The effect of EDTA instillations on the rate of development of encrustation and biofilms in Foley catheters.

The aim of this research was to examine whether a daily instillation of tetra sodium ethylenediaminetetraacetic acid (EDTA) solution could reduce the rate at which encrustation by crystalline Proteus mirabilis biofilms blocks urinary catheters. Sets of three bladder models were fitted with size 14 all-silicone catheters. Tetra sodium EDTA solution was instilled into the catheter following biofilm development. Catheters were examined by digital photography and scanning electron microscopy for evidence of encrustation. The results showed that the mean time to blockage of the control catheters was 45 h for saline, 57 h for water and 67 h for those exposed to daily instillations of the EDTA solution. Statistical analysis confirmed that the mean encrustation rate on the EDTA-treated catheters was significantly lower than on the control-treated devices (P = 0.047). This in vitro study indicates that EDTA may have beneficial effects in reducing the complication of catheter encrustation and blockage by crystalline biofilms.

Tetrasodium EDTA as a novel central venous catheter lock solution against biofilm.

BACKGROUND: Central venous catheter (CVC)-related bloodstream infections (BSIs) are known to increase rates of morbidity and mortality in both inpatients and outpatients, including hematology-oncology patients and those undergoing hemodialysis or home infusion therapy. Biofilm-associated organisms on the lumens of these catheters have reduced susceptibility to antimicrobial chemotherapy. This study tested the efficacy of tetrasodium EDTA as a catheter lock solution on biofilms of several clinically relevant microorganisms. METHODS: Biofilms of Staphylococcus epidermidis, methicillin-resistant S. aureus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumoniae, and Candida albicans were grown to levels of approximately 1 x 10(5) colony-forming units (CFU)/cm(-1) on CVC segments in a model system, then subjected to the tetrasodium EDTA lock treatment. RESULTS: Comparisons of biofilms before and after exposure to the 40-mg/mL(-1) tetrasodium EDTA lock for 21 hours showed that the biofilm viable cell counts of all organisms tested were significantly reduced (P < .05) after exposure to the treatment. CONCLUSION: Antimicrobial lock treatment using 40 mg/mL(-1) of tetrasodium EDTA for at least 21 hours could significantly reduce or potentially eradicate CVC-associated biofilms of clinically relevant microorganisms.

In situ diagnosis of intravascular catheter-related bloodstream infection: a comparison of quantitative culture, differential time to positivity, and endoluminal brushing.

OBJECTIVE: To compare the accuracy of three techniques that do not require central venous catheter removal to diagnose catheter-related bloodstream infection. DESIGN: Prospective cohort study of central venous catheters from suspected cases of catheter-related bloodstream infection. SETTING: University teaching hospital. PATIENTS: One hundred and twenty-five central venous catheters from patients with suspected catheter-related bloodstream infection (a raised peripheral white blood cell count, temperature >37 degrees C, and/or local signs of infection at the catheter skin entry site) in intensive care and surgical patients in a large teaching hospital were assessed. INTERVENTIONS: None. MEASUREMENTS: Three techniques were compared: the differential time to positivity of central venous catheter vs. peripheral-blood cultures, quantitative culture of central venous catheter vs. peripheral blood, and the endoluminal brush with peripheral blood culture. MAIN RESULTS: Central venous catheters with a median dwell time of 11 days were examined. There were 36 episodes of catheter-related bloodstream infection, defined as a positive result from at least two of the three tests in the presence of a peripheral blood culture growing the same microorganism and without an identifiable alternative source of sepsis. The sensitivities of the endoluminal brush, quantitative culture, and differential time to positivity techniques were 100%, 89%, and 72%, respectively, with corresponding specificities of 89%, 97%, and 95%. Blood could be directly aspirated from only 231 of 312 (74%) lumens. In the 20 cases of catheter-related bloodstream infection associated with multiple-lumen central venous catheters, endoluminal brushing was positive for one, two, and three lumens in nine (45%), six (30%), and five (25%) cases, respectively. CONCLUSIONS: All three techniques had relatively high sensitivity. However, inability to obtain samples via central venous catheters is a major drawback of the differential time to positivity and quantitative blood culture approaches. Differential time to positivity is simple to perform and has high specificity and therefore could be used as a first line approach, with the endoluminal brush reserved for cases where blood cannot be obtained. All lumens of multiple-lumen central venous catheters must be sampled to ensure maximal sensitivity.

The routine microbiological screening of central venous catheters in home parenteral nutrition patients.

BACKGROUND & AIMS: Catheter-related bloodstream infection (CRBSI) is a major complication for patients receiving home parenteral nutrition (HTPN). Endoluminal sampling techniques allow the diagnosis of CRBSI without catheter removal and may allow the screening of asymptomatic patients. METHODS: Over a 5-year period, patients receiving HTPN were offered screening on a 3 monthly basis. All patients had tunnelled cuffed Hickman lines. All were asymptomatic at the time of screening, which took the form of either endoluminal brushing or quantitative cultures on through-line blood. RESULTS: Thirty-two patients were suitable for inclusion within the study period (10 male, median age 51 (iqr 46-61)) years with 30 of these having a least one screening performed. Four had positive screening results and underwent appropriate treatment. Of the remainder, 12 presented with at least one clinical episode of CRBSI and 14 had neither clinical CRBSI nor a positive screening result. The combined clinical and screening CRBSI rate was 0.39 episodes per catheter year. CONCLUSION: Although routine microbiological catheter screening can detect subclinical infections in HTPN patients the positive rate is low with the majority of patients still presenting clinical. Identification of higher risk patients and appropriate alterations to screening frequency may improve its value further.

Each lumen is a potential source of central venous catheter-related bloodstream infection.

OBJECTIVE: To determine the relative rates of microbial colonization of individual lumens in triple-lumen central venous catheters (CVCs) and calculate the chance of detecting catheter-related blood stream infection (CRBSI) if only one lumen is sampled. DESIGN: Prospective evaluation of CVCs from suspected and nonsuspected CRBSI cases. SETTING: University teaching hospital. PATIENTS: Triple-lumen CVCs from 50 cases of suspected CRBSI (a raised peripheral white blood cell count, temperature >37 degrees C, and/or local signs of infection at the catheter skin entry site) were evaluated. For comparison, 50 triple-lumen CVCs routinely removed at the end of use were evaluated. MEASUREMENTS: In both groups, peripheral blood cultures were taken before CVC removal. After CVC removal, each lumen was sampled in vitro using the endoluminal brush, and the tip was then cultured using the Maki roll technique. MAIN RESULTS: CVCs causing CRBSI had significant microbial colonization in one, two, or three lumens in ten (40%), ten (40%), or five (20%) cases, respectively. Overall, random sampling of only one lumen in CVCs causing CRBSI had a 60% chance of detecting significant colonization. CONCLUSIONS: If only one CVC lumen is sampled, a negative result does not reliably rule out infection. Each lumen of multiple-lumen CVCs should be considered as a potential source of CRBSI.

The use of a rapid in situ test in the detection of central venous catheter-related bloodstream infection: a prospective study.

BACKGROUND: Acridine orange leukocyte cytospin (AOLC) is a highly sensitive and specific test for the detection of catheter-related bloodstream infection (CRBSI). We evaluated the role of the AOLC test in early detection or exclusion of CRBSI and compared the cost of managing patients with suspected CRBSI. METHODS: On the day of clinical suspicion of CRBSI, blood samples were obtained from the catheters for the AOLC test, and peripheral blood samples were obtained for quantitative blood cultures. Catheters with positive AOLC results were immediately removed for culture and replaced if necessary. Catheters with negative AOLC tests were left in situ. We compared the catheter lifespan in patients with suspected CRBSI who had positive and negative AOLC tests and calculated the cost of using the AOLC test to prevent indiscriminate catheter removal. RESULTS: Fifty patients with suspected CRBSI were tested and prospectively followed up. Catheters were removed in 10 patients (20%) with a positive AOLC test, and CRBSI was confirmed in each case subsequently. Selective removal of catheters based on AOLC tests significantly extended the lifespan of catheters compared with an indiscriminate removal of catheters based on clinical suspicion of CRBSI (median, 24 versus 11 days; p < .0001). The cost of an AOLC test and selective catheter replacement strategy was significantly lower than the cost of routine removal and replacement of catheters (median, pounds sterling 9.53 versus pounds sterling 64.20; p < .0001). CONCLUSION: The AOLC test enables a rapid detection of CRBSI, avoids unnecessary removal of catheters, and provides a cost-efficient management approach in patients with suspected CRBSI.

Enterococcal intravascular catheter-related bloodstream infection: management and outcome of 61 consecutive cases.

Enterococci are an increasingly important cause of intravascular catheter-related bloodstream infection (CRBSI), but the evidence base for treating such cases is limited. Successful antimicrobial treatment of CRBSI while leaving the central venous catheter (CVC) in situ has been reported for some bacteria, such as coagulase-negative staphylococci, but the effectiveness of this approach for treating enterococcal CRBSI is unknown. We aimed to determine the effectiveness of treatment options for enterococcal CRBSI and whether CVC removal is mandatory. Treatment and outcome was determined in a 3 year cohort of patients with enterococcal CRBSI from a university teaching hospital. All episodes of enterococcal bacteraemia during the study (n = 268) were examined to identify the cohort of 61 CRBSIs. Outcomes were determined for various antimicrobial regimens with or without CVC removal. Forty-eight episodes were managed with CVC removal and 13 were managed with the CVC in situ. Forty of 48 (83%) and five of 13 (38%) episodes were cured with the CVC removed or left in situ, respectively. All five episodes cured with the CVC in situ were treated with a cell wall-acting antimicrobial plus an aminoglycoside. This antimicrobial combination was significantly more effective than either ampicillin or vancomycin monotherapy (P < 0.05), or antimicrobials to which isolates were not susceptible (P < 0.01) when the CVC remained in situ. We conclude that enterococcal CRBSI can be treated successfully without CVC removal. The combination of a cell wall-acting antimicrobial with an aminoglycoside was the most effective regimen when the CVC remained in situ in this small group of patients. Although CVC removal was associated with a high cure rate, it did not guarantee treatment success.

Typing of Epidemiologically Associated Environmental and Clinical Strains of Listeria monocytogenes by Random Amplification of Polymorphic DNA.

One hundred and three strains of Listeria monocytogenes (Lm), Listeria seeligeri and Listeria innocua of clinical, food, and environmental origin were examined by generating randomly amplified polymorphic DNA (RAPD). Using one 10 bp and two 13 bp random primers, epidemiologically related strains, previously shown to be indistinguishable by phage typing, yielded identical RAPD profiles. Strains isolated from the hands of three workers in a retail food establishment showed the presence of a single predominant Lm isolate. RAPD analysis is a rapid, reproducible, and relatively inexpensive method for the differentiation of epidemiologically linked isolates of Listeria spp.