Inflammation-Induced CCR7 Oligomers Form Scaffolds to Integrate Distinct Signaling Pathways for Efficient Cell Migration.

Host defense depends on orchestrated cell migration guided by chemokines that elicit selective but biased signaling pathways to control chemotaxis. Here, we showed that different inflammatory stimuli provoked oligomerization of the chemokine receptor CCR7, enabling human dendritic cells and T cell subpopulations to process guidance cues not only through classical G protein-dependent signaling but also by integrating an oligomer-dependent Src kinase signaling pathway. Efficient CCR7-driven migration depends on a hydrophobic oligomerization interface near the conserved NPXXY motif of G protein-coupled receptors as shown by mutagenesis screen and a CCR7-SNP demonstrating super-oligomer characteristics leading to enhanced Src activity and superior chemotaxis. Furthermore, Src phosphorylates oligomeric CCR7, thereby creating a docking site for SH2-domain-bearing signaling molecules. Finally, we identified CCL21-biased signaling that involved the phosphatase SHP2 to control efficient cell migration. Collectively, our data showed that CCR7 oligomers serve as molecular hubs regulating distinct signaling pathways.

FAT10 localises in dendritic cell aggresome-like induced structures and contributes to their disassembly.

Dendritic cell (DC) aggresome-like induced structures (DALIS) are protein aggregates of polyubiquitylated proteins that form transiently during DC maturation. DALIS scatter randomly throughout the cytosol and serve as antigen storage sites synchronising DC maturation and antigen presentation. Maturation of DCs is accompanied by the induction of the ubiquitin-like modifier FAT10 (also known as UBD), which localises to aggresomes, structures that are similar to DALIS. FAT10 is conjugated to substrate proteins and serves as a signal for their rapid and irreversible degradation by the 26S proteasome similar to, yet independently of ubiquitin, thereby contributing to antigen presentation. Here, we have investigated whether FAT10 is involved in the formation and turnover of DALIS, and whether proteins accumulating in DALIS can be modified through conjunction to FAT10 (FAT10ylated). We found that FAT10 localises to DALIS in maturing DCs and that this localisation occurs independently of its conjugation to substrates. Additionally, we investigated the DALIS turnover in FAT10-deficient and -proficient DCs, and observed FAT10-mediated disassembly of DALIS. Thus, we report further evidence that FAT10 is involved in antigen processing, which may provide a functional rationale as to why FAT10 is selectively induced upon DC maturation.

Prevalence, risk factors, and mortality for ventilator-associated pneumonia in middle-aged, old, and very old critically ill patients*.

OBJECTIVE: We investigated the epidemiology of ventilator-associated pneumonia in elderly ICU patients. More precisely, we assessed prevalence, risk factors, signs and symptoms, causative bacterial pathogens, and associated outcomes. DESIGN: Secondary analysis of a multicenter prospective cohort (EU-VAP project). SETTING: Twenty-seven European ICUs. PATIENTS: Patients who were mechanically ventilated for greater than or equal to 48 hours. We compared middle-aged (45-64 yr; n = 670), old (65-74 yr; n = 549), and very old patients (≥ 75 yr; n= 516). MEASUREMENTS AND MAIN RESULTS: Ventilator-associated pneumonia occurred in 103 middle-aged (14.6%), 104 old (17.0%), and 73 very old patients (12.8%). The prevalence (n ventilator-associated pneumonia/1,000 ventilation days) was 13.7 in middle-aged patients, 16.6 in old patients, and 13.0 in very old patients. Logistic regression analysis could not demonstrate older age as a risk factor for ventilator-associated pneumonia. Ventilator-associated pneumonia in elderly patients was more frequently caused by Enterobacteriaceae (24% in middle-aged, 32% in old, and 43% in very old patients; p = 0.042). Regarding clinical signs and symptoms at ventilator-associated pneumonia onset, new temperature rise was less frequent among very old patients (59% vs 76% and 74% for middle-aged and old patients, respectively; p = 0.035). Mortality among patients with ventilator-associated pneumonia was higher among elderly patients: 35% in middle-aged patients versus 51% in old and very old patients (p = 0.036). Logistic regression analysis confirmed the importance of older age in the risk of death (adjusted odds ratio for old age, 2.1; 95% CI, 1.2-3.9 and adjusted odds ratio for very old age, 2.3; 95% CI, 1.2-4.4). Other risk factors for mortality in ventilator-associated pneumonia were diabetes mellitus, septic shock, and a high-risk pathogen as causative agent. CONCLUSIONS: In this multicenter cohort study, ventilator-associated pneumonia did not occur more frequently among elderly, but the associated mortality in these patients was higher. New temperature rise was less common in elderly patients with ventilator-associated pneumonia, whereas more episodes among elderly patients were caused by Enterobacteriaceae.

Ecological effects of selective oral decontamination on multidrug-resistance bacteria acquired in the intensive care unit: a case-control study over 5 years.

PURPOSE: This case-control study investigated the long-term evolution of multidrug-resistant bacteria (MDRB) over a 5-year period associated with the use of selective oropharyngeal decontamination (SOD) in the intensive care unit (ICU). In addition, effects on health care-associated infections and ICU mortality were analysed. METHODS: We investigated patients undergoing mechanical ventilation > 48 h in 11 adult ICUs located at 3 campuses of a university hospital. Administrative, clinical, and microbiological data which were routinely recorded electronically served as the basis. We analysed differences in the rates and incidence densities (ID, cases per 1000 patient-days) of MDRB associated with SOD use in all patients and stratified by patient origin (outpatient or inpatient). After propensity score matching, health-care infections and ICU mortality were compared. RESULTS: 5034 patients were eligible for the study. 1694 patients were not given SOD. There were no differences in the incidence density of MDRB when SOD was used, except for more vancomycin-resistant Enterococcus faecium (0.72/1000 days vs. 0.31/1000 days, p < 0.01), and fewer ESBL-producing Klebsiella pneumoniae (0.22/1000 days vs. 0.56/1000 days, p < 0.01). After propensity score matching, SOD was associated with lower incidence rates of ventilator-associated pneumonia and death in the ICU but not with ICU-acquired bacteremia or urinary tract infection. CONCLUSIONS: Comparisons of the ICU-acquired MDRB over a 5-year period revealed no differences in incidence density, except for lower rate of ESBL-producing Klebsiella pneumoniae and higher rate of vancomycin-resistant Enterococcus faecium with SOD. Incidence rates of ventilator-associated pneumonia and death in the ICU were lower in patients receiving SOD.

Treatment with tigecycline of recurrent urosepsis caused by extended-spectrum-beta-lactamase-producing Escherichia coli.

A 25-year-old female was admitted to our intensive care unit with septic shock and multiorgan failure caused by extended-spectrum beta-lactamase-producing Escherichia coli originating from the right renal pelvis. A 16-day course of treatment with meropenem reversed the septic condition, but the infection recurred thereafter. The patient recovered fully after therapy was changed to tigecycline.

Continuous infusion of beta-lactam antibiotics in severe infections: a review of its role.

Continuous infusion of beta-lactam antibiotics has been widely promoted to optimise their time-dependent activity. Increasing evidence is emerging suggesting potential benefits in patient populations with altered pathophysiology, such as seriously ill patients. From a pharmacokinetic viewpoint, much information supports higher trough concentrations of beta-lactam antibiotics when administered by continuous infusion. This advantage of continuous infusion translates into a superior ability to achieve pharmacodynamic targets, particularly when the minimum inhibitory concentration (MIC) of the pathogen is >or=4 mg/L. One drawback of continuous infusion may be limited physicochemical stability. This issue exists particularly for carbapenem antibiotics whereby prolonged infusions (i.e. >3h) can be used to improve the time above the MIC compared with conventional bolus dosing. Few studies have examined clinical outcomes of bolus and continuous dosing of beta-lactam antibiotics in seriously ill patients. No statistically significant differences have been shown for: mortality; time to normalisation of leukocytosis or pyrexia; or duration of mechanical ventilation, intensive care unit stay or hospital stay. Some evidence suggests improved clinical cure and resolution of illness with continuous infusion in seriously ill patients. Pharmacoeconomic advantages of continuous infusion of beta-lactam antibiotics are well characterised. Available data suggest that seriously ill patients with severe infections requiring significant antibiotic courses (>or=4 days) may be the subgroup that will achieve better outcomes with continuous infusion.

Effects of long-term routine use of selective digestive decontamination on antimicrobial resistance.

OBJECTIVE: To assess the distribution of bacterial species and antimicrobial resistance in an ICU during long-term use of selective digestive decontamination (SDD) in the context of national reference data. DESIGN AND SETTING: Five-year prospective observational study in a 24-bed interdisciplinary surgical ICU of a university hospital (study ICU) participating in the project "Surveillance of Antimicrobial Use and Antimicrobial Resistance in German Intensive Care Units" (SARI; reference ICUs). PATIENTS: Resistance data were obtained from all patients; patients intubated for at least 2 days received SDD (colistin, tobramycin, amphotericin B). INTERVENTIONS AND MEASUREMENTS: SDD was performed in 1,913 of 7,270 patients. Antimicrobial resistance was examined in 4,597 (study ICU) and 46,346 (reference ICUs) isolates. RESULTS: Methicillin-resistant Staphylococcus aureus (MRSA) remained stable (2.76 and 2.58 isolates/1000 patient days) in the study ICU; this was below the German average (4.26 isolates/1000 patient days). Aminoglycoside- and betalactam-resistant Gram-negative rods did not increase during SDD use. Aminoglycoside resistance of Pseudomonas aeruginosa was 50% below the mean value of SARI (0.24 vs. 0.52 isolates/1,000 patient days). The relative frequency of enterococci and coagulase-negative staphylococci (CNS) was higher than in the SARI ICUs (23.2% vs. 17.3%, and 25.0% vs. 20.6%, respectively). CONCLUSION: Routine 5-year-use of SDD was not associated with increased antimicrobial resistance in our ICU with low baseline resistance rates. Vigorous surveillance and control measures to search and destroy MRSA were considered a mandatory component of the SDD program. The relative increase in enterococci and CNS is of concern requiring further investigation.

Distinct CCR7 glycosylation pattern shapes receptor signaling and endocytosis to modulate chemotactic responses.

The homeostatic chemokines CCL19 and CCL21 and their common cognate chemokine receptor CCR7 orchestrate immune cell trafficking by eliciting distinct signaling pathways. Here, we demonstrate that human CCR7 is N-glycosylated on 2 specific residues in the N terminus and the third extracellular loop. Conceptually, CCR7 glycosylation adds steric hindrance to the receptor N terminus and extracellular loop 3, acting as a "swinging door" to regulate receptor sensitivity and cell migration. We found that freshly isolated human B cells, as well as expanded T cells, but not naïve T cells, express highly sialylated CCR7. Moreover, we identified that human dendritic cells imprint T cell migration toward CCR7 ligands by secreting enzymes that deglycosylate CCR7, thereby boosting CCR7 signaling on T cells, permitting enhanced T cell locomotion, while simultaneously decreasing receptor endocytosis. In addition, dendritic cells proteolytically convert immobilized CCL21 to a soluble form that is more potent in triggering chemotactic movement and does not desensitize the receptor. Furthermore, we demonstrate that soluble CCL21 functionally resembles neither the CCL19 nor the CCL21 phenotype but acts as a chemokine with unique features. Thus, we advance the concept of dendritic cell-dependent generation of micromilieus and lymph node conditioning by demonstrating a novel layer of CCR7 regulation through CCR7 sialylation. In summary, we demonstrate that leukocyte subsets express distinct patterns of CCR7 sialylation that contribute to receptor signaling and fine-tuning chemotactic responses.

Attributable mortality of ventilator-associated pneumonia: a meta-analysis of individual patient data from randomised prevention studies.

BACKGROUND: Estimating attributable mortality of ventilator-associated pneumonia has been hampered by confounding factors, small sample sizes, and the difficulty of doing relevant subgroup analyses. We estimated the attributable mortality using the individual original patient data of published randomised trials of ventilator-associated pneumonia prevention. METHODS: We identified relevant studies through systematic review. We analysed individual patient data in a one-stage meta-analytical approach (in which we defined attributable mortality as the ratio between the relative risk reductions [RRR] of mortality and ventilator-associated pneumonia) and in competing risk analyses. Predefined subgroups included surgical, trauma, and medical patients, and patients with different categories of severity of illness scores. FINDINGS: Individual patient data were available for 6284 patients from 24 trials. The overall attributable mortality was 13%, with higher mortality rates in surgical patients and patients with mid-range severity scores at admission (ie, acute physiology and chronic health evaluation score [APACHE] 20-29 and simplified acute physiology score [SAPS 2] 35-58). Attributable mortality was close to zero in trauma, medical patients, and patients with low or high severity of illness scores. Competing risk analyses could be done for 5162 patients from 19 studies, and the overall daily hazard for intensive care unit (ICU) mortality after ventilator-associated pneumonia was 1·13 (95% CI 0·98-1·31). The overall daily risk of discharge after ventilator-associated pneumonia was 0·74 (0·68-0·80), leading to an overall cumulative risk for dying in the ICU of 2·20 (1·91-2·54). Highest cumulative risks for dying from ventilator-associated pneumonia were noted for surgical patients (2·97, 95% CI 2·24-3·94) and patients with mid-range severity scores at admission (ie, cumulative risks of 2·49 [1·81-3·44] for patients with APACHE scores of 20-29 and 2·72 [1·95-3·78] for those with SAPS 2 scores of 35-58). INTERPRETATION: The overall attributable mortality of ventilator-associated pneumonia is 13%, with higher rates for surgical patients and patients with a mid-range severity score at admission. Attributable mortality is mainly caused by prolonged exposure to the risk of dying due to increased length of ICU stay. FUNDING: None.

Characteristics and determinants of outcome of hospital-acquired bloodstream infections in intensive care units: the EUROBACT International Cohort Study.

PURPOSE: The recent increase in drug-resistant micro-organisms complicates the management of hospital-acquired bloodstream infections (HA-BSIs). We investigated the epidemiology of HA-BSI and evaluated the impact of drug resistance on outcomes of critically ill patients, controlling for patient characteristics and infection management. METHODS: A prospective, multicentre non-representative cohort study was conducted in 162 intensive care units (ICUs) in 24 countries. RESULTS: We included 1,156 patients [mean ± standard deviation (SD) age, 59.5 ± 17.7 years; 65 % males; mean ± SD Simplified Acute Physiology Score (SAPS) II score, 50 ± 17] with HA-BSIs, of which 76 % were ICU-acquired. Median time to diagnosis was 14 [interquartile range (IQR), 7-26] days after hospital admission. Polymicrobial infections accounted for 12 % of cases. Among monomicrobial infections, 58.3 % were gram-negative, 32.8 % gram-positive, 7.8 % fungal and 1.2 % due to strict anaerobes. Overall, 629 (47.8 %) isolates were multidrug-resistant (MDR), including 270 (20.5 %) extensively resistant (XDR), and 5 (0.4 %) pan-drug-resistant (PDR). Micro-organism distribution and MDR occurrence varied significantly (p < 0.001) by country. The 28-day all-cause fatality rate was 36 %. In the multivariable model including micro-organism, patient and centre variables, independent predictors of 28-day mortality included MDR isolate [odds ratio (OR), 1.49; 95 % confidence interval (95 %CI), 1.07-2.06], uncontrolled infection source (OR, 5.86; 95 %CI, 2.5-13.9) and timing to adequate treatment (before day 6 since blood culture collection versus never, OR, 0.38; 95 %CI, 0.23-0.63; since day 6 versus never, OR, 0.20; 95 %CI, 0.08-0.47). CONCLUSIONS: MDR and XDR bacteria (especially gram-negative) are common in HA-BSIs in critically ill patients and are associated with increased 28-day mortality. Intensified efforts to prevent HA-BSIs and to optimize their management through adequate source control and antibiotic therapy are needed to improve outcomes.

Local anesthetics time-dependently inhibit staphylococcus aureus phagocytosis, oxidative burst and CD11b expression by human neutrophils.

BACKGROUND AND OBJECTIVES: Local anesthetics have been shown to modulate neutrophil functions in a time-dependent manner, which might help to prevent inflammatory injury to the organism. However, if host defense mechanisms are affected similarly, the ability to eliminate bacteria might be reduced. We hypothesized that local anesthetics have time-dependent effects on phagocytosis of S. aureus, oxidative burst, and CD11b expression by human neutrophils. To test this hypothesis, we reanalyzed data from a previous study. METHODS: Blood samples from 11 healthy volunteers were incubated with lidocaine (1,846 mumol/L), bupivacaine (770 mumol/L) or ropivacaine (801 mumol/L) for 30 minutes. Thereafter, bacteria were added, either fluorescently labeled for determination of phagocytosis, or unstained for determination of oxidative burst and CD11b expression. After an additional incubation for 0, 10, 30, or 60 minutes, phagocytosis was stopped and neutrophils were stained with monoclonal antibodies for flow cytometric analysis. Data were analyzed by analysis of variance for repeated measurements. RESULTS: Lidocaine and bupivacaine inhibited neutrophil functions in a time-dependent manner (P < .05). Prolonged local anesthetic exposure reduced the fraction of ingesting neutrophils by 20% +/- 12% (mean +/- SD) and 7% +/- 7%, bacterial uptake by 19% +/- 16% and 14% +/- 12%, oxidative burst by 29% +/- 23% and 28% +/- 25%, and CD11b expression by 66% +/- 24% and 25% +/- 21% for lidocaine and bupivacaine, respectively. Ropivacaine exerted a time-dependent effect on CD11b expression only (24% +/- 34%; P < .05). CONCLUSIONS: Our results indicate that in a whole blood model, time-dependent effects of local anesthetics affect key neutrophil functions necessary for bacterial elimination. However, these effects only occur at concentrations that are unlikely to be routinely attained in the clinical setting, and concern about interfering with the host defense is likely unwarranted.

Selective decontamination of the digestive tract: cumulating evidence, at last?

Selective decontamination of the digestive tract (SDD), an infection-control strategy designed to prevent nosocomial pneumonia in mechanically ventilated patients, has been implemented in numerous studies for more than 2 decades, but its role remains controversial. Sentinel studies in the 1960s and 1970s identified a link between colonization of the upper respiratory tract and subsequent increased risk of developing nosocomial pneumonia in critically ill patients. Studies in the 1980s found that prophylaxis with topical and systemic antibiotics to decontamination of the upper respiratory tract and gastrointestinal tract (particularly depleting gram-negative aerobic bacteria) was associated with lower rates of infections. However, impact on survival was not substantiated. However, several recent studies (including randomized trials and meta-analyses) suggest that SDD may improve survival in selected cohorts of critically ill patients in intensive care units (ICUs). Because liberal use of SDD (or any antimicrobial prophylactic strategy) may lead to escalating antimicrobial resistance, the risk of resistance varies according to local pathogens and resistance patterns. This review describes the development of the SDD concept, discusses recently published trials, and develops points for discussion and research. Additional studies are required to further define appropriate indications and limitations of this preventative strategy.

Dose-dependent influence of barbiturates but not of propofol on human leukocyte phagocytosis of viable Staphylococcus aureus.

OBJECTIVE: Deep sedation with barbiturates or propofol is a standard therapy for patients with critically elevated intracranial pressure. Such patients are prone to infectious complications, especially to pneumonias, which are most commonly caused by Staphylococcus aureus. Although various immunomodulatory effects of barbiturates have been described in vitro, their influence on the phagocytosis of viable S. aureus has yet to be investigated. Therefore, we examined the effects of thiopentone, methohexitone, and propofol on the phagocytosis of viable S. aureus. DESIGN: Laboratory study. SETTING: University laboratory. PATIENTS: Ten healthy volunteers aged 32.5 +/- 7 yrs. INTERVENTIONS: Blood sampling. MEASUREMENTS AND MAIN RESULTS: Whole blood samples were preincubated with different concentrations of thiopentone, methohexitone, and propofol, which is an isopropylphenol derivate. After viable S. aureus was added, phagocytosis was stopped at different time points. Leukocytes were then stained with monoclonal antibodies for flow cytometric analysis of granulocyte recruitment (ratio of ingesting granulocytes) and phagocytosis activity (fluorescence intensity of ingested bacteria). Both barbiturates inhibited granulocyte recruitment and phagocytosis activity in a dose-dependent manner, whereas propofol did not affect any of the investigated variables. At concentrations higher than 7.6 x 10(-3) M (for thiopentone, p < .008) and 1.1 x 10(-3) M (for methohexitone, p < .04), granulocyte recruitment and phagocytosis activity were significantly inhibited. The calculated inhibitory concentrations (IC50) of thiopentone for granulocyte recruitment and for phagocytosis activity were 1.3 x 10(-2) M and 1.1 x 10(-2) M, respectively. The corresponding values for methohexitone were 3.6 x 10(-3) M and 1.1 x 10(-3) M. CONCLUSIONS: Our in vitro model points at substantially different effects of barbiturates and propofol on phagocytosis of S. aureus, which is one of the most important pathogens in patients who need neuroprotective therapy. The inhibitory effects of both barbiturates demonstrate a strong dose-dependency, with more pronounced effects for methohexitone. Impairment of phagocytosis activity was more pronounced than granulocyte recruitment.

Evaluation by monte carlo simulation of the pharmacokinetics of two doses of meropenem administered intermittently or as a continuous infusion in healthy volunteers.

Meropenem is a broad-spectrum carbapenem antibacterial agent. In order to optimize levels in plasma relative to the MICs, the ideal dose level and dosage regimen need to be determined. The pharmacokinetics of meropenem were studied in two groups, each comprising eight healthy volunteers who received the following doses: 500 mg as an intravenous infusion over 30 min three times a day (t.i.d.) versus a 250-mg loading dose followed by a 1,500 mg continuous infusion over 24 h for group A and 1,000 mg as an intravenous infusion over 30 min t.i.d. versus a 500-mg loading dose followed by a 3,000-mg continuous infusion over 24 h for group B. Meropenem concentrations in plasma and urine were determined by liquid chromatography-mass spectrometry/mass spectrometry and high-performance liquid chromatography with UV detection, respectively. Pharmacokinetic calculations were done by use of a two-compartment open model, and the data were extrapolated by Monte Carlo simulations for 10,000 simulated subjects for pharmacodynamic evaluation. There were no significant differences in total clearance and renal clearance between group A and group B or between the intermittent treatment and the continuous infusion. The analyses of the probability of target attainment by MIC for the high- and low-dose continuous infusions were robust up to MICs of 4 mg/liter and 2 mg/liter, respectively. The corresponding values for intermittent infusions were only 0.5 mg/liter and 0.25 mg/liter. When these observations were correlated with MICs obtained from the MYSTIC database, intermittent infusion results in adequate activity against two of the most common nosocomially acquired pathogens, Klebsiella pneumoniae and Enterobacter cloacae. However, against Pseudomonas aeruginosa, the evaluation shows a clear advantage of high-dose therapy administered as a continuous infusion. We believe that in the empirical therapy situation, the continuous-infusion mode of administration is most worth the extra efforts. We conclude that clinical trials for evaluation of the continuous infusions of meropenem in critically ill patients are warranted.

Selective decontamination of the digestive tract.

Ventilator-associated pneumonia usually originates from the patient's oropharyngeal microflora. In selective digestive decontamination, topical antibiotics are applied to the oropharynx and stomach for prevention of pneumonia and other infections, possibly reducing infection-related mortality. Selective digestive decontamination is also used for the prevention of gut-derived infections in acute necrotizing pancreatitis and liver transplantation. Despite numerous clinical trials, selective digestive decontamination remains controversial. Reduction of the incidence of pneumonia is accepted, but the extent of reduction is debated. Mortality was not reduced in most individual trials, but this finding was calculated in meta-analyses, especially for combined use of topical and systemic antibiotics in surgical ICU patients. Some investigators reported increased resistance and a shift to Gram-positive pathogens. Today, it appears that selective means not only selective suppression of pathogenic bacteria but also selection of appropriate groups of patients for underlying diseases and severity of illness, and selection of ICUs, where the endemic resistance patterns might allow the use of selective digestive decontamination at a relatively low risk for increased selection pressure.

Rationale for the development of immunotherapy regimens against enterococcal infections.

Enterococci are the third most common pathogen isolated in bloodstream infections. Increasing resistance against multiple antimicrobial agents has left few treatment options for enterococcal infections, and alternative therapeutic approaches are needed. Although a variety of virulence factors have been described for Enterococcus faecalis, only aggregation substance (AS) and a teichoic acid-like capsular polysaccharide have been evaluated for their potential for vaccine development. Antibodies raised against purified capsular polysaccharide are highly opsonic and protect mice against bacteremia after active and passive immunization. Since E. faecalis expresses only a limited number of capsular serotypes, this antigen may be an attractive candidate for development of a conjugate vaccine.

Ventilator-associated pneumonia.

Ventilator-associated pneumonia is the most serious infectious complication in critically ill patients, associated with increased length of intensive care unit treatment and high mortality rates. Investigations focused on outcome variables have improved the database to estimate diagnostic and therapeutic management strategies. This knowledge has diminished the importance of the discussion on how to diagnose the pneumonia. This review summarizes recent data on epidemiology and mortality, risk factors and prevention, diagnosis, microbiology and antimicrobial treatment of ventilator-associated pneumonia.

Assessment of the role of antibiotics and enterococcal virulence factors in a mouse model of extraintestinal translocation.

OBJECTIVE: To study the relative contribution of antibiotics and bacterial virulence factors in the process of translocation of Enterococcus faecalis from the gut to extraintestinal organs. DESIGN: Prospective controlled animal study. SETTING: Animal experimental laboratory at a university medical center. SUBJECTS: Fifty-two female Balb/c mice. INTERVENTIONS: We developed a mouse model to study the translocation of Enterococcus faecalis from the intestinal tract. Balb/c mice received sterile drinking water or antibiotic combinations to deplete their indigenous intestinal microflora. The animals subsequently were fed genetically engineered enterococci expressing different combinations of the putative enterococcal virulence factors aggregation substance and binding substance. Animals were killed, and their livers, spleens, and mesenteric lymph nodes were aseptically removed and cultured along with fecal samples for enumeration of bacteria. MEASUREMENTS AND MAIN RESULTS: All animals were colonized with the test strains at 2-6 x 109 colony forming units/g of feces; in the antibiotic-treated animals, feces were free from anaerobes and Enterobacteriaceae. In animals fed the identical bacterial mutant, the colony counts in mesenteric lymph nodes were significantly lower in mice not treated with antibiotics than in those treated with antibiotics (p =.016). Multigroup analysis of variance revealed no significant differences of the translocation frequencies for the different mutant strains; however, the differences were statistically significant for all groups receiving antibiotics vs. the group not receiving antibiotics (p <.05-.01). There was a trend (although not statistically significant) for a higher proportion of positive cultures from either spleen or liver in mice that had enterococci recovered from their mesenteric lymph nodes (28%) relative to those that did not have enterococci isolated from the lymph nodes (12%; rate ratio 2.39, p =.30 by logistic regression analysis). CONCLUSIONS: Oral antibiotics can select for extraintestinal translocation of Enterococcus faecalis, and neither aggregation substance nor binding substance seems to be required for this process. The experiments encourage further exploration of host and microbial factors contributing to translocation and may provide a better understanding of the pathogenesis of enterococcal infections in patients in intensive care units.