Spontaneous bacterial empyema caused by Aeromonas veronii biotype sobria

Early thoracentesis correlated with survival benefit in patients with spontaneous bacterial empyema

BACKGROUND

Spontaneous bacterial empyema (SBEM) is a rare complication of hepatic hydrothorax characterized by hydrothorax infection in the absence of pneumonia.

AIMS AND METHODS

We conducted this study to compare clinical outcomes in SBEM patients who underwent early thoracentesis (ET) (≤ 24 h from presentation) versus those who underwent delayed thoracentesis (DT). All patients diagnosed with SBEM at Mayo Clinic Rochester, Minnesota from January 1st 1999 to December 31st 2020 were reviewed. Demographics, pleural fluid studies, laboratory results and clinical outcomes were analyzed.

RESULTS

A total of 54 SBEM patients (27 ET and 27 DT) were identified with 38 (70.4%) of patients presenting with right-sided effusions. Both groups had similar baseline characteristics. The rate of ICU admission was significantly higher in the DT group (15 (55.6%) vs. 7 (25.9%) patients, P = 0.027). Patients with DT had similar rate of AKI (11 (40.7%) vs. 6 (22.2%) patients, P = 0.074). In-hospital mortality (11 (40.7%) vs. 2 (7.4%) patients, P = 0.004), 3-month mortality (16 (59.3%) vs. 2 (7.4%) patients, P < 0.001) and 1-year mortality rate (21 (77.8%) vs. 6 (22.2%) patients, P < 0.001) were higher in the DT group.

CONCLUSION

Patients with SBEM who underwent thoracentesis after 24 h from presentation (DT) had higher rates of mortality and ICU admission compared to patients who received early thoracentesis. Thoracentesis should be performed early in patients with suspected SBEM since it may improve survival.

Empyema and bacteremia caused by Aeromonas hydrophila: Case report and review of the literature

INTRODUCTION

Despite the advance in antibiotics and widespread chest tube drainage, acute empyema still shows a high mortality rate, accounting for 10-25%. We experienced a case of acute empyema caused by A. hydrophila, which is extremely uncommon, and reviewed all previously published articles.

CASE PRESENTATION

A 76-year older man with a medical history of liver cirrhosis (LC) due to chronic hepatitis C and hepatic cell carcinoma was admitted to our institute. Elevated inflammatory reaction and effusions on chest CT were seen, and he was suspected of having acute empyema. Although an empiric antibiotic therapy of meropenem with chest tube drainage was performed as an initial treatment, he died within 8 hours of admission. Postmortem, both blood and left pleural fluid cultures yielded Aeromonas hydrophila. The final diagnosis was acute empyema caused by A. hydrophila. We reviewed previously reported empyema caused by Aeromonas species cases (4 A. hydrophila, and 1 A. veronii) in 4 previous reports written in English, including ours. Of 5, all were male, and the mean age was 52 years (range 27-76 years). All patients had LC due to alcohol or viral infections. As for antibiotics initially prescribed, third-generation cephalosporins were most frequently used in 3/5 (60%). Thoracentesis was performed in all patients (100%). As for prognosis, 2 (40%) survived, and 3 (60%) died.

CONCLUSION

Physicians should be aware of the possibility of acute empyema caused by A. hydrophila among patients with chronic hepatic disease.

Evaluation of a New Culture-Based AtbFinder Test-System Employing a Novel Nutrient Medium for the Selection of Optimal Antibiotics for Critically Ill Patients with Polymicrobial Infections within 4 h

Here, we describe the validation of a new phenotypic culture-based AtbFinder method for rapid selection of antibiotics in vitro using specimens with mono- and polybacterial infections. AtbFinder, which can be applied to any type of non-blood tissue, does not require isolation of pure bacterial cultures. The method uses a novel TGV medium that allows more rapid bacterial growth of Gram-positive and Gram-negative monoisolates compared with that achieved with conventional laboratory media, demonstrating overall sensitivity, specificity, PPV, NPV values of 99.6%, 98.1%, 98.5%, and 99.4%, respectively, after 4 h. For polymicrobial infections, AtbFinder utilized a novel paradigm of the population response to antibiotics, enabling bacterial growth in the form of a mixed microbial community and selecting antibiotics targeting not only the principal pathogen, but also those bacteria that support their growth. TGV medium allowed culturing of a more diverse set of bacteria from polymicrobial biospecimens, compared with that achieved with the standard media, and enabled, within 4 h, accurate selection of the antibiotics that completely eliminated all cultivatable bacteria from clinical samples. In conclusion, the AtbFinder system may be a valuable tool in improving antibiotic selection, and enabling targeted empirical therapy and accurate antibiotic replacement, which is especially important in high-risk patients.

Comparative genomic analysis of different virulence strains reveals reasons for the increased virulence of Aeromonas veronii

Aeromonas veronii is an important zoonotic and aquatic agent. More and more cases have shown that it has caused huge economic losses in the aquaculture industry in addition to threatening human health. But the reasons for the increasing virulence of A. veronii are still unclear. In order to further understand the reasons for the increased virulence of A. veronii, we conducted a comparative analysis of the genomes of A. veronii with different virulence. The analysis revealed that there are multiple virulence factors, such as those related to fimbriae, flagella, toxins, iron ion uptake systems and type II, type III and type VI secretion systems in the virulent strain TH0426 genome. And comparative analysis showed that there were two complete type III secretion systems (API1 and API2), of which the API2 and iron ion transport system were unique to the TH0426 strain. In addition, TH0426 strain also has unique functional gene clusters, which may play important roles in terms of resisting infection, adapting to different environments and genetic evolution. These particular virulence factors and gene clusters may be the important reasons for the increased virulence. These insights will provide a reference for the study of the pathogenesis of A. veronii.

Cadaverine reverse transporter (CadB protein) contributes to the virulence of Aeromonas veronii TH0426

Aeromonas veronii is one of the main pathogens causing sepsis and ulcer syndrome in freshwater fish. Analysis of the results of epidemiological investigations in recent years has revealed that the virulence of A. veronii and its tolerance to drugs have been increasing year by year. Currently, most of the research on A. veronii focuses on its isolation, identification, and drug susceptibility, whereas research on its virulence factors and pathogenesis mechanisms is relatively rare. In this study, we identified and obtained the highly expressed TH0426 cadaverine reverse transporter (CadB) of A. veronii. We used efficient suicide plasmid-mediated homologous recombination to delete the cadB gene in TH0426 and constructed a cadB deletion strain. The LD50 of ΔcadB was 93.2 times higher than that of TH0426 in zebrafish, the toxicity of ΔcadB was 9.5 times less than that of TH0426 in EPC cells, and the biofilm formation ability of ΔcadB was 5.6-fold greater than that of TH0426. In addition, motility detection results indicated that ΔcadB had lost its swimming ability. The results of flagellar staining and TEM demonstrated that ΔcadB shed the flagella. In summary, the virulence and adhesion of A. veronii TH0426 were significantly decreased by the deletion of cadB, which might provide a theoretical basis for research into A. veronii virulence factors.

Hepatic Hydrothorax

Hepatic hydrothorax (HH) is a pleural effusion that develops in a patient with cirrhosis and portal hypertension in the absence of cardiopulmonary disease. Although the development of HH remains incompletely understood, the most acceptable explanation is that the pleural effusion is a result of a direct passage of ascitic fluid into the pleural cavity through a defect in the diaphragm due to the raised abdominal pressure and the negative pressure within the pleural space. Patients with HH can be asymptomatic or present with pulmonary symptoms such as shortness of breath, cough, hypoxemia, or respiratory failure associated with large pleural effusions. The diagnosis is established clinically by finding a serous transudate after exclusion of cardiopulmonary disease and is confirmed by radionuclide imaging demonstrating communication between the peritoneal and pleural spaces when necessary. Spontaneous bacterial empyema is serious complication of HH, which manifest by increased pleural fluid neutrophils or a positive bacterial culture and will require antibiotic therapy. The mainstay of therapy of HH is sodium restriction and administration of diuretics. When medical therapy fails, the only definitive treatment is liver transplantation. Therapeutic thoracentesis, indwelling tunneled pleural catheters, transjugular intrahepatic portosystemic shunt and thoracoscopic repair of diaphragmatic defects with pleural sclerosis can provide symptomatic relief, but the morbidity and mortality is high in these extremely ill patients.

Unusual microorganisms and antimicrobial resistances in a group of Syrian migrants: Sentinel surveillance data from an asylum seekers centre in Italy

BACKGROUND

Three years of civil war in Syria have caused death and increase of communicable diseases. The suffering population has been forced to migrate creating a fertile condition for epidemic spread of infection within the refugee camps.

METHODS

Forty-eight Syrian migrants, upon their arrival in Italy, were accommodated at the asylum seekers centre of Castelnuovo di Porto. They received a physical examination and were subjected to microbiological surveillance by blood, rectal, pharyngeal and nasal swabs collection and delivering to the Clinical Pathology and Microbiology Laboratory of the University Campus Bio-Medico of Rome.

RESULTS

All refugees resulted negative for HBV, HCV and HIV infections. In swabs a large number of unusual gram-negative bacteria species were isolated, such as Pseudomonas putida, Pseudomonas monteilii, Pseudomonas fulva, Pseudomonas moselii, Aeromonas veronii, Aeromonas caviae, Aeromonas hydrophila, Acinteobacter guilloviae, Acinteobacter lowffii; Acinetobacter johnsonii; Acinteobacter tjernbergae; Pantoea agglomerans; Pantoea calida. Among isolates, strains resistant to carbapenems, ESBL producers and methicillin resistant were found.

CONCLUSIONS

The microbiological surveillance performed represents a useful action to understand refugees health status and to trace unusual microorganisms movement even carriers of antimicrobial resistance during migrants traveling.

Hepatic hydrothorax

Hepatic hydrothorax is defined as a pleural effusion in patients with liver cirrhosis in the absence of cardiopulmonary disease. The estimated prevalence among patients with liver cirrhosis is approximately 5-6%. The pathophysiology involves the passage of ascitic fluid from the peritoneal cavity to the pleural space through diaphragmatic defects. The diagnosis is made from clinical presentation and confirmed by diagnostic thoracentesis with pleural fluid analysis. The initial medical management is sodium restriction and diuretics, but liver transplantation provides the only definitive therapy. For patients who are not transplant candidates and those who await organ availability, other therapeutic modalities that are to be considered include transjugular intrahepatic portosystemic shunt placement, videoassisted thoracoscopic surgery repair, pleurodesis, and vasoconstrictors (eg, octreotide and terlipressin). The primary therapeutic goals are to reduce ascitic fluid production and improve symptoms to bridge the time for liver transplantation.

Empyema caused by Aeromonas species in Taiwan

Strains of Aeromonas species are prevalent bacteria in coastal areas of southern Taiwan. Aeromonad is known as a cause of epidemic diarrheal disease, and the most common clinical manifestation is acute gastroenteritis. Extra-intestinal infections by Aeromonas species, such as pleural cavity, are rare. Herein, we described the six patients who developed Aeromonas spp.-related empyema, and was successfully treated with antimicrobial agent and drainage.

The genus Aeromonas: taxonomy, pathogenicity, and infection

Over the past decade, the genus Aeromonas has undergone a number of significant changes of practical importance to clinical microbiologists and scientists alike. In parallel with the molecular revolution in microbiology, several new species have been identified on a phylogenetic basis, and the genome of the type species, A. hydrophila ATCC 7966, has been sequenced. In addition to established disease associations, Aeromonas has been shown to be a significant cause of infections associated with natural disasters (hurricanes, tsunamis, and earthquakes) and has been linked to emerging or new illnesses, including near-drowning events, prostatitis, and hemolytic-uremic syndrome. Despite these achievements, issues still remain regarding the role that Aeromonas plays in bacterial gastroenteritis, the extent to which species identification should be attempted in the clinical laboratory, and laboratory reporting of test results from contaminated body sites containing aeromonads. This article provides an extensive review of these topics, in addition to others, such as taxonomic issues, microbial pathogenicity, and antimicrobial resistance markers.

Aerolysin is activated by metalloprotease in Aeromonas veronii biovar sobria

Aeromonas veronii is an opportunistic human pathogen that causes diarrhoea and extraintestinal infections, such as wound infection and septicaemia. An A. veronii protease (AVP) from a biovar sobria strain, AeG1, was partially purified and characterized. Mature AVP hydrolysed casein but not elastin, and protease activity was inhibited by metalloprotease inhibitors. Nucleotide sequence analysis showed that AVP belongs to the thermolysin family of proteases. An AVP-deficient mutant was constructed to investigate the role of AVP in aerolysin activation. Western blot analysis using anti-aerolysin antisera revealed that proaerolysin (52 kDa) in the AVP-deficient mutant was not completely activated to mature aerolysin (47 kDa) as seen in the wild-type strain. The AVP-deficient mutant showed lower cytotoxic and haemolytic activities than wild type. AVP and proaerolysin had no haemolytic activity; however, activity appeared after incubating both proteins. Taken together, these results suggested that AVP plays an indirect role in virulence through activating aerolysin, which is an essential step for cytotoxic activity.

Hepatic hydrothorax: pathophysiology, diagnosis, and management

Hepatic hydrothorax occurs in approximately 5 to 12% of patients with cirrhosis and portal hypertension. Various therapeutic modalities ranging from dietary and pharmacologic interventions to surgical approaches are available for the management of this condition. Treatment must be individualized based on the patient's response to conservative management as well as the severity of the underlying liver disease. Hepatic hydrothorax may be complicated by spontaneous bacterial empyema, which portends a poor prognosis with a mortality rate of up to 20%. All patients with hepatic hydrothorax should be evaluated for possible liver transplantation.

Hepatic hydrothorax

A hepatic hydrothorax is a pleural effusion that develops in a patient with cirrhosis and portal hypertension in the absence of cardiopulmonary disease. The pleural effusion is derived from ascitic fluid that enters the chest because of the negative pressure within the pleural space via defects in the diaphragm. The peritoneal-to-pleural flow of fluid can be demonstrated by nuclear scanning, even when the ascites is not clinically apparent. The pleural fluid usually has the characteristics of a transudate. However, an occasional patient with hepatic hydrothorax will develop spontaneous bacterial pleuritis manifest by increased pleural fluid neutrophils or a positive bacterial culture and will require antibiotic therapy. Treatment of the hydrothorax is directed at the underlying liver disease but a dyspneic patient can obtain relief from a thoracentesis or paracentesis. When medical therapy fails, liver transplantation is the treatment of choice. Both transjugular intrahepatic portosystemic shunting and thoracoscopic repair of diaphragmatic defects with pleural sclerosis can provide symptomatic relief, but the morbidity and mortality of these procedures are high because of the fragile nature of the patients.