Colonization Of Lower Respiratory Tract Research Articles

English

BACKGROUND The term tracheostomy refers to forming an opening in the trachea.1,2 Its advantages include easy and direct access to lower respiratory tract, reduced risk of aspiration, faster weaning from ventilation support and improved physical and psychological comfort. But a common problem in tracheostomised patients is increased risk of colonisation of lower respiratory tract by exogenous bacteria because of direct exposure.1,3 This study was done to recognise pathogens in tracheal secretions collected from tracheostomised patients and their antibiotic sensitivity to treat them with appropriate antibiotics. METHODS This prospective study was done in 138 tracheostomised patients from October 2020 to March 2021 in intensive care unit (ICU) of Chettinad Hospital and Research Institute. Under sterile aseptic precautions, Day 0 and Day 7 cultures posttracheostomy was obtained and their antibiotic sensitivity was studied. Data was analysed using Statistical Package for Social Sciences (SPSS version 19) and presented in proportion, mean and standard deviation (Descriptive statistics). RESULTS In this study, of the 56 cases who had growth in their culture and sensitivity reports on day 0, the most common organism was Pseudomonas aeruginosa (33.9 %) sensitive to imipenem (94.7 %) followed by klebsiella (25 %) sensitive to teicoplanin, vancomycin, amikacin, cefoperazone/tazobactam, linezolid and piperacillin/tazobactam. On day 7, the growth of organisms isolated in tracheal culture got reduced from 56 cases to 16 cases. The prevalence of Pseudomonas reduced to 18.8 % in day 7 whereas Klebsiella pneumonia and Acinetobacter remained almost same from day 0 to day 7. CONCLUSIONS This study concludes the predominant pathogen as Pseudomonas aeruginosa with sensitivity to imipenem followed by Klebsiella with sensitivity to teicoplanin, vancomycin, amikacin, cefoperazone/tazobactam, linezolid and piperacillin/tazobactam on day 0 with reduction in the number of organisms on day 7 due to the fact that all our patients were admitted in ICU several days prior to tracheostomy and were started on antibiotics soon after admission as per choice of the treating physician. Hence, a clear understanding of bacterial colonisation post tracheostomy and its change in course is essential for timely intervention with empirical antibiotics for reducing the incidence of lower respiratory tract infections after tracheostomy in future. KEY WORDS Tracheostomy, Lower Respiratory Tract Infections, Pseudomonas Aeruginosa, Empirical Antibiotics.

Prophylactic application of antibiotics selects extended‐spectrum β‐lactamase and carbapenemases producing Gram‐negative bacteria in the oral cavity

Prophylactic administration of broad-spectrum antibiotics in surgery can change the oral microbiome and induce colonization of oral cavity with Gram-negative bacteria including multidrug (MDR) or extensively drug resistant (XDR) organisms which can lead to lower respiratory tract infections. The aim of the study was to analyse the Gram-negative isolates obtained from oral cavity of the mechanically ventilated patients in ICUs, after prophylactic application of antibiotics and their resistance mechanisms and to compare them with the isolates obtained from tracheal aspirates from the same patients. The antibiotic susceptibility was determined by broth dilution method. PCR was applied to detect genes encoding β-lactamases. Marked diversity of Gram-negative bacteria and resistance mechanisms was found. High resistance rates and high rate of blaCTX-M and carbapenemase encoding genes (blaVIM-1 , blaOXA-48 ) were found among Klebsiella pneumoniae. Pseudomonas aeruginosa was found to harbour blaVIM and in one strain blaPER-1 gene, whereas Acinetobacter baumannii produced OXA-23-like and OXA-24/40-like oxacillinases and was XDR in all except one case. All XDR isolates belong to international clonal lineage II (IC II). The main finding of the study is that the prophlylactic application of antibiotics in surgery intensive care units (ICUs) is associated with the colonization of oral cavity and lower respiratory tract with Gram-negative bacteria. The identity of Gram-negative bacteria in oral cavity reflected those found in endotracheal aspirates leading to conclusion that oral swab as non-invasive specimen can predict the colonization of lower respiratory tract with resistant Gram-negative organisms and the risk for development of ventilator-associated pneumonia.

Role of colonizers and value of routine surveillance culture of endotracheal aspirate of patients in the diagnosis of ventilator associated pneumonia

Background: Ventilator associated pneumonia (VAP) is considered to be second most common nosocomial infection patients requiring critical care.
 Aims and Objective: The present study was conducted to study the role of colonizers and importance of surveillance cultures of endotracheal aspirate (ETA) in the diagnosis of ventilator associated pneumonia in a tertiary care hospital in Lucknow.
 Materials and Methods: An observational longitudinal study was conducted over a period of 2 years, on a total of 210 critically ill patients on mechanical ventilation for >48hrs, to identify the common isolates from ETA culture. Follow up of such patients was done to know the role of these isolates in causation of Ventilator Associated Pneumonia (VAP). Patients fulfilling both clinical Pulmonary infection score (CPIS>6) and microbiological criteria were diagnosed as VAP. Those microorganisms with a colony count of less<105 cfu/ml in both the patients with VAP and those without VAP were considered as colonizers.
 Results: Klebseilla pneumonia (46.2%), Pseudomonas aeruginosa (16.2%) and E.coli (13.8%) were found be the commonest colonisers followed by Acinetobacterbaumanii (8.6%), Citrobacterkoseri (3.8%), Coagulase Negative Staphylococci (2.9%), Staphylococcus aureus (2.4%) and Proteus vulgaris (1%). Of the total patients 28 developed VAP out of which 21 had late onset VAP and 7 had early onset VAP. Among the VAP positive patients the causative organism was Klebsiella pneumonia (53.6%) for majority of cases followed by Pseudomonas aeruginosa (21.4%) and Acinetobacter baumanii (17.9%).
 Conclusion: Prolonged duration of mechanical ventilation increased the chances of colonization by MDR microorganisms leading to nosocomial or Hospital acquired infections (HAI) such as VAP which in turn lead to increased rate of morbidity and mortality. VAP considered to be a leading cause of HAI, routine quantitative surveillance culture of ETA(endotracheal aspirate) will allow prospectively to determine prevalence and progression of colonization in lower respiratory tract, so that strict and prompt preventive measures can be taken rather than cure.

Occurrence of ventilator associated pneumonia using a tracheostomy tube with subglottic secretion drainage.

Ventilator-associated pneumonia (VAP) is a significant cause of morbidity and mortality in critically ill patients who require mechanical ventilation (MV). Subglottic secretions above the endotracheal cuff are associated with bacteria colonization of lower respiratory tract, causing VAP. A preventive strategy to avoid subglottic secretion progression is the drainage with special tracheal tubes effective in preventing both early onset and late onset VAP. The purpose of this study was to measure VAP incidence in tracheostomized patients with suction above the cuff. The authors performed a matched cohort study with historical control in three academic Intensive Care Units (ICUs): upon ICU admission, patients requiring MV were submitted to tracheostomy with a tracheal tube allowing drainage of subglottic secretions (treatment group). A control group without suctioning above the cuff was selected applying the propensity score matching on dataset of previous ELT Study. VAP occurrence at 28-days from intubation was the primary endpoint; hospital mortality and ICU-free days at 28-days were the secondary endpoints. Between July 2014 and April 2016, 125 tracheostomized patients were included in the analysis. 232 tracheostomized patients without suctioning were selected as a control group for the matched cohort study. The application of propensity score matching selected 60 patients to compare the two groups. Incidence of VAP was 8% in treatment group and 19.4% in the control group (P value =0.004). After balance with propensity score matching VAP was 8.3% and 21.7% (P value =0.0408), respectively. Subglottic secretion drainage reduces incidence of VAP in critically ill patients requiring ongoing MV via tracheostomy.

Kardiyov Kardiyovaskuler Cerrahi Hastalarında Alt Solunum Yolu ve Üriner Sistem Kolonizasyonu

Kardiyov Kardiyovaskuler Cerrahi Hastalarında Alt Solunum Yolu ve Üriner Sistem Kolonizasyonu

1557. Population Pharmacokinetics of Suvratoxumab (MEDI4893), an Extended Half-life Staphylococcus aureus Alpha Toxin-Neutralizing Human Monoclonal Antibody, in Healthy Adults and Patients on Mechanical Ventilation in Intensive Care Units

BackgroundSuvratoxumab (suvra), an extended half-life (~80 days), Staphylococcus aureus (SA) alpha toxin-neutralizing IgG monoclonal antibody, is under investigation for prevention of SA pneumonia in patients on mechanical ventilation (MV). We characterized the serum PK of suvra using population pharmacokinetics (popPK) in both healthy volunteers and MV patients and quantified the proportion of patients reaching the serum target of 211 μg/mL at 30 days post-dose.MethodsThe popPK analysis included 1,368 serum samples from two early phase studies (NCT02296320; EudraCT 2014-001097-34): (1) Phase 1 study in 26 healthy adults receiving single IV suvra doses ranging from 0.225g to 5g, with PK sampled up to 360 days; and (2) Phase 2 study in MV patients with PCR-confirmed SA colonization of lower respiratory tract receiving one suvra IV dose of 2g (n = 15) or 5g (n = 96), with PK sampled up to 100 days.ResultsA two-compartment linear model with weight-based scaling of the PK parameters adequately described the serum PK data (Figure 1). MV status, number of days on MV, and age impacted the PK of suvra. A moderate between-subject variability (<45% CV) was estimated for key PK parameters. An estimated two-fold increase in MV patients’ volume of distribution parameters compared with healthy volunteers explained the observed Cmax differences between the two groups (1145±369 μg/mL vs. 1783±396 μg/mL) (Figures 2 and 3). Although age, MV status and days on MV post-dose appeared to be associated with higher systemic clearance (CL) in the model, this estimate could be biased due to limited PK data available for only one half-life (~90 days) of the drug in MV patients (Figure 2). More patients achieved suvra levels above the PK target following the 5 g (73.5%; 50/68) vs. 2 g dose (7.6%; 1/13) at 30 days post-dose.ConclusionMV status, post-dose duration on MV, body weight, and age were identified as statistically significant covariates influencing the PK of suvra. Serum PK and popPK analyses support the 5g dose for future studies with suvra in MV patients. Disclosures All authors: No reported disclosures.

Lower respiratory tract microbial composition was diversified in Pseudomonas aeruginosa ventilator-associated pneumonia patients

BackgroundProbiotics could prevent Pseudomonas aeruginosa colonization in lower respiratory tract (LRT) and reduced P. aeruginosa ventilator-associated pneumonia (VAP) rate. Recent studies also suggested that probiotics could improve lung inflammation in mice infected with P. aeruginosa. It seems that microbiota regulation may be a potential therapy for P. aeruginosa VAP patients. However, we know less about the LRT microbial composition and its correlation with prognosis in P. aeruginosa VAP patients. This study aimed to characterize LRT microbiota in P. aeruginosa VAP patients and explore the relationship between microbiota and patient prognosis.MethodsDeep endotracheal secretions were sampled from subjects via intubation. Communities were identified by 16S ribosomal RNA gene sequencing. The relationship between microbiota and the prognosis of P. aeruginosa VAP patients were evaluated. Clinical pulmonary infection score and the survival of intensive care unit were both the indicators of patient prognosis.ResultsIn this study, the LRT microbial composition of P. aeruginosa VAP patients was significantly different from non-infected intubation patients, and showed significant individual differences, forming two clusters. According to the predominant phylum of each cluster, these two clusters were named Pro cluster and Fir-Bac cluster respectively. Patients from Pro cluster were dominated by Proteobacteria (adj.P < 0.001), while those from Fir-Bac cluster were dominated by Firmicutes, and Bacteroidetes (both adj.P < 0.001). These two varied clusters (Pro and Fir-Bac cluster) were associated with the patients’ primary disease (χ2-test, P < 0.0001). The primary disease of the Pro cluster mainly included gastrointestinal disease (63%), and the Fir-Bac cluster was predominantly respiratory disease (89%). During the two-week dynamic observation period, despite the use of antibiotics, the dominant genera and Shannon diversity of the LRT microbiota did not change significantly in patients with P. aeruginosa VAP. In prognostic analysis, we found a significant negative correlation between Lactobacillus and clinical pulmonary infection score on the day of diagnosis (P = 0.014); but we found no significant difference of microbial composition between survivors and non-survivors.ConclusionsLRT microbial composition was diversified among P. aeruginosa VAP patients, forming two clusters which were associated with the primary diseases of the patients.

Elevated IgM levels as a marker for a unique phenotype in patients with Ataxia telangiectasia

BackgroundAtaxia telangiectasia (AT) is a rare, multi-systemic, genetic disorder. Mutations in the ATM gene cause dysfunction in cell-cycle, apoptosis and V (D) J recombination leading to neurodegeneration, cellular, humoral immunodeficiencies and predisposition to malignancies. Previous studies have suggested that a sub-group of AT patients with elevated IgM levels have a distinct and more severe phenotype. In the current study we aimed to better characterize this group of patients.MethodsWe performed a retrospective review of 46 patient records, followed from January 1986 to January 2015 at the Israeli National AT Center. Demographic, clinical, radiological, laboratory data was reviewed and compared between AT patients with elevated IgM levels (EIgM) and patients with normal IgM levels (NIgM).Results15/46(32.6%) patients had significantly elevated IgM levels. This group had a unique phenotype characterized mainly by increased risk of infection and early mortality. Colonization of lower respiratory tract with Mycobacterium gordonae and Pseudomonas aeruginosa as well as viral skin infections were more frequent in EIgM patients. Patients with NIgM had a significantly longer survival as compared to patients with EIgM but had an increased incidence of fatty liver or cirrhosis. T-cell recombination excision circles and kappa-deleting element recombination circle levels were significantly lower in the EIgM group, suggesting an abnormal class switching in this group.ConclusionsEIgM in AT patients are indicative of a more severe phenotype that probably results from a specific immune dysfunction. EIgM in AT should be considered a unique AT phenotype that may require different management.

The effect of percutaneous endoscopic gastrostomy on aspiration pneumonia of patients with dysphagia

Objective To explore the preventive effect of percutaneous endoscopic gastrostomy (PEG) on aspiration pneumonia in patients with dysphagia. Methods The clinical data of 43 patients undertaking PEG was retrospectively collected and the incidence of aspiration pneumonia, microbiological examination of sputum and antibiotics use before and after PEG in all the patients were compared. Results After PEG, the incidence of aspiration pneumonia decreased significantly from 90.7% to 53.5% according to clinical diagnosis, from 70.4% to 18.5% according to the chest imaging. The use of β-lactamase inhibitor compound decreased significantly, but the detection rate of pseudomonas aeruginosa increased significantly compared with that before PEG. Conclusion PEG can decrease the incidence of aspiration and antibiotics use, and may increase the chances of pseudomonas aeruginosa colonization in the lower respiratory tract. Key words: Gastrostomy; Aspiration pneumonia; Dysphagia

Impact of antifungal therapy in mechanically ventilated patients with Candida spp. colonization in lower respiratory tract

Objective: To explore the impact of antifungal therapy in mechanically ventilated patients with Candida spp. colonization in lower respiratory tract. Methods: In this retrospective study, patients required mechanical ventilation with pulmonary Candida spp. colonization admitted into the intensive care unit (ICU) between July 2012 and June 2016 were included. The patients were divided into the treatment group and control group according to whether or not they received antifungal therapy. The isolation rate of multidrug-resistant (MDR) bacteria, the incidence of ventilator-associated pneumonia (VAP), duration of mechanical ventilation, length of ICU stay, total length of hospital stay, the 28-day mortality and the overall mortality were compared between the two groups. Results: Totally, 101 patients were studied. The number of cases in treatment group was 56 and the control group was 45. The treatment group had a lower incidence of MDR bacteria isolation rate and VAP compared with the control group (16.1% vs 33.3%, 5.4% vs 17.8% respectively, both P<0.05). There were significant differences in the duration of mechanical ventilation [(17.3±5.7) days vs (22.5±7.2) days, P<0.05], length of ICU stay [(23.3±5.6) days vs (28.7 ±4.8) days, P<0.05] and the average length of hospital stay [(36.2±8.7) days vs (43.6±9.0) days, P<0.05)] in the treatment group compared with the control group. There were no statistical difference between the two groups in the 28-day mortality and the overall mortality. Conclusion: Treatment of respiratory Candida spp. colonization in mechanically ventilated patients may reduce isolation rate of MDR bacteria, the incidence of VAP, duration of mechanical ventilation, length of ICU stay and total length of hospital stay.

Correlation analysis of lower respiratory tract bacterial colonization and airway infammafion in stable COPD patients

Objective To detect sputum quantitative bacterial culture and sputum cell counts in stable chronic obstructive pulmonary disease（SCOPD） patients, and explore the correlation between lower airway bacterial colonization（LABC） and airway inflammation. Methods 47 patients with SCOPD were chosen,all patients induced sputum specimens to sputum quantitative bacterial culture and sputum cell counts, sputum and serum IL-8 levels were also detected. Results There were 13 patients whose bacterial colonization of the lower respiratory tract in patients was higher than 107CFU/mL. Serum IL-8 levels of 13 patients was （ 70.65 ± 19.89 ） pg/mL, sputum IL-8 levels was （ 364.65 ±74.19 ） pg/mL, all significantly higher than those whose bacterial colonization of the lower respiratory tract lower than 107CFU/mL, （ 15.87 ±3.01 ） pg/mL and （ 146.65 ±28.11 ） pg/mL, there were statistically significant difference（t = 13.43,9.76,all P 〈0.05）. After 1-year follow-up,FEV1 decline（0.071 ±0.016） L in patients whose bacterial colonization of the lower respiratory tract ≥ 107CFU/mL, it was significantly higher than those whose bacterial colonization of the lower respiratory tract 〈 107CFU/mL; the frequency of acute exacerbation was （2.93 ±1.07 ） times, significantly more than those whose bacterial colonization of the lower respiratory tract 〈 107CFU/mL, the differences were statistically significant （ t = 5.43,6.54, all P 〈 0.05 ）. Conclusion Lower respiratory tract bacterial colonization in patients with SCOPD can aggravate the inflammatory response and increase degree of airflow limitation. Key words: Pulmonary disease, chronic obstructive; Colonization; Sputum culture

From ventilator-associated tracheobronchitis to ventilator-associated pneumonia

Ventilator-associated complications (VACs) are those complications that develop during the period of intubation. The most frequent VAC is infection. Ventilator-associated tracheobronchitis (VAT) is one of the ventilator-associated complications occurring in the critically ill patient. This infection represents an intermediate process between lower respiratory tract colonization and ventilator-associated pneumonia. Increased duration of mechanical ventilation has been reported in patients with VAT because of increased sputum production and airway inflammation. Two studies have shown a beneficial effect of antimicrobial treatment in patients with VAT. The optimal duration of antimicrobial treatment in patients with VAT should be further investigated because short courses of antimicrobials might be sufficient. Aerosolized antibiotics also need to be compared to systemic antibiotics in these patients.

Elastase/LPS-Exposed Mice Exhibit Impaired Innate Immune Responses to Bacterial Challenge: Role of Scavenger Receptor A

Nontypeable Haemophilus influenzae (NTHi) is an important bacterial pathogen associated with lower respiratory tract colonization and with acute exacerbations and disease progression in chronic obstructive pulmonary disease (COPD). Why the immune system fails to eliminate NTHi and the exact contribution of the organism to COPD progression are not well understood, in part because we lack an animal model that mimics all aspects of COPD. For this study, we used an established murine model that exhibits typical features of COPD. Elastase/LPS-exposed mice infected with NTHi showed persistence of bacteria up to 5 days after infection, whereas mice exposed to elastase, LPS, or PBS cleared all bacteria by 3 days. Elastase/LPS-exposed mice also showed sustained lung neutrophilic inflammation, goblet cell metaplasia, airway hyperresponsiveness, and progression of emphysema at 15 days after infection. Alveolar macrophages isolated from elastase/LPS-exposed mice showed impaired bacterial phagocytosis, reduced expression of MARCO and of mannose receptor, and absent expression of scavenger receptor-A (SR-A). Neutralization of SR-A significantly decreased phagocytosis of NTHi by normal alveolar macrophages. Our results suggest that elastase/LPS-exposed mice show impaired bacterial clearance and sustained lung inflammation. Lack of SR-A expression may, in part, be responsible for impaired phagocytosis of bacteria by alveolar macrophages of elastase/LPS-exposed mice. These data validate the suitability of elastase/LPS model for investigating NTHi pathogenesis and progression of disease in COPD.

Pathophysiology of Airway Colonization in Critically ill COPD Patient

Although noninvasive ventilation (NIV) use in severe acute exacerbation of COPD has substantially reduced the need for intubation, an important number of COPD patients still are mechanically ventilated through a tracheal tube in the ICU. Intubation is a major risk factor for lower respiratory tract colonization (LRTC) in ICU patients. Other risk factors for LRTC include colonization of the oral cavity, nasopharynx, and gastric content. Aspiration of contaminated oropharyngeal secretions is increased by supine position, underinflation of tracheal cuff, coma, and sedation. Tracheal tube biofilm formation plays an important role as a reservoir for microorganisms. Reduced cough reflex, altered mucocilliary clearance, hypersecretion and retention of mucus are frequent in COPD patients. In addition, malnutrition and corticosteroid use are common in this population resulting in altered cellular, and humoral immunity and higher risk for LRTC. Incidence of LRTC varies from 22-95% of intubated patients. Pseudomonas aeruginosa is the most frequently isolated microorganism at day 3 after intubation in COPD patients. LRTC is a major risk factor for ventilator-associated pneumonia, which is associated with increased mortality and morbidity in ICU patients. Several measures could be suggested to reduce LRTC in critically ill COPD patients. NIV use in severe acute exacerbations reduces the need for intubation. In addition, the early use of NIV averts respiratory failure after extubation and could reduce the duration of invasive mechanical ventilation. Other measures might be efficient in preventing LRTC such as semirecumbent position, avoidance of gastric distension, polyurethane-cuffed tracheal tubes, silver-coated tracheal tubes, subglottic aspiration, and continuous control of cuff pressure. Further studies should determine the impact of preventive measures aiming at preventing LRTC on outcome of COPD patients requiring intubation and mechanical ventilation in the ICU.

Ventilator-associated Tracheobronchitis

The incidence of ventilator-associated tracheobronchitis (VAT) varies from 10% to 16.5% of intubated critically ill patients. This infection represents an intermediate process between lower respiratory tract colonization and ventilator-associated pneumonia (VAP). VAT definition is still controversial. However, the most specific definition includes all the following criteria: fever (>38°C) with no other recognizable cause, purulent sputum production, positive culture of a respiratory specimen at significant threshold concentrations, and no radiographic signs of a new pneumonia. This infection is frequently caused by Pseudomonas aeruginosa, and is characterized by lower respiratory tract inflammation and increased sputum production resulting in weaning difficulties and longer duration of mechanical ventilation. Two recent randomized trials reported beneficial effects of antimicrobial therapy in patients with VAT. In a randomized blinded placebo-controlled trial, aerosolized antibiotics significantly reduced the incidence of subsequent VAP. Further, aerosolized antibiotics increased weaning from mechanical ventilation, reduced usage of systemic antibiotics, and antibiotic resistance. The impact of systemic antibiotics on outcomes of VAT patients was evaluated in a randomized unblinded controlled study. Antibiotic treatment increased mechanical ventilation-free days, and reduced the incidence of subsequent VAP and intensive care unit mortality. The beneficial effects of antibiotic treatment in VAT patients should be confirmed, and the best duration of antimicrobial therapy should be determined by future studies.

Selective digestive decontamination is superior to selective oropharyngeal decontamination

We are interested in the debate on the efficacy and safety of selective digestive decontamination (SDD) and selective oropharyngeal decontamination (SOD) raised by Schultz and Haas in their review [1]. The authors concluded that 'SDD and SOD are equally effective with respect to the prevention of mortality' [1]. This statement is based on the results of a Dutch randomized controlled trial [2], which was the first to demonstrate a survival benefit of SOD. However, the mortality reduction was higher, albeit not significantly, in the SDD group than in the SOD group. Additionally, a recent meta-analysis, including nine SOD randomized controlled trials and 4,733 patients, failed to show any significant mortality reduction (odds ratio (OR) = 0.93; 95% confidence interval (CI) = 0.81 to 1.07) [3]. In contrast, there is robust evidence indicating that SDD including parenteral and enteral antimicrobials significantly reduces mortality [4]. The authors wrote that 'whether SDD or SOD are favorable with regard to development of antibiotic resistance is yet unknown' [1]. The Dutch randomized controlled trial, however, showed that patients with aerobic Gram-negative bacilli in rectal swabs resistant to the marker antibiotics numbered less with SDD than with SOD [2]. Additionally, bacteremia due to highly resistant pathogens was significantly reduced by SDD compared with SOD (OR = 0.37, 95% CI = 0.16 to 0.85), and lower respiratory tract colonization due to highly resistant pathogens was lower with SDD (OR = 0.58, 95% CI = 0.43 to 0.78) than with SOD (OR = 0.65, 95% CI = 0.49 to 0.87) compared with standard care [5]. We believe that SDD is superior to SOD in terms of both mortality reduction and emergence of resistance.

Nosocomial tracheobronchitis

Nosocomial tracheobronchitis is common among intubated critically ill patients. Ventilator-associated tracheobronchitis (VAT) represents an intermediate process between lower respiratory tract colonization and ventilator-associated pneumonia. The aim of this review is to discuss recent findings on VAT. VAT is defined using all the following criteria: fever (>38 degrees C) with no other recognizable cause, purulent sputum production, positive culture of respiratory specimen at significant threshold, and no radiographic signs of new pneumonia. This infection is frequently caused by Pseudomonas aeruginosa and characterized by lower respiratory tract inflammation and increased sputum production resulting in weaning difficulties and longer duration of mechanical ventilation. The effect of aerosolized antibiotics on outcomes in VAT patients was evaluated in a randomized blinded placebo-controlled trial. Aerosolized antibiotics significantly increased weaning from mechanical ventilation and reduced subsequent ventilator-associated pneumonia and usage of systemic antibiotics and antibiotic resistance. A randomized unblinded controlled study assessed the impact of systemic antibiotics on outcome of VAT patients. Antibiotic treatment increased mechanical ventilation-free days and reduced the incidence of subsequent ventilator-associated pneumonia and ICU mortality. Antibiotic treatment is beneficial in VAT patients. Future studies should confirm these promising results and determine the best duration of antimicrobial therapy in these patients.

Antimicrobial-coated endotracheal tubes: an experimental study

Antibiotic-resistant bacterial biofilm may quickly form on endotracheal tubes (ETTs) and can enter the lungs, potentially causing pneumonia. In an attempt to prevent bacterial colonization, we developed and tested in an in-vitro study and animal study several antibacterial-coated ETTs (silver sulfadiazine with and without carbon in polyurethane, silver sulfadiazine and chlorhexidine with and without carbon in polyurethane, silver-platinum with and without carbon in polyurethane, chlorhexidine in polyurethane, and rose bengal for UV light). DESIGN, SETTING, ANIMALS, INTERVENTIONS: After preliminary studies, silver sulfadiazine in polyurethane (SSD-ETT) was selected among the coatings to be challenged every 24 h with 10(4)-10(6) Pseudomonas aeruginosa/ml and evaluated at 6 h, 24 h, and 72 h with standard microbiological studies, scanning electron microscopy, and confocal scanning microscopy. Subsequently, eight sheep were randomized to receive either a SSD-ETT or a standard ETT (St-ETT). After 24 h of mechanical ventilation, standard microbiological studies were performed together with scanning electron microscopy and confocal microscopy. In the in-vitro study SSD-ETT remained bacteria-free for up to 72 h, whereas St-ETT showed heavy P. aeruginosa growth and biofilm formation (p < 0.01). In sheep, the SSD-ETT group showed no bacterial growth in the ETT, ventilator tubing, and lower respiratory tract, while heavy colonization was found in the St-ETT (p < 0.01), ventilator tubing (p=0.03), and lower respiratory tract (p < 0.01). This study describes several effective and durable antibacterial coatings for ETTs. Particularly, SSD-ETT showed prevention against P. aeruginosa biofilm formation in a 72-h in-vitro study and lower respiratory tract colonization in sheep mechanically ventilated for 24 h.

Analysis of bacterial colonization in lower respiratory tract and pathogens for ventilator-associated pneumonia in ventilated premature

目的 了解机械通气早产儿下呼吸道定植细菌菌谱,并进一步探讨呼吸机相关性肺炎(VAP)的病原学细菌谱及耐药性.方法 对2004年1月～2005年12月我院早产儿监护病房住院的165例机械通气患儿行支气管肺泡灌洗液定量培养和药敏试验,进行细菌监测.结果 机械通气3 d以上的患儿全部出现下呼吸道的细菌定植,其中有37.5%(62/165)的患儿诊断为VAP.支气管肺泡灌洗液定量培养均以G-杆菌为主,其中肺炎克雷白杆菌、铜绿假单胞菌、鲍曼不动杆菌分别占前3位;VAP的病原菌耐药性分析显示对头孢类抗生素广泛耐药,而对亚胺培南-西司他丁、头胞哌酮/舒巴坦钠、环丙沙星仍保持较高敏感性.结论 G-杆菌是机械通气患儿下呼吸道定植和VAP的优势菌群,对目前临床常用抗生素有多重耐药现象。

Ureaplasma urealyticum: no independent role in the pathogenesis of bronchopulmonary dysplasia

Ureaplasma urealyticum has been linked to short and long-term morbidity of preterm infants. We wanted to analyze if it has an independent role in the pathogenesis of bronchopulmonary dysplasia if prenatal history with possible exposure to intrauterine infection is taken into account. Lower respiratory tract colonization with U. urealyticum was analyzed from 49 infants born before the 30th week of gestation. The need for supplemental oxygen at the age of 28 days and 36 gestational weeks was studied. Forty-five percent of the 33 infants born after spontaneous onset of labor were colonized with U. urealyticum, while none of the electively born were. If analyzed based on the Ureaplasma colonization, bronchopulmonary dysplasia was more common in the colonized infants at the age of 28 days (OR 4.57, 95% CI 1.18-17.68), but not at the gestational age of 36 weeks (OR 1.00). Based on the prenatal history, the OR of bronchopulmonary dysplasia in infants born after spontaneous onset of labor was greater than in infants born electively both at the age of 28 days (OR 4.33, 95% CI 0.83-22.75) and at 36 weeks of gestation (OR 2.8, 95% CI 0.30-26.42). If possible exposure to intra-amniotic inflammation is taken into account, U. urealyticum seems not to have an independent role in the pathogenesis of bronchopulmonary dysplasia. Its role has been overemphasized, as it is the most common cause of intra-amniotic bacterial infection.