Noninvasive Biophotonic Imaging for Monitoring of Catheter-Associated Urinary Tract Infections and Therapy in Mice

Abstract

Urinary tract infections (UTIs) are among the most common bacterial infections acquired by humans, particularly in catheterized patients. A major problem with catheterization is the formation of bacterial biofilms on catheter material and the risk of developing persistent UTIs that are difficult to monitor and eradicate. To better understand the course of UTIs and allow more accurate studies of in vivo antibiotic efficacy, we developed a catheter-based biofilm infection model with mice, using bioluminescently engineered bacteria. Two important urinary tract pathogens, Pseudomonas aeruginosa and Proteus mirabilis, were made bioluminescent by stable insertion of a complete lux operon. Segments of catheter material (precolonized or postimplant infected) with either pathogen were placed transurethrally in the lumen of the bladder by using a metal stylet without surgical manipulation. The bioluminescent strains were sufficiently bright to be readily monitored from the outside of infected animals, using a low-light optical imaging system, including the ability to trace the ascending pattern of light-emitting bacteria through ureters to the kidneys. Placement of the catheter in the bladder not only resulted in the development of strong cystitis that persisted significantly longer than in mice challenged with bacterial suspensions alone but also required prolonged antibiotic treatment to reduce the level of infection. Treatment of infected mice for 4 days with ciprofloxacin at 30 mg/kg of body weight twice a day cured cystitis and renal infection in noncatheterized mice. Similarly, ciprofloxacin reduced the bacterial burden to undetectable levels in catheterized mice but did not inhibit rebound of the infection upon cessation of antibiotic therapy. This methodology easily allows spatial information to be monitored sequentially throughout the entire disease process, including ascending UTI, treatment efficacy, and relapse, all without exogenous sampling, which is not possible with conventional methods.Urinary tract infections (UTI) are one of the most common bacterial infections in humans (9, 35). The majority of these infections follow instrumentation of the urinary tract, mainly urinary catheterization, with the development of catheter-associated bacteriuria being directly related to the duration of implant (6,18,37,44). Thus, it is commonplace for the incidence of bacteriuria to be as high as 95% in catheterized patients with implants present for 30 days or more (6, 44). Complications with such infections can lead to fever, cystitis, acute pyelonephritis, bacteremia, and death (44). Catheter-associated urinary tract infections are caused by a variety of uropathogens, including Escherichia coli, Klebsiella, Proteus, Enterococcus, Pseudomonas, Enterobacter, Serratia, and Candida (6,44).Typically, the bacterial biofilm growth on urinary catheter and adjacent mucosa accounts for the pathophysiology of catheter-associated UTI (25,26,31). Diseases involving bacterial biofilms are generally chronic and difficult to treat, be...

Bladder catheterization increases susceptibility to infection that can be prevented by prophylactic antibiotic treatment

“…Our findings are in line with previous reports demonstrating that CFU recovered from experimental E. faecalis and Pseudomonas aeruginosa infections are higher in catheterized animals as compared with noncatheterized animals (14,35,37). Indeed, that the ID 90 for E. faecalis and UPEC are greatly reduced in catheter-bearing animals compared with noncatheterized mice highlights the truly vulnerable host state induced by catheter implantation.…”

The Limitations of In Vitro Experimentation in Understanding Biofilms and Chronic Infection

“…There are a range of in vivo models that simulate chronic infections, such as surface wounds [75,76], subcutaneous wounds [77,78], implant-related (such as catheter, orthopaedic, and dental) [79][80][81][82][83], otitis media [84][85][86], and CF [87][88][89][90] to name but a few. As with all models, some are deemed more applicable than others.…”

Optical imaging of bacterial infection models

“…In both of these cases, antibiotic treatment mitigated light output from the invading cells. A urinary tract infection model was developed using bioluminescent Pseudomonas aeruginosa injected into the bladder via the urethra (Figure 2, left) [25]. In this example, researchers were able to follow the infection to the kidneys and monitor antibiotic treatment efficacy by measuring light output.…”