Development and characterization of a new swine model of invasive pneumococcal pneumonia.

Streptococcus pneumoniae is the most common microbial cause of community-acquired pneumonia. Currently, there are no available models of severe pneumococcal pneumonia in mechanically ventilated animals to mimic clinical conditions of critically ill patients. We studied endogenous pulmonary flora in 4 healthy pigs and in an additional 10 pigs in which we intra-bronchially instilled S. pneumoniae serotype 19 A, characterized by its resistance to penicillin, macrolides and tetracyclines. The pigs underwent ventilation for 72 h. All pigs that were not challenged with S. pneumoniae completed the 72-h study, whereas 30% of infected pigs did not. At 24 h, we clinically confirmed pneumonia in the infected pigs; upon necropsy, we sampled lung tissue for microbiological/histological confirmation of pneumococcal pneumonia. In control pigs, Streptococcus suis and Staphylococcus aureus were the most commonly encountered pathogens, and their lung tissue mean ± s.e.m. concentration was 7.94 ± 20 c.f.u./g. In infected pigs, S. pneumoniae was found in the lungs of all pigs (mean ± s.e.m. pulmonary concentration of 1.26 × 105 ± 2 × 102 c.f.u./g). Bacteremia was found in 50% of infected pigs. Pneumococcal pneumonia was confirmed in all infected pigs at 24 h. Pneumonia was associated with thrombocytopenia, an increase in prothrombin time, cardiac output and vasopressor dependency index and a decrease in systemic vascular resistance. Upon necropsy, microbiological/histological pneumococcal pneumonia was confirmed in 8 of 10 pigs. We have therefore developed a novel model of penicillin- and macrolide-resistant pneumococcal pneumonia in mechanically ventilated pigs with bacteremia and severe hemodynamic compromise. The model could prove valuable for appraising the pathogenesis of pneumococcal pneumonia, the effects associated with macrolide resistance and the outcomes related to the use of new diagnostic strategies and antibiotic or complementary therapies.

Diagnostic accuracy of Gram staining when predicting staphylococcal hospital-acquired pneumonia and ventilator-associated pneumonia: a systematic review and meta-analysis.

BACKGROUND: There is no clear guidance on empirical antibiotic coverage against Staphylococcus aureus for hospital-acquired pneumonia (HAP) and ventilator-associated pneumonia (VAP). OBJECTIVE: To evaluate whether the presence of clusters of Gram-positive cocci in Gram staining of respiratory samples predicts S. aureus as HAP/VAP pathogen. METHODS: Data sources were MEDLINE, PubMed, Embase, Scielo, CINAHL and Scopus, from inception to 15/07/2017 (update on 31/10/2019), and original data from a single-centre database (PROSPERO: CRD42017072138). We included studies reporting the diagnostic accuracy of a Gram-staining evaluation suggestive of Staphylococcus compared with a positive culture for S. aureus in any type of lower respiratory tract sample. Participants were adult patients with HAP/VAP. The index test was morphological evaluation of Gram staining of respiratory samples. We followed PRISMA guidelines and assessed risk of bias and applicability with the QUADAS-2 tool. We conducted a meta-analysis using a bivariate random effects model. RESULTS: We selected five studies that included only VAP and data from a single-centre database including VAP and HAP. We pooled six studies for VAP and analysed 1665 respiratory samples. Pooled sensitivity was 68% (95%CI 49-83 and specificity 95% (95%CI 86-98). The pooled positive likelihood ratio was 12.7 (95%CI 5.1-31.6), negative likelihood ratio 0.34 (95%CI 0.20-0.57), diagnostic odds ratio 38 (95%CI 13-106) and area under the summary receiver operating curve (SROC) 0.91 (95%CI 0.88-0.93). There was great heterogeneity between sensitivity and specificity. In scenarios in which the prevalence of S. aureus was between 5% and 20%, the positive and negative predictive values were 62% (95%CI 47-77) and 95% (95%CI 82-100), respectively. CONCLUSIONS: Detection of Gram-positive cocci in clusters in respiratory samples of patients with VAP has the potential to guide risk assessments of S. aureus for more personalized antibiotic coverage. Randomized clinical trials with patient-centred outcomes are needed for strong clinical recommendations.

Short-Term Appraisal of the Effects and Safety of Manual Versus Ventilator Hyperinflation in an Animal Model of Severe Pneumonia.

BACKGROUND: In patients on mechanical ventilation, lung hyperinflation is often performed to reverse atelectasis and clear retained mucus. We evaluated the effects of manual hyperinflation and ventilator hyperinflation on mucus clearance, gas exchange, pulmonary mechanics, and hemodynamics. METHODS: Six mechanically ventilated pigs with severe Pseudomonas aeruginosa pneumonia randomly received either 12 manual hyperinflation breaths over a period of 2 min (through a gradual manual compression of a resuscitation bag within 4 s to achieve 40 cm H2O of airway pressure), or 12 ventilator hyperinflation over 2 min to achieve the same ventilatory end points as in manual hyperinflation. Mucus clearance rate was measured through fluoroscopic tracking of tracheal markers. Prior to each maneuver and 15 min thereafter, we assessed arterial and mixed gas exchange, pulmonary mechanics, and hemodynamics. RESULTS: Both manual hyperinflation and ventilator hyperinflation significantly decreased inspiratory flow by approximately 16 L/min (P < .001) and increased peak expiratory flow by roughly 44 L/min (P < .001). The median (interquartile range) mucus clearance rate was 1.31 (0.84-2.30) prior to the interventions, and 0.70 (0.00-2.58) and 0.65 (0.45-1.47) during manual hyperinflation and ventilator hyperinflation, respectively (P = .09). Hyperinflations, whether delivered manually or through the ventilator, did not significantly modify pulmonary or hemodynamic parameters. CONCLUSIONS: In an animal model of severe P. aeruginosa pneumonia, neither manual hyperinflation nor ventilator hyperinflation improved mucus clearance. If confirmed in comprehensive clinical experimentations, these findings should promote reappraisal of indications for both manual hyperinflation and ventilator hyperinflation as a therapeutic technique for mucus clearance and atelectasis reversal.

Nebulized Amikacin and Fosfomycin for Severe Pseudomonas aeruginosa Pneumonia: An Experimental Study.

OBJECTIVES: Latest trials failed to confirm merits of nebulized amikacin for critically ill patients with nosocomial pneumonia. We studied various nebulized and IV antibiotic regimens in a porcine model of severe Pseudomonas aeruginosa pneumonia, resistant to amikacin, fosfomycin, and susceptible to meropenem. DESIGN: Prospective randomized animal study. SETTING: Animal Research, University of Barcelona, Spain. SUBJECTS: Thirty female pigs. INTERVENTIONS: The animals were randomized to receive nebulized saline solution (CONTROL); nebulized amikacin every 6 hours; nebulized fosfomycin every 6 hours; IV meropenem alone every 8 hours; nebulized amikacin and fosfomycin every 6 hours; amikacin and fosfomycin every 6 hours, with IV meropenem every 8 hours. Nebulization was performed through a vibrating mesh nebulizer. The primary outcome was lung tissue bacterial concentration. Secondary outcomes were tracheal secretions P. aeruginosa concentration, clinical variables, lung histology, and development of meropenem resistance. MEASUREMENTS AND MAIN RESULTS: We included five animals into each group. Lung P. aeruginosa burden varied among groups (p < 0.001). In particular, IV meropenem and amikacin and fosfomycin + IV meropenem groups presented lower P. aeruginosa concentrations versus amikacin and fosfomycin, amikacin, CONTROL, and fosfomycin groups (p < 0.05), without significant difference between these two groups undergoing IV meropenem treatment. The sole use of nebulized antibiotics resulted in dense P. aeruginosa accumulation at the edges of the interlobular septa. Amikacin, amikacin and fosfomycin, and amikacin and fosfomycin + IV meropenem effectively reduced P. aeruginosa in tracheal secretions (p < 0.001). Pathognomonic clinical variables of respiratory infection did not differ among groups. Resistance to meropenem increased in IV meropenem group versus amikacin and fosfomycin + meropenem (p = 0.004). CONCLUSIONS: Our findings corroborate that amikacin and fosfomycin alone efficiently reduced P. aeruginosa in tracheal secretions, with negligible effects in pulmonary tissue. Combination of amikacin and fosfomycin with IV meropenem does not increase antipseudomonal pulmonary tissue activity, but it does reduce development of meropenem-resistant P. aeruginosa, in comparison with the sole use of IV meropenem. Our findings imply potential merits for preemptive use of nebulized antibiotics in order to reduce resistance to IV meropenem.

Intensive care unit-acquired pneumonia due to Pseudomonas aeruginosa with and without multidrug resistance.

OBJECTIVE: Pseudomonas aeruginosa often presents multi-drug resistance (MDR) in intensive care unit (ICU)-acquired pneumonia (ICUAP), possibly resulting in inappropriate empiric treatment and worse outcomes. We aimed to identify patients with ICUAP at risk for these pathogens in order to improve treatment selection and outcomes. METHODS: We prospectively assessed 222 consecutive immunocompetent ICUAP patients confirmed microbiologically. We determined the characteristics, risk factors, systemic inflammatory response and outcomes of P. aeruginosa pneumonia (Pa-ICUAP), compared to other aetiologies. We also compared patients with MDR vs. non-MDR Pa-ICUAP. RESULTS: Pseudomonas aeruginosa was the most frequent aetiology (64, 29%); 22 (34%) cases had MDR. Independent predictors for Pa-ICUAP were prior airway colonization by P. aeruginosa, previous antibiotic treatment, solid cancer and shock; alcohol abuse and pleural effusion were independently associated to lower risk for Pa-ICUAP. Chronic liver disease independently predicted MDR among Pa-ICUAP. The inflammatory biomarkers were similar between all groups. Patients with Pa-ICUAP had lower unadjusted 90-day survival (p = 0.049). However, the 90-day survival adjusted for confounding factors using a propensity score did not differ between all groups. CONCLUSION: Pseudomonas aeruginosa remains the most frequent aetiology of ICUAP, with high prevalence of MDR. These risk factors should be taken into account to avoid inappropriate empiric antibiotics for Pa-ICUAP. Pseudomonas aeruginosa, regardless multidrug resistance, was not associated with different propensity-adjusted survival.

The effects of direct hemoperfusion using a polymyxin B-immobilized column in a pig model of severe Pseudomonas aeruginosa pneumonia.

BACKGROUND: Hemoperfusion through a column containing polymyxin B-immobilized fiber (PMX-HP) is beneficial in abdominal sepsis. We assessed the effects of PMX-HP in a model of severe Pseudomonas aeruginosa pneumonia. METHODS: Eighteen pigs with severe P. aeruginosa pneumonia were mechanically ventilated for 76 h. Pigs were randomized to receive standard treatment with fluids and vasoactive drugs, or standard treatment with two 3-h PMX-HP sessions. Antibiotics against P. aeruginosa were never administered. We assessed endotoxemia through the endotoxin activity assay (EA). We measured the static lung elastance, ratio of arterial partial pressure per inspiratory fraction of oxygen (PaO2/FIO2), mean arterial pressure, cardiac output, systemic vascular resistance and inotropic score. Finally, every 24 h, we assessed complete blood count. RESULTS: In comparison with the control group, PMX-HP decreased percentage of circulating neutrophils from 47.4 ± 13.8 to 40.8 ± 11.5 % (p = 0.009). In a subgroup of animals with the worst hemodynamic impairment, EA in the control and PMX-HP groups was 0.50 ± 0.29 and 0.29 ± 0.14, respectively (p = 0.018). Additionally, in the control and PMX-HP groups, static lung elastance was 26.9 ± 8.7 and 25.3 ± 7.5 cm H2O/L (p = 0.558), PaO2/FIO2 was 347.3 ± 61.9 and 356.4 ± 84.0 mmHg (p = 0.118), mean arterial pressure was 81.2 ± 10.3 and 81.6 ± 13.1 mmHg (p = 0.960), cardiac output was 3.30 ± 1.11 and 3.28 ± 1.19 L/min (p = 0.535), systemic vascular resistance was 1982.6 ± 608.4 and 2011.8 ± 750.0 dyne/s/cm(-5) (p = 0.939), and inotropic score was 0.25 ± 0.10 and 0.26 ± 0.18 (p = 0.864). CONCLUSIONS: In mechanically ventilated pigs with severe P. aeruginosa pneumonia, PMX-HP does not have any valuable clinical benefit, and studies are warranted to fully evaluate a potential role of PMX-HP in septic shock associated with severe pulmonary infections.

Community-Acquired Pneumonia Due to Multidrug- and Non-Multidrug-Resistant Pseudomonas aeruginosa.

BACKGROUND: Pseudomonas aeruginosa is not a frequent pathogen in community-acquired pneumonia (CAP). However, in patients with severe CAP, P aeruginosa can be the etiology in 1.8% to 8.3% of patients, with a case-fatality rate of 50% to 100%. We describe the prevalence, clinical characteristics, outcomes, and risk factors associated with CAP resulting from multidrug-resistant (MDR) and non-MDR P aeruginosa. METHODS: Prospective observational study of 2,023 consecutive adult patients with CAP with definitive etiology. RESULTS: P aeruginosa was found in 77 (4%) of the 2,023 cases with microbial etiology. In 22 (32%) of the 68 cases of P aeruginosa with antibiogram data, the isolates were MDR. Inappropriate therapy was present in 49 (64%) cases of P aeruginosa CAP, including 17/22 (77%) cases of MDR P aeruginosa CAP. Male sex, chronic respiratory disease, C-reactive protein <12.35 mg/dL, and pneumonia severity index risk class IV to V were independently associated with P aeruginosa CAP. Prior antibiotic treatment was more frequent in MDR P aeruginosa CAP compared with non-MDR P aeruginosa (58% vs 29%, P = .029), and was the only risk factor associated with CAP resulting from MDR P aeruginosa. In the multivariate analysis, age ≥65 years, CAP resulting from P aeruginosa, chronic liver disease, neurologic disease, nursing home, criteria of ARDS, acute renal failure, ICU admission, and inappropriate empiric treatment were the factors associated with 30-day mortality. CONCLUSIONS: P aeruginosa is an individual risk factor associated with mortality in CAP. The risk factors described can help clinicians to suspect P aeruginosa and MDR P aeruginosa.

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.

Pattern of soluble CD5 and CD6 lymphocyte receptors in critically ill patients with septic syndromes.

PURPOSE: Soluble forms of CD5 and CD6 lymphocyte surface receptors (sCD5 and sCD6) are molecules that seem to prevent experimental sepsis when exogenously administered. The aim of this study was to assess sCD5 and sCD6 levels in patients with septic syndromes. MATERIALS AND METHODS: The study population consisted of 218 patients admitted to the medical intensive care unit (ICU) presenting either septic syndromes or noninfectious systemic inflammatory response syndrome at admission or within the first 48 hours. The sCD5 and sCD6 levels were analyzed by sandwich enzyme-linked immunosorbent assay. RESULTS: Almost 50% of the patients had undetectable levels of sCD5 or sCD6, with no differences in clinical or biological variables with detectable patients. There was a correlation between the delta Sequential Organ Failure Assessment score and both sCD6 and sCD5 levels in all groups. Patients with sCD5 or sCD6 levels greater than 1500 ng/mL presented a higher in-ICU mortality (P < .05). Logistic regression analysis showed that increased sCD6 levels were associated with an increased risk of in-ICU mortality. CONCLUSIONS: Levels of sCD5 and sCD6 in critically ill patients with systemic inflammatory response syndrome present a high variation and an elevated proportion of undetectability. Levels of sCD6 are associated with an increased risk of mortality in these patients.

Acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill medical patients: role of colonization pressure and antibiotic exposure.

INTRODUCTION: The objective of this work was to investigate the risk factors for the acquisition of Pseudomonas aeruginosa and its resistance phenotypes in critically ill patients, taking into account colonization pressure. METHODS: We conducted a prospective cohort study in an 8-bed medical intensive care unit during a 35-month period. Nasopharyngeal and rectal swabs and respiratory secretions were obtained within 48 hours of admission and thrice weekly thereafter. During the study, a policy of consecutive mixing and cycling periods of three classes of antipseudomonal antibiotics was followed in the unit. RESULTS: Of 850 patients admitted for ≥ 3 days, 751 (88.3%) received an antibiotic, 562 of which (66.1%) were antipseudomonal antibiotics. A total of 68 patients (8%) carried P. aeruginosa upon admission, and among the remaining 782, 104 (13%) acquired at least one strain of P. aeruginosa during their stay. Multivariate analysis selected shock (odds ratio (OR) = 2.1; 95% confidence interval (CI), 1.2 to 3.7), intubation (OR = 3.6; 95% CI, 1.7 to 7.5), enteral nutrition (OR = 3.6; 95% CI, 1.8 to 7.6), parenteral nutrition (OR = 3.9; 95% CI, 1.6 to 9.6), tracheostomy (OR = 4.4; 95% CI, 2.3 to 8.3) and colonization pressure >0.43 (OR = 4; 95% CI, 1.2 to 5) as independently associated with the acquisition of P. aeruginosa, whereas exposure to fluoroquinolones for >3 days (OR = 0.4; 95% CI, 0.2 to 0.8) was protective. In the whole series, prior exposure to carbapenems was independently associated with carbapenem resistance, and prior amikacin use predicted piperacillin-tazobactam, fluoroquinolone and multiple-drug resistance. CONCLUSIONS: In critical care settings with a high rate of antibiotic use, colonization pressure and non-antibiotic exposures may be the crucial factors for P. aeruginosa acquisition, whereas fluoroquinolones may actually decrease its likelihood. For the acquisition of strains resistant to piperacillin-tazobactam, fluoroquinolones and multiple drugs, exposure to amikacin may be more relevant than previously recognized.

ADAMTS-13 in Critically Ill Patients With Septic Syndromes and Noninfectious Systemic Inflammatory Response Syndrome.

PURPOSE: Decreased ADAMTS-13 (A Disintegrin and Metalloprotease with a ThromboSpondin type 1 motif, member 13) seems to be associated with a poor prognosis in sepsis. However, its role in different septic syndromes and other causes of systemic inflammatory response syndrome (SIRS) remains unclear. The aims of this study were to assess ADAMTS-13 levels in patients with septic syndromes or noninfectious SIRS and to determine their association with morbidity and mortality. METHODS: The study population consisted of 178 patients admitted to the medical intensive care unit presenting either septic syndromes or noninfectious SIRS. ADAMTS-13 levels were analyzed. RESULTS: Patients with septic syndromes showed significantly lower levels of ADAMTS-13 compared with those with noninfectious SIRS (P = 0.014). Patients with severe sepsis or septic shock presented lower levels than those of patients with sepsis (P = 0.086). A significant negative correlation was found between ADAMTS-13 levels and delta Sequential Organ Failure Assessment and Acute Physiology and Chronic Health Evaluation II scores at admission in the septic patients. Patients who died had significantly lower levels of ADAMTS-13 compared with survivors, both in the whole population and among the septic patients (P = 0.002 and P = 0.009, respectively). Logistic regression analysis showed that decreased ADAMTS-13 levels were associated with an increased risk of in-intensive care unit mortality (odds ratio, 0.985; 95% confidence interval, 0.973-0.998; P = 0.023). CONCLUSIONS: Septic patients have lower levels of ADAMTS-13 than do patients with noninfectious SIRS. Levels of ADAMTS-13 are correlated with illness severity in patients with septic syndromes. ADAMTS-13 levels were associated with an increased risk of mortality in critically ill patients with SIRS especially those with septic syndromes.

Impact of COPD in the outcome of ICU-acquired pneumonia with and without previous intubation.

BACKGROUND: COPD seems related to poor outcome in patients with ventilator-associated pneumonia (VAP). However, many patients in the ICU with COPD do not require intubation but can also develop pneumonia in the ICU. We, therefore, compared the characteristics and outcomes of patients with ICU-acquired pneumonia (ICUAP) with and without underlying COPD. METHODS: We prospectively assessed the characteristics, microbiology, systemic inflammatory response, and survival of 279 consecutive patients with ICUAP clustered according to underlying COPD or not. The primary end point was 90-day survival. RESULTS: Seventy-one patients (25%) had COPD. The proportion of VAP was less frequent in patients with COPD: 30 (42%) compared with 126 (61%) in patients without COPD (P = .011). Patients with COPD were older; were more frequently men, smokers, and alcohol abusers; and more frequently had previous use of noninvasive ventilation. The rate of microbiologic diagnosis was similar between groups, with a higher rate of Aspergillus species and a lower rate of Enterobacteriaceae in patients with COPD. We found lower levels of IL-6 and IL-8 in patients with COPD without previous intubation. The 90-day mortality was higher in patients with COPD (40 [57%] vs 74 [37%] in patients without COPD, P = .003). Among others, COPD was independently associated with decreased 90-day survival in the overall population (adjusted hazard ratio, 1.94; 95% CI, 1.11-3.40; P = .020); this association was observed only in patients with VAP but not in those without previous intubation. CONCLUSIONS: COPD was independently associated with decreased 90-day survival in patients with VAP but not in those without previous intubation.

Resistance patterns and outcomes in intensive care unit (ICU)-acquired pneumonia. Validation of European Centre for Disease Prevention and Control (ECDC) and the Centers for Disease Control and Prevention (CDC) classification of multidrug resistant organisms.

INTRODUCTION: Bacterial resistance has become a major public health problem. OBJECTIVE: To validate the definition of multidrug-resistant organisms (MDRO) based on the European Centre for Disease Prevention and Control (ECDC) and the Centers for Disease Control and Prevention (CDC) classification. MATERIAL: Prospective, observational study in six medical and surgical Intensive-Care-Units (ICU) of a University hospital. RESULTS: Three-hundred-and-forty-three patients with ICU-acquired pneumonia (ICUAP) were prospectively enrolled, 140 patients had no microbiological confirmation (41%), 82 patients (24%) developed ICUAP for non-MDRO, whereas 121 (35%) were MDROs. Non-MDRO, MDRO and no microbiological confirmation patients did not present either a significant different previous antibiotic use (p 0.18) or previous hospital admission (p 0.17). Appropriate antibiotic therapy was associated with better ICU survival (105 [92.9%] vs. 74 [82.2%]; p = 0.03). An adjusted multivariate regression logistic analysis identified that only MDRO had a higher ICU-mortality than non-MDRO and no microbiological confirmation patients (OR 2.89; p < 0.05; 95% CI for Exp [ß]. 1.02-8.21); Patients with MDRO ICUAP remained in ICU for a longer period than MDRO and no microbiological confirmation respectively (p < 0.01) however no microbiological confirmation patients had more often antibiotic consumption than culture positive ones. CONCLUSIONS: Patients who developed ICUAP due to MDRO showed a higher ICU-mortality than non-MDRO ones and use of ICU resources. No microbiological confirmation patients had more often antibiotic consumption than culture positive patients. Risk factors for MDRO may be important for the selection of initial antimicrobial therapy, in addition to local epidemiology.

Endotracheal tubes for critically ill patients: an in vivo analysis of associated tracheal injury, mucociliary clearance, and sealing efficacy.

BACKGROUND: Improvements in the design of the endotracheal tube (ETT) have been achieved in recent years. We evaluated tracheal injury associated with ETTs with novel high-volume low-pressure (HVLP) cuffs and subglottic secretions aspiration (SSA) and the effects on mucociliary clearance (MCC). METHODS: Twenty-nine pigs were intubated with ETTs comprising cylindrical or tapered cuffs and made of polyvinylchloride (PVC) or polyurethane. In specific ETTs, SSA was performed every 2 h. Following 76 h of mechanical ventilation, pigs were weaned and extubated. Images of the tracheal wall were recorded before intubation, at extubation, and 24 and 96 h thereafter through a fluorescence bronchoscope. We calculated the red-to-green intensity ratio (R/G), an index of tracheal injury, and the green-plus-blue (G+B) intensity, an index of normalcy, of the most injured tracheal regions. MCC was assessed through fluoroscopic tracking of radiopaque markers. After 96 h from extubation, pigs were killed, and a pathologist scored injury. RESULTS: Cylindrical cuffs presented a smaller increase in R/G vs tapered cuffs (P = .011). Additionally, cuffs made of polyurethane produced a minor increase in R/G (P = .012) and less G+B intensity decline (P = .022) vs PVC cuffs. Particularly, a cuff made of polyurethane and with a smaller outer diameter outperformed all cuffs. SSA-related histologic injury ranged from cilia loss to subepithelial inflammation. MCC was 0.9 ± 1.8 and 0.4 ± 0.9 mm/min for polyurethane and PVC cuffs, respectively (P < .001). CONCLUSIONS: HVLP cuffs and SSA produce tracheal injury, and the recovery is incomplete up to 96 h following extubation. Small, cylindrical-shaped cuffs made of polyurethane cause less injury. MCC decline is reduced with polyurethane cuffs.

Gravity predominates over ventilatory pattern in the prevention of ventilator-associated pneumonia.

OBJECTIVE: In the semirecumbent position, gravity-dependent dissemination of pathogens has been implicated in the pathogenesis of ventilator-associated pneumonia. We compared the preventive effects of a ventilatory strategy, aimed at decreasing pulmonary aspiration and enhancing mucus clearance versus the Trendelenburg position. DESIGN: Prospective randomized animal study. SETTING: Animal research facility, University of Barcelona, Spain. SUBJECTS: Twenty-four Large White-Landrace pigs. INTERVENTIONS: Pigs were intubated and on mechanical ventilation for 72 hours. Following surgical preparation, pigs were randomized to be positioned: 1) in semirecumbent/prone position, ventilated with a duty cycle (TITTOT) of 0.33 and without positive end-expiratory pressure (control); 2) as in the control group, positive end-expiratory pressure of 5 cm H2O and TITTOT to achieve a mean expiratory-inspiratory flow bias of 10 L/min (treatment); 3) in Trendelenburg/prone position and ventilated as in the control group (Trendelenburg). Following randomization, Pseudomonas aeruginosa was instilled into the oropharynx. MEASUREMENTS AND MAIN RESULTS: Mucus clearance rate was measured through fluoroscopic tracking of tracheal markers. Microspheres were instilled into the subglottic trachea to assess pulmonary aspiration. Ventilator-associated pneumonia was confirmed by histological/microbiological studies. The mean expiratory-inspiratory flow in the treatment, control, and Trendelenburg groups were 10.7 ± 1.7, 1.8 ± 3.7 and 4.3 ± 2.8 L/min, respectively (p < 0.001). Mucus clearance rate was 11.3 ± 9.9 mm/min in the Trendelenburg group versus 0.1 ± 1.0 in the control and 0.2 ± 1.0 in the treatment groups (p = 0.002). In the control group, we recovered 1.35% ± 1.24% of the instilled microspheres per gram of tracheal secretions, whereas 0.22% ± 0.25% and 0.97% ± 1.44% were recovered in the treatment and Trendelenburg groups, respectively (p = 0.031). Ventilator-associated pneumonia developed in 66.67%, 85.71%, and 0% of the animals in the control, treatment, and Trendelenburg groups (p < 0.001). CONCLUSIONS: The Trendelenburg position predominates over expiratory flow bias and positive end-expiratory pressure in the prevention of gravity-dependent translocation of oropharyngeal pathogens and development of ventilator-associated pneumonia. These findings further substantiate the primary role of gravity in the pathogenesis of ventilator-associated pneumonia.

A novel porcine model of ventilator-associated pneumonia caused by oropharyngeal challenge with Pseudomonas aeruginosa.

BACKGROUND: Animal models of ventilator-associated pneumonia (VAP) in primates, sheep, and pigs differ in the underlying pulmonary injury, etiology, bacterial inoculation methods, and time to onset. The most common ovine and porcine models do not reproduce the primary pathogenic mechanism of the disease, through the aspiration of oropharyngeal pathogens, or the most prevalent human etiology. Herein the authors characterize a novel porcine model of VAP due to aspiration of oropharyngeal secretions colonized by Pseudomonas aeruginosa. METHODS: Ten healthy pigs were intubated, positioned in anti-Trendelenburg, and mechanically ventilated for 72 h. Three animals did not receive bacterial challenge, whereas in seven animals, a P. aeruginosa suspension was instilled into the oropharynx. Tracheal aspirates were cultured and respiratory mechanics were recorded. On autopsy, lobar samples were obtained to corroborate VAP through microbiological and histological studies. RESULTS: In animals not challenged, diverse bacterial colonization of the airways was found and monolobar VAP rarely developed. In animals with P. aeruginosa challenge, colonization of tracheal secretion increased up to 6.39 ± 0.34 log colony-forming unit (cfu)/ml (P < 0.001). VAP was confirmed in six of seven pigs, in 78% of the cases developed in the dependent lung segments (right medium and lower lobes, P = 0.032). The static respiratory system elastance worsened to 41.5 ± 5.8 cm H2O/l (P = 0.001). CONCLUSIONS: The authors devised a VAP model caused by aspiration of oropharyngeal P. aeruginosa, a frequent causative pathogen of human VAP. The model also overcomes the practical and legislative limitations associated with the use of primates. The authors' model could be employed to study pathophysiologic mechanisms, as well as novel diagnostic/preventive strategies.

Assessment of severity of ICU-acquired pneumonia and association with etiology.

OBJECTIVES: We evaluated the association between severity of illness and microbial etiology of ICU-acquired pneumonia to define if severity should be used to guide empiric antibiotic choices. DESIGN: Prospective observational study. SETTING: ICUs of a university hospital. PATIENTS: Three hundredy forty-three consecutive patients with ICU-acquired pneumonia clustered, according to the presence of multidrug resistant pathogens. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Two hundred eight patients had ventilator-associated pneumonia and 135 had nonventilator ICU-acquired pneumonia. We determined etiology in 217 patients (63%). The most frequent pathogens were Pseudomonas aeruginosa, Enterobacteriaceae, and methicillin-sensitive and methicillin-resistant Staphylococcus aureus. Fifty-eight patients (17%) had a multidrug-resistant causative agent. Except for a longer ICU stay and a higher rate of microbial persistence at the end of the treatment in the multidrug-resistant group, no differences were found in clinical and inflammatory characteristics, severity criteria, and mortality or survival between patients with and without multidrug-resistant pathogens, even after adjusting for potential confounders. Patients with higher severity scores (Acute Physiology and Chronic Health Evaluation II and Sepsis-related Organ Failure Assessment) and septic shock at onset of pneumonia had significantly lower 28- and 90-day survival and higher systemic inflammatory response. The results were similar when only patients with microbial diagnosis were considered, as well as when stratified into ventilator-associated pneumonia and nonventilator ICU-acquired pneumonia. CONCLUSIONS: In patients with ICU-acquired pneumonia, severity of illness seems not to affect etiology. Risk factors for multidrug resistant, but not severity of illness, should be taken into account in selecting empiric antimicrobial treatment.

Impact of chronic liver disease in intensive care unit acquired pneumonia: a prospective study.

PURPOSE: To assess the impact of chronic liver disease (CLD) on ICU-acquired pneumonia. METHODS: This was a prospective, observational study of the characteristics, microbiology, and outcomes of 343 consecutive patients with ICU-acquired pneumonia clustered according to the presence of CLD. RESULTS: Sixty-seven (20%) patients had CLD (67% had liver cirrhosis, LC), MELD score 26 ± 9, 20% Child-Pugh class C). They presented higher severity scores than patients without CLD both on admission to the ICU (APACHE II, LC 19 ± 6 vs. other CLD 18 ± 6 vs. no CLD 16 ± 6; p < 0.001; SOFA, 10 ± 3 vs. 8 ± 4 vs. 7 ± 3; p < 0.001) and at onset of pneumonia (APACHE II, 19 ± 6 vs. 17 ± 6 vs. 16 ± 5; p = 0.001; SOFA, 11 ± 4 vs. 9 ± 4 vs. 7 ± 3; p < 0.001). Levels of CRP were lower in patients with LC than in the other two groups (day 1, 6.5 [2.5-11.5] vs. 13 [6-23] vs. 15.5 [8-24], p < 0.001, day 3, 6 [3-12] vs. 16 [9-21] vs. 11 [5-20], p = 0.001); all the other biomarkers were higher in LC and other CLD patients. LC patients had higher 28- and 90-day mortality (63 vs. 28%, p < 0.001; 72 vs. 38%, p < 0.001, respectively) than non-CLD patients. Presence of LC was independently associated with decreased 28- and 90-day survival (95% confidence interval [CI], 1.982-17.250; p = 0.001; 95% confidence interval [CI], 2.915-20.699, p = 0.001, respectively). CONCLUSIONS: In critically ill patients with ICU-acquired pneumonia, CLD is associated with a more severe clinical presentation and poor clinical outcomes. Moreover, LC is independently associated with 28- and 90-day mortality. The results of this study are important for future trials focused on mortality.