Clinical-epidemiological characteristics of deaths due to dengue during an outbreak in northern Peru. / Características clínicas y epidemiológicas de las muertes por dengue durante un brote en el norte del Perú.

Motivation for the study. To describe the characteristics of patients who died from severe dengue fever during the 2017 El Niño in Piura. Main findings. Mortality from severe dengue was higher in adult women. First contact with healthcare took place mostly in higher level hospitals. Admission to a specialized unit was late for severe dengue cases. Implications. Control of dengue fever involves several aspects, such as, access to health, prevention, water availability, vector control and education; therefore, it is important to strengthen public health policies in this regard. In order to achieve this goal, local and central government sectors must be involved.

Motivación para realizar el estudio. Describir las características de los pacientes fallecidos por dengue grave durante el fenómeno de El Niño del 2017 en Piura. Principales hallazgos. La mortalidad del dengue grave fue mayoritaria en las mujeres adultas, la primera atención se realizó en hospitales de mayor nivel y la atención para casos graves de dengue en una unidad especializada fue tardía. Implicancias. La mortalidad del dengue grave fue mayoritaria en las mujeres adultas, la primera atención se realizó en hospitales de mayor nivel y la atención para casos graves de dengue en una unidad especializada fue tardía.

Características clínicas y epidemiológicas de las muertes por dengue durante un brote en el norte del Perú / Clinical-epidemiological characteristics of dengue deaths during an outbreak in northern Peru

Con el objetivo de describir las características clínicas y epidemiológicas de los pacientes fallecidos por dengue durante el 2017 en Piura, se realizó un estudio retrospectivo de revisión de 24 historias clínicas. El 67% de los casos fueron mujeres y tres (12,5%) estaban embarazadas. La diabetes (12,5%) y la hipertensión (16,7%) fueron las comorbilidades más frecuentes. Sólo en el 12,5% se reportó dengue previo. El tiempo transcurrido desde asistencia sanitaria hasta la muerte fue de 4,10 (DE: 5,34) días. Se hicieron transfusiones de glóbulos rojos en el 45,8% de los casos, plasma en el 25%, plaquetas en el 16,8% y crioprecipitado en el 16,8%. También fueron frecuentes la terapia con cristaloides (91,7%) y el tratamiento con fármacos vasoactivos (70,8%). En conclusión, la mortalidad del dengue grave fue mayoritaria en las mujeres adultas y el tiempo de atención desde el primer establecimiento de salud hasta una unidad especializada fue prolongada.

Objective: To describe the clinical-epidemiological characteristics of patients who died from dengue during 2017. Methods: We conducted a retrospective study of the information related to cases of dengue deaths in the department of Piura. Results: We reviewed 24 medical records. Sixty-seven percent were women and 3 (12.5%) were pregnant. Diabetes (12.5%) and hypertension (16.7%) were the most frequent comorbidities. Previous dengue fever was reported in only 12.5%. The time from health care and death was 4.10 ± 5.34 days. Red blood cell transfusions were performed in 45.8%, plasma in 25%, platelets in 16.8% and cryoprecipitate in 16.8% of cases. Crystalloid therapy (91.7%) and treatment with vasoactive drugs (70.8%) were also frequent. In conclusion, mortality from severe dengue fever was predominantly in adult women, and the time of care from the first health facility to a specialized unit was prolonged.

KPC-2-NDM-1-producing Serratia marcescens: first description in Peru.

Two clonal extensively-resistant S. marcescens were isolated in Peru. The presence and transferability of extended-spectrum ß-lactamases and IMP, KPC, NDM, OXA-48 and VIM were determined. The concomitant presence of KPC-2 and NDM-1 was confirmed in both isolates, with KPC-2 being able to be transferred.

Worrying levels of antimicrobial resistance in Gram-negative bacteria isolated from cell phones and uniforms of Peruvian intensive care unit workers.

BACKGROUND: Healthcare worker (HCW) uniforms and cell phones are involved in pathogen transmission. This study aimed to characterize pathogenic microorganism isolates from HCW uniforms and cell phones. METHODS: Gram-negative microorganisms were recovered from HCW uniforms and cell phones. Antimicrobial susceptibility and the presence of extended-spectrum ß-lactamases (ESBL) and carbapenemases were determined. RESULTS: Escherichia coli was the most prevalent microorganism. Overall, high levels of resistance to cephalosporins, quinolones, co-trimoxazole and colistin were found. ESBL were mainly related to blaCTX-M-15 and blaSHV- genes. Carbapenem-resistant isolates presented as blaKPC or blaNDM. CONCLUSIONS: High levels of antimicrobial resistance, including colistin, were detected. Therefore, strategies are urgently needed to prevent bacterial dissemination.

Retrospective analysis of the emergence of antibiotic-resistant Salmonella enterica infections in a level IV hospital from Lima, Peru.

This study retrospectively analysed the emergence of multidrug-resistant Salmonella enterica in a level IV hospital in Lima, Peru. A total of 64 S. enterica from January 2009 to June 2010 (Period 1, 24 isolates) and January 2012 to December 2014 (Period 2, 40 isolates) were included. Some 25 were from non-hospitalized and 39 from hospitalized patients. Antimicrobial susceptibility to 15 antimicrobial agents was established by automated methods. Most of the isolates were from blood (46.9%), urine (21.9%) and faeces (14.1%). There was a reduction in blood isolates in Period 2, while all the faecal isolates were from this period. In Period 1, only 3/24 (12.5%) isolates showed antibiotic resistance, whereas 25/39 isolates (64.1%) from Period 2 were antibiotic-resistant, with multidrug-resistant and extensively drug-resistant rates of 17.9% and 20.5%, respectively. Multidrug-resistant/extensively drug-resistant Salmonella isolates were introduced in the hospital in 2013, with Salmonella recovered from faeces from non-hospitalized patients suggested an increase in community-acquired multidrug-resistant/extensively drug-resistant Salmonella infections.

Evolution of the prevalence and antimicrobial resistance among Escherichia coli isolated as a cause of infection in patients admitted to a iv-level hospital in Lima, Peru

The levels and evolution of antimicrobial resistance of Escherichia coli during 01/2009-06/2010 (Period 1), 01/2012-06-2013 (Period 2) and 07/2013-12/2014 (Period 3) were analyzed. Identification, susceptibility levels to 13 antibiotics and the presence of extendedspectrum ß-lactamases (ESBLs) were determined. Overall, 9,918 microorganisms were isolated as a cause of infection. Of these 3,016 (30.4%) were E. coli, with 1,770 (59%), 992 (33%) and 254 (8%), from the Medicine and the Surgery Departments and the Intensive Care Unit (ICU), respectively. There was a significant increase (p=0.0002) of E. coli throughout considered periods. The isolates presented high levels of resistance (>60%) to cephalosporins, ciprofloxacin and cotrimoxazole, being only susceptible to imipenem (0.3% of resistance) and tigecycline. Overall the analysis of evolution of antimicrobial resistance showed that resistance to cephalosporins and amikacin significantly increased, while, the ones of piperacillintazobactam, cotrimoxazole and gentamicin had significantly decreased. Nevertheless, the ICU isolates showed an inverse scenario for cephalosporins. These findings agree with an increase of ESBLs on the Medicine (56% to 66%; p<0.0001) and on the Surgery (54% to 62%; p=0.0197) departments, with a parallel decrease in the ICU (76% to 68%). In summary, high levels of antimicrobial resistance have been reported among E. coli, with worrisome levels of ESBL. A continuous surveillance of antimicrobial resistance levels in the area is needed.

Evolution of Antimicrobial Resistance Levels of ESKAPE Microorganisms in a Peruvian IV-Level Hospital.

BACKGOUND: The members of the so-called ESKAPE group (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa and Enterobacter spp.) are a frequent cause of severe infection, ranking among the most relevant causes of hospital infections. In Peru, few studies, often focused in a single ESKAPE microorganism, have been performed, but none providing an overall and comprehensive long-time analysis of the antibiotic resistance of ESKAPE microorganisms. In the present study, the evolution of antimicrobial resistance levels of ESKAPE microorganisms isolated during 2009 - 2010 (Period 1) and 2012 - 2014 (Period 2) in a IV-level hospital in Lima was analyzed. MATERIALS AND METHODS: ESKAPE microorganisms were isolated from inpatients clinical samples. Bacterial identification, as well as antimicrobial susceptibility levels for up to 29 antimicrobial agents and presence of Extended-Spectrum ß-Lactamases (only established in K. pneumoniae) were determined using automatic methods. RESULTS: Of 9,918 clinical isolates, 1,917/3,777 (50.8%) [JAN/2009-JUN/2010 (Period 1)] and 4764/6141 (46.4%) [JAN/2012-DEC/2014 (Period 2)] belonged to the ESKAPE group (P <0.0001). ESKAPE were more frequent in the intensive care unit (ICU) (P <0.0001). E. faecium decreased from 5.1% to 4.1% (P <0.5), S. aureus from 10.5% to 7.0% (P <0.05), and P. aeruginosa from 12.9% to 11.6% (P <0.05), while, A. baumannii increased from 5.0% to 6.7% (P <0.05), mainly related to an increase in ICU isolates (8.4% vs. 17.1%; P <0.05). Overall, high levels of antimicrobial resistance were detected, but with few exceptions (e.g. vancomycin in E. faecium), antibiotic resistance levels remained stable or lower in Period 2. Contrarily, A. baumannii showed significantly increased resistance to different cephalosporins, carbapenems and amoxicillin plus sulbactam. CONCLUSION: The introduction of a successful extensively drug-resistant A. baumannii clone in the ICU is suspected. The isolation of ESKAPE and levels of antibiotic resistance levels have reduced over time.

Tolerance to disinfectants (chlorhexidine and isopropanol) and its association with antibiotic resistance in clinically-related Klebsiella pneumoniae isolates.

Disinfectants play an essential role in controlling the dissemination of bacteria in health care settings, but it may also contribute to the selection of antibiotic resistance bacteria. This study looked at Klebsiella pneumoniae isolates collected from three hospitals in Lima, Peru, in order to evaluate: their susceptibility to chlorhexidine [CHG] and isopropanol [ISP]), and their association with antimicrobial susceptibility. We analyzed 59 K. pneumoniae isolates and assessed their CHG and ISP susceptibility by minimum inhibitory concentrations (MICs). Additionally, we performed a regression analysis to assess the association between disinfectant tolerance and antibiotic resistance (measured by the disc diffusion method), colistin resistance (by microdilution), carbapenemases presence (by polymerase chain reaction [PCR]), and clonal relationships (by pulsed-field gel electrophoresis [PFGE]). Eleven K. pneumoniae strains were isolated from fomites, and 48 strains from clinical samples. The MIC range of these isolates was 8-128 µg/ml for CHG and 16-256 mg/ml for ISP. We found that resistance to trimethoprim/sulfamethoxazole (TMP/SMX) was the main factor associated with CHG log2 MIC (ß = 0.65; 95%CI: 0.03, 1.27; R2 = 0.07). In the case of ISP, the log2(MIC) was associated with the institution of origin, showing lower ISP log2(MIC) in fomites compared to clinical samples(ß = -0.77; 95%CI: -1.54, -0.01; R2 = 0.08). Resistance to CHG and ISP among K. pneumoniae isolates found in Peruvian hospitals seems to be elevated and highly variable. Further studies are needed to confirm our results and implement actionable interventions if necessary.

Hippocampal Damage During Mechanical Ventilation in Trendelenburg Position: A Secondary Analysis of an Experimental Study on the Prevention of Ventilator-Associated Pneumonia.

We previously corroborated benefits of the Trendelenburg position in the prevention of ventilator-associated pneumonia (VAP). We now investigate its potential effects on the brain versus the semirecumbent position. We studied 17 anesthetized pigs and randomized to be ventilated and positioned as follows: duty cycle (TI/TTOT) of 0.33, without positive end-expiratory pressure (PEEP), placed with the bed oriented 30° in anti-Trendelenburg (control group); positioned as in the control group, with TI/TTOT adjusted to achieve an expiratory flow bias, PEEP of 5 cm H2O (IRV-PEEP); positioned in 5° TP and ventilated as in the control group (TP). Animals were challenged into the oropharynx with Pseudomonas aeruginosa. We assessed hemodynamic parameters and systemic inflammation throughout the study. After 72 h, we evaluated incidence of microbiological/histological VAP and brain injury. Petechial hemorrhages score was greater in the TP group (P = 0.013). Analysis of the dentate gyrus showed higher cell apoptosis and deteriorating neurons in TP animals (P < 0.05 vs. the other groups). No differences in systemic inflammation were found among groups. Cerebral perfusion pressure was higher in TP animals (P < 0.001), mainly driven by higher mean arterial pressure. Microbiological/histological VAP developed in 0%, 67%, and 86% of the animals in the TP, control, and IRV-PEEP groups, respectively (P = 0.003). In conclusion, the TP prevents VAP; yet, we found deleterious neural effects in the dentate gyrus, likely associated with cerebrovascular modification in such position. Further laboratory and clinical studies are mandatory to appraise potential neurological risks associated with long-term TP.

Appraisal of systemic inflammation and diagnostic markers in a porcine model of VAP: secondary analysis from a study on novel preventive strategies.

BACKGROUND: We previously evaluated the efficacy of a ventilatory strategy to achieve expiratory flow bias and positive end-expiratory pressure (EFB + PEEP) or the Trendelenburg position (TP) for the prevention of ventilator-associated pneumonia (VAP). These preventive measures were aimed at improving mucus clearance and reducing pulmonary aspiration of bacteria-laden oropharyngeal secretions. This secondary analysis is aimed at evaluating the effects of aforementioned interventions on systemic inflammation and to substantiate the value of clinical parameters and cytokines in the diagnosis of VAP. METHODS: Twenty female pigs were randomized to be positioned in the semirecumbent/prone position, and ventilated with duty cycle 0.33 and without PEEP (control); positioned as in the control group, PEEP 5 cmH2O, and duty cycle to achieve expiratory flow bias (EFB+PEEP); ventilated as in the control group, but in the Trendelenburg position (Trendelenburg). Following randomization, P. aeruginosa was instilled into the oropharynx. Systemic cytokines and tracheal secretions P. aeruginosa concentration were quantified every 24h. Lung biopsies were collected for microbiological confirmation of VAP. RESULTS: In the control, EFB + PEEP, and Trendelenburg groups, lung tissue Pseudomonas aeruginosa concentration was 2.4 ± 1.5, 1.9 ± 2.1, and 0.3 ± 0.6 log cfu/mL, respectively (p = 0.020). Whereas, it was 2.4 ± 1.9 and 0.6 ± 0.9 log cfu/mL in animals with or without VAP (p < 0.001). Lower levels of interleukin (IL)-1ß (p = 0.021), IL-1RA (p < 0.001), IL-4 (p = 0.005), IL-8 (p = 0.008), and IL-18 (p = 0.050) were found in Trendelenburg animals. VAP increased IL-10 (p = 0.035), tumor necrosis factor-α (p = 0.041), and endotracheal aspirate (ETA) P. aeruginosa concentration (p = 0.024). A model comprising ETA bacterial burden, IL-10, and TNF-α yielded moderate discrimination for the diagnosis of VAP (area of the receiver operating curve 0.82, 95% CI 0.61-1.00). CONCLUSIONS: Our findings demonstrate anti-inflammatory effects associated with the Trendelenburg position. In this reliable model of VAP, ETA culture showed good diagnostic accuracy, whereas systemic IL-10 and TNF-α marginally improved accuracy. Further clinical studies will be necessary to confirm clinical value of the Trendelenburg position as a measure to hinder inflammation during mechanical ventilation and significance of systemic IL-10 and TNF-α in the diagnosis of VAP.

Endotracheal tube biofilm translocation in the lateral Trendelenburg position.

INTRODUCTION: Laboratory studies demonstrated that the lateral Trendelenburg position (LTP) is superior to the semirecumbent position (SRP) in the prevention of ventilator-associated pulmonary infections. We assessed whether the LTP could also prevent pulmonary colonization and infections caused by an endotracheal tube (ETT) biofilm. METHODS: Eighteen pigs were intubated with ETTs colonized by Pseudomonas aeruginosa biofilm. Pigs were positioned in LTP and randomized to be on mechanical ventilatin (MV) up to 24 hour, 48 hour, 48 hour with acute lung injury (ALI) by oleic acid and 72 hour. Bacteriologic and microscopy studies confirmed presence of biofilm within the ETT. Upon autopsy, samples from the proximal and distal airways were excised for P.aeruginosa quantification. Ventilator-associated tracheobronchitis (VAT) was confirmed by bronchial tissue culture ≥3 log colony forming units per gram (cfu/g). In pulmonary lobes with gross findings of pneumonia, ventilator-associated pneumonia (VAP) was confirmed by lung tissue culture ≥3 log cfu/g. RESULTS: P.aeruginosa colonized the internal lumen of 16 out of 18 ETTs (88.89%), and a mature biofilm was consistently present. P.aeruginosa colonization did not differ among groups, and was found in 23.6% of samples from the proximal airways, and in 7.1% from the distal bronchi (P = 0.001). Animals of the 24 hour group never developed respiratory infections, whereas 20%, 60% and 25% of the animals in group 48 hour, 48 hour-ALI and 72 hour developed P.aeruginosa VAT, respectively (P = 0.327). Nevertheless, VAP never developed. CONCLUSIONS: Our findings imply that during the course of invasive MV up to 72 hour, an ETT P.aeruginosa biofilm hastily colonizes the respiratory tract. Yet, the LTP compartmentalizes colonization and infection within the proximal airways and VAP never develops.

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.

Effects of manual rib cage compressions on expiratory flow and mucus clearance during mechanical ventilation.

OBJECTIVES: We investigated the effects of two different types of manual rib cage compression on expiratory flow and mucus clearance during prolonged mechanical ventilation in pigs. DESIGN: Prospective randomized animal study. SETTING: Animal research facility, University of Barcelona, Spain. SUBJECTS: Nine healthy pigs. MEASUREMENT AND MAIN RESULTS: Pigs were tracheally intubated, sedated, paralyzed, and mechanically ventilated. The animals were prone on a surgical bed in the anti-Trendelenburg position. The experiments were carried out at approximately 60 and 80 hrs from the beginning of mechanical ventilation. Two types of manual rib cage compressions were tested: Hard and brief rib cage compressions synchronized with early expiratory phase (hard manual rib cage compression) and soft and gradual rib cage compressions applied during the late expiratory phase (soft manual rib cage compression). The interventions were randomly applied for 15min with a 15-min interval between treatments. Respiratory flow and mucus movement were assessed during the interventions. Respiratory mechanics and hemodynamics were assessed prior to and after the interventions. Peak expiratory flow increased to 60.1±7.1L/min in comparison to 51.2±4.6L/min without treatment (p < 0.0015) and 48.7±4.3L/min with soft manual rib cage compression (p = 0.0002). Similarly, mean expiratory flow increased to 28.4±5.2L/min during hard manual rib cage compression vs. 15.9±2.2 and 16.6±2.8L/min without treatment and soft manual rib cage compression, respectively (p = 0.0006). During hard manual rib cage compression, mucus moved toward the glottis (1.01 ± 2.37mm/min); conversely, mucus moved toward the lungs during no treatment and soft manual rib cage compression, -0.28 ± 0.61 and -0.15±0.95mm/min, respectively (p = 0.0283). Soft manual rib cage compression slightly worsened static lung elastance and cardiac output (p = 0.0391). CONCLUSIONS: Hard manual rib cage compression improved mucus clearance in animals positioned in the anti-Trendelenburg position. The technique appeared to be safe. Conversely, soft manual rib cage compression was not effective and potentially unsafe. These findings corroborate the predominant role of peak expiratory flow on mucus clearance.

An in vitro study to assess determinant features associated with fluid sealing in the design of endotracheal tube cuffs and exerted tracheal pressures.

OBJECTIVE: To assess the structural characteristics involved in the design of high-volume low-pressure endotracheal tube cuffs that are associated with fluid sealing effectiveness and to determine the extent of transmitted tracheal pressures upon cuff inflation. DESIGN: In vitro study. SETTINGS: Pneumology laboratories. INTERVENTIONS: Eight high-volume low-pressure cuffs of cylindrical or tapered shape, made of polyvinylchloride or polyurethane, were studied. Cuffs were tested within a tracheal model, oriented 30° above horizontal to assess 1 hr leakage of oropharyngeal secretions simulant at cuff internal pressures of 15-30 cm H2O. The four best performing cuffs were evaluated for 24 hrs using an internal pressure of 30 cm H2O. The extent of transmitted tracheal wall pressure throughout the cuff-trachea contact area was determined using an internal pressure sensor within a tracheal model upon cuff inflation up to 30 cm H2O. MEASUREMENTS AND MAIN RESULTS: Outer diameter, length, and compliance of each cuff were assessed. Multivariate regression analysis was performed to identify the main determinants of simulant leakage rate. The cuff-trachea contact area and the percentage of tracheal wall pressure measurements greater than 50 cm H2O were computed. Cuff design characteristics significantly differ among tubes. The cuffs made of polyurethane showed the best short- and long-term sealing efficacy. Nevertheless, in the multivariate analysis, the cuff outer diameter (n: 288, p = 0.003) and length (n: 288, p < 0.001), along with the internal pressure (n: 288, p < 0.001), were the only predictors of simulant leakage rate. The tapered cuffs showed the lowest tracheal wall contact area (n: 96, p < 0.001). The tracheal wall pressure distribution pattern was heterogeneous, and the percentage of high tracheal wall pressure significantly differs among the cuffs (n: 96, p < 0.001). CONCLUSIONS: The high-volume low-pressure cuffs' outer diameter, length, material, and internal pressure are the main determinants of sealing efficacy. Despite internal pressure within the safe range, transmitted tracheal pressure is extremely heterogeneous and differs among cuffs, occasionally reaching localized, very high, unsafe levels.

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.

Direct analysis of bacterial viability in endotracheal tube biofilm from a pig model of methicillin-resistant Staphylococcus aureus pneumonia following antimicrobial therapy.

Confocal laser scanning microscopy (CLSM) helps to observe the biofilms formed in the endotracheal tube (ETT) of ventilated subjects and to determine its structure and bacterial viability using specific dyes. We compared the effect of three different treatments (placebo, linezolid, and vancomycin) on the bacterial biofilm viability captured by CLSM. Eight pigs with pneumonia induced by methicillin-resistant Staphylococcus aureus (MRSA) were ventilated up to 96 h and treated with linezolid, vancomycin, or placebo (controls). ETT images were microscopically examined after staining with the live/dead(®) BacLight(™) Kit (Invitrogen, Barcelona, Spain) with a confocal laser scanning microscope. We analyzed 127 images obtained by CLSM. The median ratio of live/dead bacteria was 0.51, 0.74, and 1 for the linezolid, vancomycin, and control groups, respectively (P = 0.002 for the three groups); this ratio was significantly lower for the linezolid group, compared with the control group (P = 0.001). Images showed bacterial biofilm attached and non-attached to the ETT surface but growing within secretions accumulated inside ETT. Systemic treatment with linezolid is associated with a higher proportion of dead bacteria in the ETT biofilm of animals with MRSA pneumonia. Biofilm clusters not necessarily attach to the ETT surface.

Efficacy of linezolid compared to vancomycin in an experimental model of pneumonia induced by methicillin-resistant Staphylococcus aureus in ventilated pigs.

OBJECTIVE: To assess the efficacy of linezolid compared with vancomycin in an experimental model of pneumonia induced by methicillin-resistant Staphylococcus aureus (MRSA) in ventilated pigs. METHODS: Forty pigs (30 kg) were intubated and challenged via bronchoscopy with a suspension of 106 colony forming units of MRSA into every lobe. Afterwards, pigs were ventilated up to 96 hours. Twelve hours after bacterial inoculation, the animals were randomized into 4 groups of treatment: group 1, control; group 2, vancomycin twice daily; group 3, continuous infusion of vancomycin; and group 4, linezolid. Clinical and laboratory parameters were monitored throughout the study. Bacterial cultures of bronchoalveolar lavage fluid and lung tissue samples were performed at the end of the study. Measurements of histopathology derangements of lung samples and studies of intrapulmonary drug penetration were performed. RESULTS: A total of 34 animals completed the study. No differences in clinical and laboratory parameters were observed. The percentage of bronchoalveolar lavage fluid and lung tissue samples with positive cultures for MRSA in controls and groups 2, 3, and 4 was respectively 75%, 11%, 11%, and 0% (p < .01); 52%, 9%, 24%, and 2.5% (p < .01). Histopathology studies demonstrated signs of pneumonia in 95%, 69%, 58%, and 57% and signs of severe pneumonia in 48%, 29%, 22%, and 0% of controls and groups 2, 3, and 4, respectively (p < .01). In addition, pharmacokinetics/pharmacodynamics profile in serum and lung tissue showed better results for linezolid compared with both vancomycin treatments. CONCLUSIONS: In this animal model of MRSA pneumonia, linezolid showed a better efficacy than vancomycin showed because of a better pharmacokinetics/pharmacodynamics index.