Expression of coagulin A with low cytotoxic activity by Pediococcus pentosaceus ST65ACC isolated from raw milk cheese.

AIMS: We aimed to evaluate some specific conditions for growth of Pediococcus pentosaceus ST65ACC and its bacteriocin expression through ABC transporters; to purify the bacteriocin and determine its sequence; and to evaluate the cytotoxicity potential of the purified bacteriocin(s). METHODS AND RESULTS: The results presented for growth behaviour of P. pentosaceus ST65ACC showed that the bacterial growth was slightly influenced when cultured in MRS broth with different amounts of inoculum: 1, 2, 5 and 10%. The bacteriocin activity increased when 5 and 10% inocula were used. The carbon source (glucose) used in different amounts (1, 2, 3 or 4%) had no significant effect on growth and bacteriocin production. The studied strain P. pentosaceus ST65ACC was able to metabolize xylooligosaccharide (XOS) as the sole carbon source, resulting in the production of an antimicrobial peptide. The genes involved in the ABC transport system and sugar metabolism of P. pentosaceus ST65ACC were expressed at different levels. The bacteriocin produced by P. pentosaceus ST65ACC was partially purified by precipitation with ammonium sulphate (40% saturation), followed by reversed-phase liquid chromatography, resulting in the identification of an active bacteriocin. Tandem mass spectrometry was used to identify the partial sequence KYYGNGVTCGKHSCSVDWGK sharing high similarity to coagulin A. The semi-purified bacteriocin had low cytotoxicity based on estimated values for maximal nontoxic concentration (MNC) and cytotoxicity concentration (CC50 ). CONCLUSIONS: The bacteriocin produced by P. pentosaceus ST65ACC is similar to coagulin, with low cytotoxicity, strong antimicrobial activity and possible additional metabolite routes in the producer cell. In addition to MRS broth, bacteriocin was produced also in medium containing XOS (as the single carbon source). SIGNIFICANCE AND IMPACT OF THE STUDY: To the best of our knowledge, this is the first report of evaluation of the role of ABC transporters in the expression of bacteriocin by P. pentosaceus, cultured in MRS and XOS.

Endoscope-assisted microsurgery of large vestibular schwannomas.

AIMS: The application of endoscope-assisted microsurgery in the treatment of small or medium-sized vestibular schwannomas is of proven value. The goal of our study is to evaluate its usefulness in cases of large schwannomas. PATIENTS AND METHODS: Eighteen patients were included in this prospective study. Their average tumor diameter was 3.9 cm. The retrosigmoid approach was used in all cases. The endoscope was applied during all stages of tumor removal. RESULTS: The facial nerve was visualized endoscopically at early stages of surgery in 9 patients and the abducent nerve in 7 patients. The source of bleeding was identified in 1 case. Tumor remnants in the region of the fundus of the internal auditory canal after apparently total removal were identified in 2 cases. Exposed and unobliterated temporal bone air cells were not observed. DISCUSSION: Even in cases of large schwannomas, the location of the facial nerve can be determined endoscopically early in the procedure. The application of endoscope-assisted microsurgery increases the rate of cranial nerve preservation and of total tumor removal. Although the application of the endoscope did not provide useful information in some cases, it is a safe procedure that did not lead to any complications and/or to considerable prolongation of the operative time. Its application is justified in all cases.