Brazilian Journal of Microbiology最新文献

Chickpea (Cicer arietinum L.) is a vital legume crop, but its productivity is often limited by poor soil fertility. This study aimed to assess the nodulation efficacy and plant growth-enhancing activities of six Mesorhizobium spp. strains in the chickpea cultivar Pusa 362 through the Leonard jar experiment and field trial. The strains, including two strains from ICRISAT (reference strains), were tested for solubilization of phosphate, potassium, and zinc, and production of Indole-3-Acetic Acid (IAA). Strain C5 excelled in phosphate solubilization (61.40 µg/ml), while C7 was superior in potassium (26.10 µg/ml) and zinc phosphate (69.15 µg/ml) solubilization; C17 showed the highest IAA production (25.75 µg/ml). In the Leonard jar experiment, inoculation of strains M. ciceri C5 and M. helmanticense C17 exhibited the highest nodule number and root dry weight, while treatments with M. ciceri C5 and M. helmanticense C7 inoculation recorded the maximum nodule dry weight and shoot dry weight. Field trials indicated significant improvements in nodulation, biomass, and nitrogen content in chickpeas inoculated with these strains. Treatment with strain C7 led to the highest increase in nodule number and root dry weight over the control, while strain C5 inoculation recorded maximum grain yield. Correlation analysis showed positive relationships between yield and several growth parameters. Nodule occupancy tests revealed that strain C7 had the highest occupancy (32.98%), followed by C5 (31.92%), indicating superior nodulation competitiveness under field conditions. These results suggest that inoculation with specific Mesorhizobium strains can significantly enhance chickpea productivity through improved nodulation and nitrogen fixation.

Salmonellosis poses a significant public health threat, potentially leading to severe complications, ranging from enteritis to life-threatening septicemia. Salmonella enterica ssp. enterica serovar Typhimurium has the ability to translocate from the intestine to the liver via the hepatic portal system, causing severe lesions in the organ. The development of new treatment strategies is crucial, due to clinical burden of this infection. In this context, probiotics have emerged as a promising therapeutic avenue due to their multifaceted mechanisms of action. The aim of this study was to investigate the probiotic potential of two strains of Limosilactobacillus reuteri (UN34 and UN41) in a murine model of salmonellosis. Although both strains demonstrated in vitro characteristics indicative of potential probiotics, only the UN41 strain improved the survival rate of mice infected with S. Typhimurium, highlighting that the probiotic effect is strain-specific. In the in vivo model, administration of UN41 also attenuated neutrophilic infiltration, reduced bacterial translocation to the liver, lowered AST levels, and mitigated liver injury. These findings underscore the potential of L. reuteri UN41 as a promising probiotic candidate for mitigating the impact of salmonellosis.

Leptospira spp. is the causative agent of leptospirosis, a zoonotic disease prevalent worldwide, particularly in tropical regions. The bacterium can be transmitted directly through the urine of infected animals or indirectly via contact with contaminated environments, including soil and water sources. Water samples from streams, rainwater accumulations and drinking water were collected from Santa Maria, Rio Grande do Sul state (southernmost Brazil). The samples were submitted to the Laboratório de Diagnóstico e Pesquisa em Leptospirose (LabLepto) for inoculation in modified Ellinghausen-McCullough-Johnson-Harris medium and incubation at 28 °C. The inocula were evaluated weekly for a minimum of 90 days to identify morphological characteristics that are typical of Leptospira spp. One of the eight samples exhibited growth and morphology consistent with spirochetes. This sample was purified by filtration and subsequently sent for molecular identification by PCR and typing by secY gene sequencing. Genetic analysis revealed Leptospira licerasiae, belonging to the subclade P2 (intermediate group). This species has been previously isolated from environmental water and soil samples and associated with mild human infections. Nevertheless, this is the first documented environmental isolation of L. licerasiae in central Rio Grande do Sul. Although it exhibits lower virulence than classic pathogenic species, L. licerasiae should be included in epidemiological surveillance and One Health approaches due to its zoonotic potential and environmental persistence.

Melioidosis is a life-threatening infectious disease prevalent in tropical and subtropical environments. Large-scale serological screening is crucial in detecting evidence of exposure to B. pseudomallei. Serological assays are usually easy to execute, cost-effective and substantially reduce the time required for laboratory diagnosis. In the present study, the stability of whole-cell ELISA (WC-ELISA) was assessed using polyclonal antibodies generated in BALB/c mice. B. pseudomallei cells at a concentration of 10⁸ CFU/mL were immobilized on immuno-modules and stored at 4℃ for subsequent evaluation. The WC-ELISA assay remained consistent for up to 2 months, showing coefficients of variation of 2.21%, 1.65%, 4.10%, and 5.12% on days 15, 30, 45, and 68, respectively, compared to day 0. The decline in WC-ELISA performance was noticed from day 68 onwards, with a coefficient of variation of 20.64% between days 0 and 90. The findings of the present study suggest that the WC-coated immuno-modules remain stable for > 2 months when stored at 4℃. These pre-coated immuno-modules offer the potential for the economical large-scale screening of serological samples and require less time than conventional ELISA methods.

Background: Western blot (WB) is a conventional confirmatory test for evaluating infection with HTLV-1; however, indeterminate WB patterns remain a significant concern. TAX is a key regulatory protein of the HTLV-1 virus that increases the expression of viral gene products. This study aimed to compare the TAX expression profile in individuals with WB-positive and WB-indeterminate and evaluate its association with HTLV-1 proviral load MATERIALS AND METHODS: This study was conducted on individuals with WB-positive and WB-indeterminate HTLV-1 who had been referred to the Iranian Blood Transfusion Organization (IBTO) between 2021 and 2023. A total of 60 WB-positive and WB-indeterminate individuals were included. To confirm the presence of the HTLV virus in samples, peripheral blood mononuclear cells (PBMCs) were separated using a Ficoll gradient, and nested PCR (nPCR) was performed on the extracted DNA. The expression of the TAX gene was determined using quantitative Real-Time PCR. Moreover, the proviral load was measured using a TaqMan™ based qRT-PCR assay.

Results: According to nPCR, TAX and LTR regions were detected in all samples (100%) with WB-positive patterns. In WB-indeterminate samples, 50% (15 out of 30) and 60% (18 out of 30) contained the TAX and LTR regions, respectively. The TAX expression in WB-indeterminate samples was significantly lower than in donors with positive WB results (p = 0.01). Furthermore, the median proviral load of HTLV-1 in WB-positive samples (28.55 Copies/106 PBMCs (IQR:9.18-78.57) was significantly higher than WB-indeterminate samples 0.46 Copies/106 PBMCs (IQR:0.15- 0.73).

Conclusion: This study revealed that TAX expression may influence indeterminate WB patterns, highlighting the importance of employing molecular testing along with serological assays.

Influenza A virus (IAV) is present in most swine-producing countries causing production losses and concerns on public health. In Brazil, influenza is endemic in pig herds, and a great genetic diversity has been described in swine IAVs due to multiple introductions of pre-2009 human-seasonal IAVs followed by reassortment events with 2009 pandemic H1N1 (H1N1pdm) virus. Here, we compile 14 years of IAV monitoring data and describe the subtypes and major lineages of H1 and H3 viruses co-circulating in Brazilian pigs. Using multiplex RT-qPCR and sequencing, we identified H1N1pdm as the most frequently detected virus, accounting for 41.3% of the subtyped samples (165/399), followed by H1huN2 (108/399), H3N2 (77/399), and H1N1hu (9/399). The three dominant subtypes were detected co-circulating annually and consistently in seven of the nine states sampled, as well as among pigs at different production phases. Other reassortants were found sporadically and included H1pdmN2 (22/399) and H1huN1pdm (4/399). The high diversity observed indicates that IAVs from distinct lineages are widely disseminated across the country. These findings strongly suggest substantial movement of pigs between regions and states, which may have implications for vaccine design, disease control, and updating of diagnostic tests. Continuous efforts to monitor IAV are crucial to better understand their ecology and to generate relevant data for pandemic preparedness.

The bovine uterus hosts a diverse microbiome whose role in reproductive physiology and pathology is increasingly recognized. While Bacillus species have been occasionally isolated from the uterus, their biofilm and exopolysaccharide (EPS) forming capabilities have not been systematically characterized. In this study, four Bacillus strains (BU13, BU14, BU15, and BU16) were isolated from the bovine uteri and examined for their taxonomic affiliation, phenotypic characteristics, EPS production, biofilm formation, and antibiotic susceptibility. Phylogenetic analyses based on nearly full-length 16S rRNA gene sequences revealed that all isolates belonged to the B. subtilis group, with BU13, BU14, and BU16 closely related to B. licheniformis, and BU15 related to B. amyloliquefaciens and B. siamensis. BU13 and BU16 demonstrated high levels of EPS and biofilm production, especially in sucrose-supplemented media and under nutrient-rich conditions. Notably, these strains also exhibited relatively smaller inhibition zones against β-lactam antibiotics, which may be associated with their robust EPS-biofilm phenotypes. In contrast, larger inhibition zones were observed with gentamicin, enrofloxacin, and trimethoprim. These findings underscore the importance of characterizing commensal Bacillus spp. in the uterus and highlight that certain strains may possess traits that facilitate persistence and reduce antimicrobial responsiveness. This is the first study to comprehensively evaluate the biofilm-forming potential of uterine Bacillus isolates and provides a foundation for future investigations into their role in reproductive health and disease.

Candida parapsilosis is a common cause of candidiasis worldwide, with biofilm formation and secretion of aspartic proteases (Saps) as key virulence factors. Conversely, serine protease secretion by this fungus is poorly understood. In this study, we investigated the secretion of serine-type proteases by planktonic- and biofilm-forming cells of C. parapsilosis cultured in brain heart infusion (BHI) medium. Cell-free supernatant from the reference strain (ATCC 22019) was screened against various serine protease substrates, revealing pronounced activity toward N-benzoyl-Phe-Val-Arg-pNa (0.74 nmol pNA.mg^- 1.min^- 1), with optimal activity at pH 9.0 and temperatures between 32 °C and 40 °C. Proteolytic activity was significantly reduced by serine protease inhibitors PMSF (32.8%), TLCK (40.2%) and benzamidine (50.7%), while inhibitors of other protease classes had no effect, confirming its serine-type specificity. Notably, serine protease activity was detected in supernatants from cells grown in BHI but absent in those cultured in albumin-supplemented yeast carbon base medium, a known inducer of Saps, suggesting culture-dependent regulation of protease expression. Serine protease activity also increased over time, rising from 0.36 pNA.mg^- 1.min^- 1 at 24-hour to 1.14 pNA.mg^- 1.min^- 1 at 72-hour. Clinical isolates of C. parapsilosis exhibited significantly higher serine protease activity than the reference strain under optimal conditions. Serine-type protease activity was also detected in the supernatant of mature biofilms, showing a correlation with metabolic activity and biomass. Infection of Galleria mellonella larvae with C. parapsilosis isolates revealed no correlation between larval mortality and serine protease production. These findings suggest that C. parapsilosis serine proteases contribute to fungal growth and biofilm development, representing potential targets for antifungal intervention.

This study investigates the immobilization of crude cellulase from Aspergillus foetidus, produced through solid-state fermentation by different methods, including entrapment in agar cube, adsorption on agar xerogel, and adsorption on agar xerogel pretreated with glutaraldehyde. The immobilization efficiency achieved was 90.80%, 84.08%, and 84.23%, while enzyme activity obtained was 1.12 IU/g, 1.52 IU/g, and 1.48 IU/g for crude cellulase immobilized by entrapment in agar cube, adsorption on agar xerogel, and adsorption on agar xerogel pretreated with glutaraldehyde respectively. The immobilized crude cellulase was characterized, revealing an optimal temperature shift from 50 °C to 60 °C for agar xerogel-adsorbed crude cellulase, which improved its thermal stability. The pH optimum for free and all immobilized crude cellulase was observed at pH 4. Also, all immobilized crude cellulases retained significant activity even after multiple cycles, depicting their reusability. The enzyme kinetics observed were K_m of 11.71 mg/mL, 57.0 mg/mL, 14.86 mg/mL, 62.32 mg/mL, while V_max was 4.20 µmol/mL/min, 6.58 µmol/mL/min, 3.25 µmol/mL/min, and 5.78 µmol/mL/min for free crude cellulase, crude cellulase immobilized by entrapment in agar cube, crude cellulase adsorbed on agar xerogel, and crude cellulase adsorbed on agar xerogel pretreated with glutaraldehyde respectively. The free and immobilized crude cellulases were applied for carrot juice extraction which showed increased juice yield, clarity, and reducing sugar content while reduced viscosity compared to untreated samples. These findings highlight agar xerogel as an encouraging support for cellulase immobilization, presenting a sustainable and economical method for enzyme reuse in food processing.