In vitro biofilm forming potential of Streptococcus suis isolated from human and swine in China

Streptococcus suis is a swine pathogen and also a zoonotic agent. The formation of biofilms allows S. suis to become persistent colonizers and resist clearance by the host immune system and antibiotics. In this study, biofilm forming potentials of various S. suis strains were characterized by confocal laser scanning microscopy (CLSM), scanning electron microscopy (SEM) and tissue culture plates stained with crystal violet. In addition, the effects of five antimicrobial agents on biofilm formation were assayed in this study. S. suis produced biofilms on smooth and rough surface. The nutritional contents including glucose and NaCl in the growth medium modulated biofilm formation. There was a significant difference in their biofilm-forming ability among all 46 S. suis strains. The biofilm-forming potential of S. suis serotype 9 was stronger than type 2 and all other types. However, biofilm formation was inhibited by five commonly used antimicrobial agents, penicillin, erythromycin, azithromycin, ciprofloxacin, and ofloxacin at subinhibitory concentrations, among which inhibition of ciprofloxacin and ofloxacin was stronger than that of other three antimicrobial agents.Our study provides a detailed analysis of biofilm formation potential in S. suis, which is a step towards understanding its role in pathogenesis, and eventually lead to a better understanding of how to eradicate S. suis growing as biofilms with antibiotic therapy.

Acetylcholinesterase inhibition by somes promising Brazilian medicinal plants / Plantas medicinais brasileiras promissoras para inibição da acetilcolinesterase

A microplate assay and a thin-layer chromatography (TLC) "in situ" assay based on the Ellman assay was used to screen for acetylcholinesterase inhibitors from ethyl acetate and methanol extracts of Brazilian medicinal plants of families that, according to the literature, have traditional uses that might be connected with acetylcholinesterase inhibition. Eighteen species belonging to Convolvulaceae, Crassulaceae, Euphorbiaceae, Leguminosae, Malvaceae, Moraceae, Nyctaginaceae and Rutaceae families were tested. The most active plants were Ipomoea asarifolia (IC50 = 0.12 mg/mL), Jatropha curcas (IC50 = 0.25 mg/mL), Jatropha gossypiifolia (IC50 = 0.05 mg/mL), Kalanchoe brasiliensis (IC50 = 0.16 mg/mL) and Senna alata (IC50 = 0.08 mg/mL). The most promising extracts were the Jatropha gossypiifolia and Senna alata species assuming there were compounds with a similar activity to galanthamine, which should contain about 1 percent of an active compound, or if present at lower levels even more active compounds than galanthamine (IC50 = 0.37 x 10-3 mg/mL) should be present.

Os ensaios de microplaca e cromatografia em camada delgada com base no ensaio de Ellman foram usados para triagem de inibidores da acetilcolinesterase dos extratos acetato de etila e metanol de plantas medicinais brasileiras de famílias que, segundo a literatura, tem usos tradicionais que podem estar relacionadas com a inibição da acetilcolinesterase, enzima associada ao mal de Alzheimer. Dezoito plantas das famílias: Convolvulaceae, Crassulaceae, Euphorbiaceae, Leguminosae, Malvaceae, Moraceae, Nyctaginaceae e Rutaceae foram testadas. As espécies mais ativas foram Ipomoea asarifolia (CI₅₀ = 0,12 mg/mL), Jatropha curcas (CI₅₀ = 0,25 mg/mL), Jatropha gossypiifolia (CI₅₀ = 0,05 mg/mL), Kalanchoe brasiliensis (CI₅₀ = 0,16 mg/mL) e Senna alata (CI₅₀ = 0,08 mg/mL). Os extratos mais promissores foram os das espécies Jatropha gossypiifolia e Senna alata, assumindo a presença de compostos com atividade semelhante à galantamina que deve conter cerca de 1 por cento de um composto ativo, ou se presentes em menores níveis ainda mais compostos ativos que a galantamina (CI₅₀ = 0,37 x10^–3 mg/mL) devem estar presentes.

A microplate-based screening method for alpha-glucosidase inhibitors / 中国临床药理学与治疗学

AIM: To establish a new sensitive microplate-based method to determine alpha-glucosidase inhibiting activity and provide a reliable high-throughput way for screening alpha-glucosidase inhibitors in vitro.METHODS: The fitting combination of enzyme and substrate in a certain reaction was tested.Acarbose,the most popular alpha-glucosidase inhibitor in clinical use was used to validate the established method.Calibration curve,wavelength fidelity and kinetic analysis,together with the effect of altered incubation time,temperature and pH were then studied.RESULTS:The details of assay procedure and evaluation of factors affecting the measurement are described.As little as 160 μl assay system was performed in a 96-well plate.The optimal action was finally achieved by incubated at 37 ℃,pH 7.0 for 15 min and measured at 400 nm.Results from the validation exercises by Acarbose strongly demonstrated the accuracy and reliability of the proposed approach.CONCLUSION: This method reported in the current paper makes it possible to rapidly examine large numbers of samples for the presence of alpha-glucosidase inhibitors in very small sample volumes.Such action may help to pace the development of potential oral medications from natural products protecting patients against postprandial hyperglycemic toxicity and therefore treating diabetes mellitus and the related complications.

Microplate assay of elevated esterase activity in individual pyrethroid-resistant mosquitoes.

Involvement of esterase-mediated hydrolysis as a mechanism of pyrethroidresistance in three species of mosquitoes, viz., Aedes aegypti, Culex quinquefasciatus and Anopheles Stephensi was investigated by microplate assay of β-esterases in individual larva and adult female and male mosquitoes. Assuming an absorbance value of 0·4 and above at 555 nm as the threshold level of elevated esterase activity which confers resistance, frequency distributions of such individual test mosquitoes were constructed in resistant and susceptible populations. The results indicate the involvement of ester hydrolysis of Pyrethroids as a predominant mechanism of pyrethroid-resistance in the larvae of Culex quinquefasciatus but not in Aedes aegypti. However, a marginal role of esterases is indicated in the larvae of Anopheles stephensi.