CA-UTI is defined as the presence of signs or symptoms of UTI with no other explainable infectious source along with ≥ 1000 colony-forming units (cfu) of ≥ 1 bacterial species per milliliter in a urine specimen from a catheter that has been changed within 48 hours of collection of the urine specimen.5 Signs and symptoms of CA-UTI include, but are not limited to: new-onset or worsening fever, chills, altered sensorium from baseline, lethargy, malaise, flank pain, pelvic pain, costovertebral angle tenderness, and acute hematuria.5 New-onset “foul-smelling” (odorous)urine and “cloudy” urine are neither sensitive nor specific when assessing for CA-UTI, and do not have significant clinical relevance when found alone.14,15 Patients who have removed or exchanged the UC during this event and then experience dysuria, increased frequency, urgency, or suprapubic pain are likely having symptoms of CA-UTI.5
What is the recommended method for collecting urine samples when CA-UTI is suspected?
In a patient with an indwelling catheter that has been in place for more than 2 weeks at the onset of a suspected CA-UTI, the catheter should be replaced (if still indicated) or removed to accelerate resolution of symptoms and to reduce the risk of subsequent catheter-associated bacteriuria and CA-UTI. The urine culture should be acquired from the freshly placed UC.5
When should a patient be empirically treated?
A patient presenting with evidence of sepsis should be empirically treated with antimicrobials. Empiric coverage should be based on risk factors for multidrug-resistant organisms and data pertaining to local antimicrobial resistance patterns. A urine specimen for urinalysis and possible culture should be sent prior to administering empiric antibiotics (if possible) in a symptomatic patient.5
What bacteria are commonly associated with CA-UTI?
The bacteria most commonly associated with CA-UTI are found in or around the gastrointestinal and genitourinary tracts and also are part of the normal skin flora. The introduction and/or facilitated ascension of these microorganisms is believed to occur during UC insertion.16,17 Two-thirds of all isolated uropathogens in those with indwelling UCs are extraluminally acquired (via ascension along the catheter-urethral mucosa interface), and one-third are believed to be intraluminally acquired.18
The most commonly isolated bacteria in CA-UTI are Enterobacteriaceae, which include Escherichia coli (most common), Klebsiella species (K. oxytoca, K. pneumoniae), Serratia species (S. marcescens), Citrobacter species (C. koseri), Enterobacter species (E. cloacae), and Proteus species; non-Enterobacteriaceae such as Pseudomonas species; and gram-positive cocci, which include coagulase-negative staphylococci (S. saprophyticus), Staphylococcus aureus, group B streptococci, and Enterococcus species (E. faecalis, E. faecium).19-21 Coagulase-negative staphylococci and Enterococcus species can lead to CA-UTI but are usually avirulent and more commonly isolated from asymptomatic individuals.19 Also, coagulase-negative staphylococci such as S. epidermidis and S. lugdunensis are usually the manifestation of contamination during the collection process and their presence should prompt a repeat sample collection under sterile techniques. Monomicrobial infection is usually seen in those with short-term catheter use and CA-UTI. In contrast, polymicrobial infection is more common in those with long-term indwelling UCs and CA-UTI.19 Providencia stuartii, Proteus mirabilis, S. aureus, and Morganella morganii have all been associated with CA-UTI in those with long-term indwelling UCs.
