BackgroundVentilator-associated pneumonia is the most prevalent acquired infection of patients on intensive care units and is associated with considerable morbidity and mortality. Evidence suggests that an improved understanding of the composition of the biofilm communities that form on endotracheal tubes may result in the development of improved preventative strategies for ventilator-associated pneumonia.Methodology/Principal FindingsThe aim of this study was to characterise microbial biofilms on the inner luminal surface of extubated endotracheal tubes from ICU patients using PCR and molecular profiling. Twenty-four endotracheal tubes were obtained from twenty mechanically ventilated patients. Denaturing gradient gel electrophoresis (DGGE) profiling of 16S rRNA gene amplicons was used to assess the diversity of the bacterial population, together with species specific PCR of key marker oral microorganisms and a quantitative assessment of culturable aerobic bacteria. Analysis of culturable aerobic bacteria revealed a range of colonisation from no growth to 2.1×108 colony forming units (cfu)/cm2 of endotracheal tube (mean 1.4×107 cfu/cm2). PCR targeting of specific bacterial species detected the oral bacteria Streptococcus mutans (n = 5) and Porphyromonas gingivalis (n = 5). DGGE profiling of the endotracheal biofilms revealed complex banding patterns containing between 3 and 22 (mean 6) bands per tube, thus demonstrating the marked complexity of the constituent biofilms. Significant inter-patient diversity was evident. The number of DGGE bands detected was not related to total viable microbial counts or the duration of intubation.Conclusions/SignificanceMolecular profiling using DGGE demonstrated considerable biofilm compositional complexity and inter-patient diversity and provides a rapid method for the further study of biofilm composition in longitudinal and interventional studies. The presence of oral microorganisms in endotracheal tube biofilms suggests that these may be important in biofilm development and may provide a therapeutic target for the prevention of ventilator-associated pneumonia.

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Critical illness can adversely effect gastrointestinal function [1]. One manifestation of this is abnormal gut motility and, in particular, impaired gastric emptying [2]. Several gastric motor abnormalities have been described in mechanically ventilated patients including antral hypokinesis and absence of phase III of the migrating motor complex (the so-called "house-keeper" of the gastrointestinal tract) [3]. The causes of these motor disturbances are poorly understood, but various factors such as medications, hyperglycaemia [4] and brain injury [5] have all been implicated. Perhaps the most obvious practical consequence of gastroparesis is that it leads to intolerance of enteral feeding, despite the presence of a functioning, intact small bowel. This has several important sequelae. Critical illness is associated with gut atrophy and increased mucosal permeability to bacteria and macromolecules such as endotoxin [6]. It has been postulated that the translocation of these products, or at least relative ischaemia and subsequent reperfusion of the splanchnic organs, are somehow implicated in the development of single or multiple organ failure [7]. Food in the lumen of the gut is an important stimulus for maintaining splanchnic blood flow [8] and hence mucosal integrity, enteral nutrients thereby exerting a cytoprotective effect throughout the gastrointestinal tract, which prevents both atrophy and ulceration [9].Moreover, the failure to establish enteral feeding in the critically ill very often results in the introduction of total parenteral nutrition [TPN] with its greater risk of septic morbidity, mortality and increased expense [10]. Aside from preventing the establishment of nasogastric feeding, impaired gastric emptying is also associated with gastro-oesophageal and duodenogastric reflux, both of which have been implicated in the development of nosocomial pneumonia [11].Given these adverse effects of gastroparesis, it is not surprising that there is increasing interest in techniques to measure gastric emptying in the critically ill. These techniques have been reviewed elsewhere [12], but briefly they include: radio nucleotide scintigraphy, ultrasonography, gastric impedance monitoring, measurement of the gastric aspirate residual volume, a paracetamol uptake assay and gastric fluid challenge. Of these, the paracetamol absorption test is becoming increasingly popular, presumably because it is relatively easy to perform in the ICU at the bedside. The test relies on the fact that, in healthy individuals, paracetamol is predominantly absorbed in the small intestine and that its absorption depends on the rate of gastric emptying [13]. A standard dose of paracetamol is administered nasogastrically and then serial measurements of its plasma concentration are obtained. From these a concentration: time curve over 60 min can be constructed and, by using the trapezoid rule, the area under the curve calculated (AUC 60 ). This is presented as a measure of gastric emptying. Given that the paracetamol plasma concentration de...

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