A systematic review of comorbidities and outcomes of adult patients with pleural infection

Outcomes of Pleural Space Infections in Patients With Indwelling Pleural Catheters for Active Malignancies

BACKGROUND

Pleural infections related to indwelling pleural catheters (IPCs) are an uncommon clinical problem. However, management decisions can be complex for patients with active malignancies due to their comorbidities and limited life expectancies. There are limited studies on the management of IPC-related infections, including whether to remove the IPC or use intrapleural fibrinolytics.

METHODS

We conducted a retrospective cohort study of patients with active malignancies and IPC-related empyemas at our institution between January 1, 2005 and May 31, 2021. The primary outcome was to evaluate clinical outcomes in patients with malignant pleural effusions and IPC-related empyemas treated with intrapleural tissue plasminogen activator (tPA) and deoxyribonuclease (DNase) compared with those treated with tPA alone or no intrapleural fibrinolytic therapy. The secondary outcome evaluated was the incidence of bleeding complications.

RESULTS

We identified 69 patients with a malignant pleural effusion and an IPC-related empyema. Twenty patients received tPA/DNase, 9 received tPA alone, and 40 were managed without fibrinolytics. Those treated with fibrinolytics were more likely to have their IPCs removed as part of the initial management strategy ( P =0.004). The rate of surgical intervention and mortality attributable to the empyema were not significantly different between treatment groups. There were no bleeding events in any group.

CONCLUSION

In patients with IPC-related empyemas, we did not find significant differences in the rates of surgical intervention, empyema-related mortality, or bleeding complications in those treated with intrapleural tPA/DNase, tPA alone, or no fibrinolytics. More patients who received intrapleural fibrinolytics had their IPCs removed, which may have been due to selection bias.

Early Video-assisted Thoracoscopic Surgery or Intrapleural Enzyme Therapy in Pleural Infection: A Feasibility Randomized Controlled Trial. The Third Multicenter Intrapleural Sepsis Trial-MIST-3

Rationale: Assessing the early use of video-assisted thoracoscopic surgery (VATS) or intrapleural enzyme therapy (IET) in pleural infection requires a phase III randomized controlled trial (RCT). Objectives: To establish the feasibility of randomization in a surgery-versus-nonsurgery trial as well as the key outcome measures that are important to identify relevant patient-centered outcomes in a subsequent RCT. Methods: The MIST-3 (third Multicenter Intrapleural Sepsis Trial) was a prospective multicenter RCT involving eight U.K. centers combining on-site and off-site surgical services. The study enrolled all patients with a confirmed diagnosis of pleural infection and randomized those with ongoing pleural sepsis after an initial period (as long as 24 h) of standard care to one of three treatment arms: continued standard care, early IET, or a surgical opinion with regard to early VATS. The primary outcome was feasibility based on >50% of eligible patients being successfully randomized, >95% of randomized participants retained to discharge, and >80% of randomized participants retained to 2 weeks of follow-up. The analysis was performed per intention to treat. Measurements and Main Results: Of 97 eligible patients, 60 (62%) were randomized, with 100% retained to discharge and 84% retained to 2 weeks. Baseline demographic, clinical, and microbiological characteristics of the patients were similar across groups. Median times to intervention were 1.0 and 3.5 days in the IET and surgery groups, respectively (P = 0.02). Despite the difference in time to intervention, length of stay (from randomization to discharge) was similar in both intervention arms (7 d) compared with standard care (10 d) (P = 0.70). There were no significant intergroup differences in 2-month readmission and further intervention, although the study was not adequately powered for this outcome. Compared with VATS, IET demonstrated a larger improvement in mean EuroQol five-dimension health utility index (five-level edition) from baseline (0.35) to 2 months (0.83) (P = 0.023). One serious adverse event was reported in the VATS arm. Conclusions: This is the first multicenter RCT of early IET versus early surgery in pleural infection. Despite the logistical challenges posed by the coronavirus disease (COVID-19) pandemic, the study met its predefined feasibility criteria, demonstrated potential shortening of length of stay with early surgery, and signals toward earlier resolution of pain and a shortened recovery with IET. The study findings suggest that a definitive phase III study is feasible but highlights important considerations and significant modifications to the design that would be required to adequately assess optimal initial management in pleural infection.The trial was registered on ISRCTN (number 18,192,121).

The clinical features and prognosis of fungal pleural infection: A case series and literature review

Fungal pleural infections are infrequent and insidious, for which there are neither large clinical studies nor targeted guidelines to provide standardized treatment options. We reported 4 cases of fungal pleural infection and reviewed the cases of fungal pleural infections in previous studies to provide a basis for the diagnosis and treatment of fungal pleural infections. There were 2 females and 2 males with a mean age of 58.5 years in our data. The average time from onset to diagnosis was 30.25 days. Risk factors most frequently included pulmonary diseases (n = 4) and malignancy (n = 1). Two patients underwent pleural biopsy through a thoracoscope, and no pathogens were detected. Pleural fluid culture was positive in 2 out of 3 cases. The diagnoses were "possible" (n = 1), "probable" (n = 1), and "proven" (n = 2). All patients received systemic antifungal therapy, and 3 received combined thoracic drainage. The outcomes were cured (n = 1), improved (n = 2) and lost to follow-up (n = 1). We reviewed 12 cases of fungal pleural infection in previous studies. The diagnosis was confirmed via culture in 7 cases and via biopsy in 8 cases. The pathogen was Aspergillus in 7 cases. After a combination of systemic antifungal (n = 12) and local treatment (n = 11), 10 patients improved and 2 patients died. Diagnosis of fungal pleural infection should incorporate risk factors, clinical presentation and fungal evidence, with pleural fluid culture being an important and feasible mean of confirming the diagnosis; and treatment should be based on systemic antifungal therapy supplemented by topical therapy.

Pleural Empyema Caused by Streptococcus intermedius and Fusobacterium nucleatum: A Distinct Entity of Pleural Infections

BACKGROUND

Many community-acquired pleural infections are caused by facultative and anaerobic bacteria from the human oral microbiota. The epidemiology, clinical characteristics, pathogenesis, and etiology of such infections are little studied. The aim of the present prospective multicenter cohort study was to provide a thorough microbiological and clinical characterization of such oral-type pleural infections and to improve our understanding of the underlying etiology and associated risk factors.

METHODS

Over a 2-year period, we included 77 patients with community-acquired pleural infection, whereof 63 (82%) represented oral-type pleural infections. Clinical and anamnestic data were systematically collected, and patients were offered a dental assessment by an oral surgeon. Microbial characterizations were done using next-generation sequencing. Obtained bacterial profiles were compared with microbiology data from previous investigations on odontogenic infections, bacteremia after extraction of infected teeth, and community-acquired brain abscesses.

RESULTS

From the oral-type pleural infections, we made 267 bacterial identifications representing 89 different species. Streptococcus intermedius and/or Fusobacterium nucleatum were identified as a dominant component in all infections. We found a high prevalence of dental infections among patients with oral-type pleural infection and demonstrate substantial similarities between the microbiology of such pleural infections and that of odontogenic infections, odontogenic bacteremia, and community-acquired brain abscesses.

CONCLUSIONS

Oral-type pleural infection is the most common type of community-acquired pleural infection. Current evidence supports hematogenous seeding of bacteria from a dental focus as the most important underlying etiology. Streptococcus intermedius and Fusobacterium nucleatum most likely represent key pathogens necessary for establishing the infection.

Associations of physical activity and quality of life in parapneumonic effusion patients

Introduction

Little is known about activity behaviours and quality of life (QoL) of patients with parapneumonic pleural effusions (PPE) after hospital discharge. This study is a secondary analysis of a randomised trial (dexamethasone versus placebo) for hospitalised patients with PPE. We: 1) described the patients' activity behaviour patterns and QoL measured at discharge and at 30 days post-discharge; and 2) examined the association between activity behaviours and QoL scores.

Methods

Activity behaviour (7-day accelerometry; Actigraph GT3X+) and QoL (Medical Outcomes Study Short-Form 36) were assessed. Repeated measures analysis of covariance controlling for baseline values and a series of linear regression models were undertaken.

Results

36 out of 53 eligible participants completed accelerometry assessments. Despite modest increases in light physical activity (+7.5%) and some domains of QoL (>2 points) from discharge to 30 days post-discharge, patients had persistently high levels of sedentary behaviour (>65% of waking wear time) and poor QoL (≤50 out of 100 points) irrespective of treatment group (p=0.135-0.903). Increasing moderate-to-vigorous physical activity was associated with higher scores on most QoL domains (p=0.006-0.037). Linear regression indicates that a clinically important difference of 5 points in physical composite QoL score can be achieved by reallocating 16.1 min·day-1 of sedentary time to moderate-to-vigorous physical activity.

Conclusion

Patients with PPE had low levels of physical activity and QoL at discharge and 30 days post-discharge irrespective of treatment. Moderate-to-vigorous physical activity participation was associated with higher QoL scores. Increasing moderate-to-vigorous physical activity following discharge from the hospital may be associated with improvements in QoL.

Effectiveness of Immediate Video-Assisted Thoracoscopic Surgery for Empyema: A Multicentre, Retrospective Cohort Study

BACKGROUND

Because of limitations in previous randomised controlled trials and observational studies, the effectiveness of immediate video-assisted thoracoscopic surgery (VATS) for patients with empyema in real-world settings remains unclear.

OBJECTIVE

This study aimed to evaluate whether immediate VATS improves clinical outcomes in patients with empyema.

METHODS

This multicentre retrospective cohort study included 744 patients with physician-diagnosed empyema from six hospitals between 2006 and 2021. The exposure was VATS performed within 3 days of empyema diagnosis, the primary outcome was 30-day mortality, and secondary outcomes were 90-day mortality, length of hospital stay, and time from diagnosis to discharge. We used propensity score weighting to account for potential confounders. For outcome analyses, we used logistic regression for mortality outcomes and gamma regression for the number of days.

RESULTS

Among the 744 patients, 53 (7.1%) underwent VATS within 3 days, and 691 (92.9%) initially received conservative treatment. After propensity score weighting, the differences in 30- and 90-day mortalities between the immediate VATS and initial conservative treatment groups were 1.18% (95% confidence interval [CI], -10.7 to 13.0%) and -0.08% (95% CI, -10.3 to 10.2%), respectively. The differences in length of hospital stay and time from diagnosis to discharge were -3.22 (95% CI, -6.19 to -0.25 days) and -5.04 days (95% CI, -8.19 to -1.90 days), respectively.

CONCLUSIONS

Our real-world study showed that immediate VATS reduced the length of hospital stay and the time from diagnosis to discharge. Considering the small sample and differences in protocols between countries, further large-scale studies are warranted.

Expert Review on Nonsurgical Management of Parapneumonic Effusion: Advances, Controversies, and New Directions

Parapneumonic effusion and empyema are rising in incidence worldwide, particularly in association with comorbidities in an aging population. Also driving this change is the widespread uptake of pneumococcal vaccines, leading to the emergence of nonvaccine-type pneumococci and other bacteria. Early treatment with systemic antibiotics is essential but should be guided by local microbial guidelines and antimicrobial resistance patterns due to significant geographical variation. Thoracic ultrasound has emerged as a leading imaging technique in parapneumonic effusion, enabling physicians to characterize effusions, assess the underlying parenchyma, and safely guide pleural procedures. Drainage decisions remain based on longstanding criteria including the size of the effusion and fluid gram stain and biochemistry results. Small-bore chest drains appear to be as effective as large bore and are adequate for the delivery of intrapleural enzyme therapy (IET), which is now supported by a large body of evidence. The IET dosing regimen used in the UK Multicenter Sepsis Trial -2 has the most evidence available but data surrounding alternative dosing, concurrent and once-daily instillations, and novel fibrinolytic agents are promising. Prognostic scores used in pneumonia (e.g., CURB-65) tend to underestimate mortality in parapneumonic effusion/empyema. Scores specifically based on pleural infection have been developed but require validation in prospective cohorts.

Parapneumonic effusions related to Streptococcus pneumoniae: serotype and disease severity trends from 2006 to 2018 in Bristol, UK

RATIONALE

Streptococcus pneumoniae epidemiology is changing in response to vaccination and some data suggest that empyema incidence is increasing. However, differences exist between the UK and US studies. We describe trends in the clinical phenotype of adult pneumococcal pleural infection, including simple parapneumonic effusions (SPE) in the pneumococcal conjugate vaccination (PCV) era.

OBJECTIVES

To determine whether there were differences in pneumococcal disease presentation and severity associated with pleural infection.

METHODS

A retrospective cohort study, all adults ≥16 years admitted to three large UK hospitals, 2006-2018 with pneumococcal disease. 2477 invasive pneumococcal cases were identified: 459 SPE and 100 pleural infection cases. Medical records were reviewed for each clinical episode. Serotype data were obtained from the UK Health Security Agency national reference laboratory.

RESULTS

Incidence increased over time, including non-PCV-serotype disease. PCV7-serotype disease declined following paediatric PCV7 introduction, but the effect of PCV13 was less apparent as disease caused by the additional six serotypes plateaued with serotypes 1 and 3 causing such parapneumonic effusions from 2011 onwards.Patients with pleural infection had a median survival 468 days (95% CI 340 to 590) vs 286 days (95% CI 274 to 335) in those with SPE. Pleural infection associated with frank pus had lower 90-day mortality than pleural infection without pus (0% vs 29%, p<0.0001). 90-day mortality could be predicted by baseline increased RAPID (Renal, Age, Purulence, Infection source, and Dietary factors) score (HR 15.01, 95% CI 1.24 to 40.06, p=0.049).

CONCLUSIONS

Pneumococcal infection continues to cause severe disease despite the introduction of PCVs. The predominance of serotype 1 and 3 in this adult UK cohort is in keeping with previous studies in paediatric and non-UK studies. Rising non-PCV serotype disease and limited impact of PCV13 on cases caused by serotypes 1 and 3 offset the reductions in adult pneumococcal parapneumonic effusion disease burden observed following the introduction of the childhood PCV7 programme.

Organotypic 3D Co-Culture of Human Pleura as a Novel In Vitro Model of Staphylococcus aureus Infection and Biofilm Development

Bacterial pleural infections are associated with high mortality. Treatment is complicated due to biofilm formation. A common causative pathogen is Staphylococcus aureus (S. aureus). Since it is distinctly human-specific, rodent models do not provide adequate conditions for research. The purpose of this study was to examine the effects of S. aureus infection on human pleural mesothelial cells using a recently established 3D organotypic co-culture model of pleura derived from human specimens. After infection of our model with S. aureus, samples were harvested at defined time points. Histological analysis and immunostaining for tight junction proteins (c-Jun, VE-cadherin, and ZO-1) were performed, demonstrating changes comparable to in vivo empyema. The measurement of secreted cytokine levels (TNF-α, MCP-1, and IL-1β) proved host-pathogen interactions in our model. Similarly, mesothelial cells produced VEGF on in vivo levels. These findings were contrasted by vital, unimpaired cells in a sterile control model. We were able to establish a 3D organotypic in vitro co-culture model of human pleura infected with S. aureus resulting in the formation of biofilm, including host-pathogen interactions. This novel model could be a useful microenvironment tool for in vitro studies on biofilm in pleural empyema.

Risk Factors for Postoperative Pulmonary Complications Leading to Increased Morbidity and Mortality in Patients Undergoing Thoracic Surgery for Pleural Empyema

OBJECTIVES

Surgery for pleural empyema carries a high burden of morbidity and mortality. The authors investigated the incidence of postoperative pulmonary complications (PPCs) and their effects on perioperative morbidity and mortality. Patient-specific, preoperative, procedural, and postoperative risk factors for PPCs were analyzed.

DESIGN

Retrospective observational study.

SETTING

A single, large university hospital.

PARTICIPANTS

A total of 250 adult patients were included who underwent thoracic surgery for pleural empyema between January 2017 and December 2021.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A total of 250 patients with pleural empyema underwent thoracic surgery by video-assisted thoracoscopic surgery (49%; n = 122) or open thoracotomy (51%; n = 128). A proportion (42% [105]) of patients had ≥1 PPCs; 28% (n = 70) had to undergo resurgery; and 10% (n = 25) were re-admitted unexpectedly to the ICU. Preoperative respiratory failure (odds ratio [OR]: 5.8, 95% CI: 2.4-13.1), general anesthesia without regional analgesia techniques (OR: 2.9, 95% CI: 1.4-5.8), open thoracotomy and subsequent resurgery (OR: 3.9, 95% CI 1.5-9.9), surgery outside the regular working hours (OR: 3.1, 95% CI 1.2-8.2), and postoperative sepsis (OR: 2.6, 95% CI 1.1-6.8) were identified as independent risk factors for PPCs. Postoperative pulmonary complications were independent factors for unplanned intensive care unit admission (OR: 10.5, 95% CI 2.1-51 for >1 PPC), death within 360 days (OR: 4.5, 95% CI 2.2-12.3 for ≥2 PPCs), and death within 30 days for ≥1 PPCs (OR: 1.2, 95% CI 1.1-1.3).

CONCLUSIONS

The incidence of PPCs is a significant risk factor for morbidity and mortality after surgery for pleural empyema. Targeting the risk factors identified in this study could improve patient outcomes.

Clinical Risk Factors for Death in Patients With Empyema and Active Malignancy

Background Pleural infection is a common clinical problem resulting in prolonged hospitalization and increased mortality. In patients with active malignancy, management decisions are based on the need for further immunosuppressive therapies, the ability to tolerate surgery, and consideration of the limited life expectancy. Identifying patients at risk for death or poor outcomes is very important as it will guide care. Study design and methods This is a retrospective cohort study of all patients with active malignancy and empyema. The primary outcome was time to death from empyema at three months. The secondary outcome was surgery at 30 days. Standard Cox regression model and cause-specific hazard regression model were used to analyze the data. Results A total of 202 patients with active malignancy and empyema were included. The overall mortality rate at three months was 32.7%. On multivariable analysis, female gender and higher urea were associated with an increased risk of death from empyema at three months. The area under the curve (AUC) of the model was 0.70. The risk factors for surgery at 30 days included the presence of frank pus and postsurgical empyema. The AUC of the model was 0.76. Interpretation Patients with active malignancy and empyema have a high probability of death. In our model, the risk factors for death from empyema included female gender and higher urea.

Intrathoracic negative pressure therapy for pleural empyema using an open-pore drainage film

BACKGROUND

We report our initial experience with intrathoracic negative pressure therapy (ITNPT) in the stage-adjusted treatment of pleural empyema (PE) based on a case series.

MATERIALS AND METHODS

ITNPT represents a further development for intrathoracic use. After thoracic surgical open debridement, an intrathoracic negative pressure dressing was inserted. The drainage elements were a thin open-pore double-layer drainage film (OF) with open-pore polyurethane foams (PUF). Only the OF was placed in direct contact with the lung parenchyma. Negative pressure was generated using an electronic pump (continuous suction, -75 mm Hg). In revision thoracotomies, ITNPT was stopped or continued depending on local findings.

RESULTS

In total, 31 patients with stage II and III pleural empyema underwent ITNPT, which was administered during the primary procedure (n = 17) or at revision (n = 14). Treatment duration was a mean of 10 days (2-18 days) with a mean change interval of 4 days (2-6 days). Intrathoracic negative pressure dressings were applied a mean of 3.5 (1-6) times. The empyema cavity continuously reduced in size and was cleansed by the suction. The OF has a minimum intrinsic volume with maximum absorption surface. Once negative pressure is established, there is no intrathoracic dead volume and the parenchyma can expand. The protective material properties of OF make ITNPT suitable for the treatment of pleural empyema. Targeted local intrathoracic drainage of the septic focus is a possible adjunct to surgery. The surgical dressings must be changed repeatedly. The method is suitable for the treatment of complex stage II and III pleural empyemas.

CONCLUSION

The OF can be used as an intrathoracic drainage element for ITNPT in pleural empyema. This new application option expands the range of indications for negative pressure therapy.

Phenotyping empyema by pleural fluid culture results and macroscopic appearance: an 8-year retrospective study

Background

The clinical impact of phenotyping empyema is poorly described. This study was designed to evaluate clinical characteristics and outcomes based on the two readily available parameters, pleural fluid culture status and macroscopic fluid appearance.

Methods

A retrospective study was conducted on patients with empyema hospitalised between 2013 and 2020. Empyema was classified into culture-positive empyema (CPE) or culture-negative empyema (CNE) and pus-appearing empyema (PAE) or non-pus-appearing empyema (non-PAE) based on the pleural fluid culture status and macroscopic fluid appearance, respectively.

Results

Altogether, 212 patients had confirmed empyema (CPE: n=188, CNE: n=24; PAE: n=118, non-PAE: n=94). The cohort was predominantly male (n=163, 76.9%) with a mean age of 65.0±13.6 years. Most patients (n=180, 84.9%) had at least one comorbidity. Patients with CPE had higher rates of in-hospital mortality (19.1% versus 0.0%, p=0.017) and 90-day mortality (18.6% versus 0.0%, p=0.017) and more extrapulmonary sources of infection (29.8% versus 8.3%, p=0.026) when compared with patients with CNE. No significant difference in mortality rate was found between PAE and non-PAE during the in-hospital stay and at 30 days and 90 days. Patients with PAE had less extrapulmonary sources of infection (20.3% versus 36.2%, p=0.010) and more anaerobic infection (40.9% versus 24.5%, p=0.017) than those with non-PAE. The median RAPID (renal, age, purulence, infection source, and dietary factors) scores were higher in the CPE and non-PAE groups. After adjusting for covariates, culture positivity was not independently associated with mortality on multivariable analysis.

Conclusion

Empyema is a heterogeneous disease with different clinical characteristics. Phenotyping empyema into different subclasses based on pleural fluid microbiological results and macroscopic fluid appearance provides insight into the underlying bacteriology, source of infection and subsequent clinical outcomes.

[Intrathoracic negative pressure therapy of pleural empyema using an open-pored drainage film]

INTRODUCTION

We report our initial experience with intrathoracic negative pressure therapy (ITNPT) in the stage-adjusted therapy of pleural empyema (PE) based on a case series.

MATERIALS AND METHODS

ITNPT represents a further development in negative pressure therapy that is designed to be used in the thoracic cavity. After thoracic surgical open debridement, an intrathoracic negative pressure dressing was inserted. The drainage elements used were a thin open-pore double-layer drainage film (OF) with open-pore polyurethane foams (PUF). Only the OF was placed in direct contact with the lung parenchyma. Negative pressure was generated using an electronic pump (continuous suction, -75 mm Hg). In revision thoracotomies, ITNPT was stopped or continued depending on local findings.

RESULTS

31 patients with stage II and III pleural empyemas were treated. ITNPT was administered at the time of primary procedure (n = 17) or revision (n = 14). ITNPT was given over a duration of m = 10 days (2-18 days), change interval m = 4 d (2-6 d). The application of intrathoracic negative pressure dressings was performed m = 3.5 (1-6) times. The empyema cavity continuously reduced in size and was cleansed by the suction. The OF has a minimum intrinsic volume with maximum absorption surface. Once negative pressure is established, there is no intrathoracic dead volume and the parenchyma can expand.

DISCUSSION

The protective material properties of OF make ITNPT suitable for the treatment of pleural empyema. Targeted local intrathoracic drainage of the septic focus is a possible adjunct to surgery. The treatment regimen requires surgical dressings to be changed repeatedly. The method is suitable for the treatment of complex stage II and III pleural empyemas.

CONCLUSION

The OF can be used as an intrathoracic drainage element for ITNPT in pleural empyema. This new application option expands the range of indications for negative pressure therapy.

A narrative review on pain control interventions for non-surgical pleural procedures

Pleural diseases are common and frequently result in disabling symptoms, impaired health-related quality of life and hospitalisation. Both diagnosis and management often require pleural procedures and despite a variety of pain control strategies available for clinicians to employ, many procedures are still complicated by pain and discomfort. This can interfere with procedure success and can limit patient satisfaction. This review examines the evidence for pain control strategies for people undergoing non-surgical pleural procedures. A systematic literature search was undertaken to identify published studies examining different pain control strategies including pharmacological (sedatives, paravertebral blocks, erector spinae blocks, intrapleural anaesthesia, epidural anaesthesia, local anaesthetic, methoxyflurane, non-steroidal anti-inflammatory drugs [NSAIDs], opioids) and non-pharmacological measures (transcutaneous electric nerve stimulation [TENS], cold application and changes to the intervention or technique). Current literature is limited by heterogeneous study design, small participant numbers and use of different endpoints. Strategies that were more effective than placebo or standard care at improving pain included intrapleural local anaesthesia, paravertebral blocks, NSAIDs, small-bore intercostal catheters (ICC), cold application and TENS. Inhaled methoxyflurane, thoracic epidural anaesthesia and erector spinae blocks may also be useful approaches but require further evaluation to determine their roles in routine non-surgical pleural procedures. Future research should utilise reliable and repeatable study designs and reach consensus in endpoints to allow comparability between findings and thus provide the evidence-base to achieve standardisation of pain management approaches.

ERS/ESTS statement on the management of pleural infection in adults

Pleural infection is a common condition encountered by respiratory physicians and thoracic surgeons alike. The European Respiratory Society (ERS) and European Society of Thoracic Surgeons (ESTS) established a multidisciplinary collaboration of clinicians with expertise in managing pleural infection with the aim of producing a comprehensive review of the scientific literature. Six areas of interest were identified: 1) epidemiology of pleural infection, 2) optimal antibiotic strategy, 3) diagnostic parameters for chest tube drainage, 4) status of intrapleural therapies, 5) role of surgery and 6) current place of outcome prediction in management. The literature revealed that recently updated epidemiological data continue to show an overall upwards trend in incidence, but there is an urgent need for a more comprehensive characterisation of the burden of pleural infection in specific populations such as immunocompromised hosts. There is a sparsity of regular analyses and documentation of microbiological patterns at a local level to inform geographical variation, and ongoing research efforts are needed to improve antibiotic stewardship. The evidence remains in favour of a small-bore chest tube optimally placed under image guidance as an appropriate initial intervention for most cases of pleural infection. With a growing body of data suggesting delays to treatment are key contributors to poor outcomes, this suggests that earlier consideration of combination intrapleural enzyme therapy (IET) with concurrent surgical consultation should remain a priority. Since publication of the MIST-2 study, there has been considerable data supporting safety and efficacy of IET, but further studies are needed to optimise dosing using individualised biomarkers of treatment failure. Pending further prospective evaluation, the MIST-2 regimen remains the most evidence based. Several studies have externally validated the RAPID score, but it requires incorporating into prospective intervention studies prior to adopting into clinical practice.

Diagnosis and Treatment of Pleural Effusion. Recommendations of the Spanish Society of Pulmonology and Thoracic Surgery. Update 2022

Pleural effusion (PE) is a common yet complex disease that requires specialized, multidisciplinary management. Recent advances, novel diagnostic techniques, and innovative patient-centered therapeutic proposals have prompted an update of the current guidelines. This document provides recommendations and protocols based on a critical review of the literature on the epidemiology, etiology, diagnosis, prognosis, and new therapeutic options in PE, and addresses some cost-effectiveness issues related to the main types of PE.

Pleural Infections: Antimicrobial Susceptibility Patterns of Bacterial Isolates and Associated Factors in Suspected Hospitalized Patients at Arba Minch General Hospital, Southern Ethiopia

Background:

Pleural infection remains a clinical problem with high morbidity and mortality all over the world. Antimicrobial options are uncertain due to the lack of understanding of the bacteriology of pleural infection. Thus, the goal of this study was to determine bacteriological profiles, antimicrobial susceptibility patterns, and factors associated with pleural infection.

Methods:

An institution-based cross-sectional study was undertaken in Arba Minch General Hospital from 1st January to 30th November 2020. Socio-demographic, clinical, and behavioral data were collected using a pre-tested, structured questionnaire. Adducted amounts of pleural fluid samples were collected aseptically with sterile test tubes. Standard procedures were utilized for bacterial identification, and antimicrobial susceptibility testing was done using Kirby–Disk Bauer's diffusion method. Version 25 of the Statistical Package for the Social Sciences (SPSS) was used to analyze the data. The p-value of 0.05 was considered statistically significant.

Results:

A total of 152 hospitalized patients were enrolled in this study. The overall magnitude of bacterial pleural infection was 27.6%. The predominant bacteria isolated were Staphylococcus aureus with 34.9%, followed by Escherichia coli with 11.6%. Multidrug-resistant (MDR) isolates account for around 48.8% of all isolates, with Gram-positive bacterial isolates accounting for 71.4%. Methicillin-resistant was found in 26.7% and 33.3% of isolated Staphylococcus aureus (MRSA) and coagulase-negative staphylococci (CoNS), respectively. One isolate of Enterococcus spp. was found to be vancomycin-resistant. All isolated Streptococcus pneumoniae and Streptococcus pyogenes were susceptible to penicillin, erythromycin, cotrimoxazole, and vancomycin. Likewise, isolated Pseudomonas aeruginosa was susceptible to piperacillin. The pleural infection showed a statistically significant association with age group less than or equal to 25 years old (p<0.001), hospital admission for more than seven days (p<0.007), chest tube drainage (p<0.021), previous history of pneumonia (p<0.029) and habit of alcohol drinking (p<0.029).

Conclusion:

The overall rate of culture-confirmed pleural infection was high, and a considerable percentage of bacteria isolates showed increased resistant to routinely used antibiotics, indicating that more attention is needed to follow the spread and emergence of drug-resistant bacterial agents.

Nonmalignant Pleural Effusions

Although the potential causes of nonmalignant pleural effusions are many, the management of a few, including complicated pleural infections and refractory heart failure and hepatic hydrothoraces, can be challenging and requires the assistance of interventional pulmonologists. A pragmatic approach to complicated parapneumonic effusions or empyemas is the insertion of a small-bore chest tube (e.g., 14-16 Fr) through which fibrinolytics (e.g., urokinase and alteplase) and DNase are administered in combination. Therapeutic thoracenteses are usually reserved for small to moderate effusions that are expected to be completely aspirated at a single time, whereas video-assisted thoracic surgery should be considered after failure of intrapleural enzyme therapy. Refractory cardiac and liver-induced pleural effusions portend a poor prognosis. In cases of heart failure-related effusions, therapeutic thoracentesis is the first-line palliative therapy. However, if it is frequently needed, an indwelling pleural catheter (IPC) is recommended. In patients with hepatic hydrothorax, repeated therapeutic thoracenteses are commonly performed while a multidisciplinary decision on the most appropriate definitive management is taken. The percutaneous creation of a portosystemic shunt may be used as a bridge to liver transplantation or as a potential definitive therapy in nontransplant candidates. In general, an IPC should be avoided because of the high risk of complications, particularly infections, that may jeopardize candidacy for liver transplantation. Even so, in noncandidates for liver transplant or surgical correction of diaphragmatic defects, IPC is a therapeutic option as valid as serial thoracenteses.

Management of Empyema Thoracis in Low-Resource Settings

Most cases of empyema thoracis are sequelae of severe pneumonia, but chest trauma and complications of chest tube insertion as cause are not uncommon in low-resource settings. Diagnosis is usually delayed due to delayed presentation to health care facilities, low index of suspicion among health care professionals, and inability to properly stage the disease with the available diagnostic tools. Early use of antibiotics and appropriate-sized and well-placed chest tube drainage is associated with good outcomes at a decreased cost. Surgical management of empyema thoracis is indicated when chest tube drainage and antibiotic treatment fail to achieve complete resolution.

Multifocal locules including the anterior mediastinum side as a surgical indicator in pleural infection

Background

The indication for and the timing of surgery in patients with pleural infection remains unclear. Determining the need for surgery in patients with pleural infection may help in the early consultation of surgeons.

Methods

Data of 167 consecutive patients with pleural infection were retrospectively reviewed. To detect a surgical indicator, the variables of patients who required surgery were compared with those of patients who were cured by non-surgical therapy (n=94) and patients resistant to the non-surgical therapy (n=73; 62 underwent surgery, and 11 showed recurrence or disease-related death after non-surgical treatment). Prognosis and timing of surgery were analyzed by comparing three groups: patients who underwent surgery within 7 days of admission (n=33), patients who underwent surgery after 7 days of admission (n=29), and patients who underwent non-surgical therapy (n=105).

Results

The presence of multifocal locules, including a locule on the anterior mediastinum side (LAMS) was a significant indicator of resistance to initial non-surgical therapy, as compared to the absence of locules (P<0.0001), a single locule (P<0.0001), or multifocal locules without a LAMS (P=0.0041). Recurrence and mortality were not observed in the patients who underwent surgery within 7 days of admission, and the hospitalization period (P=0.0071) and duration of C-reactive protein (CRP) improvement (P<0.0001) were significantly shorter in these patients compared with those who that underwent surgery after 7 days.

Conclusions

In patients with pleural infection, the presence of multifocal locules, including a LAMS, was associated with resistance to non-surgical therapy. Early surgery should be considered for these patients to shorten the hospitalization period and improve the prognosis.

Steroid Therapy and Outcome of Parapneumonic Pleural Effusions (STOPPE): A Pilot Randomized Clinical Trial

Rationale: Pleural effusion commonly complicates community-acquired pneumonia and is associated with intense pleural inflammation. Whether antiinflammatory treatment with corticosteroids improves outcomes is unknown. Objectives: To assess the effects of corticosteroids in an adult population with pneumonia-related pleural effusion. Methods: The STOPPE (Steroid Therapy and Outcome of Parapneumonic Pleural Effusions) trial was a pilot, multicenter, double-blinded, placebo-controlled, randomized trial involving six Australian centers. Patients with community-acquired pneumonia and pleural effusion were randomized (2:1) to intravenous dexamethasone (4 mg twice daily for 48 h) or placebo and followed for 30 days. Given the diverse effects of corticosteroids, a comprehensive range of clinical, serological, and imaging outcomes were assessed in this pilot trial (ACTRN12618000947202). Measurements and Main Results: Eighty patients were randomized (one withdrawn before treatment) and received dexamethasone (n = 51) or placebo (n = 28). This pilot trial found no preliminary evidence of benefits of dexamethasone in improving time to sustained (>12 h) normalization of vital signs (temperature, oxygen saturations, blood pressure, heart, and respiratory rates): median, 41.0 (95% confidence interval, 32.3-54.5) versus 27.8 (15.4-49.5) hours in the placebo arm (hazard ratio, 0.729 [95% confidence interval, 0.453-1.173]; P = 0.193). Similarly, no differences in C-reactive protein or leukocyte counts were observed, except for a higher leukocyte count in the dexamethasone group at Day 3. Pleural drainage procedures were performed in 49.0% of dexamethasone-treated and 42.9% of placebo-treated patients (P = 0.60). Radiographic pleural opacification decreased over time with no consistent intergroup differences. Mean duration of antibiotic therapy (22.4 [SD, 15.4] vs. 20.4 [SD, 13.8] d) and median hospitalization (6.0 [interquartile range, 5.0-10.0] vs. 5.5 [interquartile range, 5.0-8.0] d) were similar between the dexamethasone and placebo groups. Serious adverse events occurred in 25.5% of dexamethasone-treated and 21.4% of placebo-treated patients. Transient hyperglycemia more commonly affected the dexamethasone group (15.6% vs. 7.1%). Conclusions: Systemic corticosteroids showed no preliminary benefits in adults with parapneumonic effusions. Clinical trial registered with www.anzctr.org.au (ACTRN12618000947202).

Successful Treatment With Daptomycin of MRSA Empyema Complicated by Right-Sided Loculated Pleural Effusion Refractory to Vancomycin

Empyema is a serious complication of pneumonia and has been reported to have a mortality rate of 8.7%. For methicillin-resistant Staphylococcus aureus (MRSA) empyema, treatment includes drainage and specific antibiotics such as vancomycin and linezolid. Strikingly, there are increasing incidences of empyema refractory to vancomycin and linezolid. Despite being inactivated in the lung parenchyma by pulmonary surfactant, daptomycin can penetrate the pleural space and may be better at treating MRSA empyema than vancomycin and linezolid. Some case reports have shown that daptomycin has been used to successfully treat MRSA empyema refractory to linezolid and vancomycin-resistant enterococcus (VRE) empyema. Here, we present a 26-year-old male with a past medical history of intravenous (IV) drug use, newly diagnosed HIV, HCV, and multifocal pneumonia complicated by a left-sided MRSA empyema that partially resolved with vancomycin and drainage. However, he subsequently developed a right-sided loculated pleural effusion. After the patient was switched to daptomycin with continued drainage, the right and left pleural effusions improved significantly. Once medically stable, he was discharged to a rehabilitation facility for further recovery. Our case report demonstrates that daptomycin could be considered as an effective treatment for MRSA empyema, particularly when refractory to vancomycin.

Diagnostic role of internal mammary lymph node involvement in tuberculous pleurisy: a multicenter study

BACKGROUND AND OBJECTIVES

Diagnosis of tuberculous pleurisy (TP) may be challenging and it often requires pleural biopsy. A tool able to increase pre-test probability of TP may be helpful to guide diagnostic work-up and enlargement of internal mammary lymph node (IMLN) has been suggested to play a potential role. The aim of the present investigation was to assess role of IMLN involvement in TP in a multi-centric case-control study, by comparing its prevalence and test performance to those observed in patients with infectious, non-tuberculous pleurisy (NTIP), and in controls free from respiratory diseases (CP).

METHODS

A total of 419 patients, from 14 Pulmonology Units across Italy were enrolled (127 patients affected by TP, 163 affected by NTIP and 129 CP). Prevalence, accuracy and predictive values of ipsilateral IMLN involvement between cases and control groups were assessed, as well as concordance between chest computed tomography (CT scan) and thoracic ultrasound (TUS) measurements.

RESULTS

The prevalence of ipsilateral IMLN involvement in TP was significantly higher than that observed in NTIP and CP groups (respectively 77.2%, 39.3% and 14.7%). Results on test performance, stratified by age, revealed a high positive predictive value in patients aged ≤50 years, while a high negative predictive value in patients aged >50 years. The comparison between CT scan and ultrasound showed moderate agreement (Kappa=0.502).

CONCLUSIONS

Evaluation of IMLN involvement plays a relevant role in assessing the pre-test probability of TP. Considering the increasing global prevalence of mycobacterial infections, a tool able to guide diagnostic work-up of suspected TP is crucial, especially where local sources are limited.

Parapneumonic Effusion and Empyema

The rising incidence and high morbidity of pleural infection remain a significant challenge to health care systems worldwide. With distinct microbiology and treatment paradigms from pneumonia, pleural infection is an area in which the evidence base has been rapidly evolving. Progress in recent years has revolved around characterizing the microbiome of pleural infection and the addition of new strategies such as intrapleural enzyme therapy to the established treatment pathway of drainage and antibiotics. The future of improving outcomes lies with personalizing treatment, establishing optimal timing of intrapleural agents and surgery, alongside wider use of risk stratification to guide treatment.

Multidisciplinary reconstructive management of residual recalcitrant empyema cavity: A retrospective observational cohort study

BACKGROUND

Patients with stage III empyema require chest wall fenestration to enable lung re-expansion and continuous drainage of the persisting empyema cavity. This chronic wound negatively affects patients' exercise tolerance, ability to carry out activities of daily living, and quality of life.

METHODS

Eight consecutive patients underwent chest wall reconstruction following fenestration and were followed up over a minimum of 12 months. This study included adult patients (over 18 years of age). There were no exclusion criteria. Data were collected retrospectively.

RESULTS

Eight patients (six male and two female), with a mean age of 56 years (range, 22-76), were included. All of them had comorbidities including history of neoplasia (n = 6), atrial fibrillation (n = 3), and hypertension (n = 2). Aetiology of empyema included lung cancer resection complicated by bronchopleural fistula (n = 4), pneumonia (n = 2), and pleural effusion (n = 2). Five patients had a low metabolic reserve evident by a low BMI (range, 16-22), and a median malnutrition universal screen tool (MUST) score of 2 (range, 1-4). Following intensive infection control and nutritional support, patients underwent reconstruction 11 months (median; range 5-51) after fenestration. Seven patients were followed up and had no recurrence of empyema and bronchopleural fistula. They all reported significant improvements in their quality of life, and their Eastern Cooperative Oncology Group (ECOG) performance status improved from three to one. One patient died 56 days post-reconstruction from cardiorespiratory failure, which required readmission to hospital.

CONCLUSION

We demonstrate that free tissue reconstruction including multidisciplinary input and optimisation at all stages of care successfully closes residual recalcitrant empyema cavity without recurrence and leads to significant improvements in the quality of life.

16S rRNA is a valuable tool in finding bacterial aetiology of community-acquired pleural empyema-a population-based observational study in South Sweden

BACKGROUND

The incidence of community-acquired pleural empyema is increasing. Knowledge of the bacterial aetiology is important in order to base recommendations on empirical antimicrobial treatment. The primary aim of the present study was to describe the bacterial aetiology of adult patients with culture proven and/or 16S rRNA-positive community-acquired pleural infection.

METHODS

We performed a retrospective, population-based observational cohort study in Skåne County, south of Sweden. We included all patients with pleural samples obtained between 1st of January 2011 to 31st of December 2017 in Skåne, south of Sweden, with a positive culture and/or 16S rRNA result. Exclusion criteria were patients with culture-negative and/or 16S rRNA-negative pleural samples, age < 18 years, pleural empyema caused by trauma or iatrogenesis, pleural infection caused by tuberculosis or fungi, simultaneous lung- or abscess of the abdomen and bacterial species considered to be contaminants.

RESULTS

A total of 291 patients were included in the study, of which 63% were men and the median age was 69 years. The dominating bacterial aetiology was viridans streptococci (36%), followed by Streptococcus pneumoniae (14%) and anaerobic bacteria (12%). 16S rRNA added information of bacterial aetiology in addition to standard culturing methods in 63% of the patients.

CONCLUSION

We found that the aetiology of adult patients with culture proven and/or 16S rRNA-positive community-acquired pleural empyema is dominated by viridans streptococci, S. pneumoniae and anaerobic bacteria. Our study shows that 16S rRNA is a valuable tool in finding the bacterial aetiology of community-acquired pleural empyema.

Comparing the outcomes of intrapleural fibrinolytic and DNase therapy versus intrapleural fibrinolytic or DNase therapy: A systematic review and meta-analysis

BACKGROUND

Multiple studies describing the benefits of intrapleural fibrinolytic over placebo and DNase therapy have been published, but few have been published on intrapleural fibrinolytic and DNase therapy.

OBJECTIVE

Our meta-analysis aims to compare the outcomes of surgical intervention, mortality, and hospital length of stay between intrapleural fibrinolytic and DNase therapy with either intrapleural fibrinolytic or DNase therapy alone in patients with pleural space infections.

METHODS

We searched Pubmed, EMBASE, Web of Science, and Cochrane library databases for observational studies and randomized controlled trials (RCTs) containing comparative data for hospitalized adults and children with pleural infections receiving intrapleural therapy of fibrinolytic and DNase versus those receiving intrapleural fibrinolytic or DNase alone. Meta-analysis was performed using the Review Manager software, and heterogeneity was tested using I² statistics.

RESULTS

A total of 2 cohorts and 2 RCTs involving 362 adult and children was included. There was significant reduction in surgical intervention requirement among patients who received intrapleural fibrinolytic and DNase (OR 0.30; 95% CI 0.11-0.83; I² = 31%; P = 0.02) than those receiving either intrapleural fibrinolytic or DNase alone. No difference was observed for mortality (OR 0.72; 95% CI 0.31-1.71; I² = 0%; P = 0.46) and complication rates (OR 3.09; 95% CI 0.75-12,74; I² = 54%; P = 0.12). The hospital length of stay (mean 13.70 vs. 16.67 days; P = 0.19) and duration of chest tube drainage (mean 6.47 vs. 6.30 days; P = 0.58) was similar between the two groups.

CONCLUSION

Combination of intrapleural fibrinolytic and DNase, compared to single-agent intrapleural therapy alone, is associated with a lesser need for surgical interventions. However, no difference was found in mortality, hospital length of stay, and chest tube drainage duration.

Recent Insights into the Management of Pleural Infection

Pleural infection in adults has considerable morbidity and continues to be a life-threatening condition. The term “pleural infection” encompasses complicated parapneumonic effusions and primary pleural infections, and includes but is not limited to empyema, which refers to collection of pus in the pleural cavity. The incidence of pleural infection in adults has been continuously increasing over the past two decades, particularly in older adults, and most of such patients have comorbidities. Management of pleural infection requires prolonged duration of hospitalization (average 14 days). There are recognized differences in microbial etiology of pleural infection depending on whether the infection was acquired in the community or in a health-care setting. Anaerobic bacteria are acknowledged as a major cause of pleural infection, and thus anaerobic coverage in antibiotic regimens for pleural infection is mandatory. The key components of managing pleural infection are appropriate antimicrobial therapy and chest-tube drainage. In patients who fail medical therapy by manifesting persistent sepsis despite standard measures, surgical intervention to clear the infected space or intrapleural fibrinolytic therapy (in poor surgical candidates) are recommended. Recent studies have explored the role of early intrapleural fibrinolytics or first-line surgery, but due to considerable costs of such interventions and the lack of convincing evidence of improved outcomes with early use, early intervention cannot be recommended, and further evidence is awaited from ongoing studies. Other areas of research include the role of routine molecular testing of infected pleural fluid in improving the rate of identification of causative organisms. Other research topics include the benefit of such interventions as medical thoracoscopy, high-volume pleural irrigation with saline/antiseptic solution, and repeated thoracentesis (as opposed to chest-tube drainage) in reducing morbidity and improving outcomes of pleural infection. This review summarizes current knowledge and practice in managing pleural infection and future research directions.

Advances in pleural infection and malignancy

Pleural infection and malignancy are among the most common causes of pleural disease and form the mainstay of pleural practice. There has been significant research and increase in scientific understanding in these areas in the past decade. With regard to pleural infection, the rising incidence remains worrying. An increased awareness allowing earlier diagnosis, earlier escalation of therapy and the use of validated risk stratification measures may improve outcomes. In pleural malignancy, research has enabled clinicians to streamline patient pathways with focus on reducing time to diagnosis, definitive management of malignant pleural effusion and achieving these with the minimum number of pleural interventions. Trials comparing treatment modalities of malignant pleural effusion continue to highlight the importance of patient choice in clinical decision-making. This article aims to summarise some of the most recent literature informing current practice in these two areas.

Epidemiology and prognostic factors of pleural empyema

BACKGROUND

Infection of the pleural cavity invariably leads to hospitalisation, and a fatal outcome is not uncommon. Our aim was to study the epidemiology of pleural empyema on a nationwide basis in the whole population and in three subgroups of patients, namely post-lung resection, associated cancer and those with no surgery and no cancer.

METHODS

Data from patients aged ≥18 years hospitalised with a diagnosis of pleural infection in France between January 2013 and December 2017 were retrieved from the medical-administrative national hospitalisation database and retrospectively analysed. Mortality, length of stay and costs were assessed.

RESULTS

There were 25 512 hospitalisations for pleural empyema. The annual rate was 7.15 cases per 100 000 habitants in 2013 and increased to 7.75 cases per 100 000 inhabitants in 2017. The mean age of patients was 62.4±15.6 years and 71.7% were men. Post-lung resection, associated cancer and no surgery-no cancer cases accounted for 9.8%, 30.1% and 60.1% of patients, respectively. These groups were significantly different in terms of clinical characteristics, mortality and risk factors for length of stay, costs and mortality. Mortality was 17.1% in the whole population, 29.5% in the associated cancer group, 17.7% in the post-lung resection group and 10.7% in the no surgery-no cancer group. In the whole population, age, presence of fistula, higher Charlson Comorbidity Index (>3), alcohol abuse, arterial hypertension, hyperlipidaemia, atheroma, atrial fibrillation, performance status >3 and three subgroups of pleural empyema independently predicted mortality.

CONCLUSIONS

Empyema is increasing in incidence. Factors associated with mortality are recent lung resection and associated diagnosis of cancer.

The effect of Cyclic-di-GMP on biofilm formation by Pseudomonas aeruginosa in a novel empyema model

Background

Pseudomonas aeruginosa (P. aeruginosa) is a common pathogenic bacterium which causes pleural empyema, and infection of P. aeruginosa is often associated with biofilm. The aim of this study was to establish a model of rabbit empyema infected by P. aeruginosa to determine whether it causes the formation of biofilm in the pleural cavity. Furthermore, we investigated the effect of cyclic diguanosine monophosphate (c-di-GMP) on biofilm formation in this P. aeruginosa empyema model.

Methods

Twenty rabbits were used and randomly divided into five groups: PAO1, PAO1ΔwspF, and PAO1/p_lac-yhjH infection groups, and Luria-Bertani (LB) broth and turpentine control groups. A drainage catheter was implanted into the pleural cavity through thoracentesis. The three infection groups were respectively infected with PAO1, PAO1ΔwspF, and PAO1/p_lac-yhjH strains, which caused empyema. The two control groups were injected with LB or turpentine. After 4 days of infection, we sacrificed the rabbits. We evaluated the pathology of pleura through hematoxylin-eosin staining. Colony count and crystal violet assay were used to analyze the biofilm formation on the surface of catheters. Scanning electron was used to observe the biofilm on the surface of the pleura. Peptide nucleic acids-fluorescence in situ hybridization (PNA-FISH) was used to observe the biofilm in the fibrinous deposition.

Results

By the PNA-FISH assay, biofilms were observed in the fibrinous deposition of the three infection groups. The red fluorescence area of the PAO1ΔwspF infection group was larger than that of the PAO1 and PAO1/p_lac-yhjH infection groups. Through electron microscopy, we observed that PAO1 strains were embedded in an electron-dense extracellular matrix on the surface of pleural tissue, and appeared to be biofilm-like structures. For the crystal violet assay, the optical density values of different groups were significantly different: PAO1ΔwspF > PAO1 > PAO1/p_lac-yhjH > control groups (P<0.05).

Conclusions

To the best knowledge of the authors, this is the first study to report P. aeruginosa forming biofilm in a novel animal model of pleural empyema. In addition, c-di-GMP signaling molecules played an important role in biofilm formation in the pleural cavity.