Antibiotic Resistance Profile of Enterococcus faecalis and Enterococcus faecium Isolates from Urine and Pleural Fluid in Two Hospitals of Cameroon

Enterococcus faecalis and Enterococcus faecium rank among the leading causes of nosocomial bacteremia and urinary tract infections. They often persist on hospital surfaces due to their ability to withstand adverse environmental conditions (low or high temperatures, high pH, and high salinity). The global Enterococcus faecalis-Enterococcus faecium ratio is currently shifting towards Enterococcus faecium. Enterococci present variable levels of resistance to certain families of antibiotics. This is the case for aminoglycosides, beta-lactams and cephalosporins. In 2017, WHO ranked Enterococci among priority pathogens for research and development of new antibiotics. The objective of our study was to determine the antibiotic resistance profile of Enterococcus faecalis and Enterococcus faecium isolates from urine and pleural fluid in two hospitals in Cameroon. This cross-sectional and analytic study was carried out between June to August 2023 on hospitalized and day patients in which a cytobacteriological test of urine and pleural fluid was done. The samples were inoculated on CLED Agar for urine and on Chocolate + polyvitex and blood agar (prepared from Columbia agar) for pleural fluid samples and incubated at 37℃ for 18 to 24 hours. Identification of isolates was carried out using the API 20 STREP micro gallery (Biomerieux, France) and tested for antimicrobial susceptibility. The data on socio-demographical and potential risk factors were recorded using self-administered questionnaires and data from laboratory analyses of the specimen were collected in a data capture sheet. Potential risk factors associated with the presence of Enterococci, were evaluated using the logistic regression in univariate and multivariate analysis. P value < 0.05 was considered as significant. A total of 511 patients were recruited who were predominantly females. Enterococcus spp were isolated in 27.79% of our samples with Enterococcus faecalis mostly encountered. Enterococcus spp showed a high level of resistance to penicilline (99.3% to Ampicilline), macrolides (66.2% to Erythromycin) and cyclines (85.2% to Doxycycline). Hospitalisation, access to health facilities, contact with urine specimen and hand hygiene practices were risk factors related to infection with Enterococcus spp while hospitalisation, health facility and hand hygiene were related to glycopeptide resistant Enterococcus. Strict compliance with hygiene rules and appropriate antibiotic consumption could help in the fight against these infections.

Enterococcus faecalis provides protection during scavenging in carrion crow (Corvus corone)

The gut microbiota significantly influences host physiology and provides essential ecosystem services.While diet can affect the composition of the gut microbiota,the gut microbiota can also help the host adapt to specific dietary habits.The carrion crow(Corvus corone),an urban facultative scavenger bird,hosts an abundance of pathogens due to its scavenging behavior.Despite this,carrion crows infrequently exhibit illness,a phenomenon related to their unique physiological adaptability.At present,however,the role of the gut microbiota remains incompletely understood.In this study,we performed a comparative analysis using 16S rRNA amplicon sequencing technology to assess colonic content in carrion crows and 16 other bird species with different diets in Beijing,China.Our findings revealed that the dominant gut microbiota in carrion crows was primarily composed of Proteobacteria(75.51%)and Firmicutes(22.37%).Significant differences were observed in the relative abundance of Enterococcus faecalis among groups,highlighting its potential as a biomarker of facultative scavenging behavior in carrion crows.Subsequently,E.faecalis isolated from carrion crows was transplanted into model mice to explore the protective effects of this bacterial community against Salmonella enterica infection.Results showed that E.faecalis down-regulated the expression of pro-inflammatory cytokines tumor necrosis factor alpha(TNF-α),interferon gamma(IFN-γ),and interleukin 6(IL-6),prevented S.enterica colonization,and regulated the composition of gut microbiota in mice,thereby modulating the host’s immune regulatory capacity.Therefore,E.faecalis exerts immunoregulatory and anti-pathogenic functions in carrion crows engaged in scavenging behavior,offering a representative case of how the gut microbiota contributes to the protection of hosts with specialized diets.

Study of the Effectiveness of Papaver Sp. Alkaloids as Future Therapeutic Alternatives against Enterococcus Sp. Causing Hospital-Acquired Septicemic Infections

Background and Objective: In recent years, control of Enterococcus sp. It has been proven in the local medical environment to be a cause of acquired septicemia in various age groups, and medical instruments are considered an effective means of transmitting enterococcal septicemia, and catheters are at the forefront in terms of danger. Based on this risk, this study aimed to monitor the spread of Enterococcus sp., which causes blood poisoning acquired from catheters, and to compare its response to antibiotics with that of those isolated from clinical samples in children, as a first study locally. The effectiveness of alkaloids of different types of Papaver sp. In Syrian plants, they were tested against infection with this bacteria. Materials and Methods: The study dealt with two parts: The first part included collecting clinical samples from the University Children’s Hospital in Damascus/bacterial diagnostic laboratories/then isolating and diagnosing the bacteria by following a set of tests to identify the most prevalent genera and species and comparing their prevalence rate with Enterococcus. The second part;It included collecting plant samples, confirming the species taxonomically, then extracting alkaloids from plant parts (fruit, stem, Flowers), then comparing the extent of resistance of bacterial strains to antibiotics compared to the Enterococcus sp., and then confirming the antibacterial activity of the Papaver sp. alkaloids against Enterococcus sp. Result:In its first part, the study confirmed the significant contribution of the Enterococcus sp. to infections acquired from various sources, largely in catheter tip infections (9.09%) and to a lesser extent in other sources (3.7%), The second part was to confirm the effective-ness of the alkaloid extract of the Papaver sp., especially the two species Papaver syriacum, and Papaver dubium, against Enterococcus sp. with areole diameters that ranged between (15 - 26 mm) for the fruit extract and at a minimum inhibitory concentration (3.12 - 6.25 mml) and then the stem (5 - 20 mm). And the effectiveness of the Flowers extract is very weak to almost non-existent. Conclusions: The catheter and medical sources surrounding the patient constitute a dangerous source of multi-resistant Enterococcus sp., which poses a real threat to the lives of children, with new mechanisms represented by colonization of the skin and the ability to form biofilms Surfaces of medical instruments, with are resistant to a wide range of antibiotics. As an alternative and effective modern source to limit its spread in the future, the alkaloid extract of the fruits and stems of the wild Papaver sp. has proven a strong antibiotic effect, especially the two types: Papaver syriacum and Papaver dubium.

Pretreatment with probiotics Enterococcus faecium NCIMB 11181 attenuated Salmonella Typhimurium-induced gut injury through modulating intestinal microbiome and immune responses with barrier function in broiler chickens

Background:Preventing Salmonella infection and colonization in young birds is key to improving poultry gut health and reducing Salmonella contamination of poultry products and decreasing salmonellosis for human consumption(poultry meat and eggs).Probiotics can improve poultry health.The present study was conducted to investigate the impact of a probiotics,Enterococcus faecium NCIMB 11181(E.faecium NCIMB 11181)on the intestinal mucosal immune responses,microbiome and barrier function in the presence or absence of Salmonella Typhimurium(S.Typh-imurium,ST)infection.Methods:Two hundred and forty 1-day-old Salmonella-free male broiler chickens(Arbor Acres AA+)were randomly allocated to four groups with 6 replicate cages of 10 birds each.The four experimental groups were follows:(1)nega-tive control(NC),(2)S.Typhimurium,challenged positive control(PC),(3)the E.faecium NCIMB 11181-treated group(EF),(4)the E.faecium NCIMB 11181-treated and S.Typhimurium-challenged group(PEF).Results:Results indicated that,although continuous feeding E.faecium NCIMB 11181 did not obviously alleviate growth depression caused by S.Typhimurium challenge(P>0.05),E.faecium NCIMB 11181 addition significantly blocked Salmonella intestinal colonization and translocation(P<0.05).Moreover,supplemental E.faecium NCIMB 11181 to the infected chickens remarkably attenuated gut morphological structure damage and intestinal cell apoptosis induced by S.Typhimurium infection,as evidenced by increasing gut villous height and reducing intes-tinal TUNEL-positive cell numbers(P<0.05).Also,E.faecium NCIMB 11181 administration notably promoting the production of anti-Salmonella antibodies in intestinal mucosa and serum of the infected birds(P<0.05).Addition-ally,16S rRNA sequencing analysis revealed that E.faecium NCIMB 11181 supplementation ameliorated S.Typhimu-rium infection-induced gut microbial dysbiosis by enriching Lachnospiracease and Alistipes levels,and suppressing Barnesiella abundance.Predicted function analysis indicated that the functional genes of cecal microbiome involved in C5-branched dibasic acid metabolism;valine,leucine and isoleucine biosynthesis;glycerolipid metabolism and lysine biosynthesis were enriched in the infected chickens given E.faecium NCIMB 11181.While alanine,asparate and glutamate metabolism;MAPK signal pathway-yeast;ubiquine and other terpenoid-quinore biosynthesis,protein processing in endoplasmic reticulum;as well as glutathione metabolism were suppressed by E.faecium NCIMB 11181 addition.Conclusion:Collectively,our data suggested that dietary E.faecium NCIBM 11181 supplementation could ameliorate S.Typhimurium infection-induced gut injury in broiler chickens.Our findings also suggest that E.faecium NCIMB 11181 may serve as an effective non-antibiotic feed additive for improving gut health and controlling Salmonella infection in broiler chickens.

Enterococcus durans产胞外多糖EPS-Ⅰ的分离纯化和结构分析

The rough crystal of exopolysaccharide produced by Enterococcus durans, a strain of lactic acid bacteria screened from the intestine of a cock in our laboratory, was purified by CM-cellulose column chromatography, DEAE-Sephadex A-25 ionexchange and Sephadex G-100 gel chromatography to give EPS-Ⅰ. The EPS-Ⅰ was eluted as a single peak in HPLC analysis, indicating the homogeneity of EPS-Ⅰ and free from low-molecular-weight polysaccharides. The molecular weight of the EPS-Ⅰ was determined as 42 000 by the light scattering method. The result of its elemental analysis was C 41.08% and H 7.23% without the elements of N, P and S. Monosaccharide analysis showed that it was composed of Glc and Man in a molar ratio of 4∶1. Sugar composition analysis, methylation analysis and 1H and 13C NMR spectroscopy revealed that the EPS-Ⅰ was composed of pentasaccharide repeating units. The sequence of sugar residues was determined by using two-dimensional NMR, including heteronuclear multiple-bond correlation(HMBC) and nuclear overhauser effect spectroscopy(NOESY). The structure of the pentasaccharide repeating unit of EPS-Ⅰ was given, a new excellular polysaccharide from lactic acid bacterium compared with other EPSs was reported.

粪肠球菌(Enterococcus faecalis)和屎肠球菌(Enterococcus faecium)产生物胺交互作用研究

粪肠球菌和屎肠球菌是发酵香肠中常检出的2种主要的产酪胺和苯乙胺微生物。将粪肠球菌和屎肠球菌按照不同比例进行混合接种培养,发现在48h连续培养过程中,当粪肠球菌和屎肠球菌以1∶9比例混和接种培养时,体系pH值、细菌数量和酪胺生成量均显著低于其他各处理组;粪肠球菌有很强的产苯乙胺能力而屎肠球菌产苯乙胺能力较弱,当两者混合接种培养时,各混合体系的产苯乙胺水平相当,屎肠球菌产苯乙胺能力不受影响,而粪肠球菌产苯乙胺能力显著降低。

耐低温肠球菌Enterococcus sp.MB2-1产细菌素的生物学特性

从新疆阿勒泰地区额尔齐斯河流域冷水鱼肠道筛选到一株产细菌素的菌株MB2-1，牛津杯法实验显示该菌株抑制革兰氏阳性菌李斯特氏菌（Listeria monocytogenes）、金黄色葡萄球菌（Staphylococcus aureus）、枯草芽孢杆菌（Bacillus subtilis）以及革兰氏阴性菌大肠杆菌（Escherichia coli）的生长。通过形态学和16S rRNA基因序列同源性分析初步鉴定该菌株隶属于Enterococcus属。菌株Enterococcus sp. MB2-1的最适生长温度在24℃左右，属于耐冷菌。细菌素MB2-1对胃蛋白酶、胰蛋白酶及尿素敏感，过氧化氢酶、Triton X-100、SDS、吐温-80、NaCl和EDTA处理抑菌活性保持稳定，该细菌素具有良好的pH值稳定性（3.0～9.0）和热稳定性（100℃、60min），但在121℃、20min处理后抑菌活性消失。在菌株生长9h后发现抑菌活性，并且在生长稳定期检测到最高抑菌活性。

Enterococcus faecalis RQ15产低温中性蛋白酶的纯化及酶学性质

采用DEAE Sepharose Fast Flow和SuperdexTM 75对Enterococcus faecalis RQ15产蛋白酶进行纯化和酶学性质研究。SDS-PAGE测定该蛋白酶分子质量为32.4kD,最适作用温度35～40℃,最适pH7.5。20～40℃之间酶活较高,pH值耐受范围广泛,具有低温蛋白酶的特征。Zn2+对蛋白酶有激活作用,Ag+、Hg2+和EDTA-Na2对酶有显著抑制作用。纯酶最适作用条件下对酪蛋白底物的Km和Vmax分别为1.31×10-4mol/L和6.92×10-6mol/(L.s)。

Enterococcus faecium AS8及其胞外多糖对发酵乳流变学特性的影响

通过红外光谱、气相色谱-质谱联用和流变仪的检测,探究产自屎肠球菌(Enterococcus faecium)AS8的胞外多糖(exopolysaccharide,EPS)(AS8-EPS)的结构组成和流变性能。采用3种发酵乳作为样品,分别为Streptococcus thermophilus+Lactobacillus bulgaricus、EPS+S. thermophilus+L. bulgaricus和E. faecium AS8。结果表明,在贮藏期间,不同发酵乳样品具有不同的流变学性质。同时,补充添加EPS和原位EPS对发酵乳流变性能具有不同的影响。通过Sephadex G-100和Sephadex G-50的分离纯化,获得2种多糖,分别为AS8-1-EPS和AS8-2-EPS。AS8-1-EPS主要单糖组成为甘露糖、葡萄糖和半乳糖(分别占59.1%、26.8%、7.9%),还有含量很少的其他单糖;AS8-2-EPS主要单糖组成为甘露糖、葡萄糖、半乳糖和鼠李糖(分别占65.4%、21.3%、8.9%、4.4%)。红外光谱检测结果表明AS8-1-EPS和AS8-2-EPS均为杂多糖。

粪肠球菌(Enterococcus faecalis)β酮脂酰ACP合成酶Ⅱ同源蛋白功能分析

FabB和FabF是大肠杆菌(Escherichia.coli)脂肪酸合成的关键酶.生物信息学分析显示,粪肠球菌基因组中有2个与大肠杆菌fabF同源的基因:fabF1和fabF2,缺少与fabB同源的基因.用粪肠球菌(Enterococcus faecalis)V583总DNA为模板,PCR扩增fabF1和fabF2基因,以pBAD24为载体,构建了重组质粒pHW13(fabF1)和pHW14(fabF2).体内体外研究显示:fabF1基因能互补大肠杆菌fabB突变,FabF1具有β酮脂酰ACP合成酶Ⅰ(FabB)活性;fabF2能互补大肠杆菌fabF突变,FabF2具有β酮脂酰ACP合成酶Ⅱ(FabF)活性.同时发现粪肠球菌FabF2不同于大肠杆菌FabF,它还拥有微弱β酮脂酰ACP合成酶Ⅰ(FabB)活性,可使大肠杆菌fabB突变株产生少量的不饱和脂肪酸.上述结果表明,FabF类酶(FabF like enzyme)同样可以具有β酮脂酰ACP合成酶Ⅰ(FabB)活性.

粪肠球菌Enterococcus faecalis EC-12的万古霉素耐药基因检测

对粪肠球菌Enterococcus faecalis EC-12的万古霉素耐药基因进行了筛查。通过PCR方法,以7种典型肠球菌万古霉素耐药基因(vanA、vanB、vanC1、vanC2/C3、vanD、vanE和vanG)进行特异性扩增,结果均为阴性。采用PCR方法检测万古霉素耐药肠球菌简便、高效、准确。

藏灵菇中Enterococcus faecalis RQ15的分离及鉴定

以民间家庭制作酸奶用藏灵菇为试材,通过有氧与厌氧相结合的分离方式,从中分离到1株乳酸球菌。经形态学、生理生化特性研究及分子生物学鉴定,该菌株为粪肠球菌,编号Enterococcus faecalis RQ15。在12%复原脱脂乳中延时培养及冷藏保存该菌株时,产生胨化现象。后续的研究表明Enterococcus faecalis RQ15产生的蛋白酶具有低温蛋白酶的特征。

海氏肠球菌(Enterococcus hirae)发酵特性及应用

对实验所得并鉴定为海氏肠球菌(Enterococcus hirae)的菌株I-2进行发酵特性的考察,结果显示I-2具有良好的发酵特性。实验还将I-2用于酸奶发酵,并对其产品品质进行测定,各项指标均达到国家标准,且在发酵及后熟20d后活菌数依然能够保持在109CFU/mL以上,说明其具有良好的乳品开发潜力及保健功能。

中草药提取物对蜜蜂屎肠球菌(Enterococcus faecium)的抑制作用研究

为了观察中草药对蜜蜂屎肠球菌(Enterococcusfaecium)的体外抑菌效果,选用14种中草药按常规法制备水提物,用纸片法和试管二倍稀释法检测中草药水提物对蜜蜂屎肠球菌的抑菌作用。试验结果表明,所选14种中草药中9种对蜜蜂屎肠球菌有中度以上抑菌作用,其中大青叶的抑菌作用最强,其次是黄连、金银花、黄芪、黄芩、大黄、板篮根、淫羊藿和青蒿。

Virulence factors of Enterococcus strains isolated from patients with inflammatory bowel disease

AIM: To determine the features of Enterococcus that contribute to the development and maintenance of the inflammatory process in patients with inflammatory bowel disease (IBD). METHODS: Multiplex polymerase chain reaction (PCR) was applied to assess the presence of genes that encode virulence factors [surface aggregating protein (asa1), gelatinase (gelE), cytolysin (cylA), extracellular surface protein (esp) and hyaluronidase (hyl)] in the genomic DNA of 28 strains of Enterococcus isolated from the intestinal tissues of children with IBD (n =16) and of children without IBD (controls; n = 12). Additionally, strains with confirmed presence of the gelE gene were tested by PCR for the presence of quorum sensing genes (fsrA, fsrB, fsrC) that control the gelatinase production. Gelatinase activity was tested on agar plates containing 1.6% gelatin. We also analysed the ability of Enterococcus strains to release and decompose hydrogen peroxide (using Analytical Merckoquant peroxide test strips) and tested their ability to adhere to Caco-2 human gut epithelium cells and form biofilms in vitro. RESULTS: A comparison of the genomes of Enterococcus strains isolated from the inflamed mucosa of patients with IBD with those of the control group showed statistically significant differences in the frequency of theasa1 gene and thegelE gene. Furthermore, the cumulative occurrence of different virulence genes in the genome of a single strain ofEnterococcus isolated from the IBD patient group is greater than in a strain from the control group, although no significant difference was found. Statistically significant differences in the decomposition of hydrogen peroxide and adherence to the Caco-2 epithelial cell line between the strains from the patient group and control group were demonstrated. The results also showed that profuse biofilm production was more frequent amongEnterococcus strains isolated from children with IBD than in control strains. CONCLUSION: Enterococcus strains that adhere strongly to the intestinal epithelium, form biofilms and possess antioxidant defence mechanisms seem to have the greatest influence on the inflammatory process.

Effects of lysedEnterococcus faecalis FK-23 on experimental allergic rhinitis in a murine model

In the current study, we sought to investigate whether lysed Enterococcus faecalis FK-23 （LFK）, a heat-killed probiotic preparation, attenuated eosinophil influx into the upper airway and had immunomodulatory activity in a murine allergic rhinitis model. Eighteen BALB/c mice were divided into three groups; the ovalbumin （OVA）-sen- sitized/challenged group, which received saline orally for 6 weeks （OVA group）, the OVA-sensitized/challenged group, which received LFK orally for 6 weeks （LFK-fed group）, and the non-sensitized group, which received saline for 6 weeks （saline control group）. Nasal rubbing and sneezing were monitored during the study. After the final challenge, interleukin （IL）-4, interferon （IFN）-y, and OVA-specific IgE levels in the sera and splenocyte culture supernatants were determined, eosinophilic infiltrate into the upper airway was quantified, and splenic CD4~CD25＋ regulatory T cells （Tregs） were examined by flow cytometry. We found that nasal rubbing was sig- nificantly reduced in LFK-fed mice compared to the OVA group on d 27 and 35, and sneezing was significantly inhibited by LFK administration for 35 d. LFK-fed mice had significantly less eosinophil influx into the nasal mucosa than the OVA group. There were no significant differences between the LFK-fed group and OVA group in the serum and splenocyte culture supernatant levels of IL-4, IFN-y, and OVA-specific IgE. Interestingly, the LFK-fed mice had a significantly greater percentage of splenic CD4＋CD25＋ Tregs than OVA group. Our results indicate that oral administration of LFK may alleviate nasal symptoms, reduce nasal eosinophilia, and increase the percentage of CD4＋CD25＋ Tregs in experimental allergic rhinitis.

Enterococcus faecium NCIMB 10415 administration improves the intestinal health and immunity in neonatal piglets infected by enterotoxigenic Escherichia coli K88

Background:This study aimed to investigate the effects of oral administration of Enterococcus faecium NCIMB10415(E.faecium)on intestinal development,immunological parameters and gut microbiota of neonatal piglets challenged with enterotoxigenic Escherichia coli K88(ETEC).A total of 961-day-old sow-reared piglets were randomly assigned to 2 groups,with 48 piglets in each group.The piglets were from 16 litters(6 piglets each litter),and 3 piglets each litter were allocated to the E.faecium-supplemented(PRO)group,while the other 3 piglets were allocated to the control(CON)group.After colostrum intake,piglets in the PRO group were orally administrated with 3×10~9 CFU E.faecium per day for a period of one week.On day 8,one piglet per litter from each group was challenged(CON+ETEC,PRO+ETEC)or not(CON-ETEC,PRO-ETEC)with ETEC in a 2×2 factorial arrangement of treatments.On day 10(2 days after challenge),blood and tissue samples were obtained from piglets.Results:Before ETEC challenge,there were no significant differences for the average daily gain(ADG)and fecal score between the two groups of piglets.After ETEC challenge,the challenged piglets had greater fecal score compared to the non-challenged piglets,whereas E.faecium administration was able to decrease the fecal score.Piglets challenged with ETEC had shorter villous height,deeper crypt depth,and reduced number of goblet cells in the jejunum and decreased m RNA abundance of claudin-1 in the ileum,whereas increased the percentage of lymphocytes,concentrations of IL-1βin the plasma and TNF-αin the ileal mucosa,as well as increased the m RNA abundances of innate immunity-related genes in the ileum tissue.These deleterious effects caused by ETEC were partly alleviated by feeding E.faecium.In addition,piglets in PRO-ETEC group had decreased the percentage of CD8^+T cells of the peripheral blood when compared to those in CON-ETEC group.Moreover,E.faecium administration increased Verrucomicrobia at phylum level and decreased Bilophila at genus level.Conclusions:These results suggest that oral administration of E.faecium alleviated the intestinal injury and diarrhea severity of neonatal piglets challenged by ETEC,partly through improving the intestinal microbiota and immune response.This offers a potential strategy of dietary intervention against intestinal impairment by ETEC in neonatal piglets.

基于转录组探究Enterococcus faecium 15A降解二乙基亚硝胺的作用机制

二乙基亚硝胺(N-nitrosodiethylamine,NDEA)是食品加工中易产生的强致癌物,研究显示,部分乳酸菌具有降解NDEA的功能,但其降解机制未明确。因此,该研究基于一株能有效降解NDEA、来源于健康人肠道的粪肠球菌(Enterococcus faecium)15A,系统考察培养温度、时间、pH值、需/厌氧的环境因素对E.faecium 15A降解作用的影响,发现菌株的降解能力与其生长情况呈正相关,环境的pH值能转变菌株的降解特性,pH2~7条件下有降解NDEA作用,而pH8环境中则表现为促进NDEA形成。经转录组学分析发现,E.faecium 15A对NDEA的作用过程是一个多基因靶点、涉及多代谢通路的过程,其中嘌呤合成/代谢途径可能为主要靶点通路。随后,采用实时反转录聚合酶链式反应技术验证了相关的关键上调基因xpt、hpt、Pyk、Ndk和下调基因guaA,揭示了E.faecium 15A降解NDEA的作用规律,探究其降解作用的分子机制。研究结果可为微生物法高效降解NDEA奠定基础,为乳酸菌类发酵剂、益生菌剂的应用提供新思路。

Residual activity of cetrimide and chlorhexidine on Enterococcus faecalis-infected root canals

Effective final irrigation regimen is an important step in order to achieve better disinfection and ensure residual antimicrobial effects after root canal preparation. The aim of this study was to compare the residual antimicrobial activity of 0.2% cetrimide, and 0.2% and 2% chlorhexidine in root canals infected with Enterococcus faecalis. Biofilms of E. faecalis were grown on uniradicular roots for 4 weeks. After root canal preparation, root canals were irrigated with 17% ethylenediaminetetraacetic acid （EDTA） to remove the smear layer. The roots were randomly divided into three experimental groups （n=26） according to the final irrigating solution： Group I, 5 mL 0.2% cetrimide; Group II, 5 mL 0.2% chlorhexidine; and Group III, 5 mL 2% chlorhexidine. Samples were collected for 50 days to denote the presence of bacterial growth. The proportion of ungrown specimens over 50 days was evaluated using the nonparametric Kaplan-Meier survival analysis. Differences among groups were tested using the log-rank test and the level of statistical significance was set at P〈0.05. The highest survival value was found with 2% chlorhexidine, showing statistically significant differences from the other two groups. At 50 days, E. faecalisgrowth was detected in 69.23% specimens in Groups I and II, and in 34.61% specimens of Group III. There were no significant differences between 0.2% cetrimide and 0.2% chlorhexidine. Final irrigation with 2% chlorhexidine showed greater residual activity than 0.2% chlorhexidine and 0.2% cetrimide in root canals infected with E. faecalis.

Antimicrobial effect of alexidine and chlorhexidine against Enterococcus faecalis infection

A previous study demonstrated that alexidine has greater affinity for the major virulence factors of bacteria than chlorhexidine.The aim of this study was to compare the antimicrobial activity of 1%alexidine with that of 2%chlorhexidine using Enterococcus faecalis-infected dentin blocks.Sixty bovine dentin blocks were prepared and randomly divided into six groups of 10 each.E.faecalis was inoculated on 60 dentin blocks using the Luppens apparatus for 24 h and then the dentin blocks were soaked in 2%chlorhexidine or 1%alexidine solutions for 5 and 10 min,respectively.Sterile saline was used as a control.The antimicrobial efficacy was assessed by counting the number of bacteria adhering to the dentin surface and observing the degradation of bacterial shape or membrane rupture under a scanning electron microscope.Significantly fewer bacteria were observed in the 2%chlorhexidine-or 1%alexidine-soaked groups than in the control group(P<0.05).However,there was no significant difference in the number of bacteria adhering to the dentinal surface between the two experimental groups or between the two soaking time groups(P>0.05).Ruptured or antiseptic-attached bacteria were more frequently observed in the 10-min-soaked chlorhexidine and alexidine groups than in the 5-min-soaked chlorhexidine and alexidine groups.In conclusion,10-min soaking with 1%alexidine or 2%chlorhexidine can be effective against E.faecalis infection.