Development of novel methods for microbiological evaluation of urology products

Abstract: Urinary tract infection (UTI) is the most common type of bacterial infection. Each year, UTIs cause morbidity, medical costs and losses in work time. For patients in long-term care settings the incidence of UTIs might be as high as 50 %. Every year, 7 million office visits are estimated to be due to UTIs at a cost to the healthcare system of over $1 billion in USA alone. It is estimated that 33% of neurogenic bladder patients have bacteriuria at any time. Nonsteroidal anti-inflammatory agents, antibiotic coatings and silver coatings have been applied to catheters in an attempt to prevent catheter associated urinary tract infections.

In this master thesis a dynamic model that simulates the lower urinary tract is developed in order to evaluate antibacterial urinary catheters. Furthermore, a novel quantitative method to analyze bacterial concentration in residual urine using the fluorescent dye resazurin has been developed.

A tailored physical glass model of the catheterized bladder was developed. Urine was supplied to the model at a rate of ~1.3 ml/min and the three different intermittent catheters tested were: Lofric Primo, Magic3 Antibacterial and Magic3 Antibacterial + Hydrophilic. Two different experimental protocols were evaluated. In experimental protocol 1 the catheters were contaminated with E.coli prior to each catheterization whereas in experimental protocol 2 catheters were contaminated only before the first catheterization. The bladder was emptied at intervals to simulate catheterization, and samples of residual urine for viable cell counts and kinetic studies with resazurin were taken. Bacteriological analysis showed no difference in inhibition of bacterial growth in the bladder in the two experimental protocols. After 22 hours of model operation the bacterial population approached ~108 CFU/ml in all experiments. No difference in results between the experimental protocols could be observed. Kinetic studies on resazurin reduction gave concentrations in the same range as CFU counts for samples taken after 4 hours. Concentrations were overestimated when comparing CFU counts to resazurin reduction for samples taken after 8 hours. No inhibition of bacterial growth could be shown using the antibacterial catheters (Magic3 antibacterial) compared to the control (LoFric Primo).