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

Since 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.

Limited vs full microbiological investigation for the management of symptomatic polymicrobial urinary tract infection in adult spinal cord-injured patients.

Spinal cord-injured (SCI) patients often suffer from symptomatic polymicrobial urinary tract infection (UTI). The objective of this study was to evaluate the clinical outcome and cost-savings associated with antibiotic therapy based on limited vs full microbiological investigation of urine cultures in adult SCI patients with symptomatic polymicrobial UTI (> or = 2 organisms growing in urine cultures). In the first part of the study, a total of 40 evaluable patients were prospectively randomized in a single-blinded fashion to receive antibiotic therapy based on either limited (21 patients) or full microbiologic investigation (19 patients) of urine cultures. The practicality of a limited microbiological investigation was further examined in the second part of the study where 12 consecutive patients with symptomatic polymicrobial UTI initially had only limited microbiological investigation of urine cultures and received antibiotic therapy accordingly. When analyzing all patients in the study, the likelihood of adequate clinical response was not significantly different between those who received antibiotic therapy based on limited (28/33 = 85%) vs full (18/19 = 95%) microbiological investigation of urine cultures (P = 0.40). An average of 183 US dollars could be saved per patient by managing symptomatic polymicrobial UTI based on a limited vs a full microbiological investigation. These results suggest that in adult SCI patients with symptomatic polymicrobial UTI antibiotic therapy guided by a limited microbiological investigation may be practical, adequate and cost-saving.