Streptococcus Anginosus Group Infection As A Predictor For The Progression Of Descending Necrotizing Mediastinitis

Background: The prognosis of descending necrotizing mediastinitis (DNM), especially that extending inferiorly to the carina, remains poor. The identification of additional prognostic factors may improve the prognosis.Methods: We retrospectively analyzed six patients who underwent thoracic surgery for DNM extending to the anterior and posterior mediastinum inferior to the carina (Endo classification type IIB) from 2014 to 2020. We reviewed their characteristics, clinical course, causative bacteria, and treatment to investigate their prognostic factors.Results: The median patient age was 62 years. Five patients were men and one patient was a woman. The causative disease in three of the patients was pharyngolaryngeal, and for the others, it was an odontogenic infection. Five patients had sepsis and four had disseminated intravascular coagulation (DIC) at surgery. Four patients had polymicrobial infections of aerobic and anaerobic bacteria, all of whom showed gas bubbles on a chest computed tomography scan and detection of Streptococcus anginosus group (SAG). All patients underwent cervicotomy, tracheostomy, and mediastinal drainage and debridement via a transthoracic approach. Three patients underwent additional surgery or drainage because an additional abscess appeared postoperatively. The median duration of hospitalization was 58 days and the mixed infections, including SAG, were all detected in the three cases of long-term hospitalization. No disease-associated death was observed during the follow-up period of 18 months.Conclusions: Mixed infection, including SAG, may be a predictor for DNM aggravation and spread. Gas bubbles on a chest computed tomography scan suggest polymicrobial aerobic and anaerobic infections including SAG, which require broad-spectrum antibiotic therapy and aggressive drainage and surgery.