Plasminogen Degradation by Neutrophil Elastase in Pleural Infection, Not High Plasminogen Activator Inhibitor 1, Is the Cause of Intrapleural Lytic Failure

BACKGROUND

Complex pleural space infections often require treatment with multiple doses of intrapleural tissue plasminogen activator (tPA) and deoxyribonuclease, with treatment failure frequently necessitating surgery. Pleural infections are rich in neutrophils, and neutrophil elastase degrades plasminogen, the target substrate of tPA, that is required to generate fibrinolysis. We hypothesized that pleural fluid from patients with pleural space infection would show high elastase activity, evidence of inflammatory plasminogen degradation, and low fibrinolytic potential in response to tPA that could be rescued with plasminogen supplementation.

RESEARCH QUESTION

Does neutrophil elastase degradation of plasminogen contribute to intrapleural fibrinolytic failure?

STUDY DESIGN AND METHODS

We obtained infected pleural fluid and circulating plasma from hospitalized adults (n = 10) with institutional review board approval from a randomized trial evaluating intrapleural fibrinolytics vs surgery for initial management of pleural space infection. Samples were collected before the intervention and on days 1, 2, and 3 after the intervention. Activity assays, enzyme-linked immunosorbent assays, and Western blot analysis were performed, and turbidimetric measurements of fibrinolysis were obtained from pleural fluid with and without exogenous plasminogen supplementation. Results are reported as median (interquartile range) or number (percentage) as appropriate, with an α value of 0.05.

RESULTS

Pleural fluid elastase activity was more than fourfold higher (P = .02) and plasminogen antigen levels were more than threefold lower (P = .04) than their corresponding plasma values. Pleural fluid Western blot analysis demonstrated abundant plasminogen degradation fragments consistent with elastase degradation patterns. We found that plasminogen activator inhibitor 1 (PAI-1), the native tPA inhibitor, showed high antigen levels before the intervention, but the overwhelming majority of this PAI-1 (82%) was not active (P = .003), and all PAI-1 activity was lost by day 2 after the intervention in patients receiving intrapleural tPA and deoxyribonuclease. Finally, using turbidity clot lysis assays, we found that the pleural fluid of 9 of 10 patients was unable to generate a significant fibrinolytic response when challenged with tPA and that plasminogen supplementation rescued fibrinolysis in all patients.

INTERPRETATION

Inflammatory plasminogen deficiency, not high PAI-1 activity, is a significant contributor to intrapleural fibrinolytic failure.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT03583931; URL: www.

CLINICALTRIALS

gov.

Microbiological diagnosis of pleural infections: a comparative evaluation of a novel syndromic real-time PCR panel

Current microbial diagnostics for pleural infections are insufficient. Studies using 16S targeted next-generation sequencing report that only 10%-16% of bacteria present are cultured and that 50%-78% of pleural fluids containing relevant microbial DNA remain culture negative. As a rapid diagnostic alternative suitable for clinical laboratories, we wanted to explore a PCR-based approach. Based on the identification of key pathogens, we developed a syndromic PCR panel for community-acquired pleural infections (CAPIs). This was a pragmatic PCR panel, meaning that it was not designed for detecting all possibly involved bacterial species but for confirming the diagnosis of CAPI, and for detecting bacteria that might influence choice of antimicrobial treatment. We evaluated the PCR panel on 109 confirmed CAPIs previously characterized using culture and 16S targeted next-generation sequencing. The PCR secured the diagnosis of CAPI in 107/109 (98.2%) and detected all present pathogens in 69/109 (63.3%). Culture secured the diagnosis in 54/109 (49.5%) and detected all pathogens in 31/109 (28.4%). Corresponding results for 16S targeted next-generation sequencing were 109/109 (100%) and 98/109 (89.9%). For bacterial species included in the PCR panel, PCR had a sensitivity of 99.5% (184/185), culture of 21.6% (40/185), and 16S targeted next-generation sequencing of 92.4% (171/185). None of the bacterial species present not covered by the PCR panel were judged to impact antimicrobial therapy. A syndromic PCR panel represents a rapid and sensitive alternative to current diagnostic approaches for the microbiological diagnosis of CAPI.IMPORTANCEPleural empyema is a severe infection with high mortality and increasing incidence. Long hospital admissions and long courses of antimicrobial treatment drive healthcare and ecological costs. Current methods for microbiological diagnostics of pleural infections are inadequate. Recent studies using 16S targeted next-generation sequencing as a reference standard find culture to recover only 10%-16% of bacteria present and that 50%-78% of samples containing relevant bacterial DNA remain culture negative. To confirm the diagnosis of pleural infection and define optimal antimicrobial therapy while limiting unnecessary use of broad-spectrum antibiotics, there is a need for rapid and sensitive diagnostic approaches. PCR is a rapid method well suited for clinical laboratories. In this paper we show that a novel syndromic PCR panel can secure the diagnosis of pleural infection and detect all bacteria relevant for choice of antimicrobial treatment with a high sensitivity.

A case of naganishial pleuritis in a kidney transplant recipient

The Naganishia species is a mycosis, previously classified as a non-neoformans Cryptococcus species. The increased number of naganishial infections occurs predominantly in immunocompromised conditions, especially in people living with HIV with low CD4 cell count, primary immunodeficiencies, and iatrogenic immunosuppression. The lungs can serve as the primary site of infection, leading to various pulmonary manifestations. However, naganishial pleural effusions are unrecognized and challenged in diagnosis because of their presentation, which can mimic tuberculous pleural effusion. Herein, we report the case of a 53-year-old man who had undergone kidney transplantation for more than 2 years and presented with chest tightness and dyspnea. Computed chest tomography demonstrated left pleural nodules and pleural effusion, later confirmed as exudative pleural effusion with a lymphocyte predominance. Pleuroscopy revealed multiple small pleural nodules, and biopsies of these nodules were performed. Naganishia spp. was identified by the 18S rRNA sequencing technique.

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.

Effects of Concurrent Dosing on the Efficacy of Tissue Plasminogen Activator and Deoxyribonuclease in the Treatment of Pleural Infection

BACKGROUND

The goal of this study was to evaluate how the administration of concurrent tissue plasminogen activator (tPA) and deoxyribonuclease (DNase) therapy with variable dosing for complicated parapneumonic effusions and empyema affects patient outcomes in an inner-city community hospital.

METHODS

This retrospective analysis was performed at an inner-city hospital located in Raleigh, North Carolina. A list of all patients treated with tPA and DNase between July 1, 2015, and December 31, 2017, was generated and screened. Data were collected through a review of past medical records, including demographics, past medical history, and details about their hospital course.

RESULTS

A total of 38 patients were found to have been treated with concurrent tPA and DNase for complicated parapneumonic effusion or empyema. Twenty (52.6%) patients received the full six doses of combined concurrent tPA/DNase. Of the 18 (47.4%) patients who did not receive the full six doses, 11 did not require the full six doses for effusion resolution, and seven had to discontinue therapy due to tube blockage or pain. Only seven (18.4%) patients had complications related to tPA/DNase administration, most commonly pain. Nineteen (50%) patients had complete radiological clearance of effusion, with 13 (34.2%) having partial clearance, and six (15.8%) having no change or worsening of their effusion. Eight (21.1%) patients needed further surgical management of their effusion.

CONCLUSIONS

The current most common dosing pattern for combined tPA and DNase therapy of twice daily for three days may not be optimal for all patients. The dosing regimen should be individualized depending on clinical response. Concurrent dosing is safe.

Actinomycosis with Fusobacterium empyema

Actinomyces, are gram-positive, non-spore forming anaerobic or microaerophilic species. Empyema due to actinomycosis is relatively rare and can be difficult to diagnose as the presenting symptoms may be indolent and the micro-organism may be difficult to culture. This case report describes a patient presenting with dyspnoea, weight loss and lethargy. The chest radiograph, CT and thoracic ultrasound revealed a left-sided pleural effusion. A chest drain was inserted under ultrasound guidance. The pleural fluid was macroscopically consistent with pus and microbiology showed growth of gram-positive bacilli, Actinomyces meyeri as well as the Fusobacterium species. The patient was treated with a drainage of the pleural fluid, a prolonged course of antibiotics and made a good recovery. The awareness that the Actinomyces species and the Fusobacterium species through their synergistic interaction may cause empyema, may lead to a timely diagnosis and treatment.

Unraveling the Predictive Potential of Rapid Scoring in Pleural Infection: A Critical Review

Pleural infection, or pleural empyema, is a severe medical condition associated with high morbidity and mortality rates. Timely and accurate prognostication is crucial for optimizing patient outcomes and resource allocation. Rapid scoring systems have emerged as promising tools in pleural infection prognostication, integrating various clinical and laboratory parameters to assess disease severity and quantitatively predict short-term and long-term outcomes. This review article critically evaluates existing rapid scoring systems, including CURB-65 (confusion, uremia, respiratory rate, blood pressure, age ≥ 65 years), A-DROP (age (male >70 years, female >75 years), dehydration, respiratory failure, orientation disturbance, and low blood pressure), and APACHE II (acute physiology and chronic health evaluation II), assessing their predictive accuracy and limitations. Our analysis highlights the potential clinical implications of rapid scoring, including risk stratification, treatment tailoring, and follow-up planning. We discuss practical considerations and challenges in implementing rapid scoring such as data accessibility and potential sources of bias. Furthermore, we emphasize the importance of validation, transparency, and multidisciplinary collaboration to refine and enhance the clinical applicability of these scoring systems. The prospects for rapid scoring in pleural infection management are promising, with ongoing research and data science advances offering improvement opportunities. Ultimately, the successful integration of rapid scoring into clinical practice can potentially improve patient care and outcomes in pleural infection management.

The Biological Role of Pleural Fluid PAI-1 and Sonographic Septations in Pleural Infection: Analysis of a Prospectively Collected Clinical Outcome Study

Rationale: Sonographic septations are assumed to be important clinical predictors of outcome in pleural infection, but the evidence for this is sparse. The inflammatory and fibrinolysis-associated intrapleural pathway(s) leading to septation formation have not been studied in a large cohort of pleural fluid (PF) samples with confirmed pleural infection matched with ultrasound and clinical outcome data. Objectives: To assess the presence and severity of septations against baseline PF PAI-1 (Plasminogen-Activator Inhibitor-1) and other inflammatory and fibrinolysis-associated proteins as well as to correlate these with clinically important outcomes. Methods: We analyzed 214 pleural fluid samples from PILOT (Pleural Infection Longitudinal Outcome Study), a prospective observational pleural infection study, for inflammatory and fibrinolysis-associated proteins using the Luminex platform. Multivariate regression analyses were used to assess the association of pleural biological markers with septation presence and severity (on ultrasound) and clinical outcomes. Measurements and Main Results: PF PAI-1 was the only protein independently associated with septation presence (P < 0.001) and septation severity (P = 0.003). PF PAI-1 concentrations were associated with increased length of stay (P = 0.048) and increased 12-month mortality (P = 0.003). Sonographic septations alone had no relation to clinical outcomes. Conclusions: In a large and well-characterized cohort, this is the first study to associate pleural biological parameters with a validated sonographic septation outcome in pleural infection. PF PAI-1 is the first biomarker to demonstrate an independent association with mortality. Although PF PAI-1 plays an integral role in driving septation formation, septations themselves are not associated with clinically important outcomes. These novel findings now require prospective validation.

Intrapleural Instillation of Sodium Bicarbonate versus Urokinase in Management of Complicated Pleural Effusion: A Comparative Cohort Study

Aim

The main target is evacuation; however, with evidence about the value of intrapleural instillation of different fibrinolytic agents still under evaluation, our aim was comparing the effectiveness and safety of intrapleural instillation of sodium bicarbonate (NaHCO₃) in comparison with urokinase in patients with infected pleural effusion.

Methods

Our prospective cohort study included 40 patients with complicated empyema; the diagnosis was based on analysis of aspirated fluid in association with radiological and bacteriological culture. The patients were subjected to instillation of two different fibrinolytic agents; the first one was NaHCO₃, the second was urokinase.

Results

The commonest underlying chest infection that was visualized by CT was pneumonia 70%. Nearly half of cases had community-acquired infection (45%), and more than half of them (55%) had anaerobic infection, and only five cases had TB pleural effusion based on ADA-positive, tuberculin skin test in addition to Abram's needles closed biopsy. The rate of repeated therapeutic thoracentesis success in each group was 85%; 80% in NaHCO₃ group, and 90% in urokinase group, both of them was significantly equal, P=0.37. Moreover, the frequency of complications in all patients was less than 13%, hence hemothorax and iatrogenic pneumothorax was 12.5%, and only 10% of cases were admitted in ICU after the maneuver, with insignificant difference in between the groups. However, looking at the smaller rate of RTT failure of NaHCO₃ or urokinase, the logistic regression model showed that RTT-NaHCO₃ was insignificantly related to failure in both unadjusted and adjusted models, P=0.37 and 0.32, respectively, and only smoking habits increase the likelihood of failure 9-fold (OR=8.9, P=0.04) with respect to age, sex, and treatment methods.

Conclusion

The efficacy of repeated therapeutic thoracentesis (RTT) with intrapleural instillation of NaHCO₃ was effective and safe, the same as urokinase, with consideration that NaHCO₃ was much more available and affordable than urokinase.

Alteplase Dose Assessment for Pleural infection Therapy (ADAPT) Study-2: Use of 2.5 mg alteplase as a starting intrapleural dose

BACKGROUND AND OBJECTIVE

Intrapleural tissue plasminogen activator/deoxyribonuclease (tPA/DNase) therapy is increasingly used in pleural infection. Bleeding risks and costs associated with tPA remain the clinical concerns. Our dose de-escalation series aims to establish the lowest effective dosing regimen for tPA/DNase. This study assesses the intrapleural use of 2.5 mg tPA/5 mg DNase for pleural infection.

METHODS

Consecutive patients with pleural infection treated with a starting regime of 2.5 mg tPA/5 mg DNase were included from two centres in Australia and UK. Escalation of tPA dose was permitted if clinical response was inadequate.

RESULTS

Sixty-nine patients (mean age 61.0 years) received intrapleural 2.5 mg tPA/5 mg DNase. Most (88.4%) were treated successfully and discharged from hospital without surgery by 90 days. Patients received a median of 5 [interquartile range [IQR] = 3-6] doses of tPA/DNase. Total amount of tPA used per patient was 12.5 mg [median, IQR = 7.5-15.0]. Seventeen patients required dose escalation of tPA; most (n = 12) for attempted drainage of distant non-communicating locule(s). Treatment success was corroborated by clearance of pleural opacities on radiographs (from median 27.0% [IQR = 17.1-44.5] to 11.0% [IQR = 6.4-23.3] of hemithorax, p < 0.0001), increased pleural fluid drainage (1.98 L [median, IQR = 1.38-2.68] over 72 h following commencement of tPA/DNase) and reduction of serum C-reactive protein level (by 45.0% [IQR = 39.3-77.0] from baseline at day 5, p < 0.0001). Two patients required surgery. Six patients with significant comorbidities (e.g., advanced cancer) had ongoing infection when palliated and died. Two patients experienced self-limiting pleural bleeding and received blood transfusion.

CONCLUSION

A starting intrapleural regime of 2.5 mg tPA/5 mg DNase, with up-titration if needed, can be effective and deserves further exploration.

Pyopneumothorax of unusual aetiology

A 50-year old diabetic male presented with cough, breathlessness, fever, and chest pain. Clinical and radiological evaluation revealed a right-sided pyopneumothorax. Surgical drainage with tube thoracostomy was performed. Pleural fluid cultures grew Enterococcus fecium as a sole organism. Our patient was treated with vancomycin and amikacin with an excellent clinical response. Enterococci are rarely implicated in the lower respiratory tract and pleural infections and are not usually considered if initiating empirical treatment. Their intrinsic resistance to empirically used antibiotics may complicate the course of the disease. Hence initial Gram staining and expeditious microbiological isolation with susceptibility testing is warranted in all cases. Gram-positive aerobes, notably staphylococcus followed by streptococcus and pneumococcus, are the commonly encountered organisms in pleural infections.

Drug use-related right-sided infective endocarditis complicated by empyema and bronchopleural fistula

Right-sided infective endocarditis is frequently accompanied by septic pulmonary emboli, which may result in a spectrum of respiratory complications. We present the case of a 25-year-old woman diagnosed with infective endocarditis secondary to intravenous drug use. During a long and arduous hospital course, the patient developed empyema with bronchopleural fistula, representing severe but uncommon sequelae that may arise from this disease process. She was treated with several weeks of antibiotics as well as surgical thorascopic decortication and parietal pleurectomy.

Saline lavage for the management of severe pleural empyema: A cohort study

BACKGROUND

Despite advances in the treatment of pleural infection, up to 20% of patients die. So far, studies assessing the role of intrapleural saline lavage for the management of all stage pleural infections are very scarce, usually excluding patients with cancer.

METHODS

The method used was a retrospective cohort study including pleural empyema managed with a pleural lavage of saline solution through a small-bore chest tube. The primary outcome was the rate of failure at 3 months (surgical referral or additional pleural manoeuver due to recurrent infection or all-cause mortality). Secondary outcomes were hospital stay, the change of the chest radiograph and inflammatory biomarkers, and complications.

RESULTS

Thirty patients with pleural empyema were included, 11 (36.7%) with an active cancer. The overall rate of failure at 3 months was 13.3% (surgical referral = 0; additional pleural manoeuver = 3; mortality = 1). Median length of pleural lavage and hospital stay were, respectively, 14 days (7-28) and 17 days (11-42). Inflammatory markers and size of the effusion on chest radiograph significantly decreased for Day 0 to Day 14. No chest tube blockade was reported, but seven (23.3%) accidentally withdrew. No other side effects were reported.

CONCLUSIONS

Intrapleural saline lavage is efficient and safe for the management of pleural empyema, even in severe status patients with cancer, at the cost of a prolonged hospitalization.

Multidisciplinary management of pleural infection after ventricular assist device implantation

Background

Postsurgical pleural infection is a life-threatening complication after implantation of artificial devices such as ventricular assist devices (VADs). The treatment can be challenging and the evidence in the literature is very limited. Here we report our multidisciplinary approach of the management of pleural infection after VAD implantation.

Methods

Between March 2014 and December 2019, 33 patients developed postoperative pleural infection after VAD implantation and underwent thoracic surgical intervention at our institution. All patients were prospectively enrolled in this analysis. Data were retrospectively analyzed. Primary outcome was the 90-day mortality rate. Length of ICU stay related to pleural infection, chest tube duration, re-thoracotomy rate and length of ventilatory support represented secondary outcomes.

Results

The 90-day mortality rate was 6% (2 patients). The mean ICU stay related to the pleural infection was 6 days (2-24 days). Video-assisted thoracoscopic surgery (VATS) was performed in all patients. Conversion to thoracotomy was necessary in 12 cases. Decortication and parietal pleurectomy in addition to hematoma and empyema removal was performed in all patients. Due to diffuse bleeding, packing of the thoracic cavity with temporary thoracic closure was necessary in 10 patients. Depacking was performed after a mean of 3 days (3-7 days). Recurrent empyema or bleeding after definitive chest closure was not observed. Lung resection was performed in 3 patients.

Conclusions

Thoracic surgical management of pleural infection in patients after VAD implantation is challenging and complicated due to the inevitable anticoagulative therapy. A perioperative multidisciplinary management which includes the early involvement of thoracic surgical expertise helps to improve survival in this very complex patient cohort.

Association between Tunneled Pleural Catheter Use and Infection in Patients Immunosuppressed from Antineoplastic Therapy. A Multicenter Study

Rationale: Patients with malignant or paramalignant pleural effusions (MPEs or PMPEs) may have tunneled pleural catheter (TPC) management withheld because of infection concerns from immunosuppression associated with antineoplastic therapy.Objectives: To determine the rate of infections related to TPC use and to determine the relationship to antineoplastic therapy, immune system competency, and overall survival (OS).Methods: We performed an international, multiinstitutional study of patients with MPEs or PMPEs undergoing TPC management from 2008 to 2016. Patients were stratified by whether or not they underwent antineoplastic therapy and/or whether or not they were immunocompromised. Cumulative incidence functions and multivariable competing risk regression analyses were performed to identify independent predictors of TPC-related infection. Kaplan-Meier method and multivariable Cox proportional hazards modeling were performed to examine for independent effects on OS.Results: A total of 1,408 TPCs were placed in 1,318 patients. Patients had a high frequency of overlap between antineoplastic therapy and an immunocompromised state (75-83%). No difference in the overall (6-7%), deep pleural (3-5%), or superficial (3-4%) TPC-related infection rates between subsets of patients stratified by antineoplastic therapy or immune status was observed. The median time to infection was 41 (interquartile range, 19-87) days after TPC insertion. Multivariable competing risk analyses demonstrated that longer TPC duration was associated with a higher risk of TPC-related infection (subdistribution hazard ratio, 1.03; 95% confidence interval [CI], 1.00-1.06; P = 0.028). Cox proportional hazards analysis showed antineoplastic therapy was associated with better OS (hazard ratio, 0.84; 95% CI, 0.73-0.97; P = 0.015).Conclusions: The risk of TPC-related infection does not appear to be increased by antineoplastic therapy use or an immunocompromised state. The overall rates of infection are low and comparable with those of immunocompetent patients with no relevant antineoplastic therapy. These results support TPC palliation for MPE or PMPEs regardless of plans for antineoplastic therapy.

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.

Forgotten disease: an atypical case of Lemierre syndrome presenting as a soft tissue abscess

Lemierre syndrome (LS) is an acute oropharyngeal infection with secondary septic thrombophlebitis and distant septic embolisation. A 29-year-old woman with sore throat, dyspnoea and left shoulder pain, who was on levofloxacin for 3 days, presented with worsening symptoms. She was tachycardic, tachypneic and hypoxic on presentation. CT of neck and chest revealed multiple loculated abscesses on her left lower neck and shoulder, right peritonsillar abscess, thrombosis of the right external jugular vein and multiple bilateral septic emboli to the lungs. She was started on clindamycin and ampicillin sulbactam for LS. She developed septic shock and required intubation due to respiratory failure. Drainage of the left shoulder abscess grew Fusobacterium nucleatum After 2 weeks of a complicated intensive care unit stay, her haemodynamic status improved and she was transferred to the floor. LS has variable presentations, but regardless of the presentation, it is a potentially fatal disease-requiring prompt diagnosis and management.

Intrapleural Fibrinolytic Therapy versus Early Medical Thoracoscopy for Treatment of Pleural Infection. Randomized Controlled Clinical Trial

Rationale: Pleural infection is frequently encountered in clinical practice and is associated with high morbidity and mortality. Limited evidence exists regarding the optimal treatment. Although both early medical thoracoscopy (MT) and tube thoracostomy with intrapleural instillation of tissue plasminogen activator and human recombinant deoxyribonuclease are acceptable treatments for patients with complicated pleural infection, there is a lack of comparative data for these modes of management.Objectives: The aim of this study was to compare the safety and efficacy of early MT versus intrapleural fibrinolytic therapy (IPFT) in selected patients with multiloculated pleural infection and empyema.Methods: This was a prospective multicenter, randomized controlled trial involving patients who underwent MT or IPFT for pleural infection. The primary outcome was the length of hospital stay after either intervention. Secondary outcomes included the total length of hospital stay, treatment failure, 30-day mortality, and adverse events.Results: Thirty-two patients with pleural infection were included in the study. The median length of stay after an intervention was 4 days in the IPFT arm and 2 days in the MT arm (P = 0.026). The total length of hospital stay was 6 days in the IPFT arm and 3.5 days in MT arm (P = 0.12). There was no difference in treatment failure, mortality, or adverse events between the treatment groups, and no serious complications related to either intervention were recorded.Conclusions: When used early in the course of a complicated parapneumonic effusion or empyema, MT is safe and might shorten hospital stays for selected patients as compared with IPFT therapy. A multicenter trial with a larger sample size is needed to confirm these findings.Clinical trial registered with ClinicalTrials.gov (NCT02973139).

Granulomatous lung disease and immune reconstitution inflammatory syndrome in Whipple's disease

We present the case of a 70-year-old woman with a history of seronegative arthritis, recurrent pleural effusion and weight loss. A prior lung biopsy had revealed non-caseating epithelioid cell granulomas without evidence for microbial organisms on special stains. Intestinal biopsy findings where suspicious for Whipple's disease, which was confirmed by PCR testing, both on the intestinal and retrospectively on the lung tissue. Treatment with ceftriaxone resulted in clinical deterioration with fever, arthritis and recurrent pleuritis consistent with immune reconstitution inflammatory syndrome. Dose increase of glucocorticoids and therapy rotation to doxycycline and hydroxychloroquine resulted in rapid clinical improvement.

Clinical utility of 16S rRNA PCR in pleural infection

Pleural infections cause major morbidity and mortality, particularly amongst paediatric and elderly populations. The aetiology is broad, but pleural culture fails to yield a causative pathogen in approximately 40 % of cases. Alternative pathogen identification methods are therefore required. The aim of the study was to investigate the yield from and impact on patient care when performing 16S rRNA PCR on culture-negative pleural fluid specimens and to determine whether any individual laboratory parameters were associated with a positive 16S rRNA PCR result. We conducted a study on 90 patients with suspected pleural infection, who had a culture-negative pleural fluid specimen, which underwent 16S rRNA PCR analysis between August 2017 and June 2019. This study was undertaken at a large NHS Trust in London, UK. Thirty-one per cent of culture-negative pleural fluid specimens tested by 16S rRNA PCR yielded a positive PCR result. Our data demonstrated that 16S rRNA PCR detected a significantly higher proportion of Streptococcus pneumoniae (P<0.0001) and fastidious, slow-growing and anaerobic pathogens (P=0.0025) compared with culture-based methods. Of the 25 16S rRNA PCR results that were positive for a causative pathogen, 76 % had a direct impact on clinical management. No single laboratory variable was found to be associated with a positive 16S rRNA PCR result. The findings from our real-world evaluation highlight the importance of 16S rRNA PCR in confirming pleural infection when the aetiology is unknown, and its direct, positive impact on clinical management.

Legionella pulmonary abscess and pleural space infection in an immunocompetent patient

A 34-year-old woman is admitted to the hospital with dyspnoea, dry cough and left-sided flank pain. Her Legionella urinary test was positive and CT imaging demonstrated multifocal pneumonia with pulmonary abscesses. Although she had initial clinical improvement on appropriate antibiotic therapy, her hospital course was complicated by worsening flank pain, hypoxemia and leucocytosis, prompting clinical re-evaluation and assessment for development of complications involving the pleural space. CT imaging revealed interval development of a loculated complicated parapneumonic effusion. Successful treatment required chest tube drainage assisted by fibrinolytic therapy. This case highlights the importance of considering Legionella in patients with pulmonary abscess, demonstrates an approach to a patient with a non-resolving pneumonia and illustrates the management of parapneumonic effusions.

Successful drainage of complex haemoserous malignant pleural effusion with a single modified low-dose intrapleural alteplase and dornase alfa

Patients with symptomatic complex malignant pleural effusion (MPE) are frequently unfit for decortication and have a poorer prognosis. Septations can develop in MPE, which may lead to failure of complete drainage and pleural infection. Intrapleural fibrinolytic therapy (IPFT) is an alternative treatment. The use of IPFT in patients with anaemia and high risk for intrapleural bleeding is not well established. We report a successful drainage of complex haemoserous MPE with a single modified low-dose of intrapleural 5 mg of alteplase and 5 mg of dornase alfa in a patient with pre-existing anaemia with no significant risk of intrapleural bleeding.

Bilateral pleural masses in an immunocompromised patient

We present a case of persistent pleural masses with mediastinal adenopathy in an immunocompromised patient initially biopsied, diagnosed and treated for Pneumocystis jiroveci pneumonia, ultimately requiring surgical thoracoscopy to diagnose pulmonary histoplasmosis. We discuss the diagnostic approach for pleural masses in immunocompromised patients, the limitations of tissue sampling, interpretation and methodology, and pitfalls of testing in making a pathogen-specific diagnosis.

Short-course intrapleural alteplase and DNase in complex effusion with bleeding risk

Pleural infection is an important clinical problem with significant morbidity. In poorly draining complex pleural effusions, the current management favours a less invasive image-guided placement of smaller bore catheters and adjunctive intrapleural fibrinolysis therapy (IPFT). We describe our experience of using IPFT in three patients with different bleeding risks with complex pleural effusions. The first was a 30-year-old with transfusion-dependent β-thalassemia with haemoglobin of 7.8 g/dL; second was an 87-year-old on dabigatran with haemoglobin of 10 g/dL; and the third was an 80-year-old with diffuse large B-cell lymphoma with haemoglobin of 8.6 g/dL. All three patients received three doses of alteplase and deoxyribonuclease (DNase) without any adverse effects of bleeding and had resolution of the effusion. This case series is an addition to the current literature on the safety of IPFT and we highlight the use of IPFT in patients with low baseline haemoglobin and on anticoagulation therapy.

Bronchopleural communication following intrapleural doses of tPA/DNase for empyema

Intrapleural tissue plasminogen activator (tPA) and deoxyribonuclease (DNase) therapy is a new treatment for pleural infection. Clinical experiences of tPA/DNase therapy, and its complications, are cumulating. We present a patient with multiloculated empyema but no initial evidence of a bronchopleural fistula. She was treated with antibiotics and chest tube drainage of the basal collection through which four doses of tPA/DNase were delivered with success. The lateral collection worsened necessitating separate tube drainage and tPA/DNase treatment. She reported chest "fullness" when instilled the second dose. The third instillation of tPA triggered immediate vigorous coughing and expectoration of salty-tasting fluid, likely the tPA/saline solution. The symptoms spontaneously settled after 15 min, with no evidence of air leak. The loculated fluid was successfully evacuated. The patient made a full recovery after an antibiotic course with no long-term consequences. Pulmonary migration of drugs via a bronchopleural communication, although rare, can occur with intrapleural tPA/DNase therapy.

Osler Centenary Papers: Management of pleural infection: Osler's final illness and recent advances

Sir William Osler's great work and achievements are extensively documented. Less well known is his prolonged battle with postinfluenza pneumonia, lung abscess and pleural infection that eventually led to his demise. At the age of 70, he was a victim of the global Spanish influenza epidemic, and subsequently developed pneumonia. In the era before antibiotics, he received supportive care and opium for symptom control. The infection extended to the pleura and he required repeated thoracentesis which failed to halt his deterioration. He proceeded to open surgical drainage involving rib resection. Unfortunately, he died shortly after the operation from massive pleuropulmonary haemorrhage. In this article, we review the events leading up to Osler's death and contrast his care 100 years ago with contemporary state-of-the-art management in pleural infection.

Pleural effusions and pneumothorax: Beyond simple plumbing: Expert opinions on knowledge gaps and essential next steps

Pleural diseases affect millions of people worldwide. Pleural infection, malignant pleural diseases and pneumothorax are common clinical challenges. A large number of recent clinical trials have provided an evidence-based platform to evaluate conventional and novel methods to drain pleural effusions/air which reduce morbidity and unnecessary interventions. These successes have generated significant enthusiasm and raised the profile of pleural medicine as a new subspecialty. The ultimate goal of pleural research is to prevent/stop development of pleural effusions/pneumothorax. Current research studies mainly focus on the technical aspects of pleural drainage. Significant knowledge gaps exist in many aspects such as understanding of the pathobiology of the underlying pleural diseases, pharmacokinetics of pleural drug delivery, etc. Answers to these important questions are needed to move the field forward. This article collates opinions of leading experts in the field in highlighting major knowledge gaps in common pleural diseases to provoke thinking beyond pleural drainage. Recognizing the key barriers will help prioritize future research in the quest to ultimately cure (rather than just drain) these pleural conditions.

Indwelling pleural catheter for outpatient management of tuberculous empyema

The use of indwelling pleural catheters (IPC) is well established in the treatment of malignant pleural effusions. They allow symptom management with intermittent drainage without requiring overnight admission to hospital. However, little is known about their effectiveness in the treatment of pleural infections. Here, we present a case where an IPC is used in the therapeutic management of tuberculous empyema. The IPC enabled outpatient treatment, allowed the patient to return to work and reduced the cost of treatment and the risk of hospital-acquired complications.

Biological effect of tissue plasminogen activator (t-PA) and DNase intrapleural delivery in pleural infection patients

Background

Pleural infection (PI) is a major global disease with an increasing incidence, and pleural fluid (PF) drainage is essential for the successful treatment. The MIST2 study demonstrated that intrapleural administration of tissue plasminogen activator (t-PA) and DNase, or t-PA alone increased the volume of drained PF. Mouse model studies have suggested that the volume increase is due to the interaction of the pleura with the t-PA via the monocyte chemoattractant protein 1 (MCP-1) pathway. We designed a study to determine the time frame of drained PF volume induction on intrapleural delivery of t-PA±DNase in humans, and to test the hypothesis that the induction is mediated by the MCP-1 pathway.

Methods

Data and samples from the MIST2 study were used (210 PI patients randomised to receive for 3 days either: t-PA and DNase, t-PA and placebo, DNase and placebo or double placebo). PF MCP-1 levels were measured by ELISA. One-way and two-way analysis of variance (ANOVA) with Tukey's post hoc tests were used to estimate statistical significance. Pearson's correlation coefficient was used to assess linear correlation.

Results

Intrapleural administration of t-PA±DNase stimulated a statistically significant rise in the volume of drained PF during the treatment period (days 1-3). No significant difference was detected between any groups during the post-treatment period (days 5-7). Intrapleural administration of t-PA increased MCP-1 PF levels during treatment; however, no statistically significant difference was detected between patients who received t-PA and those who did not. PF MCP-1 expression was not correlated to the drug given nor the volume of drained PF.

Conclusions

We conclude that the PF volume drainage increment seen with the administration of t-PA does not appear to act solely via activation of the MCP-1 pathway.

Gastropleural fistula masquerading as chylothorax in a child with lymphoma

We report the case of an 8-year-old boy with diffuse large B cell lymphoma who developed a right-sided spontaneous pneumothorax with pleural effusion after recovery from septic shock. The pleural fluid was thought to be malignancy-associated chylothorax concomitant with complicated pleural effusion due to a milky-like appearance, a high level of triglycerides and Gram-negative bacteria staining in the fluid. He was put on total parental nutrition and octreotide for 2 weeks, but did not improve. The laboratory results also showed a persistent bacterial infection in the pleural fluid despite appropriate antibiotics. Eventually, a CT scan revealed a fistulous tract between the right pleural cavity and the stomach. Fistula repair was successful by right open thoracotomy with decortication. Even though the gastropleural fistula is a very rare condition in paediatric patients, the physician should consider this diagnosis in a patient who has an unusual presentation or refractory chylothorax-like pleural effusion.

Interpreting pleural fluid results

Interpreting pleural fluid results correctly requires an awareness of the possible aetiologies of a pleural effusion and an understanding of the reliability of the outcome of each investigation. All results must be interpreted within each different clinical context and knowledge of the pitfalls for each test is necessary when the diagnosis is unclear. This review aims to discuss the common aetiologies of a pleural effusion and some of the pitfalls in interpretation that can occur when the diagnosis is unclear.

Empyema thoracis secondary to community-acquired Panton-Valentine leukocidin (PVL) methicillin-resistant Staphylococcus aureus (MRSA) infection

We report a case of a previously fit middle-aged man presenting to the outpatient setting with unilateral pleural effusion, with minimal symptoms. On subsequent investigations, he was diagnosed with empyema thoracis secondary to Panton-Valentine leukocidin (PVL)-toxin positive community-acquired methicillin-resistant Staphylococcus aureus (MRSA). The patient was treated with prolonged antibiotics and pleural drainage, and he remained haemodynamically stable throughout hospital admission. PVL is a cytolytic exotoxin produced by some strains of S. aureus Such strains often cause recurrent skin and soft tissue infections, usually in previously fit and healthy individuals. Less commonly, invasive infections occur; these carry a high mortality rate if associated with necrotising pneumonia or septic shock. PVL genes are present in approximately 2% of clinical isolates of S. aureus in the UK. PVL-producing MRSA infections are on the rise and present significant clinical and public health challenges.

Successful management of pleural infection with very low dose intrapleural tissue plasminogen activator/deoxyribonuclease regime

Pleural infection managed with intrapleural therapy using a combination of 10 mg of tissue plasminogen activator (tPA) and 5 mg of deoxyribonuclease (DNase) has been shown in randomized and open-label studies to successfully treat >90% of patients without resorting to surgery. Potential bleeding risks, although low, and costs associated with tPA remain important concerns. No phase I studies exist for intrapleural tPA therapy and the lowest effective dose has not been established. In patients with high bleeding risks, lower doses may present a safer alternative. We report a case of a complex parapneumonic effusion in a patient with coagulopathy that was successfully treated with a very low dose tPA (1 mg) and DNase (5 mg) regime.

Hepatic hydrothorax: indwelling catheter-related Acinetobacter radioresistens infection

Hepatic hydrothorax, a rare and debilitating complication of cirrhosis, carries high morbidity and mortality. First-line treatment consists of dietary sodium restriction and diuretic therapy. Some patients, mainly those who are refractory to medical management, will require invasive pleural drainage. The authors report the case of a 76-year-old man in a late cirrhotic stage of alcoholic chronic liver disease, presenting with recurrent right-sided hepatic hydrothorax, portal hypertension, hepatosplenomegaly and thrombocytopaenia. After recurrent admissions and complications, the potential for adjusting diuretic therapy was limited. After unsuccessful talc pleurodesis, an indwelling tunnelled pleural catheter was placed with effective symptomatic control. One month later, the patient was readmitted with empyema due to Acinetobacter radioresistens Despite optimised medical and surgical treatment, the patient died 4 weeks later.

Diagnosis of infectious pleural effusion using predictive models based on pleural fluid biomarkers

INTRODUCTION:

Diagnosis of pleural infection (PI) may be challenging. The purpose of this paper is to develop and validate a clinical prediction model for the diagnosis of PI based on pleural fluid (PF) biomarkers.

METHODS:

A prospective study was conducted on pleural effusion. Logistic regression was used to estimate the likelihood of having PI. Two models were built using PF biomarkers. The power of discrimination (area under the curve) and calibration of the two models were evaluated.

RESULTS:

The sample was composed of 706 pleural effusion (248 malignant; 28 tuberculous; 177 infectious; 48 miscellaneous exudates; and 212 transudates). Areas under the curve for Model 1 (leukocytes, percentage of neutrophils, and C-reactive protein) and Model 2 (the same markers plus interleukin-6 [IL-6]) were 0.896 and 0.909, respectively (not significant differences). However, both models showed higher capacity of discrimination than their biomarkers when used separately (P < 0.001 for all). Rates of correct classification for Models 1 and 2 were 88.2% (623/706: 160/177 [90.4%] with infectious pleural effusion [IPE] and 463/529 [87.5%] with non-IPE) and 89.2% (630/706: 153/177 [86.4%] of IPE and 477/529 [90.2%] of non-IPE), respectively.

CONCLUSIONS:

The two predictive models developed for IPE showed a good diagnostic performance, superior to that of any of the markers when used separately. Although IL-6 contributes a slight greater capacity of discrimination to the model that includes it, its routine determination does not seem justified.

Intrapleural alteplase therapy: what are the knowns and unknowns?

In pneumology, enzymatic properties of plasmin are used to disrupt fibrin adhesions and septations formed during pathological conditions of the pleural cavity. In that case, fibrinolytics are administrated locally via a chest tube in the pleural cavity to evacuate pathological effusion. Although the first intrapleural administration of fibrinolytic occurred seventy years ago, there has been no consensus on dosing or a uniform procedure of their application. The aim of the article is to summarize current knowledge of alteplase usage in pneumology and discuss practical aspects of its intrapleural application regarding specific possibilities in the Czech Republic.

A Pilot Feasibility Study in Establishing the Role of Ultrasound-Guided Pleural Biopsies in Pleural Infection (The AUDIO Study)

BACKGROUND

Pleural infection is a common complication of pneumonia associated with high mortality and poor clinical outcome. Treatment of pleural infection relies on the use of broad-spectrum antibiotics because reliable pathogen identification occurs infrequently. We performed a feasibility interventional clinical study assessing the safety and significance of ultrasound (US)-guided pleural biopsy culture to increase microbiological yield. In an exploratory investigation, the 16S ribosomal RNA technique was applied to assess its utility on increasing speed and accuracy vs standard microbiological diagnosis.

METHODS

Twenty patients with clinically established pleural infection were recruited. Participants underwent a detailed US scan and US-guided pleural biopsies before chest drain insertion, alongside standard clinical management. Pleural biopsies and routine clinical samples (pleural fluid and blood) were submitted for microbiological analysis.

RESULTS

US-guided pleural biopsies were safe with no adverse events. US-guided pleural biopsies increased microbiological yield by 25% in addition to pleural fluid and blood samples. The technique provided a substantially higher microbiological yield compared with pleural fluid and blood culture samples (45% compared with 20% and 10%, respectively). The 16S ribosomal RNA technique was successfully applied to pleural biopsy samples, demonstrating high sensitivity (93%) and specificity (89.5%).

CONCLUSIONS

Our findings demonstrate the safety of US-guided pleural biopsies in patients with pleural infection and a substantial increase in microbiological diagnosis, suggesting potential niche of infection in this disease. Quantitative polymerase chain reaction primer assessment of pleural fluid and biopsy appears to have excellent sensitivity and specificity.

Cryptococcus neoformans empyema in a patient receiving ibrutinib for diffuse large B-cell lymphoma and a review of the literature

We report a case of Cryptococcus neoformans pulmonary infection complicated by empyema in a 79-year-old man with diffuse large B-cell lymphoma treated with R-CHOP and ibrutinib. A literature review identified 25 cases of cryptococcal pleural disease published since 1980. Most cases were caused by the C. neoformans species in immunocompromised hosts with an exudative pleural effusion and lymphocyte-predominant infiltrate. The cryptococcal antigen test was often positive when pleural fluid and serum were tested. The outcome was favourable in most cases with antifungal therapy and either thoracocentesis or surgical resection. We also identified 40 cases of opportunistic infections, most commonly aspergillosis, cryptococcosis and Pneumocystis jirovecii pneumonia, in patients treated with ibrutinib. In vitro studies indicate Bruton tyrosine kinase inhibition impairs phagocyte function and offer a mechanism for the apparent association between ibrutinib and invasive fungal infections.

Pleural infection in a New Zealand centre: high incidence in Pacific people and RAPID score as a prognostic tool

BACKGROUND

Whilst there is an increase in incidence of pleural infection worldwide, there is a paucity of New Zealand data.

AIMS

This study looked at the epidemiology of pleural infection in a single New Zealand institution and evaluated the RAPID score as a prognostic tool.

METHODS

A retrospective review was performed on patients with pleural infection over a 3-year period. Pleural infection was defined as having clinical evidence of infection and fulfilling one of the following: (i) positive pleural fluid Gram stain or culture, (ii) frank pus, (iii) pH <7.2 or (iv) radiological evidence of complex effusion.

RESULTS

There were 108 patients; 76% were male, and mean age was 54 years. Two thirds of patients came from the most deprived areas. The dominant ethnic group was Pacific people (42%), which was twice as high as the Pacific population in the area (19%), P < 0.0001. After adjusting for deprivation, Pacific people were still over-represented, P = 0.0002. There were 14 deaths (13%), and these were associated with increasing age (P = 0.001) and urea (P = 0.007) but not ethnicity or socioeconomic deprivation. The RAPID score found that those in the high-risk (P = 0.026) and moderate-risk (P = 0.036) groups had significantly higher mortality compared with the low-risk group.

CONCLUSION

The over-representation of Pacific people with pleural infection is not fully explained by socioeconomic deprivation, highlighting other factors at play, such as genetic susceptibility. The RAPID score was of clinical utility in predicting mortality in our population.

A Quality Improvement Intervention to Reduce Indwelling Tunneled Pleural Catheter Infection Rates

RATIONALE

The indwelling tunneled pleural catheter has altered the management of patients with dyspnea related to malignant pleural effusions. However, indwelling tunneled pleural catheter placement does not remain free from risk. The most commonly reported risk is infection.

OBJECTIVES

The aim of this paper is to describe our continuous quality improvement program for infection rate recognition, the process changes implemented for improvement, and subsequent outcomes.

METHODS

All patients undergoing indwelling tunneled pleural catheter placement at The Johns Hopkins Medical Institutions between May 2009 and April 2014 were identified. The primary outcome was the incidence of infection within the preintervention and intervention cohorts. Intervention was identified as use of preoperative antibiotics, full sterile draping, and limiting placement to a single defined location.

MEASUREMENTS AND MAIN RESULTS

A total of 225 indwelling tunneled pleural catheter placements were performed in 201 patients during the study period, and the overall infection rate was 5.8%. During the preintervention period, 134 placements were performed, and 91 placements occurred during the intervention period. A preintervention infection rate was identified as 8.2%, with a significant decrease to 2.2% (P = 0.049) within the intervention cohort.

CONCLUSIONS

The use of a continuous quality improvement program to review indwelling tunneled pleural catheter practices can result in the identification of infectious complications and lead to implementation of measures to improve patient outcomes.

Tissue plasminogen activator potently stimulates pleural effusion via a monocyte chemotactic protein-1-dependent mechanism

Pleural infection is common. Evacuation of infected pleural fluid is essential for successful treatment, but it is often difficult because of adhesions/loculations within the effusion and the viscosity of the fluid. Intrapleural delivery of tissue plasminogen activator (tPA) (to break the adhesions) and deoxyribonuclease (DNase) (to reduce fluid viscosity) has recently been shown to improve clinical outcomes in a large randomized study of pleural infection. Clinical studies of intrapleural fibrinolytic therapy have consistently shown subsequent production of large effusions, the mechanism(s) of which are unknown. We aimed to determine the mechanism by which tPA induces exudative fluid formation. Intrapleural tPA, with or without DNase, significantly induced pleural fluid accumulation in CD1 mice (tPA alone: median [interquartile range], 53.5 [30-355] μl) compared with DNase alone or vehicle controls (both, 0.0 [0.0-0.0] μl) after 6 hours. Fluid induction was reproduced after intrapleural delivery of streptokinase and urokinase, indicating a class effect. Pleural fluid monocyte chemotactic protein (MCP)-1 levels strongly correlated with effusion volume (r = 0.7302; P = 0.003), and were significantly higher than MCP-1 levels in corresponding sera. Mice treated with anti-MCP-1 antibody (P < 0.0001) or MCP-1 receptor antagonist (P = 0.0049) demonstrated a significant decrease in tPA-induced pleural fluid formation (by up to 85%). Our data implicate MCP-1 as the key molecule governing tPA-induced fluid accumulation. The role of MCP-1 in the development of other exudative effusions warrants examination.