Screening bacterial metabolites for inhibitory effects against Batrachochytrium dendrobatidis using a spectrophotometric assay

Certain bacteria present on frog skin can prevent infection by the pathogenic fungus Batrachochytrium dendrobatidis (Bd), conferring disease resistance. Previous studies have used agar-based in vitro challenge assays to screen bacteria for Bd-inhibitory activity and to identify candidates for bacterial supplementation trials. However, agar-based assays can be difficult to set up and to replicate reliably. To overcome these difficulties, we developed a semi-quantitative spectrophotometric challenge assay technique. Cell-free supernatants were prepared from filtered bacterial cultures and added to 96-well plates in replicated wells containing Bd zoospores suspended in tryptone-gelatin hydrolysate-lactose (TGhL) broth medium. Plates were then read daily on a spectrophotometer until positive controls reached maximum growth in order to determine growth curves for Bd. We tested the technique by screening skin bacteria from the Australian green-eyed tree frog Litoria serrata. Of bacteria tested, 31% showed some degree of Bd inhibition, while some may have promoted Bd growth, a previously unknown effect. Our cell-free supernatant challenge assay technique is an effective in vitro method for screening bacterial isolates for strong Bd-inhibitory activity. It contributes to the expanding field of bioaugmentation research, which could play a significant role in mitigating the effects of chytridiomycosis on amphibians around the world.

The use of a rapid assay to detect the neuraminidase production in oral Porphyromonas spp. isolated from dogs and humans

Neuraminidase was produced by 32.1% and 28.5% of Porphyromonas from dogs with and without periodontitis, respectively; and by 31.8% of bacteria from humans. The presence of neuraminidase in Porphyromonas spp. suggests that this enzyme can be involved with the pathogenesis of the periodontal disease, and the use of this assay to detect the neuraminidase production in oral Porphyromonas species is suggested.

Rapid screening of potential autophagic inductor agents using mammalian cell lines

Recent progress in understanding the molecular basis of autophagy has demonstrated its importance in several areas of human health. Affordable screening techniques with higher sensitivity and specificity to identify autophagy are, however, needed to move the field forward. In fact, only laborious and/or expensive methodologies such as electron microscopy, dye-staining of autophagic vesicles, and LC3-II immunoblotting or immunoassaying are available for autophagy identification. Aiming to fulfill this technical gap, we describe here the association of three widely used assays to determine cell viability - Crystal Violet staining (CVS), 3-[4, 5-dimethylthiaolyl]-2, 5-diphenyl-tetrazolium bromide (MTT) reduction, and neutral red uptake (NRU) - to predict autophagic cell death in vitro. The conceptual framework of the method is the superior uptake of NR in cells engaging in autophagy. NRU was then weighted by the average of MTT reduction and CVS allowing the calculation of autophagic arbitrary units (AAU), a numeric variable that correlated specifically with the autophagic cell death. The proposed strategy is very useful for drug discovery, allowing the investigation of potential autophagic inductor agents through a rapid screening using mammalian cell lines B16-F10, HaCaT, HeLa, MES-SA, and MES-SA/Dx5 in a unique single microplate.

A quantitative TaqMan PCR assay for the detection of Ureaplasma diversum

Ureaplasma diversum in veterinary studies is an undesirable microbe, which may cause infection in bulls and may result in seminal vesiculitis, balanopostitis, and alterations in spermatozoids, whereas in cows, it may cause placentitis, fetal alveolitis, abortion, and birth of weak calves. U. diversum is released through organic secretions, especially semen, preputial and vaginal mucus, conjunctival secretion, and milk. The aim of the present study was to develop a TaqMan probe, highly sensitive and specific quantitative PCR (qPCR) assay for the detection and quantification of U. diversum from genital swabs of bovines. Primers and probes specific to U. diversum 16S rRNA gene were designed. The specificity, detection limit, intra- and inter-assay variability of qPCR to detect this ureaplasma was compared with the results of the conventional PCR assay (cPCR). Swabs of vaginal mucus from 169 cows were tested. The qPCR assay detected as few as 10 copies of U. diversum and was 100-fold more sensitive than the cPCR. No cross-reactivity with other Mollicutes or eubacteria was observed. U. diversum was detected in 79 swabs (46.42%) by qPCR, while using cPCR it was detected in 42 (25%) samples. The difference in cPCR and qPCR ureaplasma detection between healthy and sick animals was not statistically significant. But the U. diversum load in samples from animals with genital disorders was higher than in healthy animals. The qPCR assay developed herein is highly sensitive and specific for the detection and quantification of U. diversum in vaginal bovine samples.

Comparison of flow cytometry and indirect immunofluorescence assay in the diagnosis and cure criterion after therapy of American tegumentary leishmaniasis by anti-live Leishmania (Viannia) braziliensis immunoglobulin G

The aim of this study was to compare the techniques of indirect immunofluorescence assay (IFA) and flow cytometry to clinical and laboratorial evaluation of patients before and after clinical cure and to evaluate the applicability of flow cytometry in post-therapeutic monitoring of patients with American tegumentary leishmaniasis (ATL). Sera from 14 patients before treatment (BT), 13 patients 1 year after treatment (AT), 10 patients 2 and 5 years AT were evaluated. The results from flow cytometry were expressed as levels of IgG reactivity, based on the percentage of positive fluorescent parasites (PPFP). The 1:256 sample dilution allowed us to differentiate individuals BT and AT. Comparative analysis of IFA and flow cytometry by ROC (receiver operating characteristic curve) showed, respectively, AUC (area under curve) = 0.8 (95% CI = 0.64–0.89) and AUC = 0.90 (95% CI = 0.75–0.95), demonstrating that the flow cytometry had equivalent accuracy. Our data demonstrated that 20% was the best cut-off point identified by the ROC curve for the flow cytometry assay. This test showed a sensitivity of 86% and specificity of 77% while the IFA had a sensitivity of 78% and specificity of 85%. The after-treatment screening, through comparative analysis of the technique performance indexes, 1, 2 and 5 years AT, showed an equal performance of the flow cytometry compared with the IFA. However, flow cytometry shows to be a better diagnostic alternative when applied to the study of ATL in the cure criterion. The information obtained in this work opens perspectives to monitor cure after treatment of ATL.

In vivo photothermal tumour ablation using gold nanorods

Less invasive and more effective cancer treatments have been the aim of research in recent decades, e.g. photothermal tumour ablation using gold nanorods. In this study we investigate the cell death pathways activated, and confirm the possibility of CTAB-coated nanoparticle use in vivo. Nanorods were synthesized by the seeding method; some of them were centrifuged and washed to eliminate soluble CTAB. The MTT cytotoxicity test was performed to evaluate cytotoxicity, and the particles' viability after their synthesis was assessed. Once it had been observed that centrifuged and washed nanorods are harmless, and that nanoparticles must be used within 48 h after their synthesis, in vivo hyperthermic treatment was performed.After irradiation, a tumour biopsy was subjected to a chemiluminescence assay to evaluate membrane lipoperoxidation, and to a TRAP assay to evaluate total antioxidant capacity. There was a 47 ºC rise in temperature observed at the tumour site. Animals irradiated with a laser (with or without nanorods) showed similar membrane lipoperoxidation, more intense than in control animals. The antioxidant capacity of experimental animal tumours was elevated. Our results indicate that necrosis is possibly the cell death pathway activated in this case, and that nanorod treatment is worthwhile.