Nosocomial tracheobronchitis

Veratryl Alcohol Attenuates the Virulence and Pathogenicity of Pseudomonas aeruginosa Mainly via Targeting las Quorum-Sensing System

Pseudomonas aeruginosa is an opportunistic pathogen that usually causes chronic infections and even death in patients. The treatment of P. aeruginosa infection has become more challenging due to the prevalence of antibiotic resistance and the slow pace of new antibiotic development. Therefore, it is essential to explore non-antibiotic methods. A new strategy involves screening for drugs that target the quorum-sensing (QS) system. The QS system regulates the infection and drug resistance in P. aeruginosa. In this study, veratryl alcohol (VA) was found as an effective QS inhibitor (QSI). It effectively suppressed the expression of QS-related genes and the subsequent production of virulence factors under the control of QS including elastase, protease, pyocyanin and rhamnolipid at sub-inhibitory concentrations. In addition, motility activity and biofilm formation, which were correlated with the infection of P. aeruginosa, were also suppressed by VA. In vivo experiments demonstrated that VA could weaken the pathogenicity of P. aeruginosa in Chinese cabbage, Drosophila melanogaster, and Caenorhabditis elegans infection models. Molecular docking, combined with QS quintuple mutant infection analysis, identified that the mechanism of VA could target the LasR protein of the las system mainly. Moreover, VA increased the susceptibility of P. aeruginosa to conventional antibiotics of tobramycin, kanamycin and gentamicin. The results firstly demonstrate that VA is a promising QSI to treat infections caused by P. aeruginosa.

Ventilator-associated tracheobronchitis: an update

Ventilator-associated lower respiratory tract infection is one of the most frequent complications in mechanically ventilated patients. Ventilator-associated tracheobronchitis has been considered a disease that does not warrant antibiotic treatment by the medical community for many years. In the last decade, several studies have shown that tracheobronchitis could be considered an intermediate process that leads to ventilator-associated pneumonia. Furthermore, ventilator-associated tracheobronchitis has a limited impact on overall mortality but shows a significant association with increased patient costs, length of stay, antibiotic use, and duration of mechanical ventilation. Although we still need clear evidence, especially concerning treatment modalities, the present study on ventilator-associated tracheobronchitis highlights that there are important impacts of including this condition in clinical management and epidemiological and infection surveillance.

Comparative efficacy of linezolid and vancomycin for endotracheal tube MRSA biofilms from ICU patients

PURPOSE

To compare the efficacy of systemic treatment with linezolid (LNZ) versus vancomycin (VAN) on methicillin-resistant Staphylococcus aureus (MRSA) burden and eradication in endotracheal tube (ETT) biofilm and ETT cuff from orotracheally intubated patients with MRSA respiratory infection.

METHODS

Prospective observational clinical study was carried out at four European tertiary hospitals. Plasma and endotracheal aspirate (ETA) levels of LNZ and VAN were determined 72 h after treatment initiation through high-performance liquid chromatography or bioassay. LNZ or VAN concentration in the ETT biofilm and MRSA burden and eradication was determined upon extubation. The minimum inhibitory concentration (MIC) for LNZ and VAN was assessed by E-test strips (Biomerieux®). Scanning electron microscopy images were obtained, and ETT biofilm thickness was compared between groups.

RESULTS

Twenty-five patients, 15 treated with LNZ and 10 with VAN, were included in the study. LNZ presented a significantly higher concentration (μg/mL) than VAN in ETT biofilm (72.8 [1.3-127.1] vs 0.4 [0.4-1.3], p < 0.001), although both drugs achieved therapeutic plasma levels 72 h after treatment initiation. Systemic treatment with LNZ achieved lower ETT cuff MRSA burdens than systemic treatment with VAN. Indeed, LNZ increased the MRSA eradication rate in ETT cuff compared with VAN (LNZ 75%, VAN 20%, p = 0.031).

CONCLUSIONS

In ICU patients with MRSA respiratory infection intubated for long periods, systemic treatment with LNZ obtains a greater beneficial effect than VAN in limiting MRSA burden in ETT cuff.

Antibiotic therapy in ventilator-associated tracheobronchitis: a literature review

The concept of ventilator-associated tracheobronchitis is controversial; its definition is not unanimously accepted and often overlaps with ventilator-associated pneumonia. Ventilator-associated tracheobronchitis has an incidence similar to that of ventilator-associated pneumonia, with a high prevalence of isolated multiresistant agents, resulting in an increase in the time of mechanical ventilation and hospitalization but without an impact on mortality. The performance of quantitative cultures may allow better diagnostic definition of tracheobronchitis associated with mechanical ventilation, possibly avoiding the overdiagnosis of this condition. One of the major difficulties in differentiating between ventilator-associated tracheobronchitis and ventilator-associated pneumonia is the exclusion of a pulmonary infiltrate by chest radiography; thoracic computed tomography, thoracic ultrasonography, or invasive specimen collection may also be required. The institution of systemic antibiotic therapy does not improve the clinical impact of ventilator-associated tracheobronchitis, particularly in reducing time of mechanical ventilation, hospitalization or mortality, despite the possible reduced progression to ventilator-associated pneumonia. However, there are doubts regarding the methodology used. Thus, considering the high prevalence of tracheobronchitis associated with mechanical ventilation, routine treatment of this condition would result in high antibiotic usage without clear benefits. However, we suggest the institution of antibiotic therapy in patients with tracheobronchitis associated with mechanical ventilation and septic shock and/or worsening of oxygenation, and other auxiliary diagnostic tests should be simultaneously performed to exclude ventilator-associated pneumonia. This review provides a better understanding of the differentiation between tracheobronchitis associated with mechanical ventilation and pneumonia associated with mechanical ventilation, which can significantly decrease the use of antibiotics in critically ventilated patients.

[Acute tracheal and bronchial tree infections]

Las infecciones agudas del tracto respiratorio son una de las principales causas de inflamación de la vía aérea, siendo especialmente frecuentes las de origen vírico. Las infecciones de la vía aérea superior son más frecuentes en niños, y es la principal causa de hospitalización en pacientes menores de 4 años. Sin embargo, la infección aguda de los bronquios es más frecuente en adultos, siendo una de las principales causas por las que consultan en las urgencias y centros de salud. La afectación puede ir desde una en fermedad autolimitada de pocos días de evolución, hasta una obstrucción de la vía aérea potencialmente mortal.

A case-control study on the clinical impact of ventilator associated tracheobronchitis in adult patients who did not develop ventilator associated pneumonia

OBJECTIVES

The main objective was to determine whether ventilator-associated tracheobronchitis (VAT) is related to increased length of ICU stay. Secondary endpoints included prolongation of hospital stay, as well as, ICU and hospital mortality.

DESIGN

A retrospective matched case-control study. Each case was matched with a control for duration of ventilation (± 2 days until development of ventilator-associated tracheobronchitis), disease severity (Acute Physiology and Chronic Health Evaluation II) at admission ± 3, diagnostic category and age ±10 years.

PATIENTS

Critically ill adults admitted to a polyvalent 30-beds ICU with the diagnosis of VAT in the period 2013-2016.

MAIN RESULTS

We identified 76 cases of VAT admitted to our ICU during the study period. No adequate controls were found for 3 patients with VAT. There were no significant differences in demographic characteristics, reasons for admission and comorbidities. Patients with VAT had a longer ICU length of stay, median 22 days (14-35), compared to controls, median 15 days (8-27), p=.02. Ventilator days were also significantly increased in VAT patients, median 18 (9-28) versus 9 days (5-16), p=.03. There was no significant difference in total hospital length of stay 40 (28-61) vs. 35days (23-54), p=.32; ICU mortality (20.5 vs. 31.5% p=.13) and hospital mortality (30.1 vs. 43.8% p=.09). We performed a subanalysis of patients with microbiologically proven VAT receiving adequate antimicrobial treatment and did not observe significant differences between cases and the corresponding controls.

CONCLUSIONS

VAT is associated with increased length of intensive care unit stay and longer duration of mechanical ventilation. This effect disappears when patients receive appropriate empirical treatment.

Ventilator-Associated Pneumonia in Critically Ill Children: A New Paradigm

Ventilator-associated pneumonia (VAP) is a serious complication of critical illness. Surveillance definitions have undergone revisions for more objective and consistent reporting. The 1 organism-1 disease paradigm for microbial involvement may not adequately apply to many cases of VAP, in which pathogens are introduced to a pre-existing and often complex microbial community that facilitates or hinders the potential pathogen, consequently determining whether progression to VAP occurs. As omics technology is applied to VAP, a paradigm is emerging incorporating simultaneous assessments of microbial populations and their activity, as well as the host response, to personalize prevention and treatment.

Clinical Features and Antimicrobial Resistance of Bacterial Agents of Ventilator-Associated Tracheobronchitis in Hamedan, Iran

OBJECTIVES

Ventilator-associated tracheobronchitis (VAT) is a common cause of mortality and morbidity in patients admitted to intensive care units (ICUs). This study was conducted to evaluate the clinical course, etiology, and antimicrobial resistance of bacterial agents of VAT in ICUs in Hamedan, Iran.

METHODS

During a 12-month period, all patients with VAT in a medical and a surgical ICU were included. The criteria for the diagnosis of VAT were fever, mucus production, a positive culture of tracheal secretions, and the absence of lung infiltration. Clinical course, including changes in temperature and tracheal secretions, and outcomes were followed. The endotracheal aspirates were cultured on blood agar and chocolate agar, and antimicrobial susceptibility testing of isolates were performed using the disk diffusion method.

RESULTS

Of the 1 070 ICU patients, 69 (6.4%) were diagnosed with VAT. The mean interval between the patient's intubation and the onset of symptoms was 4.7±8.5 days. The mean duration of response to treatment was 4.9±4.7 days. A total of 23 patients (33.3%) progressed to ventilator-associated pneumonia (VAP), and 38 patients (55.0%) died. The most prevalent bacterial isolates included Acinetobacter baumannii (24.6%), Pseudomonas aeruginosa (20.2%), and Enterobacter (13.0%). P. aeruginosa and Enterobacter were the most prevalent bacteria in surgical ICU, and A. baumannii and K. pneumoniae were the most common in the medical ICU. All A. baumannii and Citrobacter species were multidrug-resistant (MDR). MDR pathogens were more prevalent in medical ICU compared to surgical ICU (p < 0.001).

CONCLUSIONS

VAT increases the rates of progression to VAP, the need for tracheostomy, and the incidence of mortality in ICUs. Most bacterial agents of VAT are MDR. Preventive policies for VAP, including the use of ventilator care bundle, and appropriate empirical antibiotic therapy for VAT may reduce the incidence of VAP.

Enteral nutrition volume is not correlated with lower respiratory tract infection in patients on mechanical ventilation

OBJECTIVE

To evaluate the effect of enteral nutrition volume, gastrointestinal function and the type of acid suppressive drug upon the incidence of lower respiratory tract infections in critically ill patients on mechanical ventilation (MV).

DESIGN

A retrospective secondary analysis was carried out.

SETTING

The Intensive Care Unit of a University Hospital.

PATIENTS OR PARTICIPANTS

Patients≥18-years-old expected to need MV for more than four days, and receiving enteral nutrition by nasogastric tube within 24h of starting MV.

INTERVENTIONS

We correlated enteral nutrition volume administered during the first 10 days, gastrointestinal function and the type of acid suppressive therapy with the episodes of lower respiratory tract infection up until day 28. Cox proportional hazards ratios in univariate and adjusted multivariate models were used. Statistical significance was considered for p<0.05.

MAIN VARIABLES OF INTEREST

Lower respiratory tract infection episodes.

RESULTS

Sixty-six out of 185 patients (35.7%) had infection; 27 patients had ventilator-associated pneumonia; and 39 presented ventilator-associated tracheobronchitis. Uninfected and infected groups were similar in terms of enteral nutrition volume (54±12 and 54±9mL/h; p=0.94) and caloric intake (19.4±4.9 and 19.6±5.2kcal/kg/d; p=0.81). The Cox proportional hazards model showed neurological indication of MV to be the only independent variable related to infection (p=0.001). Enteral nutrition volume, the type of acid suppressive therapy, and the use of prokinetic agents were not significantly correlated to infection.

CONCLUSIONS

Enteral nutrition volume and caloric intake, gastrointestinal dysfunction and the type of acid suppressive therapy used were not associated to lower respiratory tract infection in patients on MV.

Biofilms in ventilator-associated pneumonia

Biofilms develop rapidly following endotracheal intubation and represent a persistent source of unnecessary pathogens in the critically ill patient. Overall, the imbalance in the lung microbiome caused by an endotracheal tube and its role in biofilm formation and in ventilator-associated pneumonia is still unclear. Although endotracheal tube–biofilm preventive measures are being tested, no outcome impact has ever been demonstrated, and therefore no approach has been clinically recommended. Nonetheless, an accurate description of the actual biofilm morphology in vivo could be useful to implement effective preventive measures. The combined use of in vitro biofilm models, in vivo animal models and clinical research is vitally important to the attainment of a comprehensive understanding of biofilms in ventilator-associated pneumonia in the near future.

Incidence and prognosis of ventilator-associated tracheobronchitis (TAVeM): a multicentre, prospective, observational study

BACKGROUND

Ventilator-associated tracheobronchitis has been suggested as an intermediate process between tracheobronchial colonisation and ventilator-associated pneumonia in patients receiving mechanical ventilation. We aimed to establish the incidence and effect of ventilator-associated tracheobronchitis in a large, international patient cohort.

METHODS

We did a multicentre, prospective, observational study in 114 intensive care units (ICU) in Spain, France, Portugal, Brazil, Argentina, Ecuador, Bolivia, and Colombia over a preplanned time of 10 months. All patients older than 18 years admitted to an ICU who received invasive mechanical ventilation for more than 48 h were eligible. We prospectively obtained data for incidence of ventilator-associated lower respiratory tract infections, defined as ventilator-associated tracheobronchitis or ventilator-associated pneumonia. We grouped patients according to the presence or absence of such infections, and obtained data for the effect of appropriate antibiotics on progression of tracheobronchitis to pneumonia. Patients were followed up until death or discharge from hospital. To account for centre effects with a binary outcome, we fitted a generalised estimating equation model with a logit link, exchangeable correlation structure, and non-robust standard errors. This trial is registered with ClinicalTrials.gov, number NCT01791530.

FINDINGS

Between Sept 1, 2013, and July 31, 2014, we obtained data for 2960 eligible patients, of whom 689 (23%) developed ventilator-associated lower respiratory tract infections. The incidence of ventilator-associated tracheobronchitis and that of ventilator-associated pneumonia at baseline were similar (320 [11%; 10·2 of 1000 mechanically ventilated days] vs 369 [12%; 8·8 of 1000 mechanically ventilated days], p=0·48). Of the 320 patients with tracheobronchitis, 250 received appropriate antibiotic treatment and 70 received inappropriate antibiotics. 39 patients with tracheobronchitis progressed to pneumonia; however, the use of appropriate antibiotic therapy for tracheobronchitis was associated with significantly lower progression to pneumonia than was inappropriate treatment (19 [8%] of 250 vs 20 [29%] of 70, p<0·0001; crude odds ratio 0·21 [95% CI 0·11-0·41]). Significantly more patients with ventilator-associated pneumonia died (146 [40%] of 369) than those with tracheobronchitis (93 [29%] of 320) or absence of ventilator-associated lower respiratory tract infections (673 [30%] of 2271, p<0·0001). Median time to discharge from the ICU for survivors was significantly longer in the tracheobronchitis (21 days [IQR 15-34]) and pneumonia (22 [13-36]) groups than in the group with no ventilator-associated lower respiratory tract infections (12 [8-20]; hazard ratio 1·65 [95% CI 1·38-1·97], p<0·0001).

INTERPRETATION

This large database study emphasises that ventilator-associated tracheobronchitis is a major health problem worldwide, associated with high resources consumption in all countries. Our findings also show improved outcomes with use of appropriate antibiotic treatment for both ventilator-associated tracheobronchitis and ventilator-associated pneumonia, underlining the importance of treating both infections, since inappropriate treatment of tracheobronchitis was associated with a higher risk of progression to pneumonia.

FUNDING

None.

Ventilator-associated infection: the role for inhaled antibiotics

PURPOSE OF REVIEW

Despite multiple protocols for the prevention of ventilator-associated pneumonia (VAP), respiratory infections have not been eliminated in the ICU. The profound disruption in both airway integrity and mucociliary clearance caused by the endotracheal tube makes it unlikely there will ever be a zero rate of respiratory infection in critically ill ventilated patients or a 100% cure rate when infection is present. In fact, options for treatment are diminishing as bacteria resistant to most, or in some hospitals all, systemic antibiotics increase in prevalence from our liberal use of systemic antibiotics. Inhaled therapy with proper delivery will result in the high concentrations of antibiotics needed in the treatment of increasingly resistant organisms.

RECENT FINDINGS

Data from many recent investigations have focused on inhaled antibiotics as: adjunctive therapy to systemic antibiotic for VAP, monotherapy for VAP, and as monotherapy for ventilator-associated tracheobronchitis. The clinical outcomes of these studies will be reviewed as well as their effect on multidrug-resistant organisms.

SUMMARY

The present review will focus on the rationale for inhaled therapy, the current studies examining the delivery and clinical efficacy of inhaled antibiotics, and the potential role for this mode of delivery actually decreasing antibiotic resistance in the respiratory tract.

Antibiotic therapy for ventilator-associated tracheobronchitis: a standard of care to reduce pneumonia, morbidity and costs?

PURPOSE OF REVIEW

The present review draws our attention to ventilator-associated tracheobronchitis (VAT) as a distinct clinical entity that has been associated with progression to ventilator-associated pneumonia (VAP) and worse patient outcomes. In contrast to VAP, which has been extensively investigated for over the past 30 years, most VAT studies have been conducted in the past decade. There are ample data which demonstrate that VAT may progress to VAP, have more ventilator days, and have longer ICU stay that may translate into higher healthcare costs.

RECENT FINDINGS

The article focuses on the diagnostic criteria for VAT, causative agents, and studies analyzing associations between VAT and patient outcomes in relation to early, appropriate intravenous, and/or aerosolized antibiotic therapy. Aerosolized antibiotic treatment delivered by improved device technology is a novel approach that has proved to be effective for the treatment and eradication of multidrug-resistant bacterial pathogens. Aerosolized antibiotics are effective in decreasing the use of systemic antibiotics, reducing bacterial resistance, and may also facilitate clinical resolution of infection.

SUMMARY

Evidence presented in this review supports treatment of VAT with early and appropriate antibiotic therapy as a standard of care to reduce VAP, ventilator days, and duration of ICU stay in high-risk patient population.

Antibiotic treatment of ventilator-associated tracheobronchitis: to treat or not to treat?

PURPOSE OF REVIEW

To evaluate the data on antimicrobial therapy for ventilator-associated tracheobronchitis (VAT) to prevent ventilator-associated pneumonia (VAP), and its impact on patient outcomes.

RECENT FINDINGS

Mechanically ventilated patients are at increased risk for tracheal colonization with bacterial pathogens that may progress to VAT and/or VAP. Previous studies suggest that 10-30% of patients with VAT progress to VAP, which results in increased morbidity but not mortality. Several natural history studies and small randomized controlled trials and a meta-analysis reported that appropriate, pre-emptive antibiotic treatment for VAT reduces VAP, duration of intubation and length of ICU stay.

SUMMARY

This review focuses on diagnostic criteria for VAT and VAP, etiologic agents, rationale and benefits of initiating pre-emptive, appropriate antibiotic treatment for VAT to prevent VAP, improve patient outcomes and associated acute and chronic healthcare costs.

α-Hemolysin activity of methicillin-susceptible Staphylococcus aureus predicts ventilator-associated pneumonia

RATIONALE

Colonization of lower airways by Staphylococcus aureus is a risk factor for the development of ventilator-associated tracheobronchitis (VAT) and ventilator-associated pneumonia (VAP). However, little is known about the virulence factors of methicillin-sensitive and -resistant S. aureus (MSSA and MRSA) that may influence host colonization and progression to VAT and VAP.

OBJECTIVES

We evaluated MRSA and MSSA endotracheal aspirates (ETA) for genotype and α-hemolysin activity in relation to the development of VAT and VAP.

METHODS

Serial S. aureus ETA isolates from ventilated patients were analyzed for methicillin resistance, molecular type by Multi-Locus Sequence Typing and spa-typing, and α-hemolysin activity by semiquantitative analysis of hemolysis on sheep blood agar and quantitative measurement of cytolysis of human lung epithelial cells. The virulence of selected strains was assessed in mice by intranasal challenge.

MEASUREMENTS AND MAIN RESULTS

We detected S. aureus from ETA samples in a quarter of the 231 ventilated patients analyzed; one-third of them developed VAP. VAP patients (n = 15) were mainly infected by MSSA strains (87%), whereas colonized individuals (n = 18) not progressing to disease mainly carried MRSA strains (68%). MSSA isolates from colonized or VAT patients exhibited significantly lower α-hemolysin activity than those from VAP cases; however, no such relationship was found with MRSA strains. α-Hemolysin activity of S. aureus isolates was predictive for virulence in mouse pneumonia model.

CONCLUSIONS

MSSA strains with strong blood agar hemolysis and high α-hemolysin activity are markers for VAP, but not VAT, and might be considered in differential diagnosis and initiation of therapy.

Impact of appropriate antimicrobial treatment on transition from ventilator-associated tracheobronchitis to ventilator-associated pneumonia

Introduction

Two small randomized controlled trials have suggested beneficial effects of antibiotic treatment in patients with ventilator-associated tracheobronchitis (VAT). The primary aim of this study is to determine the impact of appropriate antibiotic treatment on transition from VAT to ventilator-associated pneumonia (VAP) in critically ill patients. The secondary objective was to determine the incidence of VAP in patients with VAT.

Methods

This was a prospective observational multicenter study. All patients with a first episode of VAT were eligible. Patients with tracheostomy at intensive care unit (ICU) admission, and those with VAP prior to VAT were excluded. VAT was defined using all the following criteria: fever > 38°C with no other cause, purulent tracheal secretions, positive tracheal aspirate (≥10⁵ cfu/mL), and absence of new infiltrate on chest X ray. Only VAP episodes diagnosed during the 96 h following VAT, and caused by the same bacteria, were taken into account. Antibiotic treatment was at the discretion of attending physicians. Risk factors for transition from VAT to VAP were determined using univariate and multivariate analysis. All variables from univariate analysis with P values <0.1 were incorporated in the multivariate logistic regression analysis.

Results

One thousand seven hundred and ten patients were screened for this study. Eighty-six, and 123 patients were excluded for tracheostomy at ICU admission, and VAP prior to VAT; respectively. One hundred and twenty two (7.1%) patients were included. 17 (13.9%) patients developed a subsequent VAP. The most common microorganisms in VAT patients were Pseudomonas aeruginosa (30%), Staphylococcus aureus (18%), and Acinetobacter baumannii (10%). Seventy-four (60%) patients received antimicrobial treatment, including 58 (47.5%) patients who received appropriate antimicrobial treatment. Appropriate antibiotic treatment was the only factor independently associated with reduced risk for transition from VAT to VAP (OR [95% CI] 0.12[0.02-0.59], P = 0.009). The number of patients with VAT needed to treat to prevent one episode of VAP, or one episode of VAP related to P. aeruginosa was 5, and 34; respectively.

Conclusions

Appropriate antibiotic treatment is independently associated with reduced risk for transition from VAT to VAP.

The lack of specificity of tracheal aspirates in the diagnosis of pulmonary infection in intubated children

OBJECTIVES

Ventilator-associated pneumonia is the first or second most commonly diagnosed nosocomial infection in the PICU. Centers for Disease Control diagnostic criteria include clinical signs or symptoms in conjunction with a "positive" tracheal aspirate, defined as more than 10 colony-forming units/mL of bacteria on quantitative culture and/or more than 25 polymorphonuclear neutrophils per low-power field on Gram stain. We hypothesized that tracheal aspirate cultures and Gram stains would not correlate with clinical signs and symptoms and would therefore not distinguish between colonization and infection.

DESIGN

Prospective observational study.

SETTING

PICU in an academic tertiary care center.

PATIENTS

Children intubated more than 48 hours.

INTERVENTIONS

Sequential tracheal aspirate quantitative cultures and Gram stains in conjunction with daily collection of concordant clinical signs and symptoms.

MEASUREMENTS AND MAIN RESULTS

Time since intubation correlated strongly (p < 0.001) with the proportion of positive (> 10 colony-forming units/mL) tracheal aspirate quantitative cultures, but Centers for Disease Control-defined clinical signs or symptoms of ventilator-associated pneumonia, either singly or in combination, did not. Use of in-line suction catheters versus new, sterile catheters to obtain tracheal aspirates was associated with significantly greater proportion of positive tracheal aspirate bacterial cultures (p < 0.001). Most subjects had more than 25 polymorphonuclear neutrophils per low-power field on Gram stain; polymorphonuclear neutrophils on Gram stain correlated with positive bacterial culture (p = 0.04). Seventy-seven percent of the bacterial isolates detected in positive quantitative cultures were "pathogens." Antibiotic use at the time tracheal aspirates were obtained was associated with a lower frequency of positive quantitative cultures only with antibiotic regimens that included cefepime.

CONCLUSIONS

Positive bacterial cultures of tracheal aspirates increase rapidly after intubation and usually include bacteria considered to be pathogens. Tracheal aspirate cultures and Gram stains do not appear to distinguish between infection and colonization. Antibiotic regimens that include cefepime decrease the frequency of positive cultures, but the significance of this is unclear.

Diagnosis of ventilator-associated pneumonia: controversies and working toward a gold standard

PURPOSE OF REVIEW

The aim is to discuss the clinical, microbiologic, and radiological criteria used in the diagnosis of ventilator-associated pneumonia (VAP), distinguish between ventilator-associated tracheobronchitis (VAT) and VAP, and reconcile the proposed Centers for Disease Control surveillance criteria with clinical practice.

RECENT FINDINGS

Numerous ventilator-associated complications (VACs), including VAP and VAT, may occur in critically ill, intubated patients. A variety of definitions for identifying VAP have been proposed, but there is no diagnostic gold standard. The proposed surveillance definition will identify infectious and noninfectious VAC, including VAP and VAT, but this definition may be inadequate for clinical practice.

SUMMARY

The clinical characteristics of VAP and VAT are similar and include fever, leukocytosis, and purulent sputum. An infiltrate on chest radiograph is consistent with VAP but lacks diagnostic precision, so it is not a criterion in the proposed surveillance definition and should be interpreted cautiously by clinicians. Microbiologically, quantitative and semiquantitative endotracheal aspirate cultures may be employed to diagnose VAP and VAT. Positive bronchoalveolar lavage and protected specimen brush cultures are useful only for the diagnosis of VAP. Experts should collaborate to develop consensus definitions for VAP and VAT that can be applied in practice.

Incidence and outcomes of ventilator-associated tracheobronchitis and pneumonia

BACKGROUND

Prolonged intubation with mechanical ventilation carries a risk for ventilator-associated respiratory infections manifest as tracheobronchitis or pneumonia. This study analyzed natural history, incidence, and outcomes of patients developing ventilator-associated tracheobronchitis and pneumonia.

METHODS

We studied 188 mixed intensive care unit (ICU) patients intubated ≥48 hours for the development of tracheobronchitis defined as quantitative endotracheal aspirate ≥10(5) cfu/mL plus at least 2 clinical criteria (fever, leukocytosis, or purulent sputum). Pneumonia was defined as microbiologic criteria for tracheobronchitis and a new and persistent infiltrate on chest radiograph.

RESULTS

Airways of 41 (22%) patients became heavily colonized with a bacterial pathogen(s) at a concentration of ≥10(5) cfu/mL. Tracheobronchitis developed in 21 (11%) study patients, of which 6 (29%) later progressed to pneumonia. Including these 6 patients, 28 (15%) study patients developed pneumonia. Multidrug-resistant pathogens were isolated in 39% of pneumonia patients. Patients with tracheobronchitis and pneumonia had significantly more ventilator days and longer stays in the ICU (P ≤.02).

CONCLUSIONS

Approximately one third of tracheobronchitis patients later developed pneumonia. Patients with tracheobronchitis or pneumonia experienced significantly more ventilator days and longer ICU stays, but had no difference in mortality. Better patient outcomes and reduced health care costs may be achieved by earlier treatment of ventilator-associated respiratory infections, manifest as tracheobronchitis or pneumonia.

Predictors and outcomes of pneumonia in patients with spontaneous intracerebral hemorrhage

OBJECTIVES

Pneumonia is an important complication of spontaneous intracerebral hemorrhage (sICH). The purpose of this study was to determine the predictors and outcomes of the development of pneumonia in patients with sICH.

METHODS

In total, 290 consecutive patients with sICH admitted within 24 hours of stroke onset were investigated in a single center, retrospective study from January 2006 to July 2009. Clinical, biochemical, and imaging variables were registered. Stroke severity and functional outcomes were evaluated with the Glasgow Coma Scale (GCS) and modified Rankin Scale (mRS). Baseline variables that predicted pneumonia were investigated and outcomes were assessed.

RESULTS

The association of our primary exposure variables, such as mechanical ventilation, tube feeding, dysphagia, and tracheostomy, with pneumonia was highly significant (P < .0001, for each variable). For mechanical ventilation, we observed an odds ratio (OR; 95% confidence interval [CI]) of 9.42 (4.24-20.9); for tube feeding, OR = 22.3 (8.91-55.8); for dysphagia, OR = 13.1 (4.66-36.7); and for tracheostomy, OR = 26.8 (8.02-89.3). After adjustment of potential confounders including GCS and mRS on admission, the use of angiotensin-converting enzyme inhibitors, proton pump inhibitors, and H2 blockers, all the adjusted OR (ORa) remained significant. For mechanical ventilation, the minimum ORa was 3.72 (95% CI: 1.68-8.26) when adjusted for GCS. For both dysphagia and tracheostomy, mRS reduced OR to 7.46 (95% CI: 3.34-10.6) in the case of dysphagia with an ORa of 16.2 (95% CI: 4.98 to 52.8) for tracheostomy. For tube feeding, both GCS and mRS reduced ORa; the former to 14.7 (95% CI: 6.16-35.0) and the latter to 15.7 (95% CI: 6.63-37.0). Pneumonia shows a significant effect on the morbidity (P = .003), length of stay (P < .0001), and mortality (P = .041) rate of the patients.

CONCLUSION

Mechanical ventilation, tube feeding, dysphagia, and tracheostomy are exposures associated with increased risk of the development of pneumonia in patients with sICH. Pneumonia is associated with an increase in morbidity, length of stay, and mortality among patients with sICH.

Aerosolized antibiotics in the intensive care unit

This review summarizes recent clinical data examining the use of aerosolized antimicrobial therapy for the treatment of respiratory tract infections in mechanically ventilated patients in the intensive care unit. Aerosolized antibiotics provide high concentrations of drug in the lung without the systemic toxicity associated with the intravenous antibiotics. First introduced in the 1960s as a treatment of tracheobronchitis and bronchopneumonia caused by Pseudomonas aeruginosa, now, more than 40 years later, there is a resurgence of interest in using this mode of delivery as a primary therapy for ventilator-associated tracheobronchitis and an adjunctive therapy for ventilator-associated pneumonia.

Diagnosis of ventilator-associated respiratory infections (VARI): microbiologic clues for tracheobronchitis (VAT) and pneumonia (VAP)

Intubated patients are at risk of bacterial colonization and ventilator-associated respiratory infection (VARI). VARI includes tracheobronchitis (VAT) or pneumonia (VAP). VAT and VAP caused by multidrug-resistant (MDR) pathogens are increasing in the United States and Europe. In patients with risk factors for MDR pathogens, empiric antibiotics are often initiated for 48 to 72 hours pending the availability of pathogen identification and antibiotic sensitivity data. Extensive data indicate that early, appropriate antibiotic therapy improves outcomes for patients with VAP. Recognizing and treating VARI may allow earlier appropriate therapy and improved patient outcomes.

The role of the endotracheal tube cuff in microaspiration

The cuff of the endotracheal tube (ETT) is designed to provide a seal within the airway, allowing airflow through the ETT but preventing passage of air or fluids around the ETT. Deliberate or inadvertent movement of the ETT may affect cuff pressure or shift folds in the cuff, mobilizing pooled secretions. When this seal is compromised, microaspirations contaminated with gastric contents or bacterially colonized oral secretions can occur that leave the patient susceptible to a host of problems, such as hypoxia, pneumonitis, and respiratory infections. These complications are costly in terms of morbidity and mortality, as well as hospital expense. We will discuss the role of the ETT cuff in microaspiration and identify potential directions for future research to improve outcomes in mechanically ventilated patients.

Inhaled antibiotic therapy for ventilator-associated tracheobronchitis and ventilator-associated pneumonia: an update

Ventilator-associated pneumonia (VAP) remains a leading cause of morbidity and mortality in mechanically-ventilated patients in the Intensive Care Unit (ICU). Ventilator-associated tracheobronchitis (VAT) was previously believed to be an intermediate stage between colonization of the lower respiratory tract and VAP. More recent data, however, suggest that VAT may be a separate entity that increases morbidity and mortality, independently of the occurrence of VAP. Some, but not all, patients with VAT progress to develop VAP. Although inhaled antibiotics alone could be effective for the treatment of VAP, the current consensus of opinion favors their role as adjuncts to systemic antimicrobial therapy for VAP. Inhaled antibiotics are increasingly employed for salvage therapy in patients with VAP due to multi-drug resistant Gram-negative bacteria. In contrast to VAP, VAT could be effectively treated with inhaled antibiotic therapy alone or in combination with systemic antimicrobials.

Ventilator-associated tracheitis in children: does antibiotic duration matter?

BACKGROUND

The optimal duration of antibiotic therapy for ventilator-associated tracheitis (VAT) has not been defined, which may result in unnecessarily prolonged courses of antibiotics. The primary objective of this study was to determine whether prolonged-course (≥7 days in duration) therapy for VAT was more protective against progression to hospital-acquired pneumonia (HAP) or ventilator-associated pneumonia (VAP), compared with short-course antibiotics (<7 days in duration). The secondary objective was to determine whether prolonged-course therapy was more likely to result in the acquisition of multidrug-resistant organisms (MDROs) compared with short-course therapy.

METHODS

We conducted a retrospective cohort study of children ≤18 years of age hospitalized in the intensive care unit and intubated for ≥48 h from January 2007 through December 2009 who received antibiotic therapy for VAT.

RESULTS

Of the 1616 patients intubated for at least 48 h, 150 received antibiotics for clinician-suspected VAT, although only 118 of these patients met VAT criteria. Prolonged-course antibiotics were not protective against subsequent development of HAP or VAP (hazard ratio [HR], 1.08; 95% confidence interval [CI], 0.40-2.91). Factors associated with subsequent MDRO colonization or infection included prolonged-course antibiotic therapy (HR, 5.15; 95% CI, 1.54-7.19), receipt of combination antibiotic therapy (HR, 3.24; 95% CI, 1.54-6.82), and days of hospital exposure prior to completing antibiotic therapy (HR, 1.08; 95% CI, 1.04-1.12).

CONCLUSIONS

A prolonged course of antibiotics for VAT does not appear to protect against progression to HAP or VAP compared with short-course therapy. Furthermore, prolonged antibiotic courses were associated with a significantly increased risk of subsequent MDRO acquisition.

The diagnostic dilemma of ventilator-associated pneumonia in critically ill children

OBJECTIVE

A review of the existing literature on ventilator-associated pneumonia in children with emphasis on problems in diagnosis.

DATA SOURCES

A systematic literature review from 1947 to 2010 using Ovid MEDLINE, PubMed, Cochrane Central Register of Controlled Trials, and ISI Web of Science using key words "ventilator associated pneumonia" and "children." Where pediatric data were lacking, appropriate adult studies were reviewed and similarly referenced.

STUDY SELECTION

Two hundred sixty-two pediatric articles were reviewed and data from 48 studies selected. Data from 61 adult articles were also included in this review.

DATA EXTRACTION AND SYNTHESIS

Ventilator-associated pneumonia is the second most common nosocomial infection and the most common reason for antibiotic use in the pediatric intensive care unit. Attributable mortality is uncertain but ventilator-associated pneumonia is associated with significant morbidity and cost. Diagnosis is problematic in that clinical, radiologic, and microbiologic criteria lack sensitivity and specificity relative to autopsy histopathology and culture. Qualitative tracheal aspirate cultures are commonly used in diagnosis but lack specificity. Quantitative tracheal aspirate cultures have sensitivity (31-69%) and specificity (55-100%) comparable to bronchoalveolar lavage (11-90% and 43-100%, respectively) but concordance for the same bacterial species when compared with autopsy lung culture was better for bronchoalveolar lavage (52-90% vs. 50-76% for quantitative tracheal aspirate). Staphylococcus aureus and Pseudomonas species are the most common organisms, but microbiologic flora change over time and with antibiotic use. Initial antibiotics should offer broad-spectrum coverage but should be narrowed as clinical response and cultures dictate.

CONCLUSIONS

Ventilator-associated pneumonia is an important nosocomial infection in the pediatric intensive care unit. Conclusions regarding epidemiology, treatment, and outcomes are greatly hampered by the inadequacies of current diagnostic methods. We recommend a more rigorous approach to diagnosis by using the Centers for Disease Control and Prevention algorithm. Given that ventilator-associated pneumonia is the most common reason for antibiotic use in the pediatric intensive care unit, more systematic studies are sorely needed.

Antimicrobial resistance of bacterial isolates from respiratory care wards in Taiwan: a horizontal surveillance study comparison of the characteristics of nosocomial infection and antimicrobial-resistant bacteria in adult Intensive Care Units and two respiratory care facilities for mechanically ventilated patients at a tertiary care centre in Taiwan

The objectives of this study were to compare the incidence of nosocomial infections (NIs) and the distribution of resistant nosocomial pathogens in adult Intensive Care Units (ICUs) and two respiratory care facilities for prolonged mechanically ventilated patients [i.e. the respiratory care centre (RCC) and the respiratory care ward (RCW)] in a 1100-bed tertiary care hospital in Taiwan from 2003 to 2006. The overall incidences of NI for adult ICUs, the RCC and the RCW were 14.0, 10.3 and 5.0 per 1000 patient-days, respectively. Urinary tract infections, bloodstream infections and pneumonias occurred most frequently. The most common reported microorganisms in adult ICUs were non-fermentative Gram-negative bacilli (NFGNB) (33.0%), Enterobacteriaceae (26.5%), Candida spp. (18.2%), Staphylococcus aureus (8.9%), coagulase-negative staphylococci (CoNS) (4.9%) and enterococci (4.5%). In comparison, RCW patients had a higher proportion of NIs caused by S. aureus [odds ratio (OR)=1.9], enterococci (OR=2.2) and Enterobacteriaceae (OR=2.2), but a lower proportion of CoNS (OR=0.3), NFGNB (OR=0.5) and Candida spp. (OR=0.2). RCW patients had higher incidence rates of methicillin-resistant S. aureus (OR=4.91) and extended-spectrum β-lactamase-producing Enterobacteriaceae (OR=4.06) than ICU patients. Further study is needed to delineate the mechanisms responsible for the differences in resistance profile amongst pathogens associated with nosocomial infection in ICUs, RCCs and RCWs.

Ventilator-associated tracheobronchitis in a mixed surgical and medical ICU population

BACKGROUND

Ventilator-associated tracheobronchitis (VAT) is considered an intermediate condition between bacterial airway colonization and ventilator-associated pneumonia (VAP). The purpose of this prospective cohort study was to further characterize VAT in terms of incidence, etiology, and impact on patient outcomes.

METHODS

Patients intubated for >48 h in the surgical and medical ICUs of Barnes-Jewish Hospital were screened daily for the development of VAT and VAP over 1 year. Patients were followed until hospital discharge or death, and patient demographics, causative pathogens, and clinical outcomes were recorded.

RESULTS

A total of 28 patients with VAT and 83 with VAP were identified corresponding to frequencies of 1.4% and 4.0%, respectively. VAP was more common in surgical than medical ICU patients (5.3% vs 2.3%; P<.001), but the occurrence of VAT was similar between surgical and medical patients (1.3% vs 1.5%; P=.845). VAT progressed to VAP in nine patients (32.1%) despite antibiotic therapy. There was no significant difference in hospital mortality between patients with VAP and VAT (19.3% vs 21.4%; P=.789). VAT was caused by a multidrug-resistant (MDR) pathogen in nine cases (32.1%).

CONCLUSION

VAT occurs less commonly than VAP but at a similar incidence in medical and surgical ICU patients. VAT frequently progressed to VAP, and patients diagnosed with VAT had similar outcomes to those diagnosed with VAP, suggesting that antimicrobial therapy is appropriate for VAT. VAT is also frequently caused by MDR organisms, and this should be taken into account when choosing antimicrobial therapy.

MDCT of trachea and main bronchi

Tracheobronchial imaging has undergone a major revolution since the advent of MDCT. The improved spatial and temporal resolution not only allows reformatting images that enhance the comprehension of disease before bronchoscopy or surgery, it has introduced newer techniques such as dynamic expiratory imaging to evaluate for tracheomalacia, which can be a subtle, but a confounding entity for patients and clinician alike. Tracheobronchial diseases can be arbitrarily divided into those that cause focal and diffuse narrowing and widening. Such groupings can help develop a practical approach in evaluating diseases of the central airways.

MDCT of trachea and main bronchi

Tracheobronchial imaging has undergone a major revolution. The improved spatial and temporal resolution has introduced newer techniques such as dynamic expiratory imaging to evaluate for tracheomalacia. This article describes these techniques.

Comparative analysis of the virulence of invertebrate and mammalian pathogenic bacteria in the oral insect infection model Galleria mellonella

Infection of Galleria mellonella by feeding a mixture of Bacillus thuringiensis spores or vegetative bacteria in association with the toxin Cry1C results in high levels of larval mortality. Under these conditions the toxin or bacteria have minimal effects on the larva when inoculated separately. In order to evaluate whether G. mellonella can function as an oral infection model for human and entomo-bacterial pathogens, we tested strains of Bacillus cereus, Bacillus anthracis, Enterococcus faecalis, Listeria monocytogenes, Pseudomonas aeruginosa and a Drosophila targeting Pseudomonas entomophila strain. Six B. cereus strains (5 diarrheal, 1 environmental isolate) were first screened in 2nd instar G. mellonella larvae by free ingestion and four of them were analyzed by force-feeding 5th instar larvae. The virulence of these B. cereus strains did not differ from the B. thuringiensis virulent reference strain 407Cry(-) with the exception of strain D19 (NVH391/98) that showed a lower virulence. Following force-feeding, 5th instar G. mellonella larvae survived infection with B. anthracis, L. monocytogenes, E. faecalis and P. aeruginosa strains in contrast to the P. entomophila strain which led to high mortality even without Cry1C toxin co-ingestion. Thus, specific virulence factors adapted to the insect intestine might exist in B. thuringiensis/B. cereus and P. entomophila. This suggests a co-evolution between host and pathogens and supports the close links between B. thuringiensis and B. cereus and more distant links to their relative B. anthracis.