Antimicrobial effect of chlorhexidine on Aggregatibacter actinomycetemcomitans biofilms associated with peri-implantitis.

Background. This study aimed to assessthe antimicrobial effect of chlorhexidine (CHX) on Aggregatibacter actinomycetemcomitans biofilms isolated from subgingival plaque of peri-implantitis lesions. Methods. Thirteen patients requiring peri-implantitis treatment were consecutively selected and their subgingival biofilm was collected by inserting fine sterile paper points into peri-implant pockets for 15 seconds. A. actinomycetemcomitans was isolated from the subgingival biofilm and cultured. In this study, the standard strain of A. actinomycetemcomitans served as the positive control group and a blank disc impregnated with water served as the negative control; 0.1 mL of the bacterial suspension was cultured on specific culture medium and blank discs (6 mm in diameter) impregnated with 0.2%CHX mouthrinse (Behsa Pharmaceutical Co.) and negative control discs were placed on two sides of the bacterial culture plate. The size of growth inhibition zone was measured by a blinded independent observer in millimetres. Results. According to the results of disc diffusion test, the mean diameter of growth inhibition zone of A. actinomycetemcomitans around discs impregnated with CHX was larger in both standard (positive control) and biofilm samples of A. actinomycetemcomitans compared to the negative control group (blank disc) (P<0.001). Conclusion . Use of0.2% CHX mouthwash had antibacterial effects on A. actinomycetemcomitans species isolated from peri-implantitis sites.

In vitro and ex vivo antimicrobial efficacy of nano-MgO in the elimination of endodontic pathogens.

OBJECTIVES: The use of metal oxide nanoparticles has attracted lots of attention, mostly because of their promising antimicrobial activity along with their biocompatibility with mammalian cells. This study aims to investigate the in vitro and ex vivo antimicrobial efficiency of nano-magnesium oxide (MgO) aqueous solution against endodontic pathogens. MATERIALS AND METHODS: The cytotoxicity of different concentrations of nano-MgO was assessed using lactate dehydrogenase cytotoxicity assay (LDH assay). A comparison of the antimicrobial efficiency of several concentrations of nano-MgO solution, sodium hypochlorite (NaOCl), and chlorhexidine (CHX) gluconate against Staphylococcus aureus, Enterococcus faecalis, and Candida albicans was made using the direct contact method. An ex vivo model of decoronated and experimentally infected human teeth was employed to compare the efficiency of nano-MgO (5 mg/L) solution with NaOCl (5.25 %) in the elimination of E. faecalis. RESULTS: There was no statistically significant difference between nano-MgO solutions (10 and 5 mg/L), 5.25 % NaOCl, and 2 % CHX gluconate in terms of the required time to inhibit the growth of the tested pathogens (p > 0.05). The LDH assay showed no cytotoxicity of different concentrations of nano-MgO used in this study (p < 0.001). In the ex vivo model of infected human teeth, 6 h post-irrigation, there was no statistically significant difference between colony-forming units (CFU) per milliliter of nano-MgO (5 mg/L) and NaOCl (5.25 %)-treated teeth (5-6 log scale reduction). However, the nano-MgO group showed a significant decrease in colony-forming units per milliliter (7 log scale), 24 h post-irrigation (p < 0.05). At other tested time points-24, 48, 72, and 168 h-the levels of CFU per milliliter were significantly less in the nano-MgO group (2-3 log scale difference) compared to the NaOCl group, indicating long-term antibacterial activity of nano-MgO (p < 0.05). At 72 and 168 h post-irrigation, no detectable bacterial growth was observed in the nano-MgO group. The detection limit was 10 CFU/mL. CONCLUSIONS: Nano-MgO aqueous solutions represent promising antimicrobial activities, both in vitro and ex vivo with minimal toxicity. CLINICAL RELEVANCE: Compared to NaOCl (5.25 %), nano-MgO (5 mg/L) exhibits statistically significant long-term efficiency in the elimination of E. faecalis in the root canal system. After further investigations, nano-MgO could be considered as a new root canal irrigant.

Improved drug loading and antibacterial activity of minocycline-loaded PLGA nanoparticles prepared by solid/oil/water ion pairing method.

BACKGROUND: Low drug entrapment efficiency of hydrophilic drugs into poly(lactic-co-glycolic acid) (PLGA) nanoparticles is a major drawback. The objective of this work was to investigate different methods of producing PLGA nanoparticles containing minocycline, a drug suitable for periodontal infections. METHODS: Different methods, such as single and double solvent evaporation emulsion, ion pairing, and nanoprecipitation were used to prepare both PLGA and PEGylated PLGA nanoparticles. The resulting nanoparticles were analyzed for their morphology, particle size and size distribution, drug loading and entrapment efficiency, thermal properties, and antibacterial activity. RESULTS: The nanoparticles prepared in this study were spherical, with an average particle size of 85-424 nm. The entrapment efficiency of the nanoparticles prepared using different methods was as follows: solid/oil/water ion pairing (29.9%) > oil/oil (5.5%) > water/oil/water (4.7%) > modified oil/water (4.1%) > nano precipitation (0.8%). Addition of dextran sulfate as an ion pairing agent, acting as an ionic spacer between PEGylated PLGA and minocycline, decreased the water solubility of minocycline, hence increasing the drug entrapment efficiency. Entrapment efficiency was also increased when low molecular weight PLGA and high molecular weight dextran sulfate was used. Drug release studies performed in phosphate buffer at pH 7.4 indicated slow release of minocycline from 3 days to several weeks. On antibacterial analysis, the minimum inhibitory concentration and minimum bactericidal concentration of nanoparticles was at least two times lower than that of the free drug. CONCLUSION: Novel minocycline-PEGylated PLGA nanoparticles prepared by the ion pairing method had the best drug loading and entrapment efficiency compared with other prepared nanoparticles. They also showed higher in vitro antibacterial activity than the free drug.

Assessing the role of the RND efflux pump in metronidazole resistance of Helicobacter pylori by RT-PCR assay.

INTRODUCTION: Metronidazole is a significant antibiotic used for eradication of Helicobacter pylori infections and it is of notice that metronidazole-resistant clinical isolates have been found in high rates worldwide. While the RND family of efflux pumps plays a central role in drug resistance among Gram-negative bacteria, this is questionable for H. pylori. METHODOLOGY: To understand whether TolC homologues of RND pumps contribute to metronidazole resistance in H. pylori isolates, expression of four TolC homologous genes of five resistant clinical isolates exposed to varying concentrations of metronidazole were evaluated by RT-PCR and transcriptional analysis. RESULTS: The results indicate that excess amounts of metronidazole are able to increase the expression level of these genes at the transcriptional stage. CONCLUSIONS: Therefore, it may be hypothesized that use of metronidazole in H. pyori infection can induce metronidazole resistance. Furthermore, the RND family of efflux pumps may contribute to metronidazole resistance in clinical isolates of H. pylori.

The incidence of nosocomial toxigenic clostridium difficile associated diarrhea in Tehran tertiary medical centers.

Clostridium difficile is the most common cause of nosocomial diarrhea. It is usually a consequence of antibiotic treatment, But sporadic cases can occur. This study was aimed to determine the frequency of the nosocomial Clostridium difficile (C. difficile) associated diarrhea in Tehran University of Medical Sciences hospitals and study of antibacterial susceptibility of isolates. In this study a total of 942 stool samples from patients with nosocomial diarrhea that were hospitalized in Imam Khomeini hospital, Shariati hospital and Children clinical center were collected. The samples were cultured on a selective cycloserine cefoxitin fructose agar (CCFA) and incubated in anaerobic conditions, at 37°C for 5 days. Isolates were characterized to species level by conventional biochemical tests. Bacterial cytotoxicity was assayed on tissue culture (vero). Antimicrobial sensitivity of isolated toxigenic C. difficile were investigated by kirby Beuer method (disk diffusion). Our findings show that, of the total patients, 57 toxigenic C. difficile (6.1%) were isolated. Results of statistical analysis show significant differences between the rate of isolated toxigenic C. difficile and age group of patients (P<0.05). Among the wards of selected hospitals, in gastroenterology of Children clinical center, Toxigenic C. difficile was isolated from patients most frequently. The sensitivity of isolates to vancomycin, Chloramphenicol and ceftriaxone were higher than other antibiotics. Toxigenic C. difficile is a common hospital-acquired infection. The organism was found in 6.1% hospitalized patients. Further studies to evaluate the rate and role of toxigenic C. difficile in nosocomial diarrheal processes, ecological and pathogenic terms are suggested.

Clonal heterogeneity of clinical isolates of vancomycin-resistant Enterococcus faecium with unique vanS.

OBJECTIVE: To examine the clonal diversity of vancomycin-resistant enterococci (VRE). METHODS: A total of 900 clinical isolates of enterococci were obtained, and VRE isolates were subjected to antimicrobial susceptibility tests, biochemical fingerprinting with the PhPlate system (PhP), ribotyping and pulsed-field gel electrophoresis (PFGE) typing. RESULTS: Forty-nine of all enterococcal isolates were resistant to high levels of vancomycin (MIC >or= 128) and identified as Enterococcus faecium. Biochemical fingerprinting with PhP showed that the VRE isolates were highly diverse (diversity index, D(i) = 0.93) and belonged to 24 PhP-types. The VRE could be separated into 34 and 27 types with PFGE and ribotyping, giving diversity indices of 0.98 and 0.97, respectively. The PFGE method was more discriminatory than ribotyping and PhP system for E. faecium isolates. A combination of either of the two typing methods resulted in at least 44 types. Furthermore, sequencing analysis of vanS of Tn1546 showed one nucleotide mutation (C-->A) at position 5727 in comparison with the prototype BM4147, which was found to be unique in all Iranian VRE isolates. CONCLUSION: The isolated clinical VRE strains were highly diverse in Tehran.

Therapeutic effect of sodium alginate in experimental chronic ulcerative colitis.

The aim of this study was to test the therapeutic efficacy of sodium alginate in a rat model of trinitrobenzene sulfonic acid (TNBS)-induced inflammatory bowel disease. This experiment was carried out using 77 Sprague-Dawley rats which were divided into six groups; normal, control, prophylactic, therapeutic and two experimental groups. Rats were sacrificed 1, 2, 3 and 6 weeks after colitis induction. Severity of colitis was graded macroscopically and assessed using serum and colonic mucosal cytokines and eicosanoids. Intrarectal TNBS (30 mg) produced a significant chronic ulcerative colitis. The lesions were most severe on day seven after TNBS instillation, and then declined, but lesions were still observed after six weeks. TNBS administration also significantly enhanced the serum and colonic mucosal cytokines (TNF-alpha and IL-6) and eicosanoids (LTB4 and PGE2) levels, which paralleled with the severity of colitis. Low viscosity sodium alginate (LVA) solution as therapeutic agent was administered orally as drinking water at concentration of 0.5% (W/V) for six weeks. Results showed that pre-treatment (in prophylactic group) and treatment with LVA were significantly able to reduce colonic damage score, serum level and colonic mucosal production of TNF-alpha, IL-6, LTB4 and PGE2 in pre-treated and treated animals compared with non-treated controls. LVA therapy is able to suppress chronic ulcerative colitis in experimental model.