymptomatic bacteriuria or mild infections that tend to be self limiting when the drainage device is removed, some patients may have more severe infections, sometimes leading to pyelonephritis, septicaemia and death. Moreover, even less severe UTIs tend to increase the length of hospitalisation and increase hospital costs because of the need for additional diagnostic tests and antibiotic therapy.

Fortunately, most UTIs are easily prevented by reducing unnecessary and inappropriately prolonged bladder catheterisation and by the use of closed drainage systems and standard aseptic techniques.

Prevention

Urinary catheters should be inserted only when there are clear medical indications. These include:

• the relief of acute obstruction or retention that cannot be treated with non-traumatic intermittent catheterisation
• the measurement of urine production in critically ill patients and
• perioperative use in patients who must have a completely empty bladder, for example, in selected gynaecological or urological procedures.

The diagnosis of UTI in hospitals depends on the microbiological support available in the hospital. Where microbiological support is good and a careful midstream specimen is collected, finding >10^4 bacterial colony forming units (cfu) per ml in a patient without an indwelling catheter is diagnostic of UTI. Bacterial concentrations >10^2 cfu per ml suggests infection if the specimen is obtained aseptically by needle aspiration of the proximal drainage tubing in a patient with an indwelling catheter. It is important to recognize that although in non-catheterised patients UTIs are usually caused by a single organism, in patients with indwelling catheters infections are frequently polymicrobial. The presence of multiple organisms does not necessarily indicate contamination.

It is essential to process urine promptly, since even with good technique urine samples may contain small numbers of contaminants. These microbes can multiply at room temperature (especially in hot climates) and give falsely high colony counts. If delay is expected, the specimen should be refrigerated.

Where microbiological support is poor or totally unavailable, clinical symptoms (e.g., fever, supra-pubic tenderness, frequency, and dysuria) may be useful in diagnosis, principally in non-catheterised patients. The presence of pyuria on either microscopic examination or by dip stick (leukocyte esterase) is highly suggestive of UTI. If dip sticks are available, a positive nitrite reaction in combination with a positive leukocyte esterase reaction is virtually diagnostic. A positive Gram stain of unspun urine also is diagnostic, but this is rarely possible without the presence of trained microbiologists.

An UTI is usually an endogenous infection caused by organisms from the patient's own bowel. In community-acquired infection, the commonest organism is E. coli, followed by Proteus species and Enterococcus faecalis . (in young sexually active women the perineal organism Staphylococcus saprophyticus is also common). Characteristically, these community-acquired infections are due to antibiotic-sensitive organisms that are relatively easy to treat.

Hospital acquired UTIs are also usually endogenous infections, but the organisms involved are commonly more resistant to antibiotics. This is because hospitalised patients become colonised with these resistant organisms, a process encouraged by increasing length of hospital stay and exposure to antibiotics. Antibiotic therapy may lead to infection with more resistant community organisms already present in the patient's bowel on admission. In addition, resistant organisms may be acquired by transfer from other patients, most commonly via contaminated staff hands, but sometimes from environmental sources. In hospital patients, Gram-negative bacteria can colonise the skin, especially in moist areas such as the groin. Hand transfer from patient to patient is usually due to contact with skin; then organisms go on to colonise the bowel. Infected urine is also a potent source of staff hand contamination. Urine and urinary catheter systems should be carefully disposed of, bottles and jugs cleaned and disinfected, and hands properly washed and decontaminated.

E. coli is still the most common cause of nosocomial UTI, however increasingly hospital-acquired infections are caused by more inherently resistant Gram-negative species, such as Klebsiella and Pseudomonas. Similarly, the ampicillin-sensitive Enterococcus faecalis is gradually replaced by the resistant E. faecium. Then, with additional antibiotic exposure, infections occur with more multiply drug resistant (MDR) versions of these and other species. Eventually, these organisms may themselves be replaced by the completely antibiotic resistant Candida spp., usually from the patient's own commensal flora.

Short term (<5 days) prophylactic antibiotic administration in catheterised patients has been shown to reduce the risk of bacteriuria and infection, but cannot be recommended because of its expense and tendency to encourage the emergence of resistant organisms. Longer prophylaxis is ineffective and predisposes to infection with even more resistant organisms. Treatment of asymptomatic bacteriuria in catheterised patients is not usually indicated and often the bladder colonisation disappears once the catheter is removed.

Principle causes of urinary tract infection and interventions that reduce infection rates (See Figure 10.1)

Cause of Infection

Preventive Measure

Poor aseptic insertion of catheter: periurethral flora inserted into bladder

• Catheter should be sterile, or if this is not possible, should be effectively disinfected
• Periurethral area should be thoroughly cleaned, preferably with a disinfectant
• Hands should be washed and non-sterile disposable or adequately processed gloves worn, if available
• Catheter should be secured to avoid movement in urethra

Migration of bacteria along outer surface of catheter

• No established method of prevention: antibiotic ointments and repeated cleaning of no value
• Hand hygiene will reduce risk for hand transmission of usual flora and also more virulent or antibiotic-resistant organisms

Open drainage

• Closed drainage with compatible tight fitting systems
• If not available, intermittent catheterisation may be preferred
• If not possible, and catheterisation is prolonged, open drainage may be used, but for as short a time as possible

Breaks in the closed drainage system

• Urine samples should be collected with a syringe and needle from a sampling area of the tubing after cleaning the area with alcohol. The bag should not be disconnected
• If irrigation is required to remove blood clots, use aseptic technique. Routine irrigation of the bladder to prevent infection is not effective
• The drainage bag should be emptied once per nursing session into a clean receptacle used only on one patient. Hands of staff emptying bag should be washed and preferably non- sterile disposable gloves should be worn

Other precautions

• The spout from the tap should be completely emptied to prevent a build-up of organisms in stagnant urine.
• The bag should not be allowed to stand on the floor or to rise above the level of the bladder.
• Disinfectants in the bag are not cost-effective unless the infection rate is high and cannot be controlled by other means.
• Catheters should not be changed routinely as this exposes the patient to increased risk of bladder and urethral trauma. They should be changed if associated with antibiotic treatment or if there is an obstruction.
• Use condom catheters for short-term drainage in co-operative patients. Frequent changes (e.g. daily) may also avoid complications, together with penile care, but they should be removed at first sign of penile irritation or skin breakdown. Condom use for 24-hour periods should also be avoided and other methods, such as napkins or absorbent pads, used at night.

Minimal Requirements

• Decontamination of staff hands and cleaning of periurethral area before insertion of sterile (or adequately decontaminated) catheter.
• Maintenance of closed drainage system.
• Hand hygiene before and after emptying draining bags.

Bibliography

• Guidelines for preventing infections associated with the insertion and maintenance of short-term indwelling urethral catheters in acute care. Journal Hospital Infection 2001;47(Suppl):S39-S46.