In recent years, the decreased efficacy of existing antibiotics toward management of emergent drug-resistant strains has necessitated the search for novel antibiotics from natural products. In this regard, Bacillus sp is well known for producing variety of secondary metabolites of potential use. Therefore, we performed an investigation to isolate and identify Bacillus sp from oral cavity for production of novel antimicrobial compounds. We extracted, purified, and identified a novel bioactive compound by B. megaterium (KC246043.1). The optimal production of compound was observed on de Man Rogosa and Sharpe broth by incubating at 37 °C, and pH 7.0 for 4 days. The bioactive compound was extracted by using n-butanol (2:1 v/v), purified on TLC plates with detection at Rf 7.8 cm; further characterized and identified as a cyclic ploypeptide sharing structural similarity with bacitracin. Minimum inhibitory concentration of bioactive compound was found to be 0.25, 0.5, 1.0, 3.125 and 6.25 μg/ml against Micrococcus luteus ATCC10240, Salmonella typhi ATCC19430, Escherichia coli ATCC35218. Pseudomonas aeruginosa ATCC27853 and Staphylococcus aureus ATCC25923 respectively, with no activity against Candida albicans ATCC10231. Our findings have revealed a novel cyclic peptide compound from B. megaterium with broad spectrum antimicrobial activity against both Gram positive and Gram negative bacteria.

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Background:The overall success of denture base resins depends on both mechanical behaviour and biocompatibility, especially in the rehabilitation of diabetic patients. The growth and nourishment of microorganisms is enhanced in diabetes mellitus specially in presence of dentures resulting in denture stomatitis. This study was prompted to assess the microbiological growth and the development of salivary immunoglobulin A (s-IgA) in relation to newly introduced denture base materials used in the rehabilitation of diabetic patients.Materials and Methods: Forty eight completely edentulous patients were selected and divided into two groups: group (A), which included controlled diabetic patients and group (B) included nondiabetic patients. Each group was further divided into four sub groups according to the denture base material. Sub group I, patients were received thermoplastic Vertex TM ThermoSens denture bases; sub group II, patients were received heat cure acrylic resin dentures reinforced with nano zirconia oxide particles (nano-ZrO2); sub group III, patients were received conventional heat cure acrylic resin dentures; where sub group VI, patients were received conventional heat cure acrylic resin dentures relined with self-cure acrylic resin. For each participant, non-stimulated saliva samples were collected before denture insertion, and one, two and three months after wearing dentures. Samples were inoculated and incubated both aerobically and anaerobically on selective media for Streptococcus mutans, Lactobacilli and Candida. Then, isolated microorganisms were identified, the characteristic colony forming units per millilitre (CFUs/ml), were calculated and the salivary immunoglobulin A level was measured by Enzyme-linked immunosorbent assay (ELISA). Results:The results revealed increase in the CFU values of Candida, Streptococcus mutans, Lactobacilli and the level of salivary immunoglobulin A in all the assessed patients following denture insertion. However, significant lower values were evident in patients rehabilitated with ThermoSens and nano-ZrO2 reinforced bases compared to heat cure acrylic and self-cure relined bases. Significant increase in CFU values and level of s-IgA were found in diabetic compared to non-diabetic patients after insertion of all denture bases.