Efficacy of trypsin in enhancing assessment of bacterial colonisation of vascular catheters

Abstract

SUMMARYSince the number of organisms isolated from a medical device is crucial in assessing the likelihood of device-associated infection, we examined whether incubation of catheters in trypsin before sonication can increase the yield of superficially colonised vascular catheters in vitro and those removed from patients. Polyurethane and silicone catheters were individually colonised in vitro with individual clinical isolates including Staphylococcus aureus and Escherichia coli. Equal numbers of 1 cm segments of colonised catheters were then individually incubated either in a trypsin-containing solution or a control solution without trypsin. Each solution containing the segment was then sonicated and cultured quantitatively. In the clinical arm, indwelling catheters removed from patients were also cut into 1 cm segments that were equally suspended in the trypsin-containing or control solution and then sonicated and cultured quantitatively. Trypsin-based sonication enhanced the detection of S. aureus on colonised polyurethane and silicone catheters in vitro by 14-and 30-fold, respectively (P = 0.03 and P = 0.04), and the detection of E. coli on colonised polyurethane and silicone catheters by 3-and 6-fold, respectively (P = 0.04 and P = 0.05). Compared with sonication alone, trypsin followed by sonication resulted in 10% increase in the detectability of significant colonisation of indwelling catheters removed from patients and 11% increase in the mean colony counts of colonising organisms (P = 0.04). Exposure of catheters to trypsin before sonication improves the sensitivity of sonication and enhances the accuracy of assessing significant catheter colonisation.

Rapid Assay to Assess Bacterial Adhesion on Textiles

“…Detachment: 100 μL 0.9% NaCl was added to each well for detachment of the cells from the textiles. Detachment was performed either mechanically after closing microplates with AlumaSeal II™ Sealing Films (Carl Roth, Karlsruhe, Germany) by horizontal vortexing (5 min, 3200 rpm), sonication (10 L water bath cooled with ice, 5 min, 40 kHz), or sonication plus vortexing, or enzymatically using 100 μL filter-sterilized 10 ×porcine trypsin solution as described previously [ 26 ] or 100 μL deconex ® POWER ZYME (7 mg/L, Borer Chemie, Zuchwil, Switzerland).…”

Facile Modification of Medical-Grade Silicone for Antimicrobial Effectiveness and Biocompatibility: A Potential Therapeutic Strategy against Bacterial Biofilms

“…Each well was filled to cover samples with a bacterial or yeast suspension (1.5 mL, ∼10 5 CFU/mL in growth medium), followed by incubation for 24 h at 37 °C. After the plate was removed, samples were gently rinsed three times with 1 mL of PB, placed in sterile 15 mL centrifuge tubes with 2 mL of trypsin (0.25%, 1X) to facilitate the detachment of cells from the surfaces, 30 held for 2 min at 37 °C, sonicated at 120 W output for 10 min at 25 °C, and vortexed for 30 s. Serial dilutions (100 μL) were plated on M3 agar plates and incubated for 24 h at 37 °C. Images were obtained and colonies counted.…”