Catheter-associated urinary tract infections

Last updated: Wednesday, March 15, 2017

Case definition
UTI is the most common hospital-acquired infection in the UK, with the majority associated with catheter use. Click to learn more.
Bacteriuria (bacteria in the urine) is universal once a catheter has been in place for more than several weeks and may be asymptomatic or lead to symptomatic UTI. This can make diagnosis difficult. Other signs and symptoms such as fever, new onset confusion and suprapubic pain are also common in catheterised patients without symptomatic UTI. However some experts have suggested that symptomatic catheter-associated UTI (CAUTI) might be defined as;

Culture growth of ≥103 colony forming units (cfu)/mL of uropathogenic bacteria in the presence of symptoms or signs compatible with UTI without other identifiable source in a patient with indwelling urethral, indwelling suprapubic, or intermittent catheterisation.

Compatible symptoms include fever, suprapubic or costovertebral angle tenderness, and otherwise unexplained systemic symptoms such as altered mental status, hypotension, or evidence of a systemic inflammatory response syndrome.

Risk factors
The duration of catheterisation is strongly correlated with the risk of developing an infection. Click to read other risk factors.
• Female gender
• Older age
• Diabetes mellitus
• Bacterial colonisation of the drainage bag
• Errors in catheter care (e.g. errors in sterile technique)
Typical pathogen profile
Most CAUTIs are derived from the patient’s own colonic flora. Some of these organisms may lack some of the virulence factors that allow the usual uropathogens to adhere to uroepithelium, but they take advantage of easy access to the bladder via the catheter. An example is Candida spp, which almost never causes UTI in the absence of an indwelling catheter. In contrast, candiduria is a common finding in patients with indwelling catheters, particularly in those who are taking antimicrobials or have diabetes. However, most patients are asymptomatic, funguria merely represents colonisation, and progression to candidemia is uncommon. Click to see the usual pathogens.
Gram positive
Klebsiella spp. 
Enterococcus spp. 
S. aureus 

Gram negative
E. coli (most common)
Proteus spp. 
Enterobacter spp. 
P. aeruginosa 
Serratia spp. 

Candida albicans

Microbiology investigations
• Only culture if signs and/or symptoms of systemic infection.
• Culture urine before starting antibiotics.
• There is no value urine microscopy or dipstick tests.
• Samples may not accurately represent the true pathogen and often contain several bacterial species. Interpret results with caution.
Evidence of infection 
Refer to Case definition above. The absence of fever does not appear to exclude UTI and hypothermia (<36⁰C) may also indicate infection. Pyuria (white blood cells in the urine) and the appearance or smell of the urine, should not be used to diagnose a UTI when found in isolation. Pyuria is frequently found in catheterised patients with bacteriuria, whether they have symptoms or not, and odorous or cloudy urine has not been demonstrated to be indicative of either bacteriuria or UTI. However the absence of pyuria in a symptomatic, catheterised patient suggests a diagnosis other than UTI.

Risk of antibiotic resistance 
• Nursing home resident
• Abnormalities of the genitourinary tract
• Renal impairment
• Exposure to trimethoprim in previous 12 months may predispose to further trimethoprim resistance
Severity assessment
Hospital admission may be required if the patient has symptoms or signs suggestive of urosepsis including nausea and vomiting, confusion, tachypnoea, tachycardia, hypotension. 
Choosing an antibiotic
Ideally base antibiotic selection on culture results. If prompt treatment is required, choice should be based upon the results of any past cultures, prior use of antibiotics, local resistance, and allergy status. Click to learn more.
Consult your local antibiotics guidelines for the preferred choice of agents. In their absence, NICE Clinical Knowledge Summaries (CKS) recommends the following for men and women with bacterial CAUTI in primary care.

Oral trimethoprim 200mg BD (avoid if received trimethoprim in last 12 months)
Oral nitrofurantoin 50mg QDS or 100mg MR BD

Refer to the relevant SPCs for prescribing guidance including contraindications and cautions.

Patients with systemic signs will need to be evaluated in terms of the severity of their infection and the risk of drug resistance before empirical antibiotic treatment can be initiated. In case of candiduria associated with urinary symptoms, or if candiduria is the sign of systemic infection, systemic therapy with antifungals is indicated.

Consider changing or removing the catheter before or when starting antibiotics in patients with symptomatic CAUTI. Check catheter is draining and not blocked.
Follow up 
Check response to treatment after an appropriate interval, for example 48 hours, depending upon clinical judgement to check response to antibiotic treatment and review urine culture results. Advise patients to seek medical attention if they develop loin pain or fever.
Duration guide 
Primary care - men and women with bacterial CAUTI in primary care 7 days.
Hospitalised patients – depending upon the clinical response, the organism and the antibiotic, 7 to 14 days is generally appropriate.