Noninvasive versus invasive microbial investigation in ventilator-associated pneumonia: evaluation of outcome

Clinical challenge of diagnosing non-ventilator hospital-acquired pneumonia and identifying causative pathogens: a narrative review

Non-ventilated hospital-acquired pneumonia (NV-HAP) is associated with a significant healthcare burden, arising from high incidence and associated morbidity and mortality. However, accurate identification of cases remains challenging. At present, there is no gold-standard test for the diagnosis of NV-HAP, requiring instead the blending of non-specific signs and investigations. Causative organisms are only identified in a minority of cases. This has significant implications for surveillance, patient outcomes and antimicrobial stewardship. Much of the existing research in HAP has been conducted among ventilated patients. The paucity of dedicated NV-HAP research means that conclusions regarding diagnostic methods, pathology and interventions must largely be extrapolated from work in other settings. Progress is also limited by the lack of a widely agreed definition for NV-HAP. The diagnosis of NV-HAP has large scope for improvement. Consensus regarding a case definition will allow meaningful research to improve understanding of its aetiology and the heterogeneity of outcomes experienced by patients. There is potential to optimize the role of imaging and to incorporate novel techniques to identify likely causative pathogens. This would facilitate both antimicrobial stewardship and surveillance of an important healthcare-associated infection. This narrative review considers the utility of existing methods to diagnose NV-HAP, with a focus on the significance and challenge of identifying pathogens. It discusses the limitations in current techniques, and explores the potential of emergent molecular techniques to improve microbiological diagnosis and outcomes for patients.

Role of bronchoscopy in the management of patients with suspected or suffering from ventilator-associated pneumonia: A meta-analysis

Background

The utility of bronchoscopy in the treatment of patients with ventilator-associated pneumonia (VAP) has been proposed, although prior research has yielded inconclusive findings. This systematic review and meta-analysis were conducted to examine the impact of bronchoscopy on mortality rates, duration of mechanical ventilation (MV), and length of stay in the intensive care unit (ICU) among patients with VAP.

Methods

Relevant randomized controlled trials (RCTs) and cohort studies were acquired by conducting a comprehensive search in the PubMed, Embase, and Cochrane Library databases. To account for the potential heterogeneity, a random-effects model was utilized to combine the findings and incorporate its potential influence.

Results

Eight RCTs and three cohort studies, including 3907 patients with highly suspected or clinically diagnosed VAP, were included. Compared to the controls, bronchoscopy use was not associated with a significant effect on all-cause mortality (relative risk [RR]: 0.81, 95 % confidence interval [CI]: 0.62 to 1.05, p = 0.12; I2 = 57 %). Subgroup analysis showed that bronchoscopy used for the microbiological diagnosis of VAP was not associated with reduced mortality (RR: 0.92, 95 % CI: 0.75 to 1.13), while therapeutic bronchoscopy use was associated with significantly reduced mortality (RR: 0.53, 95 % CI: 0.35 to 0.81). The duration of MV or length of ICU stay was not significantly different between groups.

Conclusions

Bronchoscopy use for the purpose of the microbiological diagnosis of VAP did not reduce short-term mortality compared to diagnosis without bronchoscopy use, while therapeutic bronchoscopy use was associated with reduced mortality in these patients.

Nonbronchoscopic Bronchoalveolar Lavage Improves Respiratory Culture Accuracy in Critically Ill Patients

OBJECTIVES

Diagnosis of pneumonia is challenging in critically ill, intubated patients due to limited diagnostic modalities. Endotracheal aspirate (EA) cultures are standard of care in many ICUs; however, frequent EA contamination leads to unnecessary antibiotic use. Nonbronchoscopic bronchoalveolar lavage (NBBL) obtains sterile, alveolar cultures, avoiding contamination. However, paired NBBL and EA sampling in the setting of a lack of gold standard for airway culture is a novel approach to improve culture accuracy and limit antibiotic use in the critically ill patients.

DESIGN

We designed a pilot study to test respiratory culture accuracy between EA and NBBL. Adult, intubated patients with suspected pneumonia received concurrent EA and NBBL cultures by registered respiratory therapists. Respiratory culture microbiology, cell counts, and antibiotic prescribing practices were examined.

SETTING

We performed a prospective pilot study at the Cleveland Clinic Main Campus Medical ICU in Cleveland, Ohio for 22 months from May 2021 through March 2023.

PATIENTS OR SUBJECTS

Three hundred forty mechanically ventilated patients with suspected pneumonia were screened. Two hundred fifty-seven patients were excluded for severe hypoxia (Fio2 ≥ 80% or positive end-expiratory pressure ≥ 12 cm H2O), coagulopathy, platelets less than 50,000, hemodynamic instability as determined by the treating team, and COVID-19 infection to prevent aerosolization of the virus.

INTERVENTIONS

All 83 eligible patients were enrolled and underwent concurrent EA and NBBL.

MEASUREMENTS AND MAIN RESULTS

More EA cultures (42.17%) were positive than concurrent NBBL cultures (26.51%, p = 0.049), indicating EA contamination. The odds of EA contamination increased by eight-fold 24 hours after intubation. EA was also more likely to be contaminated with oral flora when compared with NBBL cultures. There was a trend toward decreased antibiotic use in patients with positive EA cultures if paired with a negative NBBL culture. Alveolar immune cell populations were recovered from NBBL samples, indicating successful alveolar sampling. There were no major complications from NBBL.

CONCLUSIONS

NBBL is more accurate than EA for respiratory cultures in critically ill, intubated patients. NBBL provides a safe and effective technique to sample the alveolar space for both clinical and research purposes.

The Association Between Bronchoscopy and the Prognoses of Patients With Ventilator-Associated Pneumonia in Intensive Care Units: A Retrospective Study Based on the MIMIC-IV Database

Background: In intensive care units (ICUs), the morbidity and mortality of ventilator-associated pneumonia (VAP) are relatively high, and this condition also increases medical expenses for mechanically ventilated patients, which will seriously affect the prognoses of critically ill patients. The purpose of this study was to determine the impact of bronchoscopy on the prognosis of patients with VAP undergoing invasive mechanical ventilation (IMV).

Methods: This was a retrospective study based on patients with VAP from the Medical Information Mart for Intensive Care IV database. The outcomes were ICU and in-hospital mortality. Patients were divided based on whether or not they had undergone bronchoscopy during IMV. Kaplan-Meier (KM) survival curves and Cox proportional-hazards regression models were used to analyze the association between groups and outcomes. Propensity score matching (PSM) and propensity score based inverse probability of treatment weighting (IPTW) were used to further verify the stability of the results. The effect of bronchoscopy on prognosis was further analyzed by causal mediation analysis (CMA).

Results: This study enrolled 1,560 patients with VAP: 1,355 in the no-bronchoscopy group and 205 in the bronchoscopy group. The KM survival curve indicated a significant difference in survival probability between the two groups. The survival probabilities in both the ICU and hospital were significantly higher in the bronchoscopy group than in the no bronchoscopy group. After adjusting all covariates as confounding factors in the Cox model, the HRs (95% CI) for ICU and in-hospital mortality in the bronchoscopy group were 0.33 (0.20–0.55) and 0.40 (0.26–0.60), respectively, indicating that the risks of ICU and in-hospital mortality were 0.67 and 0.60 lower than in the no-bronchoscopy group. The same trend was obtained after using PSM and IPTW. CMA showed that delta-red blood cell distribution width (RDW) mediated 8 and 7% of the beneficial effects of bronchoscopy in ICU mortality and in-hospital mortality.

Conclusion: Bronchoscopy during IMV was associated with reducing the risk of ICU and in-hospital mortality in patients with VAP in ICUs, and this beneficial effect was partially mediated by changes in RDW levels.

The Role of Lung Ultrasound Monitoring in Early Detection of Ventilator-Associated Pneumonia in COVID-19 Patients: A Retrospective Observational Study

Specific lung ultrasound signs combined with clinical parameters allow for early diagnosis of ventilator-associated pneumonia in the general ICU population. This retrospective cohort study aimed to determine the accuracy of lung ultrasound monitoring for ventilator-associated pneumonia diagnosis in COVID-19 patients. Clinical (i.e., clinical pulmonary infection score) and ultrasound (i.e., presence of consolidation and a dynamic linear−arborescent air bronchogram, lung ultrasound score, ventilator-associated lung ultrasound score) data were collected on the day of the microbiological sample (pneumonia-day) and 48 h before (baseline) on 55 bronchoalveolar lavages of 33 mechanically-ventilated COVID-19 patients who were monitored daily with lung ultrasounds. A total of 26 samples in 23 patients were positive for ventilator-associated pneumonia (pneumonia cases). The onset of a dynamic linear−arborescent air bronchogram was 100% specific for ventilator-associated pneumonia. The ventilator-associated lung ultrasound score was higher in pneumonia-cases (2.5 (IQR 1.0 to 4.0) vs. 1.0 (IQR 1.0 to 1.0); p < 0.001); the lung ultrasound score increased from baseline in pneumonia-cases only (3.5 (IQR 2.0 to 6.0) vs. −1.0 (IQR −2.0 to 1.0); p = 0.0001). The area under the curve for clinical parameters, ventilator-associated pneumonia lung ultrasound score, and lung ultrasound score variations were 0.472, 0.716, and 0.800, respectively. A newly appeared dynamic linear−arborescent air bronchogram is highly specific for ventilator-associated pneumonia in COVID-19 patients. A high ventilator-associated pneumonia lung ultrasound score (or an increase in the lung ultrasound score) orients to ventilator-associated pneumonia.

A Narrative Review on the Approach to Antimicrobial Use in Ventilated Patients with Multidrug Resistant Organisms in Respiratory Samples—To Treat or Not to Treat? That Is the Question

Multidrug resistant organisms (MDRO) are commonly isolated in respiratory specimens taken from mechanically ventilated patients. The purpose of this narrative review is to discuss the approach to antimicrobial prescription in ventilated patients who have grown a new MDRO isolate in their respiratory specimen. A MEDLINE and PubMed literature search using keywords “multidrug resistant organisms”, “ventilator-associated pneumonia” and “decision making”, “treatment” or “strategy” was used to identify 329 references as background for this review. Lack of universally accepted diagnostic criteria for ventilator-associated pneumonia, or ventilator-associated tracheobronchitis complicates treatment decisions. Consideration of the clinical context including signs of respiratory infection or deterioration in respiratory or other organ function is essential. The higher the quality of respiratory specimens or the presence of bacteremia would suggest the MDRO is a true pathogen, rather than colonization, and warrants antimicrobial therapy. A patient with higher severity of illness has lower safety margins and may require initiation of antimicrobial therapy until an alternative diagnosis is established. A structured approach to the decision to treat with antimicrobial therapy is proposed.

Compared the Microbiota Profiles between Samples from Bronchoalveolar Lavage and Endotracheal Aspirates in Severe Pneumonia: A Real-World Experience

Lower respiratory tract sampling from endotracheal aspirate (EA) and bronchoalveolar lavage (BAL) are both common methods to identify pathogens in severe pneumonia. However, the difference between these two methods in microbiota profiles remains unclear. We compared the microbiota profiles of pairwise EA and BAL samples in ICU patients with respiratory failure due to severe pneumonia. We prospectively enrolled 50 ICU patients with new onset of pneumonia requiring mechanical ventilation. EA and BAL were performed on the first ICU day, and samples were analyzed for microbial community composition via 16S rRNA metagenomic sequencing. Pathogens were identified in culture medium from BAL samples in 21 (42%) out of 50 patients. No difference was observed in the antibiotic prescription pattern, ICU mortality, or hospital mortality between BAL-positive and BAL-negative patients. The microbiota profiles in the EA and BAL samples are similar with respect to diversity, microbial composition, and microbial community correlations. The antibiotic treatment regimen was rarely changed based on the BAL findings. The samples from BAL did not provide more information than EA in the microbiota profiles. We suggest that EA is more useful than BAL for microbiome identification in mechanically ventilated patients.

Clinical Value of Bronchoscopy in Acute Respiratory Failure

Bronchoscopy may be considered the “added value” in the diagnostic and therapeutic pathway of different clinical scenarios occurring in acute respiratory critically ill patients. Rigid bronchoscopy is mainly employed in emergent clinical situations due to central airways obstruction, haemoptysis, and inhaled foreign body. Flexible bronchoscopy (FBO) has larger fields of acute applications. In intensive care settings, FBO is useful to facilitate intubation in difficult airways, guide percutaneous dilatational tracheostomy, and mucous plugs causing lobar/lung atelectasis. FBO plays a central diagnostic role in acute respiratory failure caused by intra-thoracic tumors, interstitial lung diseases, and suspected severe pneumonia. “Bronchoscopic” sampling has to be considered when “non-invasive” techniques are not diagnostic in suspected ventilator-associated pneumonia and in non-ventilated immunosuppressed patients. The combined use of either noninvasive ventilation (NIV) or High-flow nasal cannula (HFNC) with bronchoscopy is useful in different scenarios; the largest body of proven successful evidence has been found for NIV-supported diagnostic FBO in non-ventilated high risk patients to prevent and avoid intubation. The expected diagnostic/therapeutic goals of acute bronchoscopy should be balanced against the potential severe risks (i.e., cardio-pulmonary complications, bleeding, and pneumothorax). Expertise of the team is fundamental to achieve the best rate of success with the lowest rate of complications of diagnostic and therapeutic bronchoscopic procedures in acute clinical circumstances.

Utilization Trends and Predictors of Non-invasive and Invasive Ventilation During Hospitalization Due to Community-Acquired Pneumonia

BACKGROUND

Community-acquired pneumonia (CAP) is associated with significant morbidity and mortality. Non-invasive ventilation (NIV) and invasive mechanical ventilation (IMV) are most important interventions for patients with severe CAP associated with respiratory failure. We analysed utilization trends and predictors of non-invasive and invasive ventilation in patients hospitalized with CAP.

METHODS

 Nationwide Inpatient Sample and Healthcare Cost and Utilization Project data for years 2008-2017 were analysed. Adult hospitalizations due to CAP were identified by previously validated International Classification of Diseases, 9th Revision, Clinical Modification (ICD-9-CM) and International Classification of Diseases, 10th Revision, Clinical Modification (ICD-10-CM) codes. We then utilized the Cochran-Armitage trend test and multivariate survey logistic regression models to analyse temporal incidence trends, predictors, and outcomes. We used SAS 9.4 software (SAS Institute Inc., Cary, NC, USA) for analysing data.

RESULTS

Out of a total of 8,385,861 hospitalizations due to CAP, ventilation assistance was required in 552,395 (6.6%). The overall ventilation use increased slightly; however, IMV utilization decreased, while NIV utilization increased. In multivariable regression analysis, males, Asian/others and weekend admissions were associated with higher odds of any ventilation utilization. Concurrent diagnoses of septicemia, congestive heart failure, alcoholism, chronic lung diseases, pulmonary circulatory diseases, diabetes mellitus, obesity and cancer were associated with increased odds of requiring ventilation assistance. Ventilation requirement was associated with high odds of in-hospital mortality and discharge to facility.

CONCLUSION

The use of NIV among CAP patients has increased while IMV use has decreased over the years. We observed numerous factors linked with a higher use of ventilation support. The requirement of ventilation support is also associated with very high chances of mortality and morbidity.

Accuracy of Molecular Amplification Assays for Diagnosis of Staphylococcal Pneumonia: a Systematic Review and Meta-analysis

Rapid and accurate identification of staphylococcal pneumonia is crucial for effective antimicrobial stewardship. We performed a meta-analysis to evaluate the diagnostic value of nucleic acid amplification tests (NAAT) from lower respiratory tract (LRT) samples from suspected pneumonia patients to avoid superfluous empirical methicillin-resistant Staphylococcus aureus (MRSA) treatment. PubMed, Scopus, Embase, Web of Science, and the Cochrane Library Database were searched from inception to 2 September 2020. Data analysis was carried out using a bivariate random-effects model to estimate pooled sensitivity, specificity, positive likelihood ratio (PLR), and negative likelihood ratio (NLR). Of 1,808 citations, 24 publications comprising 32 data sets met our inclusion criteria. Twenty-two studies (n = 4,630) assessed the accuracy of the NAAT for methicillin-sensitive S. aureus (MSSA) detection, while 10 studies (n = 2,996) demonstrated the accuracy of the NAAT for MRSA detection. The pooled NAAT sensitivity and specificity (with 95% confidence interval [CI]) for all MSSA detection were higher (sensitivity of 0.91 [95% CI, 0.89 to 0.94], specificity of 0.94 [95% CI, 0.94 to 0.95]) than those of MRSA (sensitivity of 0.75 [95% CI, 0.69 to 0.80], specificity of 0.88 [95% CI, 0.86 to 0.89]) in lower respiratory tract (LRT) samples. NAAT pooled sensitivities differed marginally among different LRT samples, including sputum, endotracheal aspirate (ETA), and bronchoalveolar lavage (BAL) fluid. Noticeably, NAAT pooled specificity against microbiological culture was consistently ≥88% across various types of LRT samples. A meta-regression and subgroup analysis of study design, sample condition, and patient selection method could not explain the heterogeneity (P > 0.05) in the diagnostic efficiency. This meta-analysis has demonstrated that the NAAT can be applied as the preferred initial test for timely diagnosis of staphylococcal pneumonia in LRT samples for successful antimicrobial therapy.

Impact of Cardiovascular Failure in Intensive CareUnit-Acquired Pneumonia: A Single-Center, Prospective Study

Background: Cardiovascular failure (CVF) may complicate intensive care unit-acquired pneumonia (ICUAP) and radically alters the empirical treatment of this condition. The aim of this study was to determine the impact of CVF on outcome in patients with ICUAP. Methods: A prospective, single-center, observational study was conducted in six medical and surgical ICUs at a University Hospital. CVS was defined as a score of 3 or more on the cardiovascular component of the Sequential Organ Failure Assessment (SOFA) score. At the onset of ICUAP, CVF was reported as absent, transient (if lasting ≤ 3 days) or persistent (>3 days). The primary outcome was 90-day mortality modelled through a Cox regression analysis. Secondary outcomes were 28-day mortality, hospital mortality, ICU length of stay (LOS) and hospital LOS. Results: 358 patients were enrolled: 203 (57%) without CVF, 82 (23%) with transient CVF, and 73 (20%) with persistent CVF. Patients with transient and persistent CVF were more severely ill and presented higher inflammatory response than those without CVF. Despite having similar severity and aetiology, the persistent CVF group more frequently received inadequate initial antibiotic treatment and presented more treatment failures than the transient CVF group. In the persistent CVF group, at day 3, a bacterial superinfection was more frequently detected. The 90-day mortality was significantly higher in the persistent CVF group (62%). The 28-day mortality rates for patients without CVF, with transient and with persistent CVF were 19, 35 and 41% respectively and ICU mortality was 60, 38 and 19% respectively. In the multivariate analysis chronic pulmonary conditions, lack of Pa0₂/FiO₂ improvement at day 3, pulmonary superinfection at day 3 and persistent CVF were independently associated with 90-day mortality in ICUAP patients. Conclusions: Persistent CVF has a significant impact on the outcome of patients with ICUAP. Patients at risk from persistent CVF should be promptly recognized to optimize treatment and outcomes.

Impact of Invasive Quantitative Respiratory Cultures on Antimicrobial Therapy for Suspected Pneumonia in Trauma

BACKGROUND

Invasive quantitative respiratory cultures are generally not recommended because of a lack of demonstrated benefit. There is insufficient literature regarding specific populations such as trauma. The objective of this study was to evaluate the effect of invasive quantitative respiratory sampling on de-escalation to targeted antimicrobial therapy for the management of pneumonia in a trauma population.

METHODS

This was a single-center retrospective cohort study conducted at an American College of Surgeons-verified Level II Trauma Center in Nashville, TN. Adult patients admitted to the trauma service and diagnosed with pneumonia from July 2013 to August 2018 were divided into 2 groups: invasive quantitative respiratory sampling versus noninvasive respiratory sampling. The primary endpoint was rate of targeted antimicrobial therapy. Secondary endpoints included in-hospital mortality, antibiotic days of therapy, and frequency of discontinuation of antibiotics when quantitative cultures were below the diagnostic threshold.

RESULTS

A total of 88 patients were sampled, with 27 in the invasive quantitative group and 66 in the noninvasive group. There was no difference in rates of targeted therapy in patients with invasive quantitative sampling (17 [63%] vs. 35 [57%]; relative risk = 1.10; 95% confidence interval [0.76, 1.57]). No statistically significant differences were observed for in-hospital mortality (8 patients vs. 6 patients, p = .35) or antimicrobial days of therapy (10.3 ± 8.8 vs. 7.8 ± 3.6, p = .161). Only 2 patients (17%) had antibiotics withheld when below the diagnostic threshold.

CONCLUSIONS

Invasive quantitative respiratory sampling did not result in significant changes in targeted antibiotic therapy in a trauma population.

PCR coupled to electrospray ionization mass spectrometry for microbiological diagnosis and surveillance of ventilator-associated pneumonia

Etiological diagnosis is essential for anti-infective therapy in patients with ventilator-associated pneumonia (VAP). The present study aimed to evaluate the capacity of sequential PCR coupled to electrospray ionization mass spectrometry (PCR/ESI-MS) tests as a rapid diagnostic technique for patients with VAP. A total of 12 patients diagnosed with VAP were enrolled at the intensive care unit in Zhongshan Hospital, Fudan University. Mini-bronchoalveolar lavage fluid specimens were prospectively collected on VAP 0, 5 and 10 days following the beginning of mechanical ventilation. Routine clinical culture and PCR/ESI-MS were compared for identification of microorganisms in the specimens. A total of 51 bacterial species were detected by either of the two methods. The positive rates of routine clinical culture and PCR/ESI-MS were 38.2 and 88.2%, respectively. Out of the 16 specimens positive in routine cultures, 15 were also positive on PCR/ESI-MS, except for one, from which a mix of three distinct bacterial isolates were reported by culture. Among the 50 bacterial species identified by PCR/ESI-MS, 15 (35.7%) of the common VAP pathogens were confirmed by paired culture. Furthermore, of the 16 bacterial isolates that were finally confirmed to be responsible for VAP, 14 were identified by a sequential PCR/ESI-MS test concurrently when the culture results were obtained. PCR/ESI-MS identified pathogens that may cause VAP in 8 subjects prior to the occurrence of associated clinical manifestations. To conclude, PCR/ESI-MS was a potential rapid technique for diagnosis of VAP within 6 h. Regular respiratory specimen monitoring using PCR/ESI-MS provides information for selecting appropriate and adequate antibiotic therapies in ventilated patients.

Antimicrobial-associated harm in critical care: a narrative review

The belief that, for the individual patient, the benefit of prompt and continued use of antimicrobials outweighs any potential harm is a significant barrier to improved stewardship of these vital agents. Antimicrobial stewardship may be perceived as utilitarian rationing, seeking to preserve the availability of effective antimicrobials by limiting the development of resistance in a manner which could conflict with the immediate treatment of the patient in need. This view does not account for the growing evidence of antimicrobial-associated harm to individual patients. This review sets out the evidence for antimicrobial-associated harm and how this should be balanced with the need for prompt and appropriate therapy in infection. It describes the mechanisms by which antimicrobials may harm patients including: mitochondrial toxicity; immune cell toxicity; adverse drug reactions; selection of resistant organisms within a given patient; and disruption of the microbiome. Finally, the article indicates how the harms of antimicrobials may be mitigated and identifies areas for research and development in this field.

Ventilator-Associated Pneumonia: Diagnostic Test Stewardship and Relevance of Culturing Practices

PURPOSE OF REVIEW

Ventilator-associated pneumonia (VAP) is one of the most common infections in the ICU. Prompt diagnosis is vital as mortality increases with delayed antibiotic therapy. However, accurate diagnosis is challenging due to non-specific clinical features in a complicated patient cohort. Microbiological culture data remains a crucial aspect in confirming diagnosis.

RECENT FINDINGS

Literature data comparing the benefit of invasive respiratory sampling to non-invasive is inconclusive. Differences in culturing practices translate in overidentification of organisms of unclear significance. Positive culture data in a low pre-test probability does not differentiate between true infection and colonization resulting in overtreatment. Furthermore, there are also opportunities for modifying the reporting of respiratory tract cultures that can better guide antimicrobial therapy. Under the umbrella of antimicrobial stewardship, diagnostic stewardship can be incorporated to create a systematic approach that would target culturing practices to match the right pre-test probability. Ideal outcome will be targeting cultures to the right patient population and minimizing unnecessary treatment.

Ventilator-Associated Pneumonia and PaO2/FIO2 Diagnostic Accuracy: Changing the Paradigm?

Background: Ventilator-associated pneumonia (VAP) is associated to longer stay and poor outcomes. Lacking definitive diagnostic criteria, worsening gas exchange assessed by PaO₂/F_IO₂ ≤ 240 in mmHg has been proposed as one of the diagnostic criteria for VAP. We aim to assess the adequacy of PaO₂/F_IO₂ ≤ 240 to diagnose VAP. Methods: Prospective observational study in 255 consecutive patients with suspected VAP, clustered according to PaO₂/F_IO₂ ≤ 240 vs. > 240 at pneumonia onset. The primary analysis was the association between PaO₂/F_IO₂ ≤ 240 and quantitative microbiologic confirmation of pneumonia, the most reliable diagnostic gold-standard. Results: Mean PaO₂/F_IO₂ at VAP onset was 195 ± 82; 171 (67%) cases had PaO₂/F_IO₂ ≤ 240. Patients with PaO₂/F_IO₂ ≤ 240 had a lower APACHE-II score at ICU admission; however, at pneumonia onset they had higher CPIS, SOFA score, acute respiratory distress syndrome criteria and incidence of shock, and less microbiological confirmation of pneumonia (117, 69% vs. 71, 85%, p = 0.008), compared to patients with PaO₂/FIO₂ > 240. In multivariate logistic regression, PaO₂/FIO₂ ≤ 240 was independently associated with less microbiological confirmation (adjusted odds-ratio 0.37, 95% confidence interval 0.15–0.89, p = 0.027). The association between PaO₂/F_IO₂ and microbiological confirmation of VAP was poor, with an area under the ROC curve 0.645. Initial non-response to treatment and length of stay were similar between both groups, while hospital mortality was higher in patients with PaO₂/F_IO₂ ≤ 240. Conclusion: Adding PaO₂/F_IO₂ ratio ≤ 240 to the clinical and radiographic criteria does not help in the diagnosis of VAP. PaO₂/F_IO₂ ratio > 240 does not exclude this infection. Using this threshold may underestimate the incidence of VAP.

Multidimensional Assessment of the Host Response in Mechanically Ventilated Patients with Suspected Pneumonia

Rationale: The identification of informative elements of the host response to infection may improve the diagnosis and management of bacterial pneumonia. Objectives: To determine whether the absence of alveolar neutrophilia can exclude bacterial pneumonia in critically ill patients with suspected infection and to test whether signatures of bacterial pneumonia can be identified in the alveolar macrophage transcriptome. Methods: We determined the test characteristics of alveolar neutrophilia for the diagnosis of bacterial pneumonia in three cohorts of mechanically ventilated patients. In one cohort, we also isolated macrophages from alveolar lavage fluid and used the transcriptome to identify signatures of bacterial pneumonia. Finally, we developed a humanized mouse model of Pseudomonas aeruginosa pneumonia to determine if pathogen-specific signatures can be identified in human alveolar macrophages. Measurements and Main Results: An alveolar neutrophil percentage less than 50% had a negative predictive value of greater than 90% for bacterial pneumonia in both the retrospective (n = 851) and validation cohorts (n = 76 and n = 79). A transcriptional signature of bacterial pneumonia was present in both resident and recruited macrophages. Gene signatures from both cell types identified patients with bacterial pneumonia with test characteristics similar to alveolar neutrophilia. Conclusions: The absence of alveolar neutrophilia has a high negative predictive value for bacterial pneumonia in critically ill patients with suspected infection. Macrophages can be isolated from alveolar lavage fluid obtained during routine care and used for RNA-Seq analysis. This novel approach may facilitate a longitudinal and multidimensional assessment of the host response to bacterial pneumonia.

Rapid Detection of Methicillin-Resistant Staphylococcus aureus in BAL: A Pilot Randomized Controlled Trial

BACKGROUND

Guidelines recommend empirical vancomycin or linezolid for patients with suspected pneumonia at risk for methicillin-resistant Staphylococcus aureus (MRSA). Unneeded vancomycin or linezolid use may unnecessarily alter host flora and expose patients to toxicity. We therefore sought to determine if rapid testing for MRSA in BAL can safely decrease use of vancomycin or linezolid for suspected MRSA pneumonia.

METHODS

Operating characteristics of the assay were initially validated against culture on residual BAL. A prospective, unblinded, randomized clinical trial to assess the effect of antibiotic management made on the basis of rapid diagnostic testing (RDT) compared with usual care was subsequently conducted, with primary outcome of duration of vancomycin or linezolid administration. Secondary end points focused on safety.

RESULTS

Sensitivity of RPCR was 95.7%, with a negative likelihood ratio of 0.04 for MRSA. The clinical trial randomized 45 patients: 22 to antibiotic management made on the basis of RDT and 23 to usual care. Duration of vancomycin or linezolid administration was significantly reduced in the intervention group (32 h [interquartile range, 22-48] vs 72 h [interquartile range, 50-113], P < .001). Proportions with complications and length of stay trended lower in the intervention group. Hospital mortality was 13.6% in the intervention group and 39.1% for usual care (95% CI of difference, -3.3 to 50.3, P = .06). Standardized mortality ratio was 0.48 for the intervention group and 1.18 for usual care.

CONCLUSIONS

A highly sensitive BAL RDT for MRSA significantly reduced use of vancomycin and linezolid in ventilated patients with suspected pneumonia. Management made on the basis of RDT had no adverse effects, with a trend to lower hospital mortality.

TRIAL REGISTRY

ClinicalTrials.gov; No. NCT02660554; URL: www.clinicaltrials.gov.

Worldwide variation in Pseudomonas associated ventilator associated pneumonia. A meta-regression

PURPOSE

The objective here is to define the extent and possible reasons for geographic variation in Pseudomonas aeruginosa associated with Ventilator Associated Pneumonia (VAP).

METHODS

A random effects meta-regression model of Pseudomonas associated VAP incidence within the published literature was undertaken incorporating group level factors such trauma admission, year of publication and use of bronchoscopic sampling towards VAP diagnosis.

RESULTS

Pseudomonas associated VAP incidence was reported in 162 studies from seven worldwide regions published over 30 years. The highest incidence is among reports from the Middle East and Mediterranean being respectively 6.8; 5.2-9.0 (mean; 95% CI) and 6.9; 5.4-8.8 per 1000 mechanical ventilation (MV) days, versus that from North American ICU's (3.7; 2.3-5.9). In a meta-regression model, the variation in the incidence of Pseudomonas associated VAP was not significantly associated with bronchoscopic sampling in the diagnosis of VAP (p = 0.12) nor with admission to a trauma ICU (p = 0.13).

CONCLUSION

Pseudomonas associated VAP incidence among reports from six geographic regions worldwide varies by less than twofold with some decline by year of publication. Trauma ICU admission is a significant factor underlying variations in incidence of VAP overall but not Pseudomonas associated VAP.

[Hospital-acquired pneumonia]

Hospital-acquired pneumonia (HAP) is a frequent complication of hospitalisation. Due to rising multidrug resistant bacteria an appropriate, empiric and targeted therapy is essential and requires an accurate assessment of risk for multidrug resistant bacteria. A targeted, temporal therapy is indispensable and should begin after a focussed diagnosis. Re-evaluation of therapy is important, as clinical course, microbiological and laboratory results might lead to de-escalation of therapy. In this review article the current German guidelines on the diagnosis and therapy of hospital-acquired pneumonia are summarized. Special focus is put on targeted, risk-adapted therapy.

Pathogen colonization of the gastrointestinal microbiome at intensive care unit admission and risk for subsequent death or infection

PURPOSE

Loss of colonization resistance within the gastrointestinal microbiome facilitates the expansion of pathogens and has been associated with death and infection in select populations. We tested whether gut microbiome features at the time of intensive care unit (ICU) admission predict death or infection.

METHODS

This was a prospective cohort study of medical ICU adults. Rectal surveillance swabs were performed at admission, selectively cultured for vancomycin-resistant Enterococcus (VRE), and assessed using 16S rRNA gene sequencing. Patients were followed for 30 days for death or culture-proven bacterial infection.

RESULTS

Of 301 patients, 123 (41%) developed culture-proven infections and 76 (25%) died. Fecal biodiversity (Shannon index) did not differ based on death or infection (p = 0.49). The presence of specific pathogens at ICU admission was associated with subsequent infection with the same organism for Escherichia coli, Pseudomonas spp., Klebsiella spp., and Clostridium difficile, and VRE at admission was associated with subsequent Enterococcus infection. In a multivariable model adjusting for severity of illness, VRE colonization and Enterococcus domination (≥ 30% 16S reads) were both associated with death or all-cause infection (aHR 1.46, 95% CI 1.06-2.00 and aHR 1.47, 95% CI 1.00-2.19, respectively); among patients without VRE colonization, Enterococcus domination was associated with excess risk of death or infection (aHR 2.13, 95% CI 1.06-4.29).

CONCLUSIONS

Enterococcus status at ICU admission was associated with risk for death or all-cause infection, and rectal carriage of common ICU pathogens predicted specific infections. The gastrointestinal microbiome may have a role in risk stratification and early diagnosis of ICU infections.

World-Wide Variation in Incidence of Staphylococcus aureus Associated Ventilator-Associated Pneumonia: A Meta-Regression

Staphylococcus aureus (S. aureus) is a common Ventilator-Associated Pneumonia (VAP) isolate. The objective here is to define the extent and possible reasons for geographic variation in the incidences of S. aureus-associated VAP, MRSA-VAP and overall VAP. A meta-regression model of S. aureus-associated VAP incidence per 1000 Mechanical Ventilation Days (MVD) was undertaken using random effects methods among publications obtained from a search of the English language literature. This model incorporated group level factors such as admission to a trauma ICU, year of publication and use of bronchoscopic sampling towards VAP diagnosis. The search identified 133 publications from seven worldwide regions published over three decades. The summary S. aureus-associated VAP incidence was 4.5 (3.9–5.3) per 1000 MVD. The highest S. aureus-associated VAP incidence is amongst reports from the Mediterranean (mean; 95% confidence interval; 6.1; 4.1–8.5) versus that from Asian ICUs (2.1; 1.5–3.0). The incidence of S. aureus-associated VAP varies by up to three-fold (for the lowest versus highest incidence) among seven geographic regions worldwide, whereas the incidence of VAP varies by less than two-fold. Admission to a trauma unit is the most important group level correlate for S. aureus-associated VAP.

Neonatal Ventilator Associated Pneumonia: A Quality Improvement Initiative Focusing on Antimicrobial Stewardship

Background and Aims: Neonatal ventilator associated pneumonia (VAP) is a common nosocomial infection and a frequent reason for empirical antibiotic therapy in NICUs. Nonetheless, there is no international consensus regarding diagnostic criteria and management. In a first step, we analyzed the used diagnostic criteria, risk factors and therapeutic management of neonatal VAP by a literature review. In a second step, we aimed to compare suspected vs. confirmed neonatal VAP episodes in our unit according to different published criteria and to analyze interrater-reliability of chest x-rays. Additionally, we aimed to evaluate the development of VAP incidence and antibiotic use after implementation of multifaceted quality improvement changes regarding antimicrobial stewardship and infection control (VAP-prevention-bundle, early-extubation policy, antimicrobial stewardship rounds). Methods: Neonates until 44 weeks of gestation with suspected VAP, hospitalized at our level-III NICU in Lucerne from September 2014 to December 2017 were enrolled. VAP episodes were analyzed according to 4 diagnostic frameworks. Agreement regarding chest x-ray interpretation done by 10 senior physicians was assessed. Annual incidence of suspected and confirmed neonatal VAP episodes and antibiotic days were calculated and compared for the years 2015, 2016, and 2017. Results: 17 studies were identified in our literature review. Overall, CDC-guidelines or similar criteria, requesting radiographic changes as main criteria, are mostly used. Comparison of suspected vs. confirmed neonatal VAP episodes showed a great variance (20.4 vs. 4.5/1,000 ventilator-days). The interrater-reliability of x-ray interpretation was poor (intra-class correlation 0.25). Implemented changes resulted in a gradual decline in annual VAP incidence and antibiotic days from 2015 compared with 2017 (28.8 vs. 7.4 suspected episodes/1,000 ventilator-days, 5.5 vs. 0 confirmed episodes/1,000 ventilator-days and 211 vs. 34.7 antibiotic days/1,000 ventilation-days, respectively). Conclusion: The incidence of suspected VAP and concomitant antibiotic use is much higher than for confirmed VAP, therefore inclusion of suspected episodes should be considered for accurate evaluation. There is a high diagnostic inconsistency and a low reliability of interpretation of chest x-rays regarding VAP. Implementation of combined antimicrobial stewardship and infection control measures may lead to an effective decrease in VAP incidence and antibiotic use.

Diagnostic Value of Endotracheal Aspirates Sonication on Ventilator-Associated Pneumonia Microbiologic Diagnosis

Microorganisms are able to form biofilms within respiratory secretions. Methods to disaggregate such biofilms before utilizing standard, rapid, or high throughput diagnostic technologies may aid in pathogen detection during ventilator associated pneumonia (VAP) diagnosis. Our aim was to determine if sonication of endotracheal aspirates (ETA) would increase the sensitivity of qualitative, semi-quantitative, and quantitative bacterial cultures in an animal model of pneumonia caused by Pseudomonas aeruginosa or by methicillin resistant Staphylococcus aureus (MRSA). Material and methods: P. aeruginosa or MRSA was instilled into the lungs or the oropharynx of pigs in order to induce severe VAP. Time point assessments for qualitative and quantitative bacterial cultures of ETA and bronchoalveolar lavage (BAL) samples were performed at 24, 48, and 72 h after bacterial instillation. In addition, at 72 h (autopsy), lung tissue was harvested to perform quantitative bacterial cultures. Each ETA sample was microbiologically processed with and without applying sonication for 5 min at 40 KHz before bacterial cultures. Sensitivity and specificity were determined using BAL as a gold-standard. Correlation with BAL and lung bacterial burden was also determined before and after sonication. Assessment of biofilm clusters and planktonic bacteria was performed through both optical microscopy utilizing Gram staining and Confocal Laser Scanning Microscopy utilizing the LIVE/DEAD^®BacLight kit. Results: 33 pigs were included, 27 and 6 from P. aeruginosa and MRSA pneumonia models, respectively. Overall, we obtained 85 ETA, 69 (81.2%) from P. aeruginosa and 16 (18.8%) from MRSA challenged pigs. Qualitative cultures did not significantly change after sonication, whereas quantitative ETA cultures did significantly increase bacterial counting. Indeed, sonication consistently increased bacterial burden in ETAs at 24, 48, and 72 h after bacterial challenge. Sonication also improved sensitivity of ETA quantitative cultures and maintained specificity at levels previously reported and accepted for VAP diagnosis. Conclusion: The use of sonication in ETA respiratory samples needs to be clinically validated since sonication could potentially improve pathogen detection before standard, rapid, or high throughput diagnostic methods used in routine microbial diagnostics.

Controversies and advances in the management of ventilator associated pneumonia

INTRODUCTION

Although national surveillance data suggests that the incidence of ventilator associated pneumonia (VAP) is down-trending, it remains one of the most commonly encountered hospital acquired infections in the United States and worldwide. Its association with increased healthcare costs and worsened patient outcomes warrants continued effort to improve the care of patients with VAP. Areas covered: The increasing prevalence of multi-drug resistant bacteria further drives the need to explore advances in diagnostic and treatment options. In this review, controversies pertaining to the definition and diagnosis of VAP as well as empiric treatment strategies will be discussed along with several developments related to rapid microbiologic testing methods and the use of non-traditional antimicrobial agents. Expert commentary: The application of rapid diagnostic techniques to identify microbial pathogens is perhaps one of the most impactful advancements in the treatment of serious nosocomial infections. This technology has the potential to reduce inappropriate initial antimicrobial therapy, unnecessary antimicrobial exposure, and mortality in patients with VAP. In addition, the anticipated approval of new antimicrobial agents within the next several years will provide a much-needed expansion of available treatment options in an era of growing antimicrobial resistance.

[Description and role of bacteriological techniques in the management of lung infections]

Les pneumopathies aiguës recouvrent des contextes cliniques variés et les étiologies bactériennes impliquées le sont tout autant. Aucun outil microbiologique n’est 100 % sensible ni 100 % spécifique et malgré les investigations, plus de 30 % des pneumopathies restent sans étiologie identifiée. Si aucun prélèvement n’est indiqué pour les patients traités en ambulatoire, les prélèvements respiratoires non invasifs sont à privilégier pour les pneumopathies aiguës hospitalisées (communautaires ou associées aux soins), tandis que les prélèvements invasifs sont indiqués en seconde ligne pour les pneumopathies aiguës communautaires en réanimation, et en première ligne pour les pneumopathies aiguës de l’immunodéprimé. La culture microbiologique garde une place importante, à condition que le malade soit prélevé avant instauration de l’antibiothérapie. Certains contextes peuvent justifier le recours aux hémocultures, à la recherche d’antigènes urinaires ou aux sérologies. Les PCR rendent déjà service au quotidien mais l’avenir à court terme appartient probablement aux panels moléculaires multiplex capables de détecter de nombreux micro-organismes en quelques heures, surtout dans les pneumopathies communautaires sévères de réanimation et les pneumopathies aiguës de l’immunodéprimé. Le séquençage nucléotidique haut débit révolutionnera bientôt le diagnostic microbiologique, en pneumologie comme dans les autres domaines de l’infectiologie.

Management of Adults With Hospital-acquired and Ventilator-associated Pneumonia: 2016 Clinical Practice Guidelines by the Infectious Diseases Society of America and the American Thoracic Society

It is important to realize that guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. IDSA considers adherence to these guidelines to be voluntary, with the ultimate determination regarding their application to be made by the physician in the light of each patient's individual circumstances.These guidelines are intended for use by healthcare professionals who care for patients at risk for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP), including specialists in infectious diseases, pulmonary diseases, critical care, and surgeons, anesthesiologists, hospitalists, and any clinicians and healthcare providers caring for hospitalized patients with nosocomial pneumonia. The panel's recommendations for the diagnosis and treatment of HAP and VAP are based upon evidence derived from topic-specific systematic literature reviews.

Evaluation of a Mixing versus a Cycling Strategy of Antibiotic Use in Critically-Ill Medical Patients: Impact on Acquisition of Resistant Microorganisms and Clinical Outcomes

Objective

To compare the effect of two strategies of antibiotic use (mixing vs. cycling) on the acquisition of resistant microorganisms, infections and other clinical outcomes.

Methods

Prospective cohort study in an 8-bed intensive care unit during 35- months in which a mixing-cycling policy of antipseudomonal beta-lactams (meropenem, ceftazidime/piperacillin-tazobactam) and fluoroquinolones was operative. Nasopharyngeal and rectal swabs and respiratory secretions were obtained within 48h of admission and thrice weekly thereafter. Target microorganisms included methicillin-resistant S. aureus, vancomycin-resistant enterococci, third-generation cephalosporin-resistant Enterobacteriaceae and non-fermenters.

Results

A total of 409 (42%) patients were included in mixing and 560 (58%) in cycling. Exposure to ceftazidime/piperacillin-tazobactam and fluoroquinolones was significantly higher in mixing while exposure to meropenem was higher in cycling, although overall use of antipseudomonals was not significantly different (37.5/100 patient-days vs. 38.1/100 patient-days). There was a barely higher acquisition rate of microorganisms during mixing, but this difference lost its significance when the cases due to an exogenous Burkholderia cepacia outbreak were excluded (19.3% vs. 15.4%, OR 0.8, CI 0.5–1.1). Acquisition of Pseudomonas aeruginosa resistant to the intervention antibiotics or with multiple-drug resistance was similar. There were no significant differences between mixing and cycling in the proportion of patients acquiring any infection (16.6% vs. 14.5%, OR 0.9, CI 0.6–1.2), any infection due to target microorganisms (5.9% vs. 5.2%, OR 0.9, CI 0.5–1.5), length of stay (median 5 d for both groups) or mortality (13.9 vs. 14.3%, OR 1.03, CI 0.7–1.3).

Conclusions

A cycling strategy of antibiotic use with a 6-week cycle duration is similar to mixing in terms of acquisition of resistant microorganisms, infections, length of stay and mortality.

Polymicrobial intensive care unit-acquired pneumonia: prevalence, microbiology and outcome

BACKGROUND

Microbial aetiology of intensive care unit (ICU)-acquired pneumonia (ICUAP) determines antibiotic treatment and outcomes. The impact of polymicrobial ICUAP is not extensively known. We therefore investigated the characteristics and outcomes of polymicrobial aetiology of ICUAP.

METHOD

Patients with ICUAP confirmed microbiologically were prospectively compared according to identification of 1 (monomicrobial) or more (polymicrobial) potentially-pathogenic microorganisms. Microbes usually considered as non-pathogenic were not considered for the etiologic diagnosis. We assessed clinical characteristics, microbiology, inflammatory biomarkers and outcome variables.

RESULTS

Among 441 consecutive patients with ICUAP, 256 (58%) had microbiologic confirmation, and 41 (16%) of them polymicrobial pneumonia. Methicillin-sensitive Staphylococcus aureus, Haemophilus influenzae, and several Enterobacteriaceae were more frequent in polymicrobial pneumonia. Multi-drug and extensive-drug resistance was similarly frequent in both groups. Compared with monomicrobial, patients with polymicrobial pneumonia had less frequently chronic heart disease (6, 15% vs. 71, 33%, p = 0.019), and more frequently pleural effusion (18, 50%, vs. 54, 25%, p = 0.008), without any other significant difference. Appropriate empiric antimicrobial treatment was similarly frequent in the monomicrobial (185, 86%) and the polymicrobial group (39, 95%), as were the initial response to the empiric treatment, length of stay and mortality. Systemic inflammatory response was similar comparing monomicrobial with polymicrobial ICUAP.

CONCLUSION

The aetiology of ICUAP confirmed microbiologically was polymicrobial in 16% cases. Pleural effusion and absence of chronic heart disease are associated with polymicrobial pneumonia. When empiric treatment is frequently appropriate, polymicrobial aetiology does not influence the outcome of ICUAP.

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.

Impact of Candida spp. isolation in the respiratory tract in patients with intensive care unit-acquired pneumonia

In immunocompetent patients with nosocomial pneumonia, the relationship between Candida spp. isolation in respiratory samples and outcomes or association with other pathogens is controversial. We therefore compared the characteristics and outcomes of patients with intensive care unit-acquired pneumonia (ICUAP), with or without Candida spp. isolation in the respiratory tract. In this prospective non-interventional study, we assessed 385 consecutive immunocompetent patients with ICUAP, according to the presence or absence of Candida spp. in lower respiratory tract samples. Candida spp. was isolated in at least one sample in 82 (21%) patients. Patients with Candida spp. had higher severity scores and organ dysfunction at admission and at onset of pneumonia. In multivariate analysis, previous surgery, diabetes mellitus and higher Simplified Acute Physiology Score II at ICU admission independently predicted isolation of Candida spp. There were no significant differences in the rate of specific aetiological pathogens, the systemic inflammatory response, and length of stay between patients with and without Candida spp. Mortality was also similar, even adjusted for potential confounders in propensity-adjusted multivariate analyses (adjusted hazard ratio 1.08, 95% CI 0.57-2.05, p 0.80 for 28-day mortality and adjusted hazard ratio 1.38, 95% CI 0.81-2.35, p 0.24 for 90-day mortality). Antifungal therapy was more frequently prescribed in patients with Candida spp. in respiratory samples but did not influence outcomes. Candida spp. airway isolation in patients with ICUAP is associated with more initial disease severity but does not influence outcomes in these patients, regardless of the use or not of antifungal therapy.

Quantitative culture of endotracheal aspirate and BAL fluid samples in the management of patients with ventilator-associated pneumonia: a randomized clinical trial

OBJECTIVE:

To compare 28-day mortality rates and clinical outcomes in ICU patients with ventilator-associated pneumonia according to the diagnostic strategy used.

METHODS:

This was a prospective randomized clinical trial. Of the 73 patients included in the study, 36 and 37 were randomized to undergo BAL or endotracheal aspiration (EA), respectively. Antibiotic therapy was based on guidelines and was adjusted according to the results of quantitative cultures.

RESULTS:

The 28-day mortality rate was similar in the BAL and EA groups (25.0% and 37.8%, respectively; p = 0.353). There were no differences between the groups regarding the duration of mechanical ventilation, antibiotic therapy, secondary complications, VAP recurrence, or length of ICU and hospital stay. Initial antibiotic therapy was deemed appropriate in 28 (77.8%) and 30 (83.3%) of the patients in the BAL and EA groups, respectively (p = 0.551). The 28-day mortality rate was not associated with the appropriateness of initial therapy in the BAL and EA groups (appropriate therapy: 35.7% vs. 43.3%; p = 0.553; and inappropriate therapy: 62.5% vs. 50.0%; p = 1.000). Previous use of antibiotics did not affect the culture yield in the EA or BAL group (p = 0.130 and p = 0.484, respectively).

CONCLUSIONS:

In the context of this study, the management of VAP patients, based on the results of quantitative endotracheal aspirate cultures, led to similar clinical outcomes to those obtained with the results of quantitative BAL fluid cultures.

Clinical and Economic Consequences of Failure of Initial Antibiotic Therapy for Hospitalized Patients With Complicated Skin and Skin-Structure Infections

Objective.

To estimate the consequences of failure of initial antibiotic therapy for patients with complicated skin and skin-structure infections.

Design.

Retrospective cohort study.

Setting.

Large US multihospital database.

Patients.

We identified a total of 47,219 patients (age 18 years or older) who were admitted to the hospital for complicated skin and skin-structure infections from April 1, 2003, through March 31, 2004, and who received intravenous antibiotics during the first 2 hospital-days (ie, initial antibiotic therapy). Failure of therapy was defined as drainage, debridement, or receipt of other intravenous antibiotics at any subsequent time (except for changes to narrower-spectrum agents or any therapy change immediately before discharge). Predictors of failure of antibiotic therapy and mortality were examined using multivariate logistic regression. Analysis of covariance was used to estimate the impact of treatment failure on duration of intravenous antibiotic therapy, length of stay, and total inpatient charges.

Results.

For 10,782 admitted patients (22.8%), there was evidence of failure of initial antibiotic therapy. In multivariate analyses, treatment failure was associated with receipt of vasoactive medications during the first 2 hospital-days (odds ratio [OR], 1.66 [95% confidence interval {CI}, 1.19-2.31]), initiation of antibiotic therapy in the intensive care unit (OR, 1.53 [95% CI, 1.28-1.84]), and the patient's Charlson comorbidity index (OR per 1-point increase, 1.06 [95% CI, 1.04-1.08]); treatment failure was also was associated with a 3-fold increase in mortality (OR, 2.91 [95% CI, 2.34-3.62]). Compared with patients for whom initial treatment was successful, patients who experienced treatment failure received intravenous antibiotic therapy for a mean of 5.7 additional days, were hospitalized for a mean of 5.4 additional days, and incurred a mean of $5,285 (in 2003 dollars) in additional inpatient charges (all P <.01).

Conclusion.

Failure of initial antibiotic therapy in the treatment of complicated skin and skin-structure infections is associated with significantly worse clinical and economic outcomes.

Quantitative versus qualitative cultures of respiratory secretions for clinical outcomes in patients with ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is a common infectious disease in intensive care units (ICUs). The best diagnostic approach to resolve this condition remains uncertain.

OBJECTIVES

To evaluate whether quantitative cultures of respiratory secretions and invasive strategies are effective in reducing mortality in immunocompetent patients with VAP, compared with qualitative cultures and non-invasive strategies. We also considered changes in antibiotic use, length of ICU stay and mechanical ventilation.

SEARCH METHODS

We searched CENTRAL (2014, Issue 9), MEDLINE (1966 to October week 2, 2014), EMBASE (1974 to October 2014) and LILACS (1982 to October 2014).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing respiratory samples processed quantitatively or qualitatively, obtained by invasive or non-invasive methods from immunocompetent patients with VAP and which analysed the impact of these methods on antibiotic use and mortality rates.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed the trials identified in the search results and assessed studies for suitability, methodology and quality. We analysed data using Review Manager software. We pooled the included studies to yield the risk ratio (RR) for mortality and antibiotic change with 95% confidence intervals (CI).

MAIN RESULTS

Of the 5064 references identified from the electronic databases (605 from the updated search in October 2014), five RCTs (1367 patients) met the inclusion criteria. Three studies compared invasive methods using quantitative cultures versus non-invasive methods using qualitative cultures, and we used them to answer the main objective of this review. The other two studies compared invasive versus non-invasive methods, both using quantitative cultures. We combined all five studies to compare invasive versus non-invasive interventions for diagnosing VAP. The studies that compared quantitative and qualitative cultures (1240 patients) showed no statistically significant differences in mortality rates (RR 0.91; 95% CI 0.75 to 1.11). The analysis of all five RCTs showed there was no evidence of reduction in mortality in the invasive group versus the non-invasive group (RR 0.93; 95% CI 0.78 to 1.11). There were no significant differences between the interventions with respect to the number of days on mechanical ventilation, length of ICU stay or antibiotic change.

AUTHORS' CONCLUSIONS

There is no evidence that the use of quantitative cultures of respiratory secretions results in reduced mortality, reduced time in ICU and on mechanical ventilation, or higher rates of antibiotic change when compared to qualitative cultures in patients with VAP. We observed similar results when invasive strategies were compared with non-invasive strategies.

Ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is a type of nosocomial pneumonia that occurs in patients who receive mechanical ventilation (MV). According to the International Nosocomial Infection Control Consortium (INICC), the overall rate of VAP is 13.6 per 1,000 ventilator days. The incidence varies according to the patient group and hospital setting. The incidence of VAP ranges from 13-51 per 1,000 ventilation days. Early diagnosis of VAP with appropriate antibiotic therapy can reduce the emergence of resistant organisms.

METHOD

The aim of this review was to provide an overview of the incidence, risk factors, aetiology, pathogenesis, treatment, and prevention of VAP. A literature search for VAP was done through the PUBMED/MEDLINE database. This review outlines VAP's risk factors, diagnostic methods, associated organisms, and treatment modalities.

CONCLUSION

VAP is a common nosocomial infection associated with ventilated patients. The mortality associated with VAP is high. The organisms associated with VAP and their resistance pattern varies depending on the patient group and hospital setting. The diagnostic methods available for VAP are not universal; however, a proper infection control policy with appropriate antibiotic usage can reduce the mortality rate among ventilated patients.

Influence of bronchoscopy on the diagnosis of and outcomes from ventilator-associated pneumonia

BACKGROUND

Ventilator-associated pneumonia (VAP) is a common healthcare-associated infection affecting as many as 27% of mechanically ventilated patients. Ventilator-associated pneumonia is an important source of morbidity and mortality in the surgical intensive care unit (SICU). The optimal diagnostic method for VAP has remained controversial and the role of therapeutic bronchoscopy in the clearance of pulmonary secretions with VAP, in essence source control, remains unknown. Our unit utilizes bronchoscopy inconsistently for these purposes and we chose to evaluate its effectiveness in our patient population with the hypothesis that bronchoscopic diagnosis and therapy results in lower mortality rates and faster clinical resolution.

METHODS

We analyzed retrospectively all patients treated for VAP in a single SICU between September 2003 and December 2011. Patients were divided into groups based upon diagnostic method and receipt of therapeutic bronchoscopy, and were analyzed for differences in time to clinical resolution and mortality.

RESULTS

A total of 360 patients were included in the study, including 493 episodes of VAP. The diagnostic bronchoscopy group had statistically higher APACHE II scores (p=0.02) and fewer days in hospital prior to diagnosis (p=0.02) when compared with the non-invasive diagnosis group. Diagnostic bronchoscopy was associated with shorter length of stay and shorter duration of antibiotics whereas receipt of a therapeutic bronchoscopy was associated with the opposite effects by multivariable analysis.

CONCLUSION

Our hypothesis was disproved and our findings are similar to those found in recent publications. This study supports no definitive conclusions, but further consideration of the role of bronchoscopy is urged in both the diagnosis and treatment of VAP. In our population, bronchoscopy for diagnostic or therapeutic purposes in VAP was not associated with better outcomes. However, differences in baseline characteristics suggest a randomized trial may be needed to answer more completely this question.

Role of linezolid in the treatment of complicated skin and soft tissue infections

Staphylococcus aureus is the most common cause of complicated skin and soft tissue infections (cSSTIs). Antibiotic choices for these infections continue to evolve. History has seen penicillin progress to antistaphylococcal penicillins and cephalosporins, but these drugs are now giving way to drugs that are effective against methicillin-resistant S. aureus (MRSA). While vancomycin has been the gold standard to treat MRSA infections, newer therapeutic options have been developed over the last 5 years. These include quinupristin-dalfopristin, daptomycin, tigecycline and linezolid, which is the focus for this review. Linezolid is efficacious in the treatment of cSSTIs (including diabetic foot infections) caused by Gram-positive organisms (including MRSA), with a well-defined safety profile and straightforward dosing. It is also approved for nosocomial pneumonia, community-acquired pneumonia and uncomplicated skin and skin structure infections. Linezolid has an oral and parenteral formulation, which are equivalent. The oral formulation has the potential to offer economic benefits as compared with other therapies. Currently, there are only a few new antibiotics in development with MRSA activity. The proper use of all antibiotics, including these newer agents, is increasingly important if we are to slow the evolution of microbial resistance.

Microbial profile of early and late onset ventilator associated pneumonia in the intensive care unit of a tertiary care hospital in bangalore, India

INTRODUCTION

Ventilator-associated pneumonia (VAP), an important form of hospital-acquired pneumonia (HAP), specifically refers to pneumonia developing in a patient on mechanical ventilator for more than 48 h after intubation or tracheostomy. Despite the advancements in antimicrobial regimes, VAP continues to be an important cause of morbidity and mortality. VAP requires a rapid diagnosis and initiation of appropriate antibiotic treatment, as there is adverse effect of inadequate antibiotic treatment on patients' prognosis and the emergence of multidrug-resistant (MDR) pathogens.

AIMS

The present study was undertaken to assess the etiological agents of early-onset and late-onset VAP and to know their sensitivity pattern.

MATERIAL AND METHODS

VAP data over a period of 12 months (February 2012 -February 2013) in a tertiary care ICU was retrospectively analysed. The patients were stratified by age, sex, duration of VAP (Early/Late onset) and the identified pathogens with their sensitivity pattern.

RESULTS

Incidence of VAP was found to be 35.14%, out of which 44.23% had early-onset (<4 days MV) VAP and 55.77% had late-onset (>4 days MV) VAP. The most common organisms isolated in early onset and late onset VAP was Pseudomonas aeruginosa, E.coli and Acinetobacter baumanii. All enterobacteriaceal isolates were extended spectrum beta lactamase (ESBL) producing organisms and all Staphylococcus aureus isolates except one were methicillin resistant. The incidence of Multidrug resistant (MDR) Pseudomonas aeruginosa and Acinetobacter were 40% and 37.5% respectively.

CONCLUSION

Due to the increasing incidence of multidrug-resistant organisms in our ICU, early and correct diagnosis of VAP is an urgent challenge for an optimal antibiotic treatment and cure. Hence, knowing the local microbial flora causing VAP and effective infection control practices are essential to improve clinical outcomes.

Developing a new, national approach to surveillance for ventilator-associated events*

OBJECTIVE

To develop and implement an objective, reliable approach to surveillance for ventilator-associated events in adult patients.

DESIGN

The Centers for Disease Control and Prevention (CDC) convened a Ventilator-Associated Pneumonia (VAP) Surveillance Definition Working Group in September 2011. Working Group members included representatives of stakeholder societies and organizations and federal partners.

MAIN RESULTS

The Working Group finalized a three-tier, adult surveillance definition algorithm for ventilator-associated events. The algorithm uses objective, readily available data elements and can identify a broad range of conditions and complications occurring in mechanically ventilated adult patients, including but not limited to VAP. The first tier definition, ventilator-associated condition (VAC), identifies patients with a period of sustained respiratory deterioration following a sustained period of stability or improvement on the ventilator, defined by changes in the daily minimum fraction of inspired oxygen or positive end-expiratory pressure. The second tier definition, infection-related ventilator-associated complication (IVAC), requires that patients with VAC also have an abnormal temperature or white blood cell count, and be started on a new antimicrobial agent. The third tier definitions, possible and probable VAP, require that patients with IVAC also have laboratory and/or microbiological evidence of respiratory infection.

CONCLUSIONS

Ventilator-associated events surveillance was implemented in January 2013 in the CDC's National Healthcare Safety Network. Modifications to improve surveillance may be made as additional data become available and users gain experience with the new definitions.

ICU-acquired pneumonia with or without etiologic diagnosis: a comparison of outcomes

OBJECTIVES

The impact of ICU-acquired pneumonia without etiologic diagnosis on patients' outcomes is largely unknown. We compared the clinical characteristics, inflammatory response, and outcomes between patients with and without microbiologically confirmed ICU-acquired pneumonia.

DESIGN

Prospective observational study.

SETTING

ICUs of a university teaching hospital.

PATIENTS

We prospectively collected 270 consecutive patients with ICU-acquired pneumonia. Patients were clustered according to positive or negative microbiologic results.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We compared the characteristics and outcomes between both groups. Negative microbiology was found in 82 patients (30%). Both groups had similar baseline severity scores. Patients with negative microbiology presented more frequently chronic renal failure (15 [18%] vs 11 [6%]; p=0.003), chronic heart disorders (35 [43%] vs 55 [29%]; p=0.044), less frequently previous intubation (44 [54%] vs 135 [72%]; p=0.006), more severe hypoxemia (PaO2/FIO2: 165±73 mm Hg vs 199±79 mm Hg; p=0.001), and shorter ICU stay before the onset of pneumonia (5±5 days vs 7±9 days; p=0.001) compared with patients with positive microbiology. The systemic inflammatory response was similar between both groups. Negative microbiology resulted in less changes of empiric treatment (33 [40%] vs 112 [60%]; p=0.005) and shorter total duration of antimicrobials (13±6 days vs 17±12 days; p=0.006) than positive microbiology. Following adjustment for potential confounders, patients with positive microbiology had higher hospital mortality (adjusted odds ratio 2.96, 95% confidence interval 1.24-7.04, p=0.014) and lower 90-day survival (adjusted hazard ratio 0.50, 95% confidence interval 0.27-0.94, p=0.031), with a nonsignificant lower 28-day survival.

CONCLUSIONS

Although the possible influence of previous intubation in mortality of both groups is not completely discarded, negative microbiologic findings in clinically suspected ICU-acquired pneumonia are associated with less frequent previous intubation, shorter duration of antimicrobial treatment, and better survival. Future studies should corroborate the presence of pneumonia in patients with suspected ICU-acquired pneumonia and negative microbiology.

Evaluation of semi-quantitative scoring of Gram staining or semi-quantitative culture for the diagnosis of ventilator-associated pneumonia: a retrospective comparison with quantitative culture

Background

Semi-quantitative Gram stain and culture methods are still commonly used for diagnosing ventilator-associated pneumonia (VAP), due to its convenience. Only a few studies, however, have assessed the reliability of these methods when compared with quantitative cultures, a current standard for the diagnosis of VAP. The objective of this study was to assess the utility of semi-quantitative scores obtained using Gram stains and cultures of endotracheal aspirates when compared with quantitative cultures in the diagnosis of VAP.

Methods

A retrospective chart review of mechanically ventilated patients with clinically suspected VAP in a single intensive care unit was performed. Semi-quantitative scores of Gram stains or culture results were compared with quantitative culture results of endotracheal aspirate for the diagnosis of VAP in 136 samples for 51 patients.

Results

The semi-quantitative scores of Gram stains and the semi-quantitative culture results significantly correlated with the log value of the quantitative culture results (r_s = 0.64 and 0.75). When using a log count ≥6 of quantitative cultures as the reference standard for the diagnosis of VAP, the sensitivity and specificity was 95% and 61% for Gram stain score of ≥1+, and was 42% and 96% for Gram stain score ≥3+, respectively. The sensitivity and specificity was 96% and 40% for the semi-quantitative culture score of ≥2+, and was 59% and 86% for the semi-quantitative culture score of ≥3+, respectively.

Conclusions

Absence of bacteria in semi-quantitative Gram stain and poor growth (≤1+) in semi-quantitative culture method could be utilized to exclude the possibility of VAP, whereas detection of abundant (≥3+) bacteria in semi-quantitative Gram stain could be utilized to strongly suspect VAP.

Suspected ventilator-associated respiratory infection in severely ill patients: a prospective observational study

Introduction

Ventilator-associated respiratory infection (VARI) is an important cause of morbidity in critically-ill patients. Clinical trials performed in heterogeneous populations have suggested there are limited benefits from invasive diagnostic testing to identify patients at risk or to target antimicrobial therapy. However, multiple patient subgroups (for example, immunocompromised, antibiotic-treated) have traditionally been excluded from randomization. We hypothesized that a prospective surveillance study would better identify patients with suspected VARI (sVARI) at high risk for adverse clinical outcomes, and who might be specifically targeted in future trials.

Methods

We performed a prospective observational study in all patients ventilated for greater than 48 hours. sVARI was identified by surveillance for changes in white blood cell count, temperature, sputum, and/or new chest X-ray infiltrates. Indices of disease co-morbidity, as well as mortality, duration of mechanical ventilation, and length of hospital or ICU stay were correlated with sVARI.

Results

Of 1806 patients admitted to the ICU over 14 months, 267 were ventilated for greater than 48 hours, and 77 developed sVARI. Incidence of sVARI was associated with iatrogenic immunosuppression or admission for respiratory illness. Any sVARI, whether suspected ventilator-associated pneumonia (sVAP) or ventilator-associated tracheobronchitis (sVAT), was associated with increased length of stay and duration of mechanical ventilation.

Conclusions

Clinical surveillance for sVARI identifies patients at risk for increased morbidity. Iatrogenically immunosuppressed patients, a subgroup previously excluded from randomized clinical trials, represent a growing proportion of the critically-ill at risk for sVARI who might be targeted for future investigations on diagnostic or therapeutic modalities.

Flexible bronchoscopy

Although bronchoscopy technology continues to evolve at a fairly rapid pace, basic procedures, such as bronchoalveolar lavage, transbronchial lung biopsy, and transbronchial needle aspiration, continue to play a paramount role in the diagnosis of bronchopulmonary diseases. Pulmonologists should be trained in these basic bronchoscopic procedures.