Plasminogen interaction and activation on Streptococcus mutans surface.

A number of pathogenic microorganisms have been previously shown to bind plasminogen. The subsequent activation of plasminogen into plasmin can contribute to their virulence. In this study, we have shown that Streptococcus mutans is able to bind both human plasminogen and plasmin. Binding of plasminogen to S. mutans was inhibited by L-lysine and epsilon-aminocaproic acid, indicating that binding is mediated via lysine-binding sites of plasminogen. S. mutans enhanced the activation of plasminogen by tissue plasminogen activator but not by urokinase. This enhancement turned out to be dependent on cell concentration. Zymogram analysis showed that the plasmin activity acquired after plasminogen binding and activation is the most important proteolytic activity in the strain tested. These results suggest a mechanism involving acquisition of a host protease that might contribute to the infective process of this microorganism.

Postlaryngectomy pharyngocutaneous fistula: incidence, predisposing factors, and therapy.

BACKGROUND: Pharyngocutaneous fistula is the most common complication following total laryngectomy. The present study was designed to determine the incidence and predisposing factors and to describe the management of the complication. METHODS: The records of 246 consecutive patients who underwent total laryngectomy for squamous cell carcinoma were reviewed. We evaluated 23 factors potentially predisposing to fistula formation (age, sex, smoking and drinking habits, hypertension, diabetes, chronic bronchitis, chronic congestive heart failure, anesthesiologic risk, cholinesterase level, pre- and postoperative hemoglobin and albumin levels, previous treatment, previous tracheotomy, site of origin of the tumor, surgical procedure, concurrent neck dissection, suture material, status of surgical margins, clinical stage, and histologic grade) using the chi-squared test and logistic regression analysis. RESULTS: A pharyngocutaneous fistula developed in 16% of patients within a mean time of 11 days from surgery. Spontaneous closure with local wound care was achieved in 70% of cases. Ten patients required surgical closure by direct suture of the pharyngeal mucosa; a deltopectoral flap and a pectoralis major myocutaneous flap were used in one case each. The mean healing time was 39+/-46 days in the group of patients requiring surgical closure, compared with 19+/-12 days in the group in which spontaneous closure occurred. The definitive model of logistic regression analysis showed that pharyngolaryngectomy, chronic congestive heart failure, and postoperative hemoglobin level lower than 12.5 g/dL carried respectively a two-, five-, and ninefold increase in the risk of fistula development. The model, with a specificity of 81%, is fairly good in identifying patients with a low risk of fistula. CONCLUSIONS: The results observed in the group of patients under analysis corroborated the relevance of factors such as the extension of laryngectomy and postoperative hemoglobin level on fistula occurrence. However, chronic congestive heart failure, which is an expression of disturbance of the organism, emerged for the first time as an additional statistically significant risk factor for pharyngocutaneous fistula formation. Our experience confirmed that most fistulas can be successfully managed with conservative treatment. Except for the rare cases in which large defects are present, direct suture is appropriate when conservative treatment has failed.