Screening agars for MRSA:evaluation of a stepwise diagnostic approach with two different selective agars for the screening for methicillin-resistant Staphylococcus aureus(MRSA)

Background: Colonization with methicillin-resistant Staphylococcus aureus(MRSA) poses a hygiene risk that does not spare field hospitals or military medical field camps during military deployments. Diagnostic options for unambiguously identifying MRSA isolates are usually scarce in military environments. In this study, we assessed the stepwise application of two different selective agars for the specific identification of MRSA in screening analyses.Methods: Nasal swabs from 1,541 volunteers were subjected to thioglycollate broth enrichment and subsequently screened on CHROMagar MRSA selective agar for the identification of MRSA. The MRSA identity of suspiciouslooking colonies was confirmed afterwards or excluded by another selective agar, chrom ID MRSA. All isolates from the selective agars with MRSA-specific colony morphology were identified by biochemical methods and mass spectrometry.Results: The initial CHROMagar MRSA screening identified suspicious colonies in 36 out of 1541 samples. A total of 25 of these 36 isolates showed MRSA-like growth on chrom ID agar. Out of these 25 isolates, 24 were confirmed as MRSA, while one isolate was identified as Staphylococcus kloosii. From the 11 strains that did not show suspicious growth on chrom ID agar, 3 were methicillin-sensitive Staphylococcus aureus(MSSA, with one instance of cocolonization with Corynebacterium spp.), 2 were confirmed as MRSA(with 1 instance of co-colonization with MSSA), 2 were lost during passaging and could not be re-cultured, one could not be identified by the applied approaches, and the remaining 3 strains were identified as Staphylococcus saprophyticus, Staphylococcus hominis(co-colonized with Macrococcus caseolyticus) and Staphylococcus cohnii, respectively.Conclusion: The application of the selective agar CHROMagar MRSA alone proved to be too non-specific to allow for a reliable diagnosis of the presence of MRSA. The combined use of two selective agars in a stepwise approach reduced this non-specificity with an acceptably low loss of sensitivity. Accordingly, such a stepwise screening approach might be an option for resource-restricted military medical field camps.

Characteristics and mechanism of Ni^(2+)and Cd^(2+)adsorption by recovered perlite from agar extraction residue

Ni^(2+)and Cd^(2+)in wastewater accumulated through the ecological chain and could jeopardize human health.Adsorption of Ni^(2+)and Cd^(2+)from wastewater using recovered perlite was an important way to solve the problem of resource utilization of solid waste from agar production.Our previous study confirmed that recovered perlite from agar extraction residue had better pore size and specific surface area than commercial perlite.However,the adsorption efficiency and adsorption mechanism of recovered perlite were the main factors limiting its adsorption application.The adsorption process of Ni^(2+)and Cd^(2+)by recovered perlite in aqueous solution was described by the pseudo-second-order kinetic equation,and the relevant adsorption mechanism was mainly chemisorption.Compared with commercial perlite,the adsorption removal rate of Ni^(2+)and Cd^(2+)by enzymatic recovered perlite could reach 92.9%and 89.2%,respectively,and were improved by 12.63%and 13.03%.Langmuir isothermal adsorption model could better describe the isothermal adsorption process of recovered perlite on heavy metal Ni^(2+)and Cd^(2+),and the relevant adsorption mechanism was mainly monolayer adsorption.The X-ray photoelectron spectroscopy(XPS)results indicated that the decrease of Si—O Si^(2+)hydroxyl coordination bond and the increase of C—Si bond might make the binding effect of recovered perlite with heavy metals stronger.The competitive adsorption of Ni^(2+)and Cd^(2+)by recovered perlite was still dominated by chemisorption and monolayer adsorption.This study was expected to provide a theoretical basis and technical support for the removal of Ni^(2+)and Cd^(2+)from wastewater using recovered perlite from seaweed residue.

A comparative study for petroleum removal capacities of the bacterial consortia entrapped in sodium alginate,sodium alginate/poly(vinyl alcohol),and bushnell haas agar

The purpose of this study was to identify and compare the degradation efficiencies of free and entrapped bacterial consortia(Staphylococcus capitis CP053957.1 and Achromobacter marplatensis MT078618.1)to different polymers such as Sodium Alginate(SA),Sodium Alginate/Poly(Vinyl Alcohol)(SA/PVA),and Bushnell Haas Agar(BHA).In addition to SA and SA/PVA,which are cost-effective,non-toxic and have different functional groups,BHA,which is frequently encountered in laboratory-scale studies but has not been used as an entrapment material until now.Based on these,the polymers with different surface morphologies and chemical compositions were analyzed by SEM and FT-IR.While the petroleum removal efficiency was higher with the entrapped bacterial consortia than with the free one,BHA-entrapped bacterial consortium enhanced the petroleum removal more than SA and SA/PVA.Accordingly,the degradation rate of bacterial consortia entrapped with BHA was 2.039 day^(-1),SA/PVA was 1.560,SA was 0.993,the half-life period of BHA-entrapped bacterial consortia is quite low(t_(1/2)=0.339)compared with SA(t_(1/2)=0.444)and SA/PVA(t_(1/2)=0.697).The effects of the four main factors such as:amount of BHA(0.5,1,1.5,2,2.5,3 g),disc size(4,5,6,7,8 mm),inoculum concentration(1,2.5,5,7.5,10 mL),and incubation period on petroleum removal were also investigated.The maximum petroleum removal(94.5%)was obtained at≥2.5 mL of bacterial consortium entrapped in 2 g BHA with a 7 mm disc size at 168 h and the results were also confirmed by statistical analysis.Although a decrease was observed during the reuse of bacterial consortium entrapped in BHA,the petroleum removal was still above 50%at 10th cycle.Based on GC-MS analysis,the removal capacity of BHA-entrapped consortium was over 90%for short-chain n-alkanes and 80%for medium-chain n-alkanes.Overall,the obtained data are expected to provide a potential guideline in cleaning up the large-scale oil pollution in the future.Since there has been no similar study investigating petroleum removal with the bacterial consortia entrapped with BHA,this novel entrapment material can potentially be used in the treatment of petroleum pollution in advanced remediation studies.

两种培养基对饮水机出水中细菌总数的测定效果比较

采用营养琼脂培养基和R2A Agar培养基对上海某高校及其附属小学公用饮水机出水细菌总数变化规律进行了测试分析比较。结果表明,在洁净饮用水受微生物微污染情况下,R2A Agar培养基更适合这种贫营养环境中的微生物的培养,比营养琼脂培养基具有更好的灵敏度。

一种基于地理位置的启发式Ad Hoc路由协议

近几年地理Ad Hoc路由以其独立选路由、避免泛洪以及有良好的可扩展性和适应性而得到快速发展。地理路由面临一个由贪婪方式转发而失败的本地最小问题,该文提出了一种启发式的地理位置辅助路由协议AGAR,利用启发函数对获得位置信息进行路径优化,克服了平面路由算法解决本地最小问题所带来的复杂性。仿真结果表明,该协议能有效地降低网络中扩展节点数目,具有较高的包投递率和较低的端到端延迟。

Cloning of Novel Tumor Metastasis-Related Genes from the Highly Metastatic Human Lung Adenocarcinoma Cell Line Anip973

A cDNA library was successfully constructed from Anip973, a human lung adenocarcinoma cell line with high metastatic potential. NIH3T3 cells were stably transfected using this cDNA library and screened for morphological changes in a soft agar assay. Genomic DNA was isolated from putative clones and the integrated sequence was retrieved by PCR and sequencing. Three known genes, ribosomal protein L23, hypothetical protein FLJ22104, and serine protease inhibitor, kazal type 6 and a number of 5＇-terminally truncated sequences were identified. Furthermore, cells transfected with ribosomal protein L23 was highly invasive compared with the empty vector as control （P 〈 0.02）. These results indicate that the expression cloning of cDNA libraries in NIH3T3 cells and subsequent screening for loss of contact inhibition in soft agar is a viable tool for identifying tumor-related genes and ribosomal protein L23 gene plays a role in cell movement and metastasis.

Comparative Studies on Detection of Antibodies against Infectious Bursal Disease Virus with Test Strips and Agar Gel Immunodiffusion Method

[Objective] This study aimed to compare the detection results of antibodies against infectious bursal disease virus with test strips and agar gel immunodiffusion method. [Method] Antibodies against infectious bursal disease virus in chicken serum were detected using test strips developed in our laboratory, and the results were comparad^with that using traditional agar diffusion method. [Result] The comparative study of the two methods showed that the sensitivity of test strips was eight times over agar gel immunodiffusion; test strips showed higher detection rate in the deter- mination test of 216 clinical samples, with high specificity, easy preservation, and simple and rapid operation, thereby being more suitable for the monitoring of clinical antibodies. [Conclusion] Test strips could replace the existing serological methods, having great promotion and application value in antibody monitoring.

CHROM agar培养基鉴定念珠菌的临床评价

目的:评价CHROM agar念珠菌培养基应用于临床标本念珠菌分离和鉴定的效果。方法:取500份临床患者的标本,分别接种至血琼脂、Sabouraud和CHROM agar念珠菌培养基,常规孵育,并进行VITEK-YBC法鉴定和药敏判断。结果:利用血琼脂、Sabouraud和CHROM agar念珠菌培养基各获得200、296和296株念珠菌,其特异性分别为67.6%、78.3%和100%。CHROM agar念珠菌培养基可对占94.26%的白色、热带、克柔和光滑念珠菌做出正确鉴定。结论:CHROM agar念珠菌培养基可用于临床标本念珠菌的初筛及快速做出病原学诊断,为抗念珠菌药物的选择提供依据。

新型产琼胶酶海洋细菌的筛选和鉴定

从大连沿海的50份石花菜中筛选出相对酶活较高的83株产琼胶酶菌株(酶活力测定采用3,5-二硝基水杨酸法),挑选琼胶酶活力最高的菌株并通过形态学特征、生理生化特征及16S r RNA基因序列分析研究其分类地位。结果表明,该菌株(暂命名为ZGR-26)为革兰氏阴性杆菌,与食琼胶弧菌(Vibrio agarivorans)序列同源性达到99%,两者生理生化特性基本相符,可初步确定为食琼胶弧菌(Vibrio agarivorans)。筛选得到了新型的产琼胶酶海洋细菌——食琼胶弧菌(Vibrio agarivorans),分泌琼胶酶活力较高(32.1 U/m L),为微生物降解法生产琼胶寡糖提供了新的出发菌株。

Resistance of Helicobacter pylori to antibiotics from 2000 to 2009 in Shanghai

AIM: To investigate the resistance of Helicobacter pylori (H. pylori ) to 6 commonly used antibiotics from 2000 to 2009 in Shanghai. METHODS: A total of 293 H. pylori strains were collected from 2000 to 2009 in Shanghai and tested for their susceptibility to metronidazole, clarithromycin, amoxicillin, furazolidone, levofloxacin and tetracycline using agar dilution. RESULTS: The resistant rates of H. pylori to clarithromycin (8.6%, 9.0% and 20.7%) and levofloxacin (10.3%, 24.0% and 32.5%) increased from 2000 to 2009 in Shanghai. The resistant rate of H. pylori to metronidazole remained stable (40%-50%). Only one strain of H. pylori isolated in 2005 was resistant to tetracycline. All strains were sensitive to amoxicillin and furazolidone.The resistant rate of H. pylori to antibiotics was not related with the sex, age and clinical outcome of patients. CONCLUSION: Resistance of H. pylori to antibiotics plays an important role in making treatment strategies against H. pylori -associated diseases.

Differentiation of murine male germ cells to spermatozoa n a soft agar culture system

Establishment of an in vitro system that allows the development of testicular germ cells to sperm will be valuable for studies of spermatogenesis and future treatments for male infertility. In the present study, we developed in vitro culture conditions using three-dimensional agar culture system （SACS）, which has the capacity to induce testicular germ cells to reach the final stages of spermatogenesis, including spermatozoa generation. Seminiferous tubules from testes of 7-day-old mice were enzymatically dissociated, and intratubular cells were cultured in the upper layer of the SACS in RPMI medium supplemented with fetal calf serum （FCS）. The lower layer of the SACS contained only RPMI medium supplemented with FCS. Colonies in the upper layer were isolated after 14 and 28 days of culture and were classified according to their size. Immunofluorescence and real-time PCR were used to analyse specific markers expressed in undifferentiated and differentiated spermatogonia （Vasa, Dazl, OCT-4, C-Kit, GFR- a-l, CD9 and a-6-integrin）, meiotic cells （LDH, Crem-1 and Boule） and post-meiotic cells （Protamine-1, Acrosin and SP-IO）. Our results reveal that it is possible to induce mouse testicular pre-meiotic germ cell expansion and induce their differentiation to spermatozoa in SACS. The spermatozoa showed normal morphology and contained acrosomes. Thus, our results demonstrate that SACS could be used as a novel in vitro system for the maturation of pre-meiotic mouse germ cells to post-meiotic stages and morphologically-normal spermatozoa.

Methods for in vitro evaluating antimicrobial activity： A review

In recent years, there has been a growing interest in researching and developing new antimicrobial agents from various sources to combat microbial resistance. Therefore, a greater attention has been paid to antimicrobial activity screening and evaluating methods. Several bioassays such as disk-diffusion, well diffusion and broth or agar dilution are well known and commonly used, but others such as flow cy- tofluorometric and bioluminescent methods are not widely used because they require specified equip- ment and further evaluation for reproducibility and standardization, even if they can provide rapid re- sults of the antimicrobial agent＇s effects and a better understanding of their impact on the viability and cell damage inflicted to the tested microorganism. In this review article, an exhaustive list of in vitro antimicrobial susceptibility testing methods and detailed information on their advantages and limita- tions are reported.

Antibacterial activities of selected medicinal plants in traditional treatment of human wounds in Ethiopia

Objective:To evaluate the activity of selected Ethiopian medicinal plants traditionally used for wound treatment against wound-causing bacteria.Methods:Samples of medicinal plants(Achyranthes aspera,Brucea antidysenteriea,Datura stramonium,Croton macrostachyus,Acokanthera xchimperi.,Phytolacca dodecandra,Milhttia ferruginea,and Solanum incanum)were extracted using absolute methanol and water and tested for their antimicrobial activities against clinical isolates and standard strains of wound-causing bacteria using agar well diffusion and micro titer plate methods.Results:Most of the plant extracts had antibacterial activities,among which Acokanthera schimperi and Brucea antidysenteriea inhibited growth of 100%and 35%of the test organisms,respectively.Methanolic extracts had higher activities compared with their corresponding aqueous extracts.The most susceptible organism to the extracts was Streptococcus pyogens while the most resistant were Escherichia coli and Proteus vulgaris.Conclusions:This finding justifies the use of the plants in wound healing and their potential activity against woundcausing bacteria.Their toxicity level and antimicrobial activity with different extraction solvents should further be studied to use them as sources and templates for the synthesis of drugs to control wound and other disease-causing bacteria.

Isolation and characterization of potential antibiotic producing actinomycetes from water and sediments of Lake Tana,Ethiopia

Objective:To isolate,evaluate and characterize potential antibiotic producing actinomycetes from water and sediments of Lake Tana,Ethiopia.Methods:A total of 31 strains of actinomycetes were isolated and tested against Gram positive and Gram negative bacterial strains by primary screening.In the primary screening.11 promising isolates were identified and subjected to solid state and submerged state fermentation methods to produce crude extracts.The fermented biomass was extracted by organic solvent extraction method and tested against bacterial strains by disc and agar well diffusion methods.The isolates were characterized by using morphological,physiological and biochemical methods.Results:The result obtained from agar well diffusion method was belter than disc diffusion method.The crude extract showed higher inhibition zone against Gram positive bacteria than Cram negative bacteria.One-way analysis of variance confirmed most of the crude extracts were statistically significant at 95%confidence interval.The minimum inhibitor)concentration and minimum bactericidal concentration of crude extracts were 1.65 mg/mL and 3.30 mg/mL against Staphylococcus aureus,and 1.84 mg/mL and 3.80 mg/mL against Escherichia coli respectively.The growth of aerial and substrate mycelium varied in different culture media used.Most of the isolates were able to hydrolysis starch and urea:able to survive at 5%concentration of sodium chloride:optimum temperature for their growth was 30°C.Conclusions:The results of the present study revealed that freshwater actinomycetes of Luke Tana appear to have immense potential as a source ol antibacterial compounds.

Biological activities of a neutral water-soluble agar polysaccharide prepared by agarase degradation

Depolymerization of agar was performed using agarase, which was extracted from the cell-free medium of a culture of marine bacterial Alterornonas sp. nov. SY 37-12. After ethanol fractionation and lyophilization, the water-soluble agar polysaccharide （WSAP3） was collected. The anti-tumor activity of the product was determined by using Sarcoma 180 tumor in mouse. The tumor inhibition rate of WSAP3 the product was determined by using Sarcoma 180 tumor in mouse. The tumor inhibition rate of WSAP3 reached 48.7% at a dose of 64mg kg^-1 after 15 days treatment. WSAP3 enhanced the aetivities of superoxide dismutase and catalase, which suggests that WSAP3 was effective in promoting the antioxidation ability and eliminating danger from free radicals. The result of flow cytometry showed that the WSAP3 had no activities of cell cycle inhibition or apoptosis-inducing activities. The anti-oxidation of WSAP3 was further confirmed by test in vitro, which might play an important role in anti-tumor activity. The immunological regulation of WSAP3, especially its effect on the phagocytosis ratio and phagocytosis index of rophage was also assayed in test in vivo.

Biochemical characters and antibiotic susceptibility of Staphylococcus aureus isolates

Objective:To observe the biochemical characters and antibiotic susceptibility of isolated Staphylococcia aureus(S.auerus) strains against some conventional and traditional antibiotics. Methods:Thirty post operative pathogenic isolated S.aureus strains were used in this study. Bacterial culture was done in Mueller-Hinton broth at 37 ℃.Characters of these strains were determined by traditional biochemical tests such as hydrolysis test of gelatin,urea,galactose, starch and protein,and fermentation of lactose and sucrose.Antibiotic susceptibility were carried out by minimum inhibilory concentration test,minium bactericidal concentration test,disc agar diffusion test and brain heart infusion oxacillin screening agar.Results:Prom this study,it was observed that 100%S.aureus isolates showed positive results in gelatin,urea and galactose hydrolysis test.50%isolates were positive in starch hydrolysis test,35%in protein hydrolysis test. 100%isolates in lactose fermenting test,but no isolate was positive in sucrose fermenting test. Antibiotic susceptibility testing suggested that 20%of isolates were resistant to kanamycin and 46.67%were resistant to oxacillin.Conclusions:These findings show that all these isolates have gelatin,urea,galactose hydrolysis and lactose fermenting activity.20%of these isolates were resistant to kanamvcin and 46.67%were resistant to oxacillin.

A Comparison of Different Gracilariopsis lemaneiformis(Rhodophyta) Parts in Biochemical Characteristics, Protoplast Formation and Regeneration

Gracilariopsis lemaneiformis is a commercially exploited alga. Its filaceous thallus can be divided into three parts, holdfast, middle segment and tip. The growth and branch forming trend and agar content of these three parts were analyzed, respectively, in this study. The results showed that the tip had the highest growth rate and branched most, although it was the last part with branch forming ability. The holdfast formed branches earliest but slowly. Holdfast had the highest agar content. We also assessed the difference in protoplast formation and regeneration among three parts. The middle segment displayed the shortest enzymolysis time and the highest protoplast yield; whereas the tip had the strongest vitality of protoplasts formation. Juvenile plants were only obtained from the protoplasts generated from the tip. These results suggested that the differentiation and function of G. lemaneiformis was different.

Study on extraction of agaropectin from Gelidium amansii and its anticoagulant activity

Gelidium amansii agar was fractionated on DEAE-cellulose and four fractions were obtained sequentially. The yields of 1.0 mol/L NaCl fraction and 2.5 mol/L NaCl fraction were 2.80% and 2.03%. They are highly sulfated agar, and named as agaropectin with sulfate content being 22.8% and 32.5%, respectively. The anticoagulant experiment results show that agaropectin could effectively prolong the coagulation time in a dose-dependent manner in vitro. Agaropection could be absorbed and effectively prolong the plasma coagulation time in vivo. After intragastric administration at the doses of 100, 200, and 400 mg/kg·d in rats for 15 days, TT (thrombin time), CT (coagulation time), PT (prothrombin time), and APTT (activated partial thromboplastin time) could be effectively prolonged and the plasma Fib level could be significantly lowered.

Production of microbial medium from defatted brebra(Milletia ferruginea)seed flour to substitute commercial peptone agar

Objective:To investigate and optimize microbial media that substitute peptone agar using brebra seed defatted flour.Methods:Defatted process.inoculums preparation,evaluation of bacterial growth,preparation of cooked and hydrolyzed media and growth turbidity of tested bacteria were determined.Results:Two percent defatted flour was found to be suitable concentration for the growth of pathogenic bacteria:Escherichia coli(ATCC 25922)(E,coli),Pseudomonas aeruginosa(ATCC27853),Salmonella(NCTC 8385)and Shigella flexneri(ATCC 12022)(S.flexneri),while 3%defatted flour was suitable for Staphylococcus aureus(ATCC 25923)(S.aureus).E.coli(93±1)and S.flexneri(524±1)colony count were significantly(P≤0.05)greater in defatted flour without supplement than in supplemented medium.E.coli[(3.72×10~9±2)CFU/mL],S.aureus[(7.4×10~9±2)CFU/mL],S.flexneri[(4.03×10~9±2)CFU/mL]and Salmonella[(2.37×10~9±1)CFU/mL]in non-hydrolyzed sample were statistically(P≤0.05)greater than hydrolyzed one and commercial peptone agar.Colony count of Salmonella[(4.55≤10~9±3)CFU/mL],S.flexneri[(5.40≤10~9±3)CFU/mL]and Lyesria moncytogenes(ATCC 19116)[(5.4×10~9±3)CFU/mL]on raw defatted flour agar was significantly(P≤0.05)greater than cooked defatted flour and commercial peptone agar.Biomass of E.coli,S.aureus.Salmonella and Enterococcus faecalis in non-hydrolyzed defatted flour is highly increased over hydrolyzed defatted flour and commercial peptone broth.Conclusions:The defatted flour agar was found to be better microbial media or comparable with peptone agar.The substances in it can serve as sources of carbon,nitrogen,vitamins and minerals that are essential to support the growth of microorganisms without any supplements.Currently,all supplements of peptone agar are very expensive in the market.