Appropriateness and delay to initiate therapy in ventilator-associated pneumonia

Impact of clinical severity index, infective pathogens, and initial empiric antibiotic use on hospital mortality in patients with ventilator-associated pneumonia

BACKGROUND

The prompt initial use of appropriate antibiotics should improve mortality rates in adults with ventilator-associated pneumonia (VAP). However, the incidence of multidrug-resistant (MDR) pathogen infections is on the rise, and the choice of the initial empiric antibiotic may be challenging. We investigated whether appropriate initial antibiotic therapy, infective pathogens, and the clinical severity index influence hospital mortality in patients with VAP and determined independent risk factors for the same.

METHODS

This study evaluated 163 adult patients (aged ≥ 18 years) at Chang Gung Memorial Hospital, Kaohsiung, Taiwan, from January 1, 2007, to January 31, 2008. Eligibility was evaluated based on criteria for VAP. Sequential Organ Failure Assessment (SOFA) scores, Acute Physiological Assessment and Chronic Health Evaluation II (APACHE II) scores, oxygenation index, underlying comorbidities, septic shock status, previous tracheostomy status, and factors related to pneumonia were collected for analysis.

RESULTS

Ninety-two patients survived from a total 163 patients with VAP during the course of their confinement in the intensive care unit. Multivariable logistic regression analysis identified that a pre-existing Charlson Comorbidity Index score (P = .011), initial oxygenation index (P = .025), SOFA score (P = .043), VAP caused by Acinetobacter baumanii (P = .030), and infection with MDR pathogens (P = .003) were independent risk factors for hospital mortality in patients with VAP.

CONCLUSION

High Charlson Comorbidity Index score, high initial oxygenation index, high SOFA score, and infection with Acinetobacter baumannii or MDR pathogens significantly affect hospital mortality in patients with VAP.

Bacterial pathogens of ventilator associated pneumonia in a tertiary referral hospital

Background

This study evaluates the bacterial pathogens of Ventilator-associated pneumonia (VAP) in a tertiary referral hospital.

Methods

A total of 109 bacterial pathogens from 91 adult patients with VAP, who were admitted to the medical intensive care unit from January 2008 to December 2009, were examined. Clinical characteristics, bacterial pathogens, and resistance profiles were analyzed.

Results

Staphylococcus aureus (44%) was the most frequently isolated. Acinetobacter baumanii (30%), Pseudomonas aeruginosa (12%), Stenotrophomonas maltophilia (7%), Klebsiella pneumoniae (6%), and Serratia marcescens (2%) were isolated from the transtracheal aspirates or bronchoalveolar lavage in patients with VAP. There was no significant difference of bacterial pathogens between early and late onset VAP. All isolated S. aureus were methicillin resistant S. aureus; the imipenem resistance rate of A. baumanii was 69%.

Conclusion

The two most frequent pathogens of VAP were S. aureus and A. baumanii. There were no pathogenic differences between early and late onset VAP.

Factors predicting ventilator dependence in patients with ventilator-associated pneumonia

Objectives. To determine risk factors associated with ventilator dependence in patients with ventilator-associated pneumonia (VAP). Study Design. A retrospective study was conducted at Chang Gung Memorial Hospital, Kaohsiung, from January 1, 2007 to January 31, 2008. Methods. This study evaluated 163 adult patients (aged ≥18 years). Eligibility was evaluated according to the criterion for VAP, Sequential Organ Failure Assessment (SOFA) score, Acute Physiological Assessment and Chronic Health Evaluation II (APACHE II) score. Oxygenation index, underlying comorbidities, septic shock status, previous tracheostomy status, and factors related to pneumonia were collected for analysis. Results. Of the 163 VAP patients in the study, 90 patients survived, yielding a mortality rate of 44.8%. Among the 90 surviving patients, only 36 (40%) had been weaned off ventilators at the time of discharge. Multivariate logistic regression analysis was used to identify underlying factors such as congestive cardiac failure (P = 0.009), initial high oxygenation index value (P = 0.04), increased SOFA scores (P = 0.01), and increased APACHE II scores (P = 0.02) as independent predictors of ventilator dependence. Results from the Kaplan-Meier method indicate that initial therapy with antibiotics could increase the ventilator weaning rate (log Rank test, P < 0.001). Conclusions. Preexisting cardiopulmonary function, high APACHE II and SOFA scores, and high oxygenation index were the strongest predictors of ventilator dependence. Initial empiric antibiotic treatment can improve ventilator weaning rates at the time of discharge.

Empiric antibiotics pending bronchoalveolar lavage data in patients without pneumonia significantly alters the flora, but not the resistance profile, if a subsequent pneumonia develops

INTRODUCTION

Ventilator-associated pneumonia (VAP) occurs in up to 25% of mechanically ventilated patients, with an associated mortality up to 50%. Early diagnosis and appropriate empiric antibiotic coverage of VAP are crucial. Given the multitude of noninfectious clinical and radiographic anomalies within trauma patients, microbiology from bronchioalveolar lavage (BAL) is often needed. Empiric antibiotics are administered while awaiting BAL culture data. Little is known about the effects of these empiric antibiotics on patients with negative BAL microbiology if a subsequent VAP occurs during the same hospital course.

METHODS

This is a retrospective chart review of intubated trauma patients undergoing BAL for suspected pneumonia over a 3-y period at a Level 1 trauma center. All patients with suspected VAP undergoing a BAL receive empiric antibiotics. If microbiology data are negative at 72 h, all antibiotics are stopped; however, if the BAL returns with ≥10(5) colony-forming units per milliliter, the diagnosis of VAP is confirmed. We divided patients into three groups. Group 1 consisted of patients in whom the initial BAL was positive for VAP. Group 2 consisted of patients with an initial negative BAL, who subsequently developed VAP at a later point in the hospital course. Group 3 consisted of patients with negative BAL who did not develop a subsequent VAP.

RESULTS

We obtained 499 BAL specimens in 185 patients over the 3-y period. A total of 14 patients with 23 BAL specimens initially negative for VAP subsequently developed VAP later during the same hospital stay. These patients did not have an increase in the hospital length of stay, intensive care unit days, ventilator days, or mortality compared with those who had a positive culture on the first suspicion of VAP. There was a significant increase in the percentage of Enterobacter (21% versus 8%) and Morganella (8% versus 0%) as the causative organism in these 14 patients when the VAP occurred. Furthermore, the profile of the top two organisms in each group changed. Enterobacter (21%) and Pseudomonas (17%) were the principal organisms in the initial BAL-negative group, whereas the two predominant strains in the initial positive BAL group were methicillin-sensitive Staphylococcus aureus (21%) and Haemophilus influenza (11%). Interestingly, methicillin-resistant S. aureus remained the third most common organism in both groups. Empiric antibiotics also did not seem to induce the growth of multidrug-resistant organisms, and there was no increased rate of secondary infections such as Clostridium difficile.

CONCLUSIONS

Ventilator-associated pneumonia remains a significant cause of morbidity and mortality in mechanically ventilated trauma patients. The diagnosis and treatment of VAP continue to be challenging. Once clinically suspected, empiric coverage decreases morbidity and mortality. Our data demonstrate that patients who receive empiric coverage exhibit a significantly different microbiologic profile compared with those who had an initial positive BAL culture. Initial empiric antibiotics in BAL-negative patients were not associated with an increase in multidrug-resistant organisms, hospital, or intensive care unit length of stay, ventilator days, and mortality or secondary infections.

Preventing ventilator-associated pneumonia: does the evidence support the practice?

Ventilator-associated pneumonia (VAP) is among the most common infections in patients requiring endotracheal tubes with mechanical ventilation. Ventilator-associated pneumonia is associated with increased hospital costs, a greater number of days in the intensive care unit, longer duration of mechanical ventilation, and higher mortality. Despite widely accepted recommendations for interventions designed to reduce rates of VAP, few studies have assessed the ability of these interventions to improve patient outcomes. As the understanding of VAP advances and new technologies to reduce VAP become available, studies should directly assess patient outcomes before the health care community implements specific prevention approaches in clinical practice.

Implications of endotracheal tube biofilm in ventilator-associated pneumonia response: a state of concept

INTRODUCTION

Biofilm in endotracheal tubes (ETT) of ventilated patients has been suggested to play a role in the development of ventilator-associated pneumonia (VAP). Our purpose was to analyze the formation of ETT biofilm and its implication in the response and relapse of VAP.

METHODS

We performed a prospective, observational study in a medical intensive care unit. Patients mechanically ventilated for more than 24 hours were consecutively included. We obtained surveillance endotracheal aspirates (ETA) twice weekly and, at extubation, ETTs were processed for microbiological assessment and scanning electron microscopy.

RESULTS

Eighty-seven percent of the patients were colonized based on ETA cultures. Biofilm was found in 95% of the ETTs. In 56% of the cases, the same microorganism grew in ETA and biofilm. In both samples the most frequent bacteria isolated were Acinetobacter baumannii and Pseudomonas aeruginosa. Nineteen percent of the patients developed VAP (N = 14), and etiology was predicted by ETA in 100% of the cases. Despite appropriate antibiotic treatment, bacteria involved in VAP were found in biofilm (50%). In this situation, microbial persistence and impaired response to treatment (treatment failure and relapse) were more frequent (100% vs 29%, P = 0.021; 57% vs 14%, P = 0.133).

CONCLUSIONS

Airway bacterial colonization and biofilm formation on ETTs are early and frequent events in ventilated patients. There is microbiological continuity between airway colonization, biofilm formation and VAP development. Biofilm stands as a pathogenic mechanism for microbial persistence, and impaired response to treatment in VAP.

Attributable mortality of ventilator-associated pneumonia

PURPOSE OF REVIEW

To critically discuss the attributable mortality of ventilator-associated pneumonia (VAP) and potential sources of variation.

RECENT FINDINGS

The review will cover the available estimates (0-50%). It will also explore the source of variation because of definition of VAP (being lower if inaccurate), case-mix issues (being lower for trauma patients), the severity of underlying illnesses (being maximal when the severity of underlying illness is intermediate), and on the characteristics and the severity of the VAP episode. Another important source of variation is the use of poorly appropriate statistical models (estimates biased by lead time bias and competing events). New extensions of survival models which take into account the time dependence of VAP occurrence and competing risks allow less biased estimation as compared with traditional models.

SUMMARY

Attributable mortality of VAP is about 6%. Accurate diagnostic methods are key to properly estimating it. Traditional statistical models should no longer be used to estimate it. Prevention efforts targeted on patients with intermediate severity may result in the most important outcome benefits.

Ventilator-associated pneumonia: a comprehensive review

Ventilator-associated pneumonia (VAP) is the most frequent and severe infection acquired in the intensive care unit, leading to prolonged mechanical ventilation and excess mortality. This article reviews the different aspects of VAP, such as risk factors, causative agents, and approaches to diagnosis, treatment, and prevention. Several aspects of VAP are still considered controversial.

Outcome of ventilator-associated pneumonia: Impact of antibiotic therapy and other factors

BACKGROUND

Ventilator-associated pneumonia (VAP) is the most frequent infection in patients intubated for longer than 48 hours. There is a great interest in determining the factors influencing the outcome of VAP, as it may help in reducing the associated morbidity and mortality. This study aimed to determine the impact of appropriate antibiotic therapy based on endotracheal aspirate cultures on the outcome of VAP. We have also studied the other factors that may influence the outcome of VAP.

METHOD

A cohort study was conducted in the intensive care units of a tertiary care hospital in South India over a period of 15 months. The outcome of VAP was assessed by prolongation of the duration of mechanical ventilation and/or death of the patient.

RESULTS

The duration of mechanical ventilation was significantly prolonged in patients with VAP (16.61 ± 8.2 d vs. 8.21 ± 5.9 d, P < 0.0001). VAP patients receiving partially or totally inappropriate therapy (defined as lack of coverage of one or all the significant VAP pathogens) were at significantly high risk for death (Relative risk, 2.00; 95% confidence interval, 1.14 to 3.52; P 0.0008). A delay of > 2 days in administering the first dose of appropriate antibiotic therapy significantly prolonged the duration of ventilation (P < 0.0001). Infection by multi-drug resistant pathogens, polymicrobial infection and time of onset of VAP did not have significant impact on the outcome of VAP.

CONCLUSION

Early administration of appropriate antibiotic therapy, based on the antibiogram of the VAP pathogens identified by quantitative culture of endotracheal aspirate, could lead to an improved outcome of patients with ventilator-associated pneumonia.

Severe sepsis and septic shock in the elderly: An overview

The incidence of severe sepsis and septic shock is increasing in the older population leading to increased admissions to the intensive care units (ICUs). The elderly are predisposed to sepsis due to co-existing co-morbidities, repeated and prolonged hospitalizations, reduced immunity, functional limitations and above all due to the effects of aging itself. A lower threshold and a higher index of suspicion is required to diagnose sepsis in this patient population because the initial clinical picture may be ambiguous, and aging increases the risk of a sudden deterioration in sepsis to severe sepsis and septic shock. Management is largely based on standard international guidelines with a few modifications. Age itself is an independent risk factor for death in patients with severe sepsis, however, many patients respond well to timely and appropriate interventions. The treatment should not be limited or deferred in elderly patients with severe sepsis only on the grounds of physician prejudice, but patient and family preferences should also be taken into account as the outcomes are not dismal. Future investigations in the management of sepsis should not only target good functional recovery but also ensure social independence and quality of life after ICU discharge.

Severe sepsis and septic shock in the elderly: An overview

The incidence of severe sepsis and septic shock is increasing in the older population leading to increased admissions to the intensive care units (ICUs). The elderly are predisposed to sepsis due to co-existing co-morbidities, repeated and prolonged hospitalizations, reduced immunity, functional limitations and above all due to the effects of aging itself. A lower threshold and a higher index of suspicion is required to diagnose sepsis in this patient population because the initial clinical picture may be ambiguous, and aging increases the risk of a sudden deterioration in sepsis to severe sepsis and septic shock. Management is largely based on standard international guidelines with a few modifications. Age itself is an independent risk factor for death in patients with severe sepsis, however, many patients respond well to timely and appropriate interventions. The treatment should not be limited or deferred in elderly patients with severe sepsis only on the grounds of physician prejudice, but patient and family preferences should also be taken into account as the outcomes are not dismal. Future investigations in the management of sepsis should not only target good functional recovery but also ensure social independence and quality of life after ICU discharge.

Empiric antibiotic selection strategies for healthcare-associated pneumonia, intra-abdominal infections, and catheter-associated bacteremia

Initial selection and early deployment of appropriate/adequate empiric antimicrobial therapy is critical to minimize the significant morbidity and mortality associated with hospital- or healthcare-associated infections (HAIs). Initial empiric therapy that inadequately covers the pathogen(s) causing a serious HAI has been associated with increased mortality, longer hospital stay, and elevated healthcare costs. Moreover, subsequent modification of initial inadequate therapy, later in the disease process when culture results become available, may not remedy the impact of the initial choice. Because of this, it is important that initial empiric therapy covers the most likely pathogens associated with infection in a particular patient, even if this initial regimen turns out to be unnecessarily broad, based on subsequent culture results. The current paradigm for management of serious HAIs is to initiate empiric therapy with a broad-spectrum regimen covering likely pathogens, based on local surveillance and susceptibility data, and presence of risk factors for involvement of a resistant microorganism. Subsequent modification (de-escalation) of the initial regimen becomes possible later, when culture results are available and clinical status can be better assessed, 2 to 4 days after initiation of empiric therapy. When possible, de-escalation and other steps to modify antimicrobial exposure are important for minimizing risk of antimicrobial resistance development. This article examines the general process for selection of initial empiric antibiotic therapy for patients with HAIs, illustrated through 3 case studies dealing with healthcare-associated pneumonia, complicated intra-abdominal infection, and catheter-associated bacteremia, respectively.

Epidemiology and outcomes of complicated skin and soft tissue infections in hospitalized patients

Complicated skin and soft tissue infections (cSSTIs) are among the most rapidly increasing reasons for hospitalization. To describe inpatients with regard to patient characteristics, cSSTI origin, appropriateness of initial antibiotics, and outcomes, we performed a retrospective cohort study in patients hospitalized for cSSTI. To identify independent predictors of outcomes, we performed multivariate analyses. Of 1,096 eligible patients, 48.7% had health care-associated (HCA) cSSTI and 51.3% had community-acquired (CA) cSSTI. After adjustment for baseline variables, hospital length of stay (LOS) was longer for HCA than for CA cSSTI (difference, 2.1 days; 95% confidence interval [CI], 0.8 to 3.5; P < 0.05). Other covariates associated with a longer LOS were need for dialysis (regression coefficient ± standard error, 4.5 ± 1.1) and diabetic wound diagnosis (2.6 ± 1.0) (all P < 0.05). In the subset with culture-positive cSSTI within 24 h of admission, the most common pathogen was Staphylococcus aureus (298/449 [66.4%]), of which 74.8% (223/298) were methicillin-resistant S. aureus (MRSA). Eighty-three patients (18.5%) received inappropriate initial antibiotics. After adjustment for other variables, the following were associated with inappropriate initial therapy: direct admission to hospital (not via emergency department), cSSTI caused by MRSA or mixed pathogens, and cSSTI caused by pathogens other than S. aureus or streptococci (all P < 0.05). We did not find an association between inappropriate therapy and outcomes, except in the subset with ulcers (adjusted odds ratio, 11.8; 95% CI, 1.3 to 111.1; P = 0.03). More studies are needed to examine the impact of HCA cSSTI and inappropriate initial therapy on outcomes.

High prevalence of multidrug-resistant nonfermenters in hospital-acquired pneumonia in Asia

RATIONALE

Hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP) remain important causes of morbidity and mortality. Increasing antimicrobial resistance has aroused the concern of the failure of antibiotic treatment.

OBJECTIVES

To determine the distribution of the bacterial isolates of HAP and VAP, their antimicrobial resistance patterns, and impact of discordant antibiotic therapy on clinical outcome in Asian countries

METHODS

A prospective surveillance study was conducted in 73 hospitals in 10 Asian countries from 2008-2009. A total of 2,554 cases with HAP or VAP in adults were enrolled and 2,445 bacterial isolates were collected from 1,897 cases. Clinical characteristics and antimicrobial resistance profiles were analyzed.

MEASUREMENT AND MAIN RESULTS

Major bacterial isolates from HAP and VAP cases in Asian countries were Acinetobacter spp., Pseudomonas aeruginosa, Staphylococcus aureus, and Klebsiella pneumoniae. Imipenem resistance rates of Acinetobacter and P. aeruginosa were 67.3% and 27.2%, respectively. Multidrug-resistant rates were 82% and 42.8%, and extensively drug-resistant rates were 51.1% and 4.9%. Multidrug-resistant rate of K. pneumoniae was 44.7%. Oxacillin resistance rate of S. aureus was 82.1%. All-cause mortality rate was 38.9%. Discordant initial empirical antimicrobial therapy increased the likelihood of pneumonia-related mortality (odds ratio, 1.542; 95% confidence interval, 1.127-2.110).

CONCLUSIONS

Acinetobacter spp., P. aeruginosa, S. aureus, and K. pneumoniae are the most frequent isolates from adults with HAP or VAP in Asian countries. These isolates are highly resistant to major antimicrobial agents, which could limit the therapeutic options in the clinical practice. Discordant initial empirical antimicrobial therapy significantly increases the likelihood of pneumonia-related mortality.

Dosing of colistin-back to basic PK/PD

The increasing prevalence of multidrug-resistant Gram-negative bacteria worldwide has led to a re-evaluation of the previously discarded antibiotic, colistin. Despite its important role as salvage therapy for otherwise untreatable infections, dosage guidelines for the prodrug colistin methanesulfonate (CMS) are not scientifically based and have led to treatment failure and increased colistin resistance. In this review we summarise the recent progress made in the understanding of the pharmacokinetics of CMS and formed colistin with an emphasis on critically ill patients. The pharmacodynamics of colistin is also reviewed, with special attention given to the relationship between pharmacokinetics and pharmacodynamics and how the emerging data can be used to inform design of optimal dosage regimens. Recent data suggest the current dosage regimens of CMS are suboptimal in many critically ill patients.

Penetration of meropenem into epithelial lining fluid of patients with ventilator-associated pneumonia

Antibiotic penetration to the infection site is critical for obtaining a good clinical outcome in patients with ventilator-associated pneumonia (VAP). Surprisingly few studies have quantified the penetration of β-lactam agents into the lung, as measured by the ratio of area under the concentration-time curve (AUC) in epithelial lining fluid (ELF) to AUC in plasma (AUC(ELF)/AUC(plasma) ratio). These have typically involved noninfected patients. This study examines the penetration and pharmacodynamics of meropenem in the ELF among patients with VAP. Meropenem plasma and ELF concentration-time data were obtained from patients in a multicenter clinical trial. Concentration-time profiles in plasma and ELF were simultaneously modeled using a three-compartment model with zero-order infusion and first-order elimination and transfer (big nonparametric adaptive grid [BigNPAG]). A Monte Carlo simulation was performed to estimate the range of ELF/plasma penetration ratios one would expect to observe in patients with VAP, as measured by the AUC(ELF)/AUC(plasma) ratio. The range of AUC(ELF)/AUC(plasma) penetration ratios predicted by the Monte Carlo simulation was large. The 10th percentile of lung penetration was 3.7%, while the 90th percentile of penetration was 178%. The variability of ELF penetration is such that if relatively high ELF exposure targets are required to attain multilog kill or resistance suppression for bacteria like Pseudomonas aeruginosa, then even receiving the largest licensed dose of meropenem with an optimal prolonged infusion may not result in target attainment for a substantial fraction of the population.

Diagnosis, management and prevention of ventilator-associated pneumonia: an update

Ventilator-associated pneumonia (VAP) affects 10-20% of mechanically ventilated patients and is associated with increased morbidity and mortality and high costs. Early diagnosis is crucial for rapid appropriate antimicrobial therapy to be instituted, but debate remains as to the optimal diagnostic strategy. Noninvasive clinical-based diagnosis is rapid but may not be as accurate as invasive techniques. Increased use of biomarkers and advances in genomics and proteomics may help speed up diagnosis. Management of VAP relies principally on appropriate antimicrobial therapy, which should be selected according to individual patient factors, such as previous antibacterial therapy and length of hospitalization or mechanical ventilation, and local infection and resistance patterns. In addition, once bacterial culture and sensitivity results are available, broad-spectrum therapy should be de-escalated to provide a more specific, narrower-spectrum cover. Optimum duration of antibacterial therapy is difficult to define and should be tailored to clinical response. Biomarker levels may be useful to monitor response to therapy. With the high morbidity and mortality, prevention of VAP is important and several strategies have been shown to reduce the rates of VAP in mechanically ventilated patients, including using noninvasive ventilation where possible, and semi-recumbent positioning. Other potentially beneficial preventive techniques include subglottal suctioning, oral decontamination strategies and antimicrobial-coated endotracheal tubes, although further study is needed to confirm the cost effectiveness of these strategies.

Systematic review and meta-analysis of the efficacy of appropriate empiric antibiotic therapy for sepsis

Quantifying the benefit of early antibiotic treatment is crucial for decision making and can be assessed only in observational studies. We performed a systematic review of prospective studies reporting the effect of appropriate empirical antibiotic treatment on all-cause mortality among adult inpatients with sepsis. Two reviewers independently extracted data. Risk of bias was assessed using the Newcastle-Ottawa score. We calculated unadjusted odds ratios (ORs) with 95% confidence intervals for each study and extracted adjusted ORs, with variance, methods, and covariates being used for adjustment. ORs were pooled using random-effects meta-analysis. We examined the effects of methodological and clinical confounders on results through subgroup analysis or mixed-effect meta-regression. Seventy studies were included, of which 48 provided an adjusted OR for inappropriate empirical antibiotic treatment. Inappropriate empirical antibiotic treatment was associated with significantly higher mortality in the unadjusted and adjusted comparisons, with considerable heterogeneity occurring in both analyses (I(2) > 70%). Study design, time of mortality assessment, the reporting methods of the multivariable models, and the covariates used for adjustment were significantly associated with effect size. Septic shock was the only clinical variable significantly affecting results (it was associated with higher ORs). Studies adjusting for background conditions and sepsis severity reported a pooled adjusted OR of 1.60 (95% confidence interval = 1.37 to 1.86; 26 studies; number needed to treat to prevent one fatal outcome, 10 patients [95% confidence interval = 8 to 15]; I(2) = 46.3%) given 34% mortality with inappropriate empirical treatment. Appropriate empirical antibiotic treatment is associated with a significant reduction in all-cause mortality. However, the methods used in the observational studies significantly affect the effect size reported. Methods of observational studies assessing the effects of antibiotic treatment should be improved and standardized.

Recommendations for improving the design, conduct, and analysis of clinical trials in hospital-acquired pneumonia and ventilator-associated pneumonia

Overall decisions on the clinical use of new antimicrobials depend on the validity and reliability of the evidence from appropriately designed, conducted, and analyzed clinical trials. Because pneumonia is the sixth leading cause of death in the United States and the leading cause of infectious disease-related death, appropriate design of trials in hospital-acquired pneumonia and ventilator-associated pneumonia are an important public health issue. Several issues with the current design of trials in hospital-acquired pneumonia and/or ventilator-associated pneumonia potentially bias their results and raise questions about their validity. These issues are magnified in the context of noninferiority trials, in which bias can make interventions appear more similar, giving false-positive results of safety and effectiveness. The goal of this article is to provide a scientific basis for improving the validity, reliability, and efficiency of clinical trials in hospital-acquired pneumonia and/or ventilator-associated pneumonia to provide better information for decision making for patients, clinicians, regulators, and other stakeholders.

Medical resource utilization among patients with ventilator-associated pneumonia: pooled analysis of randomized studies of doripenem versus comparators

Introduction

Ventilator-associated pneumonia (VAP) is associated with increased medical resource utilization, but few randomized studies have been conducted to evaluate the effect of initial antibiotic therapy. To assess medical resource utilization in patients with VAP, we conducted a pooled analysis of two prospective, randomized, open-label, multicenter, phase III studies, which also showed that doripenem was clinically noninferior to comparators.

Methods

We assessed durations of mechanical ventilation, intensive care unit (ICU) stay, and hospitalization in patients with VAP who received at least 1 dose of doripenem or a comparator in the phase III studies. Comparators were piperacillin/tazobactam (study 1) and imipenem (study 2). We analyzed between-group differences in medical resource utilization endpoints by comparison of Kaplan-Meier curves with generalized Wilcoxon test and in microbiologic eradication rates by two-sided Fisher's exact test.

Results

625 patients with VAP were evaluated and received at least 1 dose of doripenem (n = 312) or a comparator (n = 313). Median durations of mechanical ventilation (7 versus 10 days; P = 0.008) and hospitalization (22 versus 26 days; P = 0.010) were shorter for doripenem than comparators; corresponding ICU stays were 12 and 13 days (P = 0.065). All-cause, overall mortality rates were similar (51/312 [16%] versus 47/313 [15%]; P = 0.648). MIC₉₀ values against Pseudomonas aeruginosa for doripenem versus imipenem were 4 versus 16 μg/mL in study 2. P. aeruginosa was eradicated from 16/24 (67%) doripenem recipients and 10/24 (42%) comparator recipients (P = 0.147). In patients with P. aeruginosa at baseline, median durations of mechanical ventilation (7 versus 13 days; P = 0.031) and ICU stay (13 versus 21 days; P = 0.027) were shorter for doripenem; corresponding hospital stays were 24 and 35 days (P = 0.129).

Conclusions

Doripenem was associated with lower medical resource utilization than comparators. Differences in antipseudomonal activity may have contributed to these findings.

Trial registration

ClinicalTrials.gov number NCT00211003 (study 1) and NCT00211016 (study 2).

Respiratory infections: a current and future threat

Despite all the medical progress in the last 50 years pulmonary infections continue to exact and extremely high human and economic cost. This review will focus on the human, pathogen and environmental factors that contribute to the continued global burden or respiratory diseases with a particular focus on areas where we might hope to see some progress in the coming decades.

Effectiveness of an aspiration risk-reduction protocol

BACKGROUND

Aspiration of gastric contents is a serious problem in critically ill, mechanically ventilated patients receiving tube feedings.

OBJECTIVES

The purpose of this study was to evaluate the effectiveness of a three-pronged intervention to reduce aspiration risk in a group of critically ill, mechanically ventilated patients receiving tube feedings.

METHODS

A two-group quasi-experimental design was used to compare outcomes of a usual care group (December 2002-September 2004) with those of an Aspiration Risk-Reduction Protocol (ARRP) group (January 2007-April 2008). The incidence of aspiration and pneumonia was compared between the usual care group (n = 329) and the ARRP group (n = 145). The ARRP had three components: maintaining head-of-bed elevation at 30 degrees or higher, unless contraindicated; inserting feeding tubes into distal small bowel, when indicated; and using an algorithmic approach for high gastric residual volumes.

RESULTS

Two of the three ARRP components were implemented successfully. Almost 90% of the ARRP group had mean head-of-bed elevations of 30 degrees or higher as compared to 38% in the usual care group. Almost three fourths of the ARRP group had feeding tubes placed in the small bowel as compared with less than 50% in the usual care group. Only three patients met the criteria for the high gastric residual volume algorithm. Aspiration was much lower in the ARRP group than that in the usual care group (39% vs. 88%, respectively). Similarly, pneumonia was much lower in the ARRP group than that in the usual care group (19% vs. 48%, respectively).

DISCUSSION

Findings from this study suggest that a combination of a head-of-bed position elevated to at least 30 degrees and use of a small-bowel feeding site can reduce the incidence of aspiration and aspiration-related pneumonia dramatically in critically ill, tube-fed patients.

[Assessing the usefulness of a permanently opened clinical microbiology laboratory]

Since 2005, the clinical microbiology laboratory of the Angers teaching hospital has implemented after hours service requiring the overnight presence of a technician specialized in bacteriology. During that time, bacterial identifications and antibiotic susceptibility testing to antimicrobial agents can be performed for critical samples.

OBJECTIVES

The authors wanted to evaluate the impact of the after-hours service on the decrease of delay from sampling to results, and from sampling to the implementation of an appropriate antimicrobial therapy. A therapy could be initiated, changed for more efficient agents, or changed to narrower-spectrum agents (major benefits).

METHODS

A 4-month prospective study was made. All samples for which identification and/or susceptibility testing were performed during after-hours service (continued analyses) were included in the study. Delays observed were compared with theoretical delays estimated in the absence of the after-hours service.

RESULTS

A minimum 24 hour-decrease of the delay for results was observed for 97 % of the 430 samples included. Overall, a major benefit was obtained for more than 25 % of the analyses, representing a cumulated 111-day benefit in days of efficient treatments and a cumulated 27-day benefit in days of prescription of narrower-spectrum agents.

DISCUSSION

This organization, unique in French hospitals, is directly related to the improvement of antimicrobial treatments, like antibiotic practice guidelines or infection disease specialists. It was evaluated as a relevant strategy, potentially cost saving, with a significant impact on both the efficiency of treatments and microbial ecology.

Delay of adequate empiric antibiotic therapy is associated with increased mortality among solid-organ transplant patients

Empiric antibiotic therapy is often prescribed prior to the availability of bacterial culture results. In some cases, the organism isolated may not be susceptible to initial empiric therapy (inadequate empiric therapy or IET). In solid-organ transplant recipients, the overall incidence and clinical importance of IET is unknown. We performed a retrospective cohort study of patients admitted from 2002 to 2004. Multiple logistic regression analyses were conducted to determine associations between potential determinants and mortality. IET was administered in 169/312 (54%) patients, with a hospital mortality rate that was significantly greater than those receiving adequate therapy (24.9% vs. 7.0%; relative risk [RR] 3.55; 95% confidence interval [CI], 1.85-6.83; p < 0.001). Regression analysis demonstrated that an increasing duration of IET (adjusted odds ratio [OR] at 24 h: 1.33; 95% CI: 1.15-1.53; p < 0.001), ICU-associated infections (adjusted OR: 6.27; 95% CI: 2.79-14.09; p < 0.001), prior antibiotic use (adjusted OR: 3.56; 95% CI: 1.51-8.41; p = 0.004) and increasing APACHE-II scores (adjusted OR: 1.26; 95% CI: 1.16-1.34; p < 0.001) were independently correlated with hospital mortality. IET is common and appears to be associated with an increased hospital mortality rate in the solid-organ transplant population.

Population pharmacokinetic analysis of colistin methanesulfonate and colistin after intravenous administration in critically ill patients with infections caused by gram-negative bacteria

Colistin is used to treat infections caused by multidrug-resistant gram-negative bacteria (MDR-GNB). It is administered intravenously in the form of colistin methanesulfonate (CMS), which is hydrolyzed in vivo to the active drug. However, pharmacokinetic data are limited. The aim of the present study was to characterize the pharmacokinetics of CMS and colistin in a population of critically ill patients. Patients receiving colistin for the treatment of infections caused by MDR-GNB were enrolled in the study; however, patients receiving a renal replacement therapy were excluded. CMS was administered at a dose of 3 million units (240 mg) every 8 h. Venous blood was collected immediately before and at multiple occasions after the first and the fourth infusions. Plasma CMS and colistin concentrations were determined by a novel liquid chromatography-tandem mass spectrometry method after a rapid precipitation step that avoids the significant degradation of CMS and colistin. Population pharmacokinetic analysis was performed with the NONMEM program. Eighteen patients (6 females; mean age, 63.6 years; mean creatinine clearance, 82.3 ml/min) were included in the study. For CMS, a two-compartment model best described the pharmacokinetics, and the half-lives of the two phases were estimated to be 0.046 h and 2.3 h, respectively. The clearance of CMS was 13.7 liters/h. For colistin, a one-compartment model was sufficient to describe the data, and the estimated half-life was 14.4 h. The predicted maximum concentrations of drug in plasma were 0.60 mg/liter and 2.3 mg/liter for the first dose and at steady state, respectively. Colistin displayed a half-life that was significantly long in relation to the dosing interval. The implications of these findings are that the plasma colistin concentrations are insufficient before steady state and raise the question of whether the administration of a loading dose would benefit critically ill patients.

Pharmacodynamic-based clinical pathway for empiric antibiotic choice in patients with ventilator-associated pneumonia

BACKGROUND

Because of the high frequency of multidrug resistant bacteria in our intensive care units (ICUs), we implemented a ventilator-associated pneumonia (VAP) clinical pathway based on unit-specific minimum inhibitory concentration (MIC) distributions and pharmacodynamic modeling in 3 of our ICUs.

METHODS

This was a prospective, observational evaluation with a historical control group in adult patients (n = 168) who met clinical and radiologic criteria for VAP. Monte Carlo simulation was used to determine antibiotic regimens having the greatest likelihood of achieving bactericidal exposures against Pseudomonas aeruginosa. Antibiotic regimens were incorporated into an ICU-specific computerized clinical pathway as empiric agents of choice.

RESULTS

Pharmacodynamic modeling found 3-hour infusions of cefepime 2 g every 8 hours or meropenem 2 g every 8 hours plus tobramycin and vancomycin would provide the greatest probability of empirically treating VAP in these ICUs. Infection-related mortality was reduced by 69% (8.5% vs 21.6%; P = .029), infection-related length of stay was shorter (11.7 +/- 8.1 vs 26.1 +/- 18.5; P < .001), and fewer superinfections were observed in patients treated on the pathway. A number of patients with nonsusceptible P aeruginosa were successfully treated with high-dose, 3-hour infusion regimens.

CONCLUSIONS

In our ICUs where multidrug resistant bacteria are common, an approach considering ICU-specific antibiotic MICs coupled with pharmacodynamic dosing strategies resulted in improved outcomes and shorter duration of treatments.

Procalcitonin kinetics within the first days of sepsis: relationship with the appropriateness of antibiotic therapy and the outcome

Introduction

Management of the early stage of sepsis is a critical issue. As part of it, infection control including appropriate antibiotic therapy administration should be prompt. However, microbiological findings, if any, are generally obtained late during the course of the disease. The potential interest of procalcitonin (PCT) as a way to assess the clinical efficacy of the empirical antibiotic therapy was addressed in the present study.

Methods

An observational cohort study including 180 patients with documented sepsis was conducted in our 15-bed medical intensive care unit (ICU). Procalcitonin measurement was obtained daily over a 4-day period following the onset of sepsis (day 1 (D1) to D4). The PCT time course was analyzed according to the appropriateness of the first-line empirical antibiotic therapy as well as according to the patient outcome.

Results

Appropriate first-line empirical antibiotic therapy (n = 135) was associated with a significantly greater decrease in PCT between D2 and D3 (ΔPCT D2–D3) (-3.9 (35.9) vs. +5.0 (29.7), respectively; P < 0.01). In addition, ΔPCT D2–D3 was found to be an independent predictor of first-line empirical antibiotic therapy appropriateness. In addition, a trend toward a greater rise in PCT between D1 and D2 was observed in patients with inappropriate antibiotics as compared with those with appropriate therapy (+5.2 (47.4) and +1.7 (35.0), respectively; P = 0.20). The D1 PCT level failed to predict outcome, but higher levels were measured in the nonsurvivors (n = 51) when compared with the survivors (n = 121) as early as D3 (40.8 (85.7) and 21.3 (41.0), respectively; P = 0.04). Moreover, PCT kinetics between D2 and D3 were also found to be significantly different, since a decrease ≥ 30% was expected in the survivors (log-rank test, P = 0.04), and was found to be an independent predictor of survival (odds ratio = 2.94; 95% confidence interval 1.22 to 7.09; P = 0.02).

Conclusions

In our study in an ICU, appropriateness of the empirical antibiotic therapy and the overall survival were associated with a greater decline in PCT between D2 and D3. Further studies are needed to assess the utility of the daily monitoring of PCT in addition to clinical evaluation during the early management of sepsis.

Ventilator-Associated Pneumonia; A Concise Review

Ventilator-associated pneumonia (VAP) continues to be the most common nosocomial infection in critically ill patients requiring mechanical ventilation. In this review data was sourced from Medline, the National Institute for Clinical Effectiveness (NICE), study authors and review articles. Development of VAP prolongs length of stay in the intensive care unit and may increase mortality. Although diagnosis is difficult, with little consensus on ideal diagnostic criteria, there is general agreement that rapid and accurate diagnosis of VAP is essential as delayed administration of appropriate antibiotic therapy increases mortality. Implementation of evidence-based strategies for the prevention of VAP may reduce morbidity, mortality and length of stay.

Predictive factors for septic shock in patients with ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is one of the most frequent infections in intensive care units (ICUs), and nearly 50% of patients with VAP develop septic shock. Septic shock is an independent predictor for mortality in these patients.

OBJECTIVE

To investigate the predictors for septic shock in VAP patients receiving appropriate antibiotic therapy.

METHODS

Eighty-nine patients with microbiologically confirmed VAP who were receiving appropriate antibiotic therapy were included in the study. They were divided into two groups according to the existence of septic shock. Clinical, hematological, biochemical and microbiological characteristics were compared.

RESULTS

Thirty-seven percent of the patients developed septic shock. Advanced age (OR 1.07, 95% CI 1.02-1.13, P = 0.009), lymphocytopenia (<1000/mm3) (OR 7.48, 95% CI 1.91-29, P = 0.004), high blood glucose levels >120 mg/dL (OR 4.75, 95% CI 1.38-16, P = 0.014), and increased clinical pulmonary infection scores (CPIS) (OR 1.64, 95% CI 1.16-2.33, P = 0.006) were identified as independent predictors for the development of septic shock.

CONCLUSION

Some clinical parameters such as lymphocytopenia, blood glucose >120 mg/dL, increasing age, and CPIS can predict septic shock during VAP, but large randomized controlled studies are needed to confirm these results.

The utility of the clinical pulmonary infection score

The most common infectious complication in critically ill patients is ventilator-associated pneumonia. Ventilator-associated pneumonia has significant morbidity and mortality, prolongs mechanical ventilation, and extends length of hospitalization. Despite its prevalence and impact, uniform diagnostic standards are lacking. The Centers for Disease Control, American Thoracic Society, and Infectious Diseases Society of America have recommended focus on improving preventive measures, establishing widely available and accurate diagnostic tools, and improving ventilator-associated pneumonia management with length of therapy guidelines. The purpose of this article is to review the evidence supporting the clinical pulmonary infection score as an adjunct to distinguish and detect clinically relevant ventilator-associated pneumonia and its use to guide length of therapy. This score combines clinical diagnostic criteria (tracheal secretion quantification and body temperature) with routinely obtained laboratory data (white blood cell count and oxygenation parameters), radiographic data, and bacteriological culture results. Limitations of clinical pulmonary infection score will be discussed.

Evidence-based algorithms for diagnosing and treating ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is widely recognized as a serious and common complication associated with high morbidity and high costs. Given the complexity of caring for heterogeneous populations in the intensive care unit (ICU), however, there is still uncertainty regarding how to diagnose and manage VAP.

OBJECTIVE

We recently conducted a national collaborative aimed at reducing health care-associated infections in ICUs of hospitals operated by the Hospital Corporation of America (HCA). As part of this collaborative, we developed algorithms for diagnosing and treating VAP in mechanically ventilated patients. In the current article, we (1) review the current evidence for diagnosing VAP, (2) describe our approach for developing these algorithms, and (3) illustrate the utility of the diagnostic algorithms using clinical teaching cases.

DESIGN

This was a descriptive study, using data from a national collaborative focused on reducing VAP and catheter-related bloodstream infections.

SETTING

The setting of the study was 110 ICUs at 61 HCA hospitals.

INTERVENTION

None.

MEASUREMENTS AND RESULTS

We assembled an interdisciplinary team that included infectious disease specialists, intensivists, hospitalists, statisticians, critical care nurses, and pharmacists. After reviewing published studies and the Centers for Disease Control and Prevention VAP guidelines, the team iteratively discussed the evidence, achieved consensus, and ultimately developed these practical algorithms. The diagnostic algorithms address infant, pediatric, immunocompromised, and adult ICU patients.

CONCLUSIONS

We present practical algorithms for diagnosing and managing VAP in mechanically ventilated patients. These algorithms may provide evidence-based real-time guidance to clinicians seeking a standardized approach to diagnosing and managing this challenging problem.

Risk factors for treatment failure in patients with ventilator-associated pneumonia receiving appropriate antibiotic therapy

PURPOSE

The aim of this study was to investigate modifiable risk factors and predictors for treatment failure (TF) in patients with ventilator-associated pneumonia (VAP) receiving appropriate antibiotic therapy.

MATERIALS AND METHODS

An observational cohort study performed in an intensive care unit (ICU) of a University hospital. Eighty-nine patients with VAP were enrolled in the study consecutively. Treatment failure was defined as lack of clinical and microbiological response to therapy within 2 weeks. Potential risk factors for TF, related with patients, microorganisms, and ICU therapies, were evaluated.

RESULTS

Mean age was 72 +/- 13 years. Fifty-three of the patients had TF. Patients with TF were older, had more comorbidities, higher admission and Acute Physiology and Chronic Health Evaluation Score (APACHE II)-VAP scores, lower daily carbohydrate intake, and lymphocyte number below 1000/mm(3) than the treatment success group. Transfusions, bacteremia, infection with multidrug-resistant microorganisms, initial bacterial load (CFU/mL), and steroid therapy were similar across the groups. Comorbidity (odds ratio [OR], 4.4; 95% CI, 1.2-16.8; P = .030), VAP-APACHE II scores above 16 (OR, 6.4; 95% CI, 2.1-18.6; P = .001), daily carbohydrate intake below 190 g/d (OR, 3; 95% CI,1.1-8.6; P = .038), lymphocyte number below 1000/mm3 (OR, 4.1; 95% CI, 1.3-12.9; P = .014) were independent predictors for TF.

CONCLUSIONS

Patients with comorbidities, who are severely ill and lymphocytopenic at the time of VAP diagnosis, are at high risk for TF.

Ventilator-associated pneumonia in adults in developing countries: a systematic review

BACKGROUND

Ventilator-associated pneumonia (VAP) is a leading cause of death in hospitalized patients, but there has been no systematic analysis of the incidence, microbiology, and outcome of VAP in developing countries or of the interventions most applicable in that setting.

METHODS

We reviewed MEDLINE (January 1966-April 2007) and bibliographies of the retrieved articles for all observational or interventional studies that examined the incidence, microbiology, outcome, and prevention of VAP in ventilated adults in developing countries. We evaluated the rates of VAP using the National Healthcare Safety Network (NHSN) definitions and the impact of VAP on the intensive care unit (ICU) length of stay (LOS) and mortality, and the impact of interventions used to reduce VAP rates.

RESULTS

The rates of VAP varied from 10 to 41.7 per 1000 ventilator-days and were generally higher than NHSN benchmark rates. Gram-negative bacilli were the most common pathogens (41-92%), followed by Gram-positive cocci (6-58%). VAP was associated with a crude mortality that ranged from 16% to 94% and with increased ICU LOS. Only a small number of VAP intervention studies were performed; these found that staff education programs, implementation of hand hygiene, and VAP prevention practice guidelines, and/or implementation of sedation protocol were associated with a significant reduction in VAP rates. Only one interventional study was a randomized controlled trial comparing two technologies, the rest were sequential observational. This study compared a heat and moisture exchanger (HME) to a heated humidifying system (HHS) and found no difference in VAP rates.

CONCLUSIONS

Based on the existing literature, the rate of VAP in developing countries is higher than NHSN benchmark rates and is associated with a significant impact on patient outcome. Only a few studies reported successful interventions to reduce VAP. There is a clear need for additional epidemiologic studies to better understand the scope of the problem. Additionally, more work needs to be done on strategies to prevent VAP, probably with emphasis on practical, low-cost, low technology, easily implemented measures.

Role of the infectious diseases specialist consultant on the appropriateness of antimicrobial therapy prescription in an intensive care unit

BACKGROUND

Use of routine microbiologic surveillance, antibiotic practice guidelines, and infectious diseases (ID) specialist consultation might contribute to achieve an early diagnosis and an appropriate antibiotic treatment of infections, particularly in an intensive care unit (ICU) setting.

METHODS

We conducted a prospective cohort study in an ICU over a period of 4 years (2001-2004). We studied all patients with a possible or definite diagnosis of infection who received antimicrobial treatment, analyzing the appropriateness of antimicrobial therapy prescription before (P1) and after (P2) the implementation (January 1, 2003) of a systematic ID specialist consultation program.

RESULTS

Among the 349 patients enrolled, we observed 205 infections during P1 and 197 during P2. Infections treated with appropriate antimicrobial therapy were 141 (68.8%) in P1 and 165 (83.7%) in P2 (P .0004). Compliance to the local guidelines for empirical antimicrobial therapy increased by 20.4% from P1 to P2 (P < .0001). Patients receiving an appropriate treatment had a significantly shorter duration of antibiotic treatment (P < .0001), mechanical ventilation (P < .0001), ICU stay (P < .0001), and reduced in-hospital mortality (P = .006). Adherence to local antibiotic therapy guidelines improved significantly from P1 (63.4%) to P2 (83.8%) (P < .0001).

CONCLUSION

The introduction of an ID specialist consultation program may improve the appropriateness of the antimicrobial therapy prescription in ICU and the adherence to the local antibiotic therapy guidelines. Furthermore, appropriate antibiotic therapy is associated with a reduction in both ICU and in-hospital mortality.

A prospective evaluation of the Infection Probability Score (IPS) in the intensive care unit

OBJECTIVES

Identification of infection remains a major challenge, particularly in acutely ill patients. The Infection Probability Score (IPS) was developed to help rule out infection in acutely ill patients. In the present study, we determined the IPS in acutely ill, intensive care unit (ICU) patients to assess its use in the diagnosis and treatment of infection.

METHODS

In this prospective, observational study, we enrolled 107 consecutive patients who were admitted to the ICU without antibiotic therapy. Patients were allocated to four groups according to the probability of infection determined from clinical and microbiological data and their IPS values were then evaluated daily throughout the ICU stay.

RESULTS

The IPS was higher in patients with the highest clinical probability of infection and decreased significantly in these patients after 5 days of effective antimicrobial therapy. The IPS remained below the cut-off value in non-infected patients. Patients in whom inadequate antimicrobial therapy was administered had a greater mortality than the other patients.

CONCLUSIONS

The IPS had a good predictive value for diagnosis of infection. In addition, dynamic evaluation of this score may help to assess the response to therapy.

Predicting pathogens causing ventilator-associated pneumonia using a Bayesian network model

BACKGROUND

We previously validated a Bayesian network (BN) model for diagnosing ventilator-associated pneumonia (VAP). Here, we report on the performance of the model to predict microbial causes of VAP and to select antibiotics.

METHODS

Pathogens were grouped into seven categories based upon the antibiotic susceptibility and epidemiological characteristics. Colonization of the upper respiratory tract was modelled in the BN and depended--in additional steps--on (i) duration of admission and ventilation, (ii) previous culture results and (iii) previous antibiotic use. A database with 153 VAP episodes and their microbial causes was used as reference standard. Appropriateness of antibiotic prescription, with fixed choices for pathogens predicted, was determined.

RESULTS

One hundred and seven VAP episodes were monobacterial and 46 were caused by two pathogens. Using duration of admission and ventilation only, areas under the receiver operating curve (AUC) ranged from 0.511 to 0.772 for different pathogen groups, and model predictions significantly improved when adding information on culture results, but not when adding information on antibiotic use. The best performing model (with all information) had AUC values ranging from 0.859 for Acinetobacter spp. to 0.929 for Streptococcus pneumoniae. With this model, 91 (85%) and 29 (63%) of all pathogen groups were correctly predicted for monobacterial and polymicrobial VAP, respectively. With fixed antibiotic choices linked to pathogen groups, 92% of all episodes would have been treated appropriately.

CONCLUSIONS

The BN models' performance to predict pathogens causing VAP improved markedly with information on colonization, resulting in excellent pathogen prediction and antibiotic selection. Prospective external validation is needed.