The contribution of leukocytes and bacteria to the low pH of empyema fluid

Comprehensive stability analysis of 13 β-lactams and β-lactamase inhibitors in in vitro media, and novel supplement dosing strategy to mitigate thermal drug degradation

Non-clinical antibiotic development relies on in vitro susceptibility and infection model studies. Validating the achievement of the targeted drug concentrations is essential to avoid under-estimation of drug effects and over-estimation of resistance emergence. While certain β-lactams (e.g., imipenem) and β-lactamase inhibitors (BLIs; clavulanic acid) are believed to be relatively unstable, limited tangible data on their stability in commonly used in vitro media are known. We aimed to determine the thermal stability of 10 β-lactams and 3 BLIs via LC-MS/MS in cation-adjusted Mueller Hinton broth at 25 and 36°C as well as agar at 4 and 37°C, and in water at -20, 4, and 25°C. Supplement dosing algorithms were developed to achieve broth concentrations close to their target over 24 h. During incubation in broth (pH 7.25)/agar, degradation half-lives were 16.9/21.8 h for imipenem, 20.7/31.6 h for biapenem, 29.0 h for clavulanic acid (studied in broth only), 23.1/71.6 h for cefsulodin, 40.6/57.9 h for doripenem, 46.5/64.6 h for meropenem, 50.8/97.7 h for cefepime, 61.5/99.5 h for piperacillin, and >120 h for all other compounds. Broth stability decreased at higher pH. All drugs were ≥90% stable for 72 h in agar at 4°C. Degradation half-lives in water at 25°C were >200 h for all drugs except imipenem (14.7 h, at 1,000 mg/L) and doripenem (59.5 h). One imipenem supplement dose allowed concentrations to stay within ±31% of their target concentration. This study provides comprehensive stability data on β-lactams and BLIs in relevant in vitro media using LC-MS/MS. Future studies are warranted applying these data to antimicrobial susceptibility testing and assessing the impact of β-lactamase-related degradation.

Differentiating necrotizing soft tissue infections from cellulitis by soft tissue infectious fluid analysis: a pilot study

Background

We conducted this study to evaluate the characteristics of the infectious fluid in soft tissue infection and investigate the utility of the biochemical tests and Gram stain smear of the infectious fluid in distinguishing necrotizing soft tissue infection (NSTI) from cellulitis.

Methods

This retrospective cohort study was conducted in a tertiary care hospital in Taiwan. From April 2019 to October 2020, patients who were clinically suspected of NSTI with infectious fluid accumulation along the deep fascia and received successful ultrasound-guided aspiration were enrolled. Based on the final discharge diagnosis, the patients were divided into NSTI group, which was supported by the surgical pathology report, or cellulitis group. The t test method and Fisher’s exact test were used to compare the difference between two groups. The receiver–operator characteristic (ROC) curves and area under the ROC curve (AUC) were used to evaluate the discriminating ability.

Results

Total twenty-five patients were enrolled, with 13 patients in NSTI group and 12 patients in cellulitis group. The statistical analysis showed lactate in fluid (AUC = 0.937) and LDH in fluid (AUC = 0.929) had outstanding discrimination. The optimal cut-off value of fluid in lactate was 69.6 mg/dL with corresponding sensitivity of 100% and specificity of 76.9%. The optimal cut-off value of fluid in LDH was 566 U/L with corresponding sensitivity of 83.3% and a specificity of 92.3%. In addition, albumin in fluid (AUC = 0.821), TP in fluid (AUC = 0.878) and pH in fluid (AUC = 0.858) also had excellent diagnostic accuracy for NSTI. The Gram stain smear revealed 50% bacteria present in NSTI group and all the following infectious fluid culture showed bacteria growth.

Conclusions

The analysis of infectious fluid along the deep fascia might provide high diagnostic accuracy to differentiate NSTI from cellulitis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13017-022-00404-4.

Pleural Fluid suPAR Levels Predict the Need for Invasive Management in Parapneumonic Effusions

Rationale: Parapneumonic effusions have a wide clinical spectrum. The majority settle with conservative management but some progress to complex collections requiring intervention. For decades, physicians have relied on pleural fluid pH to determine the need for chest tube drainage despite a lack of prospective validation and no ability to predict the requirement for fibrinolytics or thoracic surgery.Objectives: To study the ability of suPAR (soluble urokinase plasminogen activator receptor), a potential biomarker of pleural fluid loculation, to predict the need for invasive management compared with conventional fluid biomarkers (pH, glucose, and lactate dehydrogenase) in parapneumonic effusions.Methods: Patients presenting with pleural effusions were prospectively recruited to an observational study with biological samples stored at presentation. Pleural fluid and serum suPAR levels were measured using the suPARnostic double-monoclonal antibody sandwich ELISA on 93 patients with parapneumonic effusions and 47 control subjects (benign and malignant effusions).Measurements and Main Results: Pleural suPAR levels were significantly higher in effusions that were loculated versus nonloculated parapneumonic effusions (median, 132 ng/ml vs. 22 ng/ml; P < 0.001). Pleural suPAR could more accurately predict the subsequent insertion of a chest tube with an area under the curve (AUC) of 0.93 (95% confidence interval, 0.89-0.98) compared with pleural pH (AUC 0.82; 95% confidence interval, 0.73-0.90). suPAR was superior to the combination of conventional pleural biomarkers (pH, glucose, and lactate dehydrogenase) when predicting the referral for intrapleural fibrinolysis or thoracic surgery (AUC 0.92 vs. 0.76).Conclusions: Raised pleural suPAR was predictive of patients receiving more invasive management of parapneumonic effusions and added value to conventional biomarkers. These results need validation in a prospective multicenter trial.

Intrapleural therapy in management of complicated parapneumonic effusions and empyema

Empyema thoracis causes high mortality, and its incidence is increasing in both children and adults. Parapneumonic effusions (PPEs) develop in about one-half of patients hospitalized with pneumonia, and their presence increases mortality by about four-fold. PPEs can be divided into simple PPEs, complicated PPEs, and frank empyema. Two guideline statements on the management of PPEs in adults have been published by the British Thoracic Society (BTS) and the American College of Chest Physicians; a third guideline statement published by the BTS focused on management of PPEs in children. The two adult guideline statements recommend drainage of the pleural space in complicated PPEs and frank empyema. They also recommend the use of intrapleural fibrinolysis in those who do not show improvement. The pediatric guideline statement recommends adding intrapleural fibrinolysis to those treated by tube thoracostomy if they have loculated pleural space or thick pus. Published guideline statements on the management of complicated PPEs and empyema in adults and children recommend the use of intrapleural fibrinolysis in those who do not show improvement after pleural space drainage. However, published clinical trial reports on the use of intrapleural fibrinolysis for the treatment of pleural space sepsis suffer from major design and methodologic limitations. Nevertheless, published reports have shown that the use of intrapleural fibrinolysis does not reduce mortality in adults with parapneumonic effusions and empyema. However, intrapleural fibrinolysis enhances drainage of infected pleural fluid and may be used in patients with large collections of infected pleural fluid causing breathlessness or respiratory failure, but a proportion of these patients will ultimately need surgery for definite cure. Intrapleural streptokinase and urokinase seem to be equally efficacious in enhancing infected pleural fluid drainage in adults. In most of the published studies in adults, the use of intrapleural fibrinolysis was not associated with serious side effects. There is emerging evidence that the combination of intrapleural tissue plasminogen activator (tPA) and deoxyribonuclease (DNase) is significantly superior to tPA or DNase alone or placebo in improving pleural fluid drainage in patients with pleural space infection. In children, intrapleural fibrinolysis has not been shown to reduce mortality, but has been shown to enhance drainage of the pleural space and was safe. In addition, two prospective, randomized trials have shown that intrapleural fibrinolysis is as effective as video-assisted thoracoscopic surgery for the treatment of childhood empyema and is a more cost-effective treatment and therefore should be the primary treatment of choice.

Exhaled breath condensate pH and exhaled nitric oxide in allergic asthma and in cystic fibrosis

BACKGROUND

It has been proposed that the pH of airway lining fluid may regulate the fractional exhaled concentration of nitric oxide (Fe(NO)) in respiratory disease.

METHODS

Fe(NO), exhaled breath condensate (EBC) pH, and EBC concentrations of nitrite plus nitrate (NO2/NO3) were compared in 12 subjects with stable asthma, 18 with stable cystic fibrosis (CF), and 15 healthy control subjects. Eight of the CF patients were studied on a separate occasion at the start of a pulmonary exacerbation.

RESULTS

Fe(NO) was significantly greater in asthmatic subjects than in control subjects (mean 35 v 9 ppb, p<0.001). EBC pH, however, was similar in the asthmatic and control groups (median 5.82 v 6.08, p=0.23). Levels of NO2/NO3 were on average higher in EBC samples from asthmatic subjects, but the difference was not significant. In patients with stable CF both the Fe(NO) (mean 4 ppb, p<0.001) and EBC pH (median 5.77, p=0.003) were lower than in the control group. Levels of EBC NO2/NO3 (median 29.9 microM; p=0.002) in patients with stable CF, in contrast, were significantly higher than in control subjects. During CF exacerbations, EBC pH was further reduced (median 5.30, p=0.017) but Fe(NO) and NO2/NO3 were unchanged.

CONCLUSIONS

These findings demonstrate a dissociation between EBC pH and Fe(NO) in inflammatory airways disease.

Randomised controlled trial of intrapleural streptokinase in community acquired pleural infection

BACKGROUND

Standard treatment for pleural infection includes catheter drainage and antibiotics. Tube drainage often fails if the fluid is loculated by fibrinous adhesions when surgical drainage is needed. Streptokinase may aid the process of pleural drainage, but there have been no controlled trials to assess its efficacy.

METHODS

Twenty four patients with infected community acquired parapneumonic effusions were studied. All had either frankly purulent/culture or Gram stain positive pleural fluid (13 cases; 54%) or fluid which fulfilled the biochemical criteria for pleural infection. Fluid was drained with a 14F catheter. The antibiotics used were cefuroxime and metronidazole or were guided by culture. Subjects were randomly assigned to receive intrapleural streptokinase, 250,000 i.u. daily, or control saline flushes for three days. The primary end points related to the efficacy of pleural drainage--namely, the volume of pleural fluid drained and the chest radiographic response to treatment. Other end points were the number of pleural procedures needed and blood indices of inflammation.

RESULTS

The streptokinase group drained more pleural fluid both during the days of streptokinase/control treatment (mean (SD) 391 (200) ml versus 124 (44) ml; difference 267 ml, 95% confidence interval (CI) 144 to 390; p < .001) and overall (2564 (1663) ml, 95% CI 465 to 2545; p < 0.01). They showed greater improvement on the chest radiograph at discharge, measured as the fall in the maximum dimension of the pleural collection (6.0 (2.7) cm versus 3.4 (2.7) cm; difference 2.9 cm, 95% CI 0.3 to 4.4; p < 0.05) and the overall reduction in pleural fluid collection size (p < 0.05, two-tailed Fisher's exact test). Systemic fibrinolysis and bleeding complications did not occur. Surgery was required by three control patients but none in the streptokinase group.

CONCLUSIONS

Intrapleural streptokinase probably aids the treatment of pleural infections by improving pleural drainage without causing systemic fibrinolysis or local haemorrhage.