OBJECTIVEThis study aimed to evaluate the biological characteristics of a human specifically targeted antimi- crobial peptide C16LL-37 against Streptococcus mutans (S. mutans).

METHODSIn this study, an antimicrobial peptide LL-37, a peptide derived from CSP(C16) (S. mutans competence stimulating peptide), and recombinant peptide C16LL-37 were synthesized by Fmoc-chemistry-based strategy. The selectivity and antibacterial activity of C16LL-37 were identified by the colony counting method on microbial culture plates. After treatment of C16LL-37 at 32 µmol · L⁻¹, the morphological changes in S. mutans were observed by using scanning electron microscopy (SEM). In addition, enzyme-linked immunosorbent assay was used to evaluate the hemolytic activity and antibacterial activity of C16LL-37 under different conditions.

RESULTS1) The minimum inhibitory concentration of C16LL-37 was 16 µmol · L⁻¹, and the minimum bactericidal concentration was 64 μmol ·L⁻¹. 2) The survival rate of S. mutans was 3.46% after C16LL-37 treatment at 64 µmo-L⁻¹ for 30 min, whereas it was 0% at 64 µmol · L⁻¹ for 60 min. The survival rates of four other kinds of bacteria were more than 60% at any time (P < 0.05). 3) The morphological change in S. mutans was observed after C16LL-37 treatment at 32 µmol · L⁻¹ by using SEM. S. mutans presented an irregular shape, rough surface, and evident splitting. 4) The hemolysis rate of C16LL-37 (≤ 64 µmol · L⁻¹) was less than 0.33%. 5) This study showed no significant in- fluence on the antibacterial activity of C16LL-37 under different conditions, such as temperature, pH, salinity, and trypsin at low concentration (P > 0.05).

CONCLUSIONC16LL-37 exhibited obvious specificity for S. mutans, strong antibacterial activity, low toxicity, and high stability. Thus, C16LL-37 has good potential in caries research and clinical application.

Anti-Infective Agents ; pharmacology ; Antimicrobial Cationic Peptides ; pharmacology ; Bacterial Proteins ; Dental Caries ; Enzyme-Linked Immunosorbent Assay ; Humans ; Microbial Sensitivity Tests ; Microscopy, Electron, Scanning ; Peptides ; Streptococcus mutans ; drug effects

Objective This paper focuses on the investigation of the occurrence and influential factors of post-traumatic stress disorder (PTSD)in SARS patients, hospital staffs and the public expo sed to SARS. Methodes Three groups were assessed by scale of self-compiled stressor Questionnaire, impact of event scale-revised (IES-R) , PSSS, SCSQ, SES and EPQ. Results 1. The incidence of PTSD symptoms in the three groups were 55.1% ,25.8 % and 31.18 %. 2. The main cause of the different incidence was the difference of the stressor intensity and characters. Negative coping was the risk factor of SARS patients and the public; Self-esteem was the protected factor of SARS patients and the hospital staffs; Social support was a protected factor on the hospital staffs. 3. Comparing to the first investigate in September,2003 ,the data of follow-up study in September,2004 showed that the prevalence items significant decreased. Conclusions 1. The investigation concludes that all three groups of people exposed o SARS exhibit PTSD symptom. SARS patients have the highest occurrence ( P ＜ 0.01 ). 2. The main influencing factors of different incidence of PTSD in different groups are intensities and characteristics of stressors. Different people who had PTSD symptoms have different influencing factors. 3. With the change of time , the PTSD symptoms significant relieve with the attenuation gradually of exposure degree of stressor.