Intravascular catheters are essential for the appropriate management of hospitalized patients as they provide clinicians with useful means to administer nutrients, obtain blood samples and deliver drugs. However, these devices are a common cause of nosocomial infections. The significant increase in this type of nosocomial infections urged new strategies to prevent them (1). Our research is focused on a new tecnique aimed at preventing catheter-related infections, based on the chemical adsorption of antibiotic molecules on functionalized urethane polymers (2), chosen because they are the most largely employed polymers for catheter construction. In particular in this work the antibiotics, amoxicillin and rifampin, were chosen for their antimicrobial action against gram-positive bacteria and for their ability, due to the presence in the molecules of suitable functional groups, to interact with our polymer surfaces. To verify the influence of functional groups on the polymer-antibiotic interaction, macromolecules provided with carboxyl groups, amino groups, positively charged groups, and sulfate groups were investigated. The evaluation of the amount of adsorbed antibiotic was made by UV-VIS spectroscopy and the kinetics of the antibiotic release was studied by placing the samples in physiological solution and changing the solution every hour for the first 5 h, and every 24 h for the longer times. To better simulate the in vivo elution, the antibiotic release with time was also studied under dynamic conditions, using a peristaltic pump, after coating of commercial catheters with our polymers. At regular sampling times catheters were disconnected from the line and their in vitro antimicrobial activity was assessed by a modified Kirby-Bauer test, using Staphylococcus epidermidis (ATCC 35984) as test microrganism. The amount of antibiotic adsorbed by the polymers is particularly elevated (about 1 mg/cm2) with respect to literature data. The antibiotic-polymer affinity increases with the introduction in the polymer side-chain of functional groups able to establish specificic interactions, such as ionic bonds. All the antibiotic-coated polymers show inhibition zone of the bacterial growth that lasts only a few hours for the amoxi-coated polymers while it remains at least for five mounths for the rifampin-coated ones. The half-life antimicrobial activity depends on the amount of the antibiotic adsorbed and on the water swell ability of the polymers. To verify the influence of the serum proteins on the duration of the antimicrobial action of the treated surfaces, they were immersed in human serum and incubated at 37°C for increasing times, and their behaviour was compared to that of the abovementioned polymers treated with physiological solution.
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|Titolo:||Prevention of catheter-related infections by catheter coating with an ansamycin and a beta-lactamic antibiotic.|
|Data di pubblicazione:||2002|
|Appartiene alla tipologia:||04a Atto di comunicazione a congresso|