Nanomodified Endotracheal Tubes: Spatial Analysis of Reduced Bacterial Colonization in a Bench Top Airway Model
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Nanomodified Endotracheal Tubes: Spatial Analysis of Reduced Bacterial Colonization in a Bench Top Airway Model Mary C. Machado1, Keiko M. Tarquinio2, and Thomas J. Webster3* 1
School of Engineering, Brown University, Providence RI, 02912, USA; 2Division of Pediatric Critical Care Medicine, Rhode Island Hospital, Providence RI, 02903, USA; 3School of Engineering and Department of Orthopaedics, Brown University, Providence RI, 02912, USA. ABSTRACT Ventilator associated pneumonia (VAP) is a serious and costly clinical problem. Specifically, receiving mechanical ventilation for over 24 hours increases the risk of VAP and is associated with high morbidity, mortality and medical costs. Cost effective endotracheal tubes (ETTs) that are resistant to bacterial infection could help prevent this problem. The objective of this study was to determine differences in the growth of Staphylococcus aureus (S. aureus) on nanomodified and unmodified polyvinyl chloride (PVC) ETTs under dynamic airway conditions. PVC ETTs were modified to have nanometer surface features by soaking them in Rhizopus arrhisus, a fungal lipase. Twenty-four hour experiments (supported by computational models) showed that air flow conditions within the ETT influenced both the location and concentration of bacterial growth on the ETTs especially within areas of tube curvature. More importantly, experiments revealed a 1.5 log reduction in the total number of S. aureus on the novel nanomodified ETTs compared to the conventional ETTs after 24 hours of air flow. This dynamic study showed that lipase etching can create nano-rough surface features on PVC ETTs that suppress S. aureus growth and, thus, may provide clinicians with an effective and inexpensive tool to combat VAP. INTRODUCTION Ventilator associated pneumonia (VAP) is a severe, costly complication of mechanical ventilation among critically ill patients. The second most common hospital acquired infection (HAI) among pediatric intensive care units (PICUs) [1, 2], VAP is particularly difficult to diagnose in pediatric patients. This can lead to delays in targeted treatment [3]. It also increases hospital stays by an average of 8.7 days and can increase hospital cost by up to $51,157 [2]. The two pathogens most commonly associated with VAP in pediatrics are Pseudomonas aeruginosa (P. aeruginosa) and Staphylococcus aureus (S. aureus) [4]. One of the main sources of bacterial colonization within the airway is the endotracheal tube (ETT). ETTs are of special concern because these tubes provide a direct conduit from the outside environment to the lungs [5]. Aggregations of microorganisms surrounded by extracellular matrix proteins (or biofilms) on the surface of the ETT make treatment difficult as they are especially resistant to both antibiotics and the immune system of the patient. The unique properties of nanomodified surfaces (or surfaces with features
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