Laia Fernández-Barat

Linezolid limits burden of methicillin-resistant Staphylococcus aureus in biofilm of tracheal tubes.

Objective: To evaluate the effects of systemic treatment with linezolid compared with vancomycin on biofilm formation in mechanically ventilated pigs with severe methicillin-resistant Staphylococcus aureus–induced pneumonia. Design: Prospective randomized animal study. Setting: Departments of Pneumology, Microbiology, and Pharmacy of the Hospital Clínic, Barcelona, and Scientific and Technological Services of the University of Barcelona. Subjects: We prospectively analyzed 70 endotracheal tube samples. Endotracheal tubes were obtained from pigs either untreated (controls, n = 20), or treated with vancomycin (n = 32) or linezolid (n = 18). Interventions: The endotracheal tubes were obtained from a previous randomized study in tracheally intubated pigs with methicillin-resistant Staphylococcus aureus severe pneumonia, and mechanically ventilated for 69 ± 16 hrs. Measurements and Main Results: Distal and medial hemisections of the endotracheal tube were assessed to quantify methicillin-resistant Staphylococcus aureus burden, antibiotic biofilm concentration by high-performance liquid chromatography or bioassay, and biofilm thickness through scanning electron microscopy. We found a trend toward a significant variation in biofilm methicillin-resistant Staphylococcus aureus burden (log colony-forming unit/mL) among groups (p = .057), and the lowest bacterial burden was found in endotracheal tubes treated with linezolid (1.98 ± 1.68) in comparison with untreated endotracheal tubes (3.72 ± 2.20, p = .045) or those treated with vancomycin (2.97 ± 2.43, p = .286). Biofilm linezolid concentration was 19-fold above the linezolid minimum inhibitory concentration, whereas biofilm vancomycin concentration (1.60 ± 0.91 µg/mL) was consistently below or close to the vancomycin minimum inhibitory concentration. Biofilm was thicker in the vancomycin group (p = .077). Conclusions: Systemic treatment with linezolid limits endotracheal tube biofilm development and methicillin-resistant Staphylococcus aureus burden. The potential clinical usefulness of linezolid in decreasing the risk of biofilm-related respiratory infections during prolonged tracheal intubation requires further investigation.

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.

New therapy options for MRSA with respiratory infection/pneumonia.

Purpose of review Methicillin-resistant Staphylococcus aureus (MRSA) is a frequent causative agent of nosocomial pneumonia. Because of important clinical consequences of inappropriate treatment, a current review of the potential modifications undergone by S. aureus and adaptation to new treatment options is necessary. Recent findings Vancomycin has been considered the treatment of choice for pneumonia due to MRSA. However, detection of a progressive increase in the minimum inhibitory concentration for this antibiotic, its limited access to the lung parenchyma, and its considerable adverse effects have called into question its position. Linezolid has been shown to have a better pharmacokinetic and safety profiles. The prior uncertainty regarding the clinical superiority of linezolid appears to have been resolved with the publication of a recent trial. Linezolid achieved a higher clinical and microbiological response rate (the latter was not statistically significant), together with a lower incidence of all types of renal adverse effects in patients with nosocomial pneumonia, compared with vancomycin. Tigecycline, teicoplanin and quinupristin/dalfopristin were inferior to the compared drug in their respective clinical trials. The clinical efficacy of telavancin was similar to that of vancomycin. The renal adverse effects of telavancin have to be clarified. Other drugs are efficacious against MRSA but their profile should be evaluated in nosocomial pneumonia. Summary Current therapeutic alternatives for nosocomial pneumonia due to MRSA appear to be limited to vancomycin and linezolid. However, vancomycin pitfalls, together with the apparent clinical superiority of linezolid, appear to restrict its indication. Telavancin could be a good alternative in patients without basal renal failure.

Phenotypic shift in Pseudomonas aeruginosa populations from cystic fibrosis lungs after 2-week antipseudomonal treatment

BACKGROUND The influence of suppressive therapy on the different P. aeruginosa phenotypes harbored in the lungs of cystic fibrosis (CF) patients remains unclear. Our aim was to investigate the phenotypic changes (mucoidy, hypermutability, antibiotic resistance, transcriptomic profiles and biofilm) in P. aeruginosa populations before and after a 2-week course of suppressive antimicrobial therapy in chronically infected CF patients in Denmark. MATERIAL AND METHODS Prospective observational clinical study. Sputum samples were assessed before and after treatment for P. aeruginosa, with regard to: a) colony-forming units (CFU/mL), b) frequency of mucoids and non-mucoids, c) resistance pattern to anti-pseudomonal drugs, d) hypermutability, e) transcriptomic profiles, and f) presence of biofilms. RESULTS We collected 23 sputum samples (12 before antibiotic treatment and 11 after) and 77 P. aeruginosa from different CF patients. After treatment, the P. aeruginosa burden diminished but antimicrobial resistance to aztreonam, tobramycin and ceftazidime rose; non-mucoid phenotypes presented increased resistance to colistin, tobramycin, meropenem, and ciprofloxacin, and hypermutable phenotypes to ciprofloxacin. In spite of biofilm persistence, a down-regulation of genes involved in denitrification was detected. CONCLUSION A 2-week course of suppressive therapy reduces P. aeruginosa lung colonization and influences nitrogen metabolism genes, but also promotes antimicrobial resistance while P. aeruginosa persists in biofilms.

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.

Tracheal tube biofilm removal through a novel closed-suctioning system: an experimental study

BACKGROUND Tracheal tube biofilm develops during mechanical ventilation. We compared a novel closed-suctioning system vs standard closed-suctioning system in the prevention of tracheal tube biofilm. METHODS Eighteen pigs, on mechanical ventilation for 76 h, with P. aeruginosa pneumonia were randomized to be tracheally suctioned via the KIMVENT* closed-suctioning system (control group) or a novel closed-suctioning system (treatment group), designed to remove tracheal tube biofilm through saline jets and an inflatable balloon. Upon autopsy, two tracheal tube hemi-sections were dissected for confocal and scanning electron microscopy. Biofilm area, maximal and minimal thickness were computed. Biofilm stage was assessed. RESULTS Sixteen animals were included in the final analysis. In the treatment and control group, the mean (sd) pulmonary burden was 3.34 (1.28) and 4.17 (1.09) log cfu gr(-1), respectively (P=0.18). Tracheal tube P. aeruginosa colonization was 5.6 (4.9-6.3) and 6.2 (5.6-6.9) cfu ml(-1) (median and interquartile range) in the treatment and control group, respectively (P=0.23). In the treatment group, median biofilm area was 3.65 (3.22-4.21) log10 μm2 compared with 4.49 (4.27-4.52) log10 μm2 in the control group (P=0.031). In the treatment and control groups, the maximal biofilm thickness was 48.3 (26.7-71.2) µm (median and interquartile range) and 88.8 (43.8-125.7) µm, respectively. The minimal thickness in the treatment and control group was 0.6 (0-4.0) µm and 23.7 (5.3-27.8) µm (P=0.040) (P=0.017). Earlier stages of biofilm development were found in the treatment group (P<0.001). CONCLUSIONS The novel CSS reduces biofilm accumulation within the tracheal tube. A clinical trial is required to confirm these findings and the impact on major outcomes.

Assessment of in vivo versus in vitro biofilm formation of clinical methicillin-resistant Staphylococcus aureus isolates from endotracheal tubes

Our aim was to demonstrate that biofilm formation in a clinical strain of methicillin-resistant Staphylococcus aureus (MRSA) can be enhanced by environment exposure in an endotracheal tube (ETT) and to determine how it is affected by systemic treatment and atmospheric conditions. Second, we aimed to assess biofilm production dynamics after extubation. We prospectively analyzed 70 ETT samples obtained from pigs randomized to be untreated (controls, n = 20), or treated with vancomycin (n = 32) or linezolid (n = 18). A clinical MRSA strain (MRSA-in) was inoculated in pigs to create a pneumonia model, before treating with antibiotics. Tracheally intubated pigs with MRSA severe pneumonia, were mechanically ventilated for 69 ± 16 hours. All MRSA isolates retrieved from ETTs (ETT-MRSA) were tested for their in vitro biofilm production by microtiter plate assay. In vitro biofilm production of MRSA isolates was sequentially studied over the next 8 days post-extubation to assess biofilm capability dynamics over time. All experiments were performed under ambient air (O2) or ambient air supplemented with 5% CO2. We collected 52 ETT-MRSA isolates (placebo N = 19, linezolid N = 11, and vancomycin N = 22) that were clonally identical to the MRSA-in. Among the ETT-MRSA isolates, biofilm production more than doubled after extubation in 40% and 50% under 5% CO2 and O2, respectively. Systemic antibiotic treatment during intubation did not affect this outcome. Under both atmospheric conditions, biofilm production for MRSA-in was at least doubled for 9 ETT-MRSA isolates, and assessment of these showed that biofilm production decreased progressively over a 4-day period after extubation. In conclusion, a weak biofilm producer MRSA strain significantly enhances its biofilm production within an ETT, but it is influenced by the ETT environment rather than by the systemic treatment used during intubation or by the atmospheric conditions used for bacterial growth.

Factors associated with hospitalization in bronchiectasis exacerbations: a one-year follow-up study

BackgroundBronchiectasis (BE) is a chronic structural lung disease with frequent exacerbations, some of which require hospital admission though no clear associated factors have been identified. We aimed to evaluate factors associated with hospitalization due to exacerbations during a 1-year follow-up period.MethodsA prospective observational study was performed in patients recruited from specialized BE clinics. We considered all exacerbations diagnosed and treated with antibiotics during a follow-up period of 1 year. The protocol recorded baseline variables, usual treatments, Bronchiectasis Severity Index (BSI) and FACED scores, comorbid conditions and prior hospitalizations.ResultsTwo hundred and 65 patients were recruited, of whom 162 required hospital admission during the follow-up period. Independent risk factors for hospital admission were age, previous hospitalization due to BE, use of proton pump inhibitors, heart failure, FACED and BSI, whereas pneumococcal vaccination was a protective factor. The area under the receiver operator characteristic curve (AUC) was 0.799 for BSI model was 0.799, and 0.813 for FACED model.ConclusionsPrevious hospitalization, use of proton pump inhibitors, heart failure along with BSI or FACED scores is associated factors for developing exacerbations that require hospitalization. Pneumococcal vaccination was protective. This information may be useful for the design of preventive strategies and more intensive follow-up plans.

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.