Interpreting carbapenem susceptibility testing results for Pseudomonas aeruginosa.

OBJECTIVES: Carbapenems are among the most powerful antipseudomonal agents. Limited data is available on drug susceptibility testing by routine methods (disc diffusion and Etest) for meropenem and doripenem. We aimed to compare the in vitro activity of imipenem, meropenem, and doripenem against Pseudomonas aeruginosa. METHODS: A total of 311 P. aeruginosa strains isolated from respiratory specimens in 170 patients who developed ventilator-associated pneumonia in two intensive care units were collected over a period of 31 months. The susceptibility of these isolates to imipenem, meropenem, and doripenem were determined by Etest and disc diffusion method. RESULTS: Considering either all isolates or only the first isolates recovered per patient (311 and 170 respectively), the susceptibility rate for doripenem was higher than that for meropenem and imipenem. When MICs determined by Etest were converted into interpretative categories (S, I, R) using French (CA-SFM) guidelines, a poor correlation was observed for meropenem and doripenem. The percentages of correlation with the disc diffusion method were 90.6% and 89.7% for imipenem, 80.5% and 82.6% for meropenem, and 80.5% and 73.3% for doripenem, for the first isolates and all isolates, respectively. The rate of minor errors was as high as 17.7% and 16.1% for meropenem and 17.7% and 25.7% for doripenem for the first isolates and all isolates, respectively. CONCLUSION: The accuracy of disc diffusion using CA-SFM guidelines appears unsatisfactory for all three carbapenems justifying guideline update for P. aeruginosa and carbapenems.

Indications for extracorporeal support: why do we need the results of the EOLIA trial?

Acute respiratory distress syndrome (ARDS) is a severe lung disease, with an associated mortality rate exceeding 60% for the most severe forms of the disease. In these situations, establishing an extracorporeal circuit, combining a centrifugal pump and a membrane oxygenator (extra-corporeal membrane oxygenation, ECMO), can ensure total pulmonary assistance and allow the lungs to rest under ultraprotective mechanical ventilation. Unfortunately, former trials of ECMO in ARDS were negative or highly criticized due to many technical and methodological shortcomings. Prior to the widespread use of venovenous ECMO for severe ARDS, new trials are needed to test the efficacy of early initiation of the technique with tight control of mechanical ventilation in the control group, initiation of ECMO prior to transportation to ECMO centers, and the use of ECMO in all patients randomly assigned to receive this treatment. Therefore, the international multicenter randomized EOLIA (ECMO to rescue Lung Injury in severe ARDS) trial was designed to test the benefit of systematic and early installation of the latest-generation ECMO circuits in patients with very severe ARDS. Patients randomized to the control group were managed with tight control of mechanical ventilation and recourse to paralyzing agents and prone positioning, while an ethical crossover option to ECMO was permitted only if refractory hypoxemia (SaO2 < 80%) lasted for > 6 h despite all possible conventional emergency interventions. The primary endpoint of the study was the 60-day mortality rate, with an expected 20% absolute mortality reduction with ECMO.

Use of nebulized antimicrobials for the treatment of respiratory infections in invasively mechanically ventilated adults: a position paper from the European Society of Clinical Microbiology and Infectious Diseases.

With an established role in cystic fibrosis and bronchiectasis, nebulized antibiotics are increasingly being used to treat respiratory infections in critically ill invasively mechanically ventilated adult patients. Although there is limited evidence describing their efficacy and safety, in an era when there is a need for new strategies to enhance antibiotic effectiveness because of a shortage of new agents and increases in antibiotic resistance, the potential of nebulization of antibiotics to optimize therapy is considered of high interest, particularly in patients infected with multidrug-resistant pathogens. This Position Paper of the European Society of Clinical Microbiology and Infectious Diseases provides recommendations based on the Grading of Recommendations Assessment, Development and Evaluation (GRADE) methodology regarding the use of nebulized antibiotics in invasively mechanically ventilated adults, based on a systematic review and meta-analysis of the existing literature (last search July 2016). Overall, the panel recommends avoiding the use of nebulized antibiotics in clinical practice, due to a weak level of evidence of their efficacy and the high potential for underestimated risks of adverse events (particularly, respiratory complications). Higher-quality evidence is urgently needed to inform clinical practice. Priorities of future research are detailed in the second part of the Position Paper as guidance for researchers in this field. In particular, the panel identified an urgent need for randomized clinical trials of nebulized antibiotic therapy as part of a substitution approach to treatment of pneumonia due to multidrug-resistant pathogens.

Key considerations on nebulization of antimicrobial agents to mechanically ventilated patients.

Nebulized antibiotics have an established role in patients with cystic fibrosis or bronchiectasis. Their potential benefit to treat respiratory infections in mechanically ventilated patients is receiving increasing interest. In this consensus statement of the European Society of Clinical Microbiology and Infectious Diseases, the body of evidence of the therapeutic utility of aerosolized antibiotics in mechanically ventilated patients was reviewed and resulted in the following recommendations: Vibrating-mesh nebulizers should be preferred to jet or ultrasonic nebulizers. To decrease turbulence and limit circuit and tracheobronchial deposition, we recommend: (a) the use of specifically designed respiratory circuits avoiding sharp angles and characterized by smooth inner surfaces, (b) the use of specific ventilator settings during nebulization including use of a volume controlled mode using constant inspiratory flow, tidal volume 8 mL/kg, respiratory frequency 12 to 15 bpm, inspiratory:expiratory ratio 50%, inspiratory pause 20% and positive end-expiratory pressure 5 to 10 cm H2O and (c) the administration of a short-acting sedative agent if coordination between the patient and the ventilator is not obtained, to avoid patient's flow triggering and episodes of peak decelerating inspiratory flow. A filter should be inserted on the expiratory limb to protect the ventilator flow device and changed between each nebulization to avoid expiratory flow obstruction. A heat and moisture exchanger and/or conventional heated humidifier should be stopped during the nebulization period to avoid a massive loss of aerosolized particles through trapping and condensation. If these technical requirements are not followed, there is a high risk of treatment failure and adverse events in mechanically ventilated patients receiving nebulized antibiotics for pneumonia.

Global survey on nebulization of antimicrobial agents in mechanically ventilated patients: a call for international guidelines.

Nebulized antimicrobial agents are increasingly administered for treatment of respiratory infections in mechanically ventilated (MV) patients. A structured online questionnaire assessing the indications, dosages and recent patterns of use for nebulized antimicrobial agents in MV patients was developed. The questionnaire was distributed worldwide and completed by 192 intensive care units. The most common indications for using nebulized antimicrobial agent were ventilator-associated tracheobronchitis (VAT; 58/87), ventilator-associated pneumonia (VAP; 56/87) and management of multidrug-resistant, Gram-negative (67/87) bacilli in the respiratory tract. The most common prescribed nebulized agents were colistin methanesulfonate and sulfate (36/87, 41.3% and 24/87, 27.5%), tobramycin (32/87, 36.7%) and amikacin (23/87, 26.4%). Colistin methanesulfonate, amikacin and tobramycin daily doses for VAP were significantly higher than for VAT (p < 0.05). Combination of parenteral and nebulized antibiotics occurred in 50 (86%) of 58 prescriptions for VAP and 36 (64.2%) of 56 of prescriptions for VAT. The use of nebulized antimicrobial agents in MV patients is common. There is marked heterogeneity in clinical practice, with significantly different in use between patients with VAP and VAT. Randomized controlled clinical trials and international guidance on indications, dosing and antibiotic combinations to improve clinical outcomes are urgently required.

Ruling out false-positive urinary Legionella pneumophila serogroup 1 and Streptococcus pneumoniae antigen test results by heating urine.

We report here false-positive urinary Legionella pneumophila serogroup 1 and Streptococcus pneumoniae antigen test results due to rabbit antilymphocyte serum treatment and provide a simple and fast solution to rule them out by heating urine.

[Viral lung disease due to herpesviridae in the intensive care unit]. / Infections respiratoires virales à herpesviridae en réanimation.

Herpesviridae, including herpes simplex virus (HSV) and cytomegalovirus (CMV), are commonly detected in the respiratory tract of non-immunocompromised patients receiving mechanical ventilation. Although their detection usually involves viral reactivation without the involvement of pulmonary tissue, viral lung disease may occur in a particular population of patients. Although histological examination for specific cytopathic effects forms the basis of diagnosis, the use of modern virological tests (amplification using real-time polymerase chain reaction to estimate the vial load) should replace the histological tests in the near future. HSV bronchopneumonitis is associated with the reactivation of HSV in oropharyngeal and oral-labial lesions. It seems to clearly affect patients' outcome due to prolonged mechanical ventilation and length of stay in the intensive care unit (ICU). However, only interventional studies will be able to determine its real impact. To date, use of acyclovir in these patients remains to be assessed. Although CMV reactivation in the blood is frequent in ICU patients, CMV pneumonia is difficult to diagnose because of the cumbersomeness of the procedure (open lung biopsies). Its true prognosis remains uncertain. The use of ganciclovir in this subset of patients also remains to be assessed.

Microsatellite analysis of HSV-1 isolates: from oropharynx reactivation toward lung infection in patients undergoing mechanical ventilation.

BACKGROUND: According to recent reports, herpes simplex virus type 1 (HSV-1) induces bronchopneumonitis (BPn) in immunocompetent patients undergoing prolonged mechanical ventilation (MV), whose respiratory functions deteriorate with a poor outcome. HSV-1 BPn is associated with HSV symptomatic or symptomless reactivation in the oropharynx. OBJECTIVES: We sought to systematically and genetically characterize HSV-1 strains isolated from immunocompetent patients receiving prolonged MV and to characterize the genetic relationship of strains sequentially isolated from oropharyngeal samples (OPS) and broncho-alveolar liquids (BAL) to determine the natural course of HSV BPn. STUDY DESIGN: In this molecular epidemiological study, microsatellite technology was used to determine genetic relationships between 211 HSV-1 strains isolated from OPS and/or BAL from 106 patients receiving MV. RESULTS: Microsatellite haplotypes of HSV-1 strains sequentially isolated from the same individual were identical, and HSV-1 isolates from the lung were genetically indistinguishable from strains isolated from the oral cavity. Each patient was characterized by their own HSV-1 microsatellite haplotype, and no nosocomial transmission of strains between patients was observed. CONCLUSION: Our results demonstrate that, in patients who receive MV, the HSV-1 pulmonary infection results from the reactivation of genetically related HSV-1 in the oropharynx, which progressively infects the lower respiratory tract.

Utilization of microsatellite polymorphism for differentiating herpes simplex virus type 1 strains.

The herpes simplex virus type 1 (HSV-1) genome is a linear double-stranded DNA of 152 kpb. It is divided into long and short regions of unique sequences termed U(L) and U(S), respectively, and these are flanked by regions of inverted internal and terminal repeats. Microsatellites are short tandem repeats of 1- to 6-nucleotide motifs; they are often highly variable and polymorphic within the genome, which raises the question of whether they may be used as molecular markers for the precise differentiation of HSV-1 strains. In this study, 79 different microsatellites (mono-, di-, and trinucleotide repeats) in the HSV-1 complete genome were identified by in silico analysis. Among those microsatellites, 45 were found to be distributed in intergenic or noncoding inverted repeat regions, while 34 were in open reading frames. Length polymorphism analysis of the PCR products was used to investigate a set of 12 distinct HSV-1 strains and allowed the identification of 23 polymorphic and 6 monomorphic microsatellites, including two polymorphic trinucleotide repeats (CGT and GGA) within the UL46 and US4 genes, respectively. A multiplex PCR method that amplified 10 polymorphic microsatellites was then developed for the rapid and accurate genetic characterization of HSV-1 strains. Each HSV-1 strain was characterized by its own microsatellite haplotype, which proved to be stable over time in cell culture. This relevant innovative tool was successfully applied both to confirm the close relationship between sequential HSV-1 isolates collected from patients with multiple recurrent infections and to investigate putative nosocomial infections.

Involvement of the endothelin system in experimental critical hind limb ischemia.

BACKGROUND: Endothelin- (ET-1) is involved in the pathogenesis of several ischemic diseases. We investigated the hypotheses that ET-1 is involved in the pathogenesis of experimental critical hind limb ischemia and that ET-1 receptor antagonists have a protective effect. MATERIALS AND METHODS: Critical hind limb ischemia was achieved by exclusion of the femoral artery and embolization of collateral vessels in rats. The induction of endothelin system components by ischemia was analyzed by reverse transcription-polymerase chain reaction (RT-PCR) (mRNAs) and immunoassay (peptides) in the plasma and ischemic muscles 5 hr (H5), 5 days (D5) and 14 days (D14) after ischemia. Two groups of rats received 100 mg/kg/day of either Bosentan, a mixed ET(A/B) receptor antagonist (n = 12), or LU 135252, a selective ET(A) receptor antagonist (n = 9), and a control group without treatment (n = 12) served as control. Muscle blood flow and ischemia were monitored in the ischemic limb by laser Doppler and phosphorylase activity, respectively. RESULTS: The procedure induced an 80% decrease in muscle blood flow and complete suppression of phosphorylase activity without necrosis. At day 14, the tissue blood flow remained reduced by 70% and phosphorylase activity was suppressed completely. There was up-regulation of preproendothelin-1, preproET-3, endothelin converting enzyme-1, and ET(A). ET(B) receptor mRNAs in ischemic muscle at day 5 and day 14 was accompanied by an increase in muscle concentration of ET-1 at day 5, without significant changes in plasma endothelin. Treatment with Bosentan and LU 135252 increased tissue blood flow and reduced muscle ischemia at day 14. CONCLUSIONS: Tissue production of ET- 1 is up-regulated in experimental critical hind limb ischemia. Inhibition of the endothelin system by a mixed ET(A/B) receptor antagonist may protect, at least in part, against muscle injury.