黄河鲤水产细菌的分离及其毒力因子和群体感应信号分子的检测

【背景】水产细菌病害制约水产养殖业健康发展,群体感应与细菌毒力因子的产生密切相关,群体感应调控细菌的毒力因子特性值得进一步研究。【目的】探究群体感应与黄河鲤细菌病害的关系,明确群体感应对细菌毒力因子特性的影响。【方法】通过16S rRNA基因测序并构建系统进化树确定筛选菌株的进化地位,通过脱脂牛奶平板法和偶氮酪蛋白法检测菌株胞外蛋白酶活力,采用结晶紫染色法对菌株的生物膜形成能力进行测定,通过报告菌株BB170和CV026分别测定菌株产信号分子AI-2和高丝氨酸内酯的能力,外源添加高丝氨酸内酯检测信号分子对菌株胞外蛋白酶活力和生物膜形成能力的影响。【结果】哈夫尼亚菌(Hafnia sp.) Z11和气单胞菌(Aeromonas sp.) Z12具有高水平的胞外蛋白酶活力和生物膜形成能力,能够分泌AHLs信号分子且具有菌体密度依赖性。外源添加HSL对菌株毒力因子特性有不同程度的影响,外源添加高浓度的N-丁酰基高丝氨酸内酯(C4-HSL)和N-己酰基高丝氨酸内酯(C6-HSL)能够分别提高菌株Z11和Z12的胞外蛋白酶活力和生物膜形成能力。【结论】高浓度群体感应信号分子AHLs对哈夫尼亚菌和气单胞菌胞外蛋白酶活性有促进作用,说明该2种菌的群体感应现象可能会影响其毒力。     

鸡源奇异变形杆菌分离鉴定及生物学特性

【背景】奇异变形杆菌(Proteusmirabilis,PM)是人畜共患病原菌,在自然界分布广泛。近年来,随着畜禽奇异变形杆菌病发病率上升和耐药性增强,亟需开展对该菌的防控研究。【目的】分离鉴定鸡源奇异变形杆菌,鉴定其耐药性、致病性、生物被膜形成能力等生物学特性。【方法】采用聚合酶链式反应(Polymerase Chain Reaction,PCR)方法鉴定了从2019-2020年病鸡中分离的52株临床奇异变形杆菌。分别采用药敏试验、PCR、结晶紫染色法对临床菌株的耐药性、毒力基因及生物膜的形成进行研究。【结果】选择14株代表性菌株进行16SrRNA基因测序,结果表明所测分离菌株均为奇异变形杆菌。所有分离菌株均对克林霉素、阿奇霉素、红霉素、四环素和利福平耐药,对氯霉素和头孢曲松外的抗生素耐药性均高于50%。对分离的奇异变形杆菌的13个毒力基因检测表明,所有菌株均能检测到hpmA、hpmB、rpoA、mrpA、fliL、zapA、ureC、atfC、atfA、pmfA,而ucaA和rsbA检出率分别为19.23%(10/52)和48.08%(25/52),hlyA未检出。对分离株生物被膜形成能力检测结果表明,所有菌株均能形成生物被膜,19.23%(10/52)的分离菌株形成生物被膜能力强,而且25℃条件下成膜能力比37℃更强。【结论】鸡源奇异变形杆菌携带多种毒力基因,具有较强生物被膜形成能力,耐药模式多样且日趋严重,应进一步加强对奇异变形杆菌在动物致病性和耐药性方面的监控,以降低其感染风险。     

一株产纤维素酶菌株的分离、鉴定及产酶特性

【目的】筛选并鉴定一株产纤维素酶的菌株,初步探究该菌的产酶特性,为综合利用纤维素筛选菌源。【方法】在常温条件下,采用滤纸培养基对菌种富集,采用CMC-Na初筛纤维素降解菌,采用LB培养基分离纯化菌株,经形态学、生理生化特征试验、16S r RNA基因序列测定等分析筛选菌株的系统分类地位。单因素试验确定培养时间、培养温度、初始p H及Na Cl浓度对筛选菌株产酶活力的影响。【结果】从腐烂的玉米秸秆中分离出一株在常温下产纤维素酶细菌KZ-2,根据菌落形态特征、生理生化特征鉴定以及16S r RNA基因序列分析,初步鉴定KZ-2为肠杆菌(Enterobacter sp.),为潜在新种。产酶条件实验显示:该菌使用产酶发酵培养基120 h产酶量达到最大值,在25–35°C、初始p H 4.5–5.5、Na Cl浓度1.0%–2.0%范围内为最佳产酶条件,在最适条件下酶活可达80.93 U/m L。该菌株所产纤维素酶最适反应p H为7.0,最适反应温度为50°C。【结论】KZ-2是一株具有降解纤维素能力的细菌,在常温下即可分泌纤维素酶,并且该菌株为潜在新种,具有潜在的开发价值。     

一株产右旋糖苷酶海洋细菌的筛选鉴定

【目的】筛选鉴定产右旋糖苷酶的海洋细菌,并对其所产右旋糖苷酶的酶学性质及在变异链球菌牙菌斑生物膜中的应用进行初步研究。【方法】利用平板透明圈法从海洋环境中筛选产右旋糖苷酶的细菌,根据菌株形态特征、生理特征及16S rDNA序列确定其分类学地位,采用体外生物膜模型研究该酶对变异链球菌牙菌斑生物膜形成的抑制作用。【结果】从海泥中筛选出一株产右旋糖苷酶的细菌KQ11,初步鉴定为节杆菌(Arthrobacter sp.)。该菌株的最适生长温度为30°C,最适生长pH 7.5,最适生长NaCl浓度为0.4%。右旋糖苷酶的最适作用温度为45°C,最适作用pH为5.5。该酶能有效地抑制变异链球菌牙菌斑生物膜的形成。【结论】菌株KQ11右旋糖苷酶能够抑制变异链球菌牙菌斑生物膜的形成,可望用于漱口液等口腔护理产品中。     

不同植入材料对表皮葡萄球菌和结核杆菌粘附和生物膜形成的影响

目的:探讨表皮葡萄球菌和结核杆菌在不同生物材料表面粘附性和生物膜形成能力的差异,为临床骨科材料的选择提供理论参考。方法:采用常规方法进行细菌分离和菌种鉴定。粘附能力检测采用菌落计数法,生物膜形成能力检测采用96孔板结晶紫染色法。结果:结核杆菌和表皮葡萄球菌在骨组织均有最强的粘附和生物膜形成能力,表皮葡萄球菌在三种材料上的粘附和生物膜形成能力均高于结核杆菌,表皮葡萄球菌和结核杆菌在铁合金和不锈钢粗糙表面上的粘附和生物膜形成能力均显著高于其光滑表面(P0.05)。结论:表皮葡萄球菌和结核杆菌在不同生物材料上具有不同的粘附和生物膜形成能力,不同种属细菌在不同材料的粘附和生物膜形成能力为临床骨科生物材料的选择提供了理论依据。     

一株产脂肽类表面活性剂的碱性Dietzia菌及特性研究

【目的】筛选降解性能良好的产生物表面活性剂的菌株,对其进行分类学鉴定,确定所产表面活性剂物质并对各影响因素进行评价。【方法】利用液体石蜡为底物筛选降解性能良好的产生物表面活性剂菌株,通过形态特征观察、生理生化测定、16S rRNA基因序列分析等实验确定菌株的分类地位。通过排油圈活性、表面张力值、薄层层析等方法确定生物表面活性剂的性质,分析碳、氮源和温度、pH、盐浓度各因素对菌株产生物表面活性剂的影响。【结果】从大连新港采集的样品中分离得到一株产表面活性剂的嗜碱菌株3372,经分类鉴定表明其是Dietzia cercidiphylli的新菌株。嗜碱菌3372发酵液粗提物的排油直径为6.1 cm,表面张力可从67.62 mN/m降到32.95 mN/m,经薄层层析分析,初步鉴定为脂肽类表面活性剂。综合各因素对发酵液表面活性的影响,菌株3372在pH为9.0、适盐浓度为3%的培养基中,经30°C培养可将发酵液表面张力值降到最低。【结论】嗜碱菌3372是脂肽类生物表面活性剂产生菌的新成员,其在高盐碱条件下产生表面活性剂的特性在工业应用上有一定的潜力。     

高效铁氧化鞘细菌的筛选与鉴定

【目的】铁氧化酶是氧化铁锰鞘细菌类在污水处理中最重要的酶,筛选铁氧化酶高产菌株,研究酶学特性及研究该菌株对水中铁、锰的吸附性能。【方法】利用尿素培养基富集、CGY平板从3份不同水样中分离产铁氧化酶菌株:富集培养铁氧化酶产生菌;摇瓶复筛铁氧化酶产量较高的菌株,通过菌落形态、镜检、生理生化试验和16S rRNA基因序列遗传分析对目的菌株进行鉴定。【结果】分离筛选到一株高产铁氧化酶的菌株S9,被鉴定为鞘细菌球衣菌属浮游球衣菌(Sphaerotilus natans);该菌株对铁锰具有较强的吸附性,当吸附时间为4h时,菌株对水中铁的吸附量为29.02mg/g,吸附率为66.77%;当吸附时间为6h时,菌株对锰的吸附量为34.49mg/g,吸附率为70.68%;该菌株产铁氧化酶的最适温度和p H分别为30℃和7.5,Mg2+、Na+、K+离子对铁氧化酶活性有一定的激活作用,Cu2+对铁氧化酶影响不大,而Mn2+、Zn2+对铁氧化酶具有很强的抑制作用,Pb2+、Ag+对铁氧化酶活性有一定的抑制作用。【结论】浮游球衣菌S9是一株具有较高铁氧化性的菌株,在治理污水和给排水工程中的应用具有潜在的应用价值。     

高产铁载体棉田土壤细菌SS05的筛选与鉴定

【目的】研究从棉田土壤中筛选得到的高产铁载体细菌产铁载体能力、分类地位和抑菌活性。【方法】通过改良蔗糖-天冬氨酸培养基选择性筛选产铁载体细菌,通过分光光度计法测定铁载体活性,通过混菌法测定产铁载体细菌上清液对棉花枯萎病致病菌尖孢镰刀菌(Fusarium oxysporum)的抑菌效果,采用形态学、生理生化鉴定及16S rDNA序列系统发育分析对高产铁载体菌株进行鉴定。【结果】从棉田土壤中筛选到162株产铁载体细菌,30株产铁载体能力较强的细菌中21株具有较高产铁载体能力,菌株SS05的铁载体活性单位达到98.3%;在低铁条件下,SS05上清液对F.oxysporum具有显著的抑制作用;SS05与莫哈韦芽孢杆菌(Bacillus mojavensis)最为接近。【结论】SS05是高产铁载体菌株,与莫哈韦芽孢杆菌(Bacillus mojavensis)最为接近,在低铁培养条件下其上清液对F.oxysporum具有显著的抑制作用。     

一株高产表面活性剂的南极土地杆菌的分离及其特性

【背景】生物表面活性剂具有毒性低、生物兼容性好和可降解等优点,是化学表面活性剂的优良替代物。目前产生物表面活性剂的微生物多为常温菌,从低温环境中挖掘高产新型生物表面活性剂的生产菌株具有重要的意义。【目的】从南极土壤中筛选产表面活性剂的低温微生物,对其表面活性剂进行纯化和结构解析并评估其性能。【方法】采用排油圈法对分离自南极菲尔德斯半岛土壤样品中的细菌菌株进行筛选,获得一株在菌苔表面产白色固体颗粒的菌株,对菌株进行形态观察和16SrRNA基因序列分析以确定该菌株系统发育地位。利用高效液相色谱法(high performance liquid chromatography, HPLC)分离产物,并用核磁共振波谱(nuclear magnetic resonance,NMR)技术对产物的化学结构进行鉴定。采用单因素试验和响应面设计方法对发酵培养基进行优化。此外,对产物的乳化性能及其对柴油的降解能力进行评估。【结果】得到了一株高产生物表面活性剂的耐冷土地杆菌属(Pedobacter)GW9-17,其最优发酵培养基(g/L)组成为：可溶性淀粉18.0、胰蛋白胨9.0、C3H3NaO3 4.4、K...     

分解玉米赤霉烯酮菌株的分离、鉴定及其产酶特征

【目的】从发酵食品材料中筛选出对玉米赤霉烯酮(ZEN)有分解作用的微生物,研究其分解效率及产酶特征并进行菌种鉴定。【方法】利用添加ZEN毒素类似物(PL)的固体培养基对25种发酵食品材料进行初筛,获得毒素类似物耐受菌株,经过用ZEN复筛,得到高效分解ZEN的细菌。用高效液相色谱法(HPLC)分析培养物残留ZEN,评价菌株对ZEN的分解效率。初步分析该菌株产纤维素酶、木聚糖酶及β-葡萄糖苷酶的特性。通过微生物形态学、分子生物学方法进行菌种鉴定,确定该菌的系统分类学地位。【结果】从发酵食品材料中筛选出一株分解ZEN的菌株BF-B-3,经初步鉴定该菌株为枯草芽孢杆菌(Bacillus subtilis)。其ZEN分解率达62.48%,测定该菌产纤维素酶、木聚糖酶及β-葡萄糖苷酶活力分别为160.38、84.51和4.14 U/mL。【结论】枯草芽孢杆菌属于饲用微生物,生物安全性高,所分离到的枯草芽孢杆菌疑似株(Bacillus subtilis)BF-B-3菌株,可作为具有分解ZEN功能的益生菌使用,具有较好的应用前景。     

猪源肠外致病性大肠埃希氏菌的生物膜形成能力及耐药性

[背景]猪源肠外致病性大肠埃希氏菌(extraintestinal pathogenic Escherichia coli,ExPEc)是一种严重危害养猪业的病原菌,有关其生物膜形成能力与耐药性的研究报道很少。[目的]探讨从病猪肺脏中分离鉴定的3株ExPEc的生物膜形成能力及耐药性,为从抗生物膜形成角度防治猪肠外大肠埃希氏菌病提供参考。[方法]采用96孔板结晶紫染色法结合正交实验优化猪源ExPEc分离株的生物膜形成最佳条件与成膜能力;通过扫描电镜观察各菌株生物膜的形态结构;利用PCR方法检测其携带的生物膜形成相关基因;采用微量肉汤稀释法测定抗生素对生物膜态与浮游态下猪源ExPEc分离株的最小抑菌浓度(minimum inhibitory concentration,MIC)。[结果]3株猪源ExPEc的最佳成膜条件并不一致,但在各自最佳条件下均能形成很强的生物被膜且同时携带10个生物膜形成相关基因(pgaA,pgaB,pgaC,pgaD,luxS,fimA,hipA,iha,flhC,flhD)。扫描电镜观察显示,菌株SE-1聚集后可形成片状生物膜,菌株SE-2和SE-3聚集后可形成多层结构的生物膜,且聚集体间有明显空隙。部分受试抗菌药物对生物膜态SE-1、SE-2和SE-3菌株的MIC值较对应浮游菌提高了2-32倍,药物敏感性由原来的敏感转为中敏或耐药。[结论]实验结果为从抗生物膜形成角度防治猪肠外大肠埃希氏菌病奠定了基础。     

禽致病性大肠杆菌江苏、安徽分离株的生物学特性分析

[目的]研究禽致病性大肠杆菌(Avian Pathogenic Escherichia coli,APEC)江苏、安徽分离株的优势血清型,并分析其生物学特性.[方法]对分离自病禽的细菌进行鉴定,采用玻片凝集法测定禽致病性大肠杆菌的血清型,PCR方法检测14种毒力基因的分布,采用美国临床和实验室标准化研究所的方法进行药物敏感性检测,改良结晶紫半定量法检测分离细菌的生物被膜形成能力. [结果]共分离到禽致病性大肠杆菌56株,血清型检测结果表明,O78血清型占64.29％,为主要血清型.毒力基因检测显示,fimC、pfs、ompA和luxS的阳性率超过90％.药物敏感性检测显示,58.93％的菌株对8种以上的药物耐受.生物被膜检测显示,有16株细菌生物被膜形成能力为中等以上,其中68.75％的菌株耐8种以上的药物.[结论]O78为主要流行的血清型.fimC、pfs、ompA和luxS基因为APEC保守基因.多重耐药性仍很普遍,细菌生物被膜与耐药性具有相关性.     

Microtiter plate assay for assessment of Listeria monocytogenes biofilm formation

Listeria monocytogenes has the ability to form biofilms on food-processing surfaces, potentially leading to food product contamination. The objective of this research was to standardize a polyvinyl chloride (PVC) microtiter plate assay to compare the ability of L. monocytogenes strains to form biofilms. A total of 31 coded L. monocytogenes strains were grown in defined medium (modified Welshimer's broth) at 32 degrees C for 20 and 40 h in PVC microtiter plate wells. Biofilm formation was indirectly assessed by staining with 1% crystal violet and measuring crystal violet absorbance, using destaining solution. Cellular growth rates and final cell densities did not correlate with biofilm formation, indicating that differences in biofilm formation under the same environmental conditions were not due to growth rate differences. The mean biofilm production of lineage I strains was significantly greater than that observed for lineage II and lineage III strains. The results from the standardized microtiter plate biofilm assay were also compared to biofilm formation on PVC and stainless steel as assayed by quantitative epifluorescence microscopy. Results showed similar trends for the microscopic and microtiter plate assays, indicating that the PVC microtiter plate assay can be used as a rapid, simple method to screen for differences in biofilm production between strains or growth conditions prior to performing labor-intensive microscopic analyses.     

Microtiter Plate Assay for Assessment of Listeria monocytogenes Biofilm Formation

Listeria monocytogenes has the ability to form biofilms on food-processing surfaces, potentially leading to food product contamination. The objective of this research was to standardize a polyvinyl chloride (PVC) microtiter plate assay to compare the ability of L. monocytogenes strains to form biofilms. A total of 31 coded L. monocytogenes strains were grown in defined medium (modified Welshimer's broth) at 32°C for 20 and 40 h in PVC microtiter plate wells. Biofilm formation was indirectly assessed by staining with 1% crystal violet and measuring crystal violet absorbance, using destaining solution. Cellular growth rates and final cell densities did not correlate with biofilm formation, indicating that differences in biofilm formation under the same environmental conditions were not due to growth rate differences. The mean biofilm production of lineage I strains was significantly greater than that observed for lineage II and lineage III strains. The results from the standardized microtiter plate biofilm assay were also compared to biofilm formation on PVC and stainless steel as assayed by quantitative epifluorescence microscopy. Results showed similar trends for the microscopic and microtiter plate assays, indicating that the PVC microtiter plate assay can be used as a rapid, simple method to screen for differences in biofilm production between strains or growth conditions prior to performing labor-intensive microscopic analyses.     

Study of the formation of a biofilm by clinical strains of Staphylococcus aureus

A study on biofilm formation was carried out using five methicillin-sensitive [MSSA] and five methicillin-resistant [MRSA] strains of S. aureus. In each group, there were four strains isolated from patients from Kinshasa (Democratic Republic of Congo, DRC) and one reference strain. All of the strains were hydrophobic. The adherence of the bacteria to an abiotic surface was studied with the Biofilm Ring Test (BFRT?) and the crystal violet staining method (CVSM). Both techniques showed that eight of the strains formed biofilms within 2-3 h. The extent of the biofilm formed by one strain could only be observed with the CVSM. Periodate prevented the formation of biofilms and, in separate experiments, destroyed the biofilm pre-formed by the MSSA reference, but not those pre-formed by the clinical strains. Proteinase K destroyed all pre-formed biofilms. Six of the strains were icaA+; the clinical MSSA strains were not. The results also indicated different mechanisms of biofilm development between MSSA and MRSA clinical strains. The BFRT? and the CVSM are complementary techniques to study the adhesion of bacteria and the development of biofilms.     

Study of the formation of a biofilm by clinical strains of Staphylococcus aureus

A study on biofilm formation was carried out using five methicillin-sensitive [MSSA] and five methicillin-resistant [MRSA] strains of S. aureus. In each group, there were four strains isolated from patients from Kinshasa (Democratic Republic of Congo, DRC) and one reference strain. All of the strains were hydrophobic. The adherence of the bacteria to an abiotic surface was studied with the Biofilm Ring Test (BFRT®) and the crystal violet staining method (CVSM). Both techniques showed that eight of the strains formed biofilms within 2–3 h. The extent of the biofilm formed by one strain could only be observed with the CVSM. Periodate prevented the formation of biofilms and, in separate experiments, destroyed the biofilm pre-formed by the MSSA reference, but not those pre-formed by the clinical strains. Proteinase K destroyed all pre-formed biofilms. Six of the strains were icaA⁺; the clinical MSSA strains were not. The results also indicated different mechanisms of biofilm development between MSSA and MRSA clinical strains. The BFRT® and the CVSM are complementary techniques to study the adhesion of bacteria and the development of biofilms.     

转座子随机插入鉴定肠炎沙门氏菌生物膜形成相关基因

[目的]生物膜在沙门氏菌的致病性和引起沙门氏菌食物中毒等方面起着重要作用,本研究为了鉴定影响沙门氏菌生物膜形成的基因.[方法]利用结晶紫染色定量法对74株鸡源的肠炎、鸡白痢和鸡伤寒沙门氏菌进行生物膜测定,选择生物膜生长较好的肠炎沙门氏菌C050041,采用转座子随机插入法构建突变株库.[结果]84%的鸡源沙门氏菌菌株可在塑料表面形成生物膜;通过转座子插入获得1924个突变株,筛选的生物膜降低突变株经生长曲线测定、测序和序列比对及Southern blot分析鉴定出15个插入基因,它们分别为metE、ompR、rpoS、,和G、rfaJ、rfaK、rfaP、rfbH、rhlE、spiA、steB、tpx、ybdN和2个未知功能的基因.[结论]我们鉴定出了多个影响生物膜形成的新基因,这些基因的发现为进一步研究沙门氏菌生物膜形成的调控机制,研制减毒沙门氏菌疫苗奠定了基础.     

Application of Biofilm-Forming Bacteria on the Enhancement of Organophosphorus Fungicide Degradation

This study aimed to develop technology enhancing the biodegradation efficacy against organophosphorus fungicide with biofilm-forming bacteria in situ. Using the crystal violet staining method, two bacterial strains having biofilm formation capability were isolated and identified as Pseudomonas sp. C7 and Bacillus sp. E5. Compared with the culture of tolclofos-methyl degrader Sphingomonas sp. 224, biofilm formation was improved by co-inoculation with biofilm-forming bacterium Bacillus sp. E5. Evaluated in liquid culture conditions, this two-species mixed consortium was observed to degrade tolclofos-methyl more effectively than Sphingomonas sp. 224 alone, with an approximately 90% degradation efficiency within 48 h of dosing. The improved effectiveness of the consortium biofilm was reflected using soil in situ with an approximately 7% increased degradation ratio over Sphingomonas sp. 224 alone. This is the first report demonstrating improved bioremediation degradation efficacy against tolclofos-methyl exhibited by a consortium biofilm. This work presents a possible effective bioremediation strategy using a specific biofilm composition against pollutants containing organophosphorus compounds in situ.     

Rapid methods to assess sanitizing efficacy of benzalkonium chloride to Listeria monocytogenes biofilms

Different methods were used to investigate biofilm growth including crystal violet staining, ATP bioluminescence and total viable count. Seven strains of Listeria monocytogenes and 8 of their derivative strains were screened for their capacity to form biofilms. Both adaptation to benzalkonium chloride (BC) and curing of plasmids did not significantly affect biofilm-forming ability. The strains of L. monocytogenes belonging to serotype 1 formed biofilms significantly better as compared to serotype 4 (P=0.0003). To estimate the efficacy of BC for biofilm elimination the best and the poorest biofilm-formers were used (C719 and LJH 381). It was observed that, L. monocytogenes strain C719 in biofilms is at least 1000 times more resistant to BC than in planktonic form. Cells present in biofilms were shown to recover and grow after BC treatment thus providing a source of recontamination. It was shown that ATP bioluminescence provides good correlation with bacterial counts of L. monocytogenes in biofilms. Staining with crystal violet, on the contrary, did not correlate with bacterial growth in biofilms in the presence of high concentrations of BC but provided information on the concentration of bacterial cells, both live and dead, attached to the surface. ATP bioluminescence was found to be a reliable method for rapid estimation of the efficacy of sanitizers for biofilm disinfection. Crystal violet staining, on the other hand, was shown to be a suitable method to monitor removal of biofilms. Our investigation showed that for Listeria biofilms concentrations of BC higher then 10 mg/ml should be applied for at least 30 min to kill almost all the live cells in biofilms. However, this concentration was still not enough to remove biofilms from the surface of plastic.     

The in vitro antibiofilm activity of selected culinary herbs and medicinal plants against Listeria monocytogenes

Aims:  The antibiofilm activity of extracts obtained from selected herbs, spices, beverages and commercially important medicinal plants was investigated on Listeria monocytogenes .
Methods and Results:  The growth and development of the biofilm was assessed using the crystal violet (CV) assay. The respiratory activity was assessed using the 2, 3-bis [2-methyloxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxanilide (XTT) reduction assay. The majority of extracts tested prevented cell adhesion to the polyvinyl chloride (PVC) surface. Seven of the 15 extracts reduced biofilm adhesion of both the clinical and the type strains by at least 50%. In contrast, inhibition of a preformed biofilm was more difficult to achieve, with only three extracts ( Rosmarinus officinalis, Mentha piperita and Melaleuca alternifolia ) inhibiting the growth of both strains by at least 50%.
Conclusions:  Although most extracts were able to reduce initial cell attachment, inhibition of growth in a preformed biofilm was more difficult to achieve.
Significance and Impact of the Study:  The ability to reduce biofilm biomass as shown by several plant extracts warrants further investigation to explore the use of natural products in antibiofilm adhesion.