Gamma-delta T cells suppress microbial metabolites that activate striatal neurons and induce repetitive/compulsive behavior in mice.

Intestinal γδ T cells play an important role in shaping the gut microbiota, which is critical not only for maintaining intestinal homeostasis but also for controlling brain function and behavior. Here, we found that mice deficient for γδ T cells (γδ-/-) developed an abnormal pattern of repetitive/compulsive (R/C) behavior, which was dependent on the gut microbiota. Colonization of WT mice with γδ-/- microbiota induced R/C behavior whereas colonization of γδ-/- mice with WT microbiota abolished the R/C behavior. Moreover, γδ-/- mice had elevated levels of the microbial metabolite 3-phenylpropanoic acid in their cecum, which is a precursor to hippurate (HIP), a metabolite we found to be elevated in the CSF. HIP reaches the striatum and activates dopamine type 1 (D1R)-expressing neurons, leading to R/C behavior. Altogether, these data suggest that intestinal γδ T cells shape the gut microbiota and their metabolites and prevent dysfunctions of the striatum associated with behavior modulation.

Potential for bifenthrin removal using microalgae from a natural source.

The accumulation of environmental pesticides can cause problems in aquatic ecosystems and adverse effects in humans. These compounds can be found in water due to runoff from agricultural, industrial and domestic applications. In Southern Brazil, tobacco cultivation is one of the most important economic agricultural activities. The bifenthrin pesticide, classified as having moderate toxicity (class II), is commonly used as an insecticide in this culture. In this context, the present research aimed to study the performance of microalgae-induced bioremediation processes. Microalgae were isolated from a natural water source in the city of Santa Cruz do Sul, RS, Brazil, which is an artificial reservoir used for public water supply. For this purpose, biodegradation, biosorption, influence of pH, percentage of inoculum and photoperiod were evaluated in batch experiments for 20 cultivation days. After the phycoremediation process, the bifenthrin pesticide (m/z = 181) was quantified by gas chromatography with mass spectrometry (GC-MS). The results indicated that microalgae isolated from the water of the lake were able to contribute to the removal of approximately 99% of bifenthrin through biodegradation and biosorption processes. Photodegradation was identified (>77%) and the best condition for the phycoremediation was 20% inoculum with a photoperiod of 18:6 h.

Assessment of short-term outcome with TiO2 mesh in laparoscopic repair of large paraesophageal hiatal hernias.

BACKGROUND: Laparoscopic large para-oesophageal hiatal hernia (LPHH) repair using mesh reinforcement significantly reduces postoperative recurrence rates compared to conventional suture repair, especially within short follow-up times. However, the ideal strategy for repairing LPHH remains disputable because no clear guidelines are given regarding indications, mesh type, shape or position. The aim of this study was to survey our short-term results of LPHH management with a biosynthetic monofilament polypropylene mesh coated with titanium dioxide to enhance biocompatibility (TiO2Mesh™). METHODS: A retrospective study was performed at Ramon y Cajal University Hospital, Spain from December 2014 to October 2018. Data were collected on 27 consecutive patients with extensive hiatal hernia defects greater than 5 cm for which a laparoscopic repair was performed by primary suture and additional reinforcement with a TiO2Mesh™. Study outcomes were investigated, including clinical and radiological recurrences, dysphagia and mesh-related drawbacks. RESULTS: Twenty-seven patients were included in our analysis; 10 patients were male, and 17 were female. The mean age was 73 years (range, 63-79 years). All operations were performed laparoscopically. The median postoperative hospital stay was 3 days. After a mean follow-up of 18 months (range, 8-29 months), only 3 patients developed clinical recurrence of reflux symptoms (11%), and 2 had radiological recurrences (7%). No mesh-related complications occurred. CONCLUSIONS: TiO2Mesh™ was found to be safe for laparoscopic repair of LPHH with a fairly low recurrence rate in this short-term study. Long-term studies conducted over a period of years with large sample sizes will be essential for confirming whether this mesh is suitable as a standard method of care with few drawbacks.

Methodology proposed for photogrammetric monitoring of the exotic species Hovenia dulcis Thunb. in the Green Belt area surrounding the city of Santa Cruz do Sul, RS, Brazil.

The spread of the exotic species Hovenia dulcis known as Japanese raisin tree, coming from Asia, detected in a protected area of 465.0 ha surrounding the city of Santa Cruz do Sul, RS, Brazil, named "Green Belt." In this context, this research aimed at developing an aerial monitoring system able to identify and quantify the extension in the Green Belt area that this species invaded, as well as describing the impacts caused on the local forest community. We collected data from an ultralight Flyer GT aircraft equipped with a vertical camera. The images were taking in June and July 2015, when H. dulcis trees have shed their leaves, displaying a gray color, and September and October 2015, when the leaves are young and with a light green color. Based on the methodology proposed trough aerial monitoring by photogrammetry, the results indicated that the total invaded area by H. dulcis in the Green Belt of Santa Cruz do Sul County, RS, was 131.8 ha, corresponding to 20.9% of the total area. To validate this method, a quantitative comparison between the result from a terrestrial fieldwork carried out and the proposed method showed no significant differences in the estimated area occupied by H. dulcis. We concluded that these results validate the proposed aerial assessment method.

The long-term recurrence rate and survival of obstructive left-sided colon cancer patients: a stent as a bridge to surgery.

BACKGROUND: a colonic stent as a bridge to elective surgery for left-sided malignant colonic obstruction is an alternative to the classical treatment. The aim of our study was to evaluate the recurrence rate as well as the morbidity and mortality of this treatment. PATIENTS AND METHODS: patients admitted to the Emergency Department with left-sided malignant colonic obstruction between June 2006 and January 2014 were analyzed in a retrospective observational study. Patients who underwent self-expanding metallic stent placement via endoscopy as a bridge to surgery were included. The observation period was performed until May 2017. RESULTS: fifty-three patients were treated with a colonic stent as a bridge to surgery; nine patients died during the postoperative period. The deceased patients were more frequently male (100% in the deceased vs 62% in the non-deceased, p = 0.02), with a more advanced age (81.4 ± 5.1 vs 71.6 ± 10.8, p < 0.001), lower hemoglobin levels on admission (12.9 vs 13.6 p < 0.001), a greater number of leukocytes (12,918 vs 9,437, p < 0.001) and greater coagulopathy (INR 1.6 vs 1, p < 0.001). Eight patients had a distant relapse with a median disease-free survival of 19.1 months. The variables were compared according to the appearance of distant disease and the mean age was lower in patients with a recurrence (65.9 ± 11.3 vs 74.9 ± 9.9, p < 0.001). CONCLUSIONS: the results of the use of a stent as a bridge to curative surgery in patients with obstructive left colon cancer in our hospital is comparable to previous studies.

Comparative study between open and minimally invasive approach in the surgical management of esophageal leiomyoma.

INTRODUCTION: Leiomyomas are the most common benign tumors of the esophagus. Although classically surgical enucleation through thoracotomy or laparotomy has been widely accepted as treatment of choice, development of endoscopic and minimally invasive procedures has completely changed the surgical management of these tumors. MATERIAL AND METHODS: We performed a retrospective review of all esophageal leiomyoma operated at Hospital Universitario Ramón y Cajal (Madrid, Spain) between January 1986 and December 2014, analyzing patients' demographic data, symptomatology, tumor size and location, diagnostic tests, surgical data, complications and postoperative stay. RESULTS: Thirteen patients were found within that period, 8 men and 5 women, with a mean age of 53.62 years (range 35-70 years). Surgical enucleation was achieved in all patients. In 8 cases (61.54%) a thoracic approach was performed (4 thoracotomies and 4 thoracoscopies), and in 5 cases (38.56%) an abdominal approach was performed (3 laparotomies and 2 laparoscopies); enucleation was carried out through a minimally invasive approach in 6 patients (46.15%). There were no cases of endoscopic resection alone. Surgery mean length was 174.38 minutes (range 70-270 minutes) and median postoperative stay was 6.5 days (range 2-27 days). There was neither mortality nor cases of intraoperative complications were described. No postoperative major complications were reported; however one patient presented important pain in his right hemithorax that required management and long term follow-up by the Pain Management Unit. With a mean follow-up of 165.57 months (median 170; range 29-336 months) no recurrences were reported. CONCLUSION: Enucleation is the treatment of choice for the majority of esophageal leiomyomas. In our experience, duration of the surgical procedure through minimally invasive approach was longer than surgery through open approach; however, postoperative stay was shorter in the first group. Paradoxically, incision pain after surgery (thoracic neuralgia) was found to be higher in the minimally invasive approach group. Nevertheless, none of the results obtained in the study reached statistical significance, probably due to the small simple size.

Duodenal fistula after gastrectomy: Retrospective study of 13 new cases.

INTRODUCTION: Duodenal stump fistula (DSF) after gastrectomy has a low incidence but a high morbidity and mortality, and is therefore one of the most aggressive and feared complications of this procedure. MATERIAL AND METHODS: We retrospectively evaluated all DSF occurred at our hospital after carrying out a gastrectomy for gastric cancer, between January 1997 and December 2014. We analyzed demographic, oncologic, and surgical variables, and the evolution in terms of morbidity, mortality and hospital stay. RESULTS: In the period covered in this study, we performed 666 gastrectomies and observed DSF in 13 patients (1.95%). In 8 of the 13 patients (61.5%) surgery was the treatment of choice and in 5 cases (38.5%) conservative treatment was carried out. Postoperative mortality associated with DSF was 46.2% (6 cases). In the surgical group, 3 patients developed severe sepsis with multiple organ failure, 2 patients presented a major hematemesis which required endoscopic haemostasis, 1 patient had an evisceration and another presented a subphrenic abscess requiring percutaneous drainage. Six patients (75%) died despite surgery, with 3 deaths in the first 24 hours of postoperative care. The 2 patients who survived after the second surgical procedure had a hospital stay of 45 and 84 days respectively. In the conservative treatment group the cure rate was 100% with no significant complications and an average postoperative hospital stay of 39.5 days (range, 26-65 days). CONCLUSION: FMD is an unusual complication but it is associated with a high morbidity and mortality. In our experience, conservative management has shown better results compared with surgical treatment.

Circulating tumor cells (Ctc) and kras mutant circulating free Dna (cfdna) detection in peripheral blood as biomarkers in patients diagnosed with exocrine pancreatic cancer.

BACKGROUND: Pancreatic cancer remains one of the most difficult cancers to treat with the poorest prognosis. The key to improving survival rates in this disease is early detection and monitoring of disseminated and residual disease. However, this is hindered due to lack reliable diagnostic and predictive markers which mean that the majority of patients succumb to their condition within a few months. METHODS: We present a pilot study of the detection circulating free DNA (cfDNA) combined with tumor specific mutation detection by digital PCR as a novel minimally invasive biomarker in pancreatic ductal adenocarcinoma (PDAC). This was compared to the detection of CTC by the CellSearch® system and a novel CTC enrichment strategy based on CD45 positive cell depletion. The aim of the study was to assess tumor specific DNA detection in plasma and CTC detection as prognostic markers in PDAC. RESULTS: We detected KRAS mutant cfDNA in 26% of patients of all stages and this correlated strongly with Overall Survival (OS), 60 days (95% CI: 19-317) for KRAS mutation positive vs 772 days for KRAS mutation negative (95% CI: 416-1127). Although, the presence of CTC detected by the CellSearch® system did correlate significantly with OS, 88 days (95% CI: 27-206) CTC positive vs 393 days CTC negative (95% CI: 284-501), CTC were detected in only 20% of patients, the majority of which had metastatic disease, whereas KRAS mutant cfDNA was detected in patients with both resectable and advanced disease. CONCLUSIONS: Tumor specific cfDNA detection and CTC detection are promising markers for the management of patients with PDAC, although there is a need to validate these results in a larger patient cohort and optimize the detection of CTC in PDAC by applying the appropriate markers for their detection.

Spatial Response of Epilithic Diatom Communities to Downstream Nutrient Increases.

To monitor water quality and investigate relationships between downstream nutrient increases and diatom communities in the Pardo River Basin, Brazil, water and diatom samples were collected between 2005 and 2009. There were significant differences in diatom community composition among all river zones, with the greatest differences found between the upper and lower reaches. Significant changes were detected in relative abundances of diatom species and spatial structuring was evident. Dissolved oxygen, phosphates, turbidity, Eicherichia coli, and total dissolved solids were the most important variables shaping diatom communities, characterizing an organic pollution and eutrophication gradient. However, the hypothesis of sensitive species prevailing upstream and their gradual downstream replacement for more tolerant species was not confirmed because shifts in relative abundances of the same group of species in both the upper and lower reaches of the rivers were identified.

Development of the Trophic Water Quality Index (TWQI) for subtropical temperate Brazilian lotic systems.

This research aimed at developing the Trophic Water Quality Index (TWQI) for subtropical temperate Brazilian lotic systems based on a review of the indicative values of diatom species obtained using multivariate analysis techniques and considering the environmental gradient defined by a series of measured physical, chemical, and microbiological variables. Sampling was conducted from 2005 to 2009 in the Pardo River Hydrographic Basin, Rio Grande do Sul (RS), Brazil, and in the Andreas Stream Hydrographic Basin, RS, from 2012 to 2013. A total of 140 biological samples and 211 abiotic samples were collected. Data were analyzed by cluster analysis based on the Ward method and canonical correspondence analysis (CCA). The results indicated that total phosphate, turbidity, ammonia nitrogen, electrical conductivity, dissolved oxygen, and thermotolerant coliforms showed a significant correlation with the sample ordination made by CCA, in relation to a gradient of eutrophication. Eutrophication was operationally defined in a broad sense, including the problem of organic pollution and eutrophication of the water. The determination of the different tolerance degrees to eutrophication of the diatom taxa was used to assign trophic values of 1, 2.5, and 4 to species, corresponding to levels of low, medium, and high tolerance, respectively. By using the trophic values obtained for each diatom species, the TWQI constituted a new technological tool for environmental monitoring studies and showed a consistent, robust, and objective database for water quality assessment in subtropical temperate Brazilian lotic systems.

Cultivation of Desmodesmus subspicatus in a tubular photobioreactor for bioremediation and microalgae oil production.

The microalgae Desmodesmus subspicatus (Chlorophyta) was cultivated in a tubular photobioreactor using effluent from the wastewater treatment plant of the University of Santa Cruz do Sul, Brazil to demonstrate the reactor's operation. The algae's ability to remove nutrients from wastewater and the oleaginous potential of the algae's biomass were also evaluated. Total phosphorus and ammonia nitrogen were measured. The photobioreactor consisted of a system of three acrylic tubes, a reservoir, connections and a CO2 supply. The gas supply was semicontinuous with CO2 added from a cylinder. The culture's growth was estimated from cell numbers counted on a daily basis. Lipid content in the biomass was analysed using gas chromatography. A maximum cell density of 9.11 x 10(6) cellsmL-1 and a dry weight of 234.00 mg L-1 were obtained during cultivation without CO2, and these values rose to 42.48 x 10(6) cells mL-1 and 1277.44 mg L-1, respectively, when CO2 was added to the cultivation. Differences in the quality of the effluent and the presence of CO2 did not result in different lipid profiles. The presence ofpalmitic acid and oleic acid was notable. The average extracted oil content was 18% and 12% for cultivation with and without the input of CO2, respectively.

The best linear unbiased prediction (BLUP) method as a tool to estimate the lifetime risk of pancreatic ductal adenocarcinoma in high-risk individuals with no known pathogenic germline variants.

Pancreatic ductal adenocarcinoma (PDAC) is the fourth leading cause of cancer-related death in the Western world. The number of diagnosed cases and the mortality rate are almost equal as the majority of patients present with advanced disease at diagnosis. Between 4 and 10% of pancreatic cancer cases have an apparent hereditary background, known as hereditary pancreatic cancer (HPC) and familial pancreatic cancer (FPC), when the genetic basis is unknown. Surveillance of high-risk individuals (HRI) from these families by imaging aims to detect PDAC at an early stage to improve prognosis. However, the genetic basis is unknown in the majority of HRIs, with only around 10-13% of families carrying known pathogenic germline mutations. The aim of this study was to assess an individual's genetic cancer risk based on sex and personal and family history of cancer. The Best Linear Unbiased Prediction (BLUP) methodology was used to estimate an individual's predicted risk of developing cancer during their lifetime. The model uses different demographic factors in order to estimate heritability. A reliable estimation of heritability for pancreatic cancer of 0.27 on the liability scale, and 0.07 at the observed data scale as obtained, which is different from zero, indicating a polygenic inheritance pattern of PDAC. BLUP was able to correctly discriminate PDAC cases from healthy individuals and those with other cancer types. Thus, providing an additional tool to assess PDAC risk HRI with an assumed genetic predisposition in the absence of known pathogenic germline mutations.

The Spanish Familial Pancreatic Cancer Registry (PANGENFAM): a decade follow-up of individuals at high-risk for pancreatic cancer.

The Spanish Familial Pancreatic Cancer Registry (PANGENFAM) was established in 2009 and aims to characterize the genotype and phenotype of familial pancreatic cancer (FPC). Furthermore, an early detection screening program for pancreatic ductal adenocarcinoma (PDAC) is provided to healthy high-risk individuals from FPC and hereditary pancreatic cancer families (first-degree relatives). This article describes our experience over the last 10 years in high-risk screening. Hereditary and familial pancreatic cancer families were identified through the oncology and gastroenterology units. High-risk individuals underwent annual screening with endoscopic ultrasound (EUS) and magnetic resonance (MRI) from age 40 or 10 years younger than the youngest affected family member. Results: PANGENFAM has enrolled 290 individuals from 143 families, including 52 PDAC cases and 238 high-risk individuals. All high-risk individuals eligible for screening were offered to enter the surveillance program, with 143 currently participating. Pancreatic abnormalities were detected in 94 individuals (median age 53 years (29-83), with common findings including cystic lesions and inhomogeneous parenchyma. Imaging test concordance was 66%. Surgical intervention was performed in 4 high-risk individuals following highly suspicious lesions detected by imaging. PANGENFAM is a valuable resource for science innovation, such as biobanking, with clinical and imaging data available for analysis. For high-risk families, it may offer a potential for early diagnosis. Collaboration with other national and international registries is needed to increase our understanding of the disease biology and to standardize criteria for inclusion and follow-up, optimizing cost-effectiveness and efficacy.

Dietary protein modulates intestinal dendritic cells to establish mucosal homeostasis.

Dietary proteins are taken up by intestinal dendritic cells (DCs), cleaved into peptides, loaded to major histocompatibility complexes, and presented to T cells to generate an immune response. Amino acid (AA)-diets do not have the same effects because AAs cannot bind to major histocompatibility complex to activate T cells. Here, we show that impairment in regulatory T cell generation and loss of tolerance in mice fed a diet lacking whole protein is associated with major transcriptional changes in intestinal DCs including downregulation of genes related to DC maturation, activation and decreased gene expression of immune checkpoint molecules. Moreover, the AA-diet had a profound effect on microbiome composition, including an increase in Akkermansia muciniphilia and Oscillibacter and a decrease in Lactococcus lactis and Bifidobacterium. Although microbiome transfer experiments showed that AA-driven microbiome modulates intestinal DC gene expression, most of the unique transcriptional change in DC was linked to the absence of whole protein in the diet. Our findings highlight the importance of dietary proteins for intestinal DC function and mucosal tolerance.

Gamma-delta T cells modulate the microbiota and fecal micro-RNAs to maintain mucosal tolerance.

BACKGROUND: Gamma-delta (γδ) T cells are a major cell population in the intestinal mucosa and are key mediators of mucosal tolerance and microbiota composition. Little is known about the mechanisms by which intestinal γδ T cells interact with the gut microbiota to maintain tolerance. RESULTS: We found that antibiotic treatment impaired oral tolerance and depleted intestinal γδ T cells, suggesting that the gut microbiota is necessary to maintain γδ T cells. We also found that mice deficient for γδ T cells (γδ-/-) had an altered microbiota composition that led to small intestine (SI) immune dysregulation and impaired tolerance. Accordingly, colonizing WT mice with γδ-/- microbiota resulted in SI immune dysregulation and loss of tolerance whereas colonizing γδ-/- mice with WT microbiota normalized mucosal immune responses and restored mucosal tolerance. Moreover, we found that SI γδ T cells shaped the gut microbiota and regulated intestinal homeostasis by secreting the fecal micro-RNA let-7f. Importantly, oral administration of let-7f to γδ-/- mice rescued mucosal tolerance by promoting the growth of the γδ-/--microbiota-depleted microbe Ruminococcus gnavus. CONCLUSIONS: Taken together, we demonstrate that γδ T cell-selected microbiota is necessary and sufficient to promote mucosal tolerance, is mediated in part by γδ T cell secretion of fecal micro-RNAs, and is mechanistically linked to restoration of mucosal immune responses. Video Abstract.

Establishment of Pancreatic Cancer-Derived Tumor Organoids and Fibroblasts From Fresh Tissue.

Tumor organoids are three-dimensional (3D) ex vivo tumor models that recapitulate the biological key features of the original primary tumor tissues. Patient-derived tumor organoids have been used in translational cancer research and can be applied to assess treatment sensitivity and resistance, cell-cell interactions, and tumor cell interactions with the tumor microenvironment. Tumor organoids are complex culture systems that require advanced cell culture techniques and culture media with specific growth factor cocktails and a biological basement membrane that mimics the extracellular environment. The ability to establish primary tumor cultures highly depends on the tissue of origin, the cellularity, and the clinical features of the tumor, such as the tumor grade. Furthermore, tissue sample collection, material quality and quantity, as well as correct biobanking and storage are crucial elements of this procedure. The technical capabilities of the laboratory are also crucial factors to consider. Here, we report a validated SOP/protocol that is technically and economically feasible for the culture of ex vivo tumor organoids from fresh tissue samples of pancreatic adenocarcinoma origin, either from fresh primary resected patient donor tissue or patient-derived xenografts (PDX). The technique described herein can be performed in laboratories with basic tissue culture and mouse facilities and is tailored for wide application in the translational oncology field.

[Perioperative management of Parkinson's disease]. / Manejo perioperatorio de la enfermedad de Parkinson.

One of the particular characteristics of Parkinson's disease (PD) is the wide clinical variation as regards the treatment that can be found in the same patient. This occurs with specific treatment for PD, as well as with other drug groups that can make motor function worse. For this reason, the perioperative management of PD requires experience and above all appropriate planning. In this article, the peculiarities of PD and its treatment are reviewed, and a strategy is set out for the perioperative management of these patients.

Anterograde intraoperative pancreatic stent placement and round ligament patch to prevent pancreatic fistula after distal pancreatectomy. / Colocación intraoperatoria anterógrada de stent pancreático y plastia de ligamento redondo para prevenir la fístula pancreática tras la pancreatectomía distal.

Postoperative pancreatic fistula in distal pancreatectomy is one of the most important complications in this surgery and it is associated with high morbidity and mortality. Pancreatic fistula after distal pancreatectomy remains an unsolved problem and none preventive procedure has been shown effectively. We present a new technique that combine pancreatic stent placement with round ligament autologous patch over pancreatic edge. A guide is introduced through Wirsung duct prior to stent placement. After stent assessment, Wirsung duct is closed. Finally, falciform ligament autologous patch is placed over pancreatic edge. After 6-8 weeks, the stent is removed by oral endoscopy. This technique introduces a new issue on the pancreatic fistula prevention.

Development of the Diatom Ecological Quality Index (DEQI) for peri-urban mountain streams in the Basin of Mexico.

In the Basin of Mexico, one of the most important economic regions in the country with over 22 million inhabitants, peri-urban streams have been transformed into sewers, drains, and pipes to avoid flooding or unsanitary conditions; the change affects not only the ecosystem's goods and services but also the aquatic communities that support the natural ecological processes. We aimed to develop a diatom-based diagnosis of the ecological quality of these aquatic ecosystems through the study of epilithic diatom response to regional environmental gradients. Samples of epilithic diatoms and water were collected in 45 sites representing 12 perennial streams, and multivariate analyses were performed on environmental and biological data. The ecological quality gradient to which diatoms responded was related to oxygen saturation, soluble reactive phosphorous, dissolved inorganic nitrogen, and hydromorphological quality. Three species groups were recognized according to their ecological preferences along CCA1 axis, indicators of high and low ecological quality, and tolerant species. By assigning an indicator value to each species group, we calculated the DEQI using the formula adapted from Pantle and Buck, indicating five different ecological quality classes. This index is proposed for complementing the ecological quality evaluation as a biological metric that responds to multiple regional stressors of the structure and function of these peri-urban streams in the Basin of Mexico.

Assessment of potential reference sites for evaluating the ecological status of subtropical and temperate Brazilian lotic systems using the epilithic diatom community.

This research aimed at determining reference sites in southern Brazilian lotic systems, using the Water Quality Trophic Index (WQTI), based on epilithic diatom communities. Within the period of 2012 and 2016, 140 epilithic diatom samples from seven sampling sites within the spring area of the Andreas Stream Hydrographic Basin, Vera Cruz County, RS, Brazil, were analyzed quarterly. Similarly, from 2012 and 2014, water samples in these sampling sites were collected for determination of physicochemical and microbiological parameters, such as water temperature, pH, turbidity, dissolved oxygen, biochemical oxygen demand, nitrate, phosphate, total dissolved solids, and fecal coliforms. The results indicated the occurrence of two diatom samples groups with significant differences (p < 0.05). Group 1 (sampling sites P1, P4, and P5) was classified in the oligotrophic category with an average WQTI of 1.3 ± 0.2, while group 2 (sampling sites P2, P3, P6, and P7) was classified in the ß-mesotrophic category with an average value of 2.0 ± 0.4). Achnanthidium minutissimum and Platessa hustedtii the dominant species were classified as oligotrophic taxa. Thus, we proposed the upper limit of the first interval of the WQTI score scale, equal to 1.5, as a reference value to differentiate the limits between the "high" and "good" ecological status to determine "reference sites" for subtropical and temperate Brazilian aquatic systems. The physical, chemical, and microbiological water quality evaluation gives support to this proposal, as far as the results indicated a significant improvement in the water quality, classifying sampling sites P1, P4, and P5 as having good quality appropriate for multiple uses.