Antifungal activity of azoles, allylamines, and 8-hidroxiquinolines, alone and in combination, against Malassezia pachydermatis in vitro and in vivo.

Malassezia pachydermatis is often reported as the causative agent of dermatitis in dogs. This study aims to evaluate the in vitro and in vivo antifungal activity of azoles and terbinafine (TRB), alone and in combination with the 8-hydroxyquinoline derivatives (8-HQs) clioquinol (CQL), 8-hydroxyquinoline-5-(n-4-chlorophenyl)sulfonamide (PH151), and 8-hydroxyquinoline-5-(n-4-methoxyphenyl)sulfonamide (PH153), against 16 M. pachydermatis isolates. Susceptibility to the drugs was evaluated by in vitro broth microdilution and time-kill assays. The Toll-deficient Drosophila melanogaster fly model was used to assess the efficacy of drugs in vivo. In vitro tests showed that ketoconazole (KTZ) was the most active drug, followed by TRB and CQL. The combinations itraconazole (ITZ)+CQL and ITZ+PH151 resulted in the highest percentages of synergism and none of the combinations resulted in antagonism. TRB showed the highest survival rates after seven days of treatment of the flies, followed by CQL and ITZ, whereas the evaluation of fungal burden of dead flies showed a greater fungicidal effect of azoles when compared to the other drugs. Here we showed for the first time that CQL is effective against M. pachydermatis and potentially interesting for the treatment of malasseziosis.

Drosophila melanogaster as a model of systemic dermatophytosis.

BACKGROUND: Dermatophytosis is one of the most common fungal infections worldwide. The distribution of dermatophytes varies across continents, but the genera Trichophyton and Microsporum have emerged as the main isolated agents in humans and animals. OBJECTIVES: To validate Drosophila melanogaster flies as a fast and feasible model to study dermatophytic infections. METHODS: Wild-type (WT) and Toll-deficient D. melanogaster flies were infected by Trichophyton rubrum, T. mentagrophytes, Microsporum canis and Nannizzia gypsea by pricking with a needle previously dipped in inoculum concentrations ranging from 103 to 108 colony-forming units/mL. Establishment of infection was confirmed by survival curves, histopathological analysis and fungal burden. Thereafter, flies were treated with terbinafine, itraconazole and clioquinol. RESULTS: WT flies were predominantly resistant to the infection, whereas Toll-deficient flies succumbed to the four dermatophyte genera tested. The antifungal drugs protected flies from the infection, except for N. gypsea whose survival curves did not differ from the untreated group. CONCLUSIONS: This pilot study confirms that D. melanogaster is a suitable model to study the virulence and antifungal drug efficacy in dermatophyte species.

Standardization of Galleria mellonella as an Infection Model for Malassezia furfur and Malassezia pachydermatis.

Galleria mellonella larva has been widely exploited as an infection model for bacteria and fungi. Our laboratory uses this insect as a model for fungal infection caused by the genus Malassezia, in particular, systemic infections caused by Malassezia furfur and Malassezia pachydermatis, which are poorly understood. Here, we describe the G. mellonella larva inoculation process with M. furfur and M. pachydermatis and the posterior assessment of the establishment and dissemination of the infection in the larvae. This assessment was done through the evaluation of larval survival, melanization, fungal burden, hemocytes populations, and histological changes. This methodology allows for the identification of virulence patterns between Malassezia species and the impact of inoculum concentration and temperature.

Clinical, radiological and laboratory characteristics of central nervous system histoplasmosis: A systematic review of a severe disease.

BACKGROUND: The knowledge of central nervous system (CNS) histoplasmosis is limited to case reports and series. OBJECTIVES: Our objective was to synthesise clinical, radiological and laboratory characteristics of CNS histoplasmosis to improve our understanding of this rare disease. METHODS: We performed a systematic review using Pubmed/MEDLINE, Embase and LILACS databases accessed on March 2023 without publication date restrictions. Inclusion criteria comprised: (1) histopathological, microbiological, antigen or serological evidence of histoplasmosis; (2) CNS involvement based on cerebrospinal fluid pleocytosis or neuroimaging abnormalities. We classified the certainty of the diagnosis in proven (CNS microbiological and histopathological confirmation), probable (CNS serological and antigen confirmation) or possible (non-CNS evidence of histoplasmosis). Metaproportion was used to provide a summary measure with 95% confidence intervals for the clinical, radiological and laboratory characteristics. Chi-squared test was used to compare mortality between pairs of antifungal drugs. RESULTS: We included 108 studies with 298 patients. The median age was 31 years, predominantly male, and only 23% were immunocompromised (134/276, 95%CI: 3-71), mainly due to HIV infection. The most common CNS symptom was headache (130/236, 55%, 95%CI: 49-61), with a duration predominantly of weeks or months. Radiological presentation included histoplasmoma (79/185, 34%, 95%CI: 14-61), meningitis (29/185, 14%, 95%CI: 7-25), hydrocephalus (41/185, 37%, 95%CI: 7-83) and vasculitis (18/185, 6%, 95%CI: 1-22). There were 124 proven cases, 112 probable cases and 40 possible cases. The majority of patients presented positive results in CNS pathology (90%), serology (CSF: 72%; serum: 70%) or CSF antigen (74%). Mortality was high (28%, 56/198), but lower in patients who used liposomal amphotericin B and itraconazole. Relapse occurred in 13% (23/179), particularly in HIV patients, but less frequently in patients who used itraconazole. CONCLUSION: Central nervous system histoplasmosis usually presents subacute-to-chronic symptoms in young adults. Neuroimaging patterns included not only focal lesions but also hydrocephalus, meningitis and vasculitis. Positive results were commonly found in CSF antigen and serology. Mortality was high, and treatment with liposomal amphotericin B followed by itraconazole may decrease mortality.

Therapeutic Prospection of Animal Venoms-Derived Antimicrobial Peptides against Infections by Multidrug-Resistant Acinetobacter baumannii: A Systematic Review of Pre-Clinical Studies.

Infections caused by multidrug-resistant Acinetobacter baumannii (MDR-Ab) have become a public health emergency. Due to the small therapeutic arsenal available to treat these infections, health agencies have highlighted the importance of developing new antimicrobials against MDR-Ab. In this context, antimicrobial peptides (AMPs) stand out, and animal venoms are a rich source of these compounds. Here, we aimed to summarize the current knowledge on the use of animal venom-derived AMPs in the treatment of MDR-Ab infections in vivo. A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. The eight studies included in this review identified the antibacterial activity of eleven different AMPs against MDR-Ab. Most of the studied AMPs originated from arthropod venoms. In addition, all AMPs are positively charged and rich in lysine residues. In vivo assays showed that the use of these compounds reduces MDR-Ab-induced lethality and bacterial load in invasive (bacteremia and pneumonia) and superficial (wounds) infection models. Moreover, animal venom-derived AMPs have pleiotropic effects, such as pro-healing, anti-inflammatory, and antioxidant activities, that help treat infections. Animal venom-derived AMPs are a potential source of prototype molecules for the development of new therapeutic agents against MDR-Ab.

Ophthalmic and immunopathological characterization of systemic infectious diseases in cats.

Ocular involvement in systemic diseases is frequent in cats; however, without concurrent clinical and ophthalmic examinations with gross and/or histologic analysis of the eye, these findings can be underdiagnosed. This article aims to provide gross, histologic, and immunohistochemical characteristics of ocular lesions from cats submitted to necropsy, focusing on those caused by systemic infectious agents. Cats that died due to a systemic infectious disease were selected based on necropsy diagnosis and presence of ocular lesions. Gross, histologic, and immunohistochemical findings were recorded. From April 2018 to September 2019, 849 eyes of 428 cats were evaluated. Histologic abnormalities were seen in 29% of cases, which were classified as inflammatory (41%), neoplastic (32%), degenerative (19%), and metabolic/vascular (8%). Macroscopic changes were present in one-third of eyes with histologic lesions. Of these, 40% were attributed to inflammatory or neoplastic diseases associated with infectious agents. The most important infectious agents causing ocular disease in this study were feline leukemia virus, feline infectious peritonitis virus, and Cryptococcus sp. The most common ocular abnormalities associated with infectious agents were uveitis (anterior, posterior, or panuveitis), optic neuritis, and meningitis of the optic nerve. Ocular lesions secondary to systemic infections in cats are frequent; however, these are not always diagnosed because gross lesions are less common than histologic lesions. Therefore, both gross and histologic evaluation of the eyes of cats is recommended, mainly for cases in which the clinical suspicion or necropsy diagnosis suggests that an infectious agent might be related to the cause of death.

Systematic review of neuroparacoccidioidomycosis: The contribution of neuroimaging.

BACKGROUND: Advanced neuroimaging demonstrated that neurological involvement occurs in up to 30% of paracoccidioidomycosis (PCM) cases. Current knowledge of neuroparacoccidioidomycosis (NPCM) is based on a 2009 systematic review. However, in the last decade, several new cases have been published, with modern neuroimaging techniques. OBJECTIVES: We believe a new systematic review is needed to summarise these advances. METHODS: We searched PubMed/MEDLINE, Embase and LILACS for studies from January 2010 to May 2022. Case series and case reports of NPCM were included. We performed a metaproportion to estimate a summary proportion with 95% confidence intervals (CI). RESULTS: Thirty-four studies including 104 patients were evaluated. We combined our data with the results from the previous review that included 257 cases, totalling 361 patients. We found no new important demographic, clinical or laboratory characteristics. On magnetic resonance imaging (MRI), we found that 72% (95%CI: 38-91) had hyperintensity on T1-weighted image; 84% (95%CI: 71%-92%) had hypointensity on T2-weighted image; 80% (95%CI: 66-89) had contrast enhancement with the classical ring-enhancing pattern. All 8 patients undergoing spectroscopy presented lipid peaks. We found a 16% mortality, lower than in the previous review (44%). CONCLUSION: NPCM presents a characteristic pattern on MRI that may help to differentiate it from other causes of single or multiple brain lesions. Albeit there is a frequent pattern, it is not specific, as other granulomatous diseases may show similar findings. Advances in neuroimaging with early diagnosis and appropriate management of the disease may have contributed to reducing its mortality.

Corrigendum: Susceptibility to infections during acute liver injury depends on transient disruption of liver macrophage niche.

[This corrects the article DOI: 10.3389/fimmu.2022.892114.].

Susceptibility to Infections During Acute Liver Injury Depends on Transient Disruption of Liver Macrophage Niche.

Kupffer cells are the primary liver resident immune cell responsible for the liver firewall function, including clearance of bacterial infection from the circulation, as they are strategically positioned inside the liver sinusoid with intimate contact with the blood. Disruption in the tissue-resident macrophage niche, such as in Kupffer cells, can lead to a window of susceptibility to systemic infections, which represents a significant cause of mortality in patients with acetaminophen (APAP) overdose-induced acute liver injury (ALI). However, how Kupffer cell niche disruption increases susceptibility to systemic infections in ALI is not fully understood. Using a mouse model of ALI induced by APAP overdose, we found that Kupffer cells upregulated the apoptotic cell death program and were markedly reduced in the necrotic areas during the early stages of ALI, opening the niche for the infiltration of neutrophils and monocyte subsets. In addition, during the resolution phase of ALI, the remaining tissue macrophages with a Kupffer cell morphology were observed forming replicating cell clusters closer to necrotic areas devoid of Kupffer cells. Interestingly, mice with APAP-induced liver injury were still susceptible to infections despite the dual cellular input of circulating monocytes and proliferation of remaining Kupffer cells in the damaged liver. Therapy with bone marrow-derived macrophages (BMDM) was shown to be effective in occupying the niche devoid of Kupffer cells following APAP-induced ALI. The rapid BMDM migration to the liver and their positioning within necrotic areas enhanced the healing of the tissue and restored the liver firewall function after BMDM therapy. Therefore, we showed that disruption in the Kupffer cell niche and its impaired function during acute liver injury are key factors for the susceptibility to systemic bacterial infections. In addition, modulation of the liver macrophage niche was shown to be a promising therapeutic strategy for liver injuries that reduce the Kupffer cell number and compromise the organ function.

Galleria mellonella for systemic assessment of anti-Candida auris using amphotericin B loaded in nanoemulsion.

Galleria mellonella is a model that uses adult larvae to assess the prophylactic, therapeutic, and acute toxic potential of substances. Given their benefits, G. mellonella models are being employed in investigations of systemic infections caused by highly resistant microorganisms. Among the multiresistant microorganisms, we highlight Candida auris, a yeast with high mortality potential and resistance. Among the potential drugs, amphotericin B (AmB) stands out; however, microbial resistance episodes and side effects caused by low selectivity have been observed. The incorporation of AmB into a nanoemulsion (NE) can contribute to the control of C. auris infections and resistance as well as decrease the side effects of this drug. This study aimed to develop AmB-loaded NE (NEA) and evaluate its antifungal action against C. auris in G. mellonella. NEs were obtained by using sunflower oil and cholesterol as the oily phase, polyoxyethylene 20 cetyl ether (Brij® 58) and soy phosphatidylcholine as the surfactant system, and PBS buffer as the aqueous phase. An alternative in vivo assay with G. mellonella for acute toxicity and infection was performed using adult stage larvae (200 mg to 400 mg). According to the obtained results, NE and NEA exhibited sizes of 43 and 48 nm, respectively. The PDI was 0.285 and 0.389 for NE and NEA, respectively. The ZP showed electronegativity for both systems, with -3.77 mV and -3.80 mV for NE and NEA, respectively. Acute toxicity showed that free AmB had greater acute toxicity potential than NEA. The survival assay showed high larval viability. NEA had a better antifungal profile against systemic infection in G. mellonella. It is concluded that the alternative model proved to be an efficient in vivo assay to determine the toxicity and evaluate the therapeutic property of free AmB and NEA in systemic infections caused by C. auris.

Screening paracoccidioidomycosis by double immunodiffusion test in a referred diagnostic center in Brazilian southeastern: an accessible tool.

PURPOSE: This article shows reports of the clinical-epidemiological characteristics and serological screening in patients assisted by a reference center for PCM care, University Hospital Cassiano Antonio Moraes, Federal University of Espirito Santo, Brazil. METHODS: The patient's sera with PCM were analyzed by DID test at the beginning and the end treatment. Clinical and demographic data were also collected to characterize the sample. RESULTS: One hundred patients with a suspected diagnosis of PCM were evaluated. Serology by DID test was used as a screen in all patients. The test was positive for 79 patients (72 for Paracoccidioides brasiliensis and 7 for Paracoccidioides lutzii). Serology was negative in 21 sera, although all of them were diagnosed PCM by histopathologic or direct exam. Serological follow-up was performed during the treatment of all patients. After treatment, 58(58%) had negative serology and 33(33%) low levels of antibodies (≤ 1:16). CONCLUSION: Our results indicate the importance of the DID test for the screening and monitoring of PCM and that the incidence of P. lutzii might be greater than expected in areas where it is not the predominant PCM species. Therefore, this article may contribute to improving the knowledge and clinical management about this disease.

Efficacy of Ebselen Against Invasive Aspergillosis in a Murine Model.

Invasive aspergillosis is one of the major causes of morbidity and mortality among invasive fungal infections. The search for new antifungal drugs becomes imperative when existing drugs are not able to efficiently treat these infections. Ebselen, is an organoselenium compound, already successfully approved in clinical trials as a repositioned drug for the treatment of bipolar disorder and prevention of noise-induced hearing loss. In this study, we aimed to reposition ebselen for the treatment of invasive aspergillosis by showing ebselen effectiveness in a murine model. For this, BALB/c mice were immunosuppressed and infected systemically with Aspergillus fumigatus. Animals were divided and treated with ebselen, voriconazole, or drug-free control, for four days. The kidneys were used for CFU count and, histopathological and cytokine analysis. Ebselen was able to significantly reduce the fungal burden in the kidneys of infected mice with efficacy comparable with voriconazole treatment as both had reductions to the same extent. The absence of hyphae and intact kidney tissue structure observed in the histopathological sections analyzed from treated groups corroborate with the downregulation of IL-6 and TNF. In summary, this study brings for the first time in vivo evidence of ebselen efficacy against invasive aspergillosis. Despite these promising results, more animal studies are warranted to evaluate the potential role of ebselen as an alternative option for the management of invasive aspergillosis in humans.

Increased incidence of candidemia in a tertiary care hospital with the COVID-19 pandemic.

BACKGROUND: The incidence of candidemia in our hospital has been stable over an 18-year period (1.3 episodes per 1000 admissions). Since March 2020, we have observed an increase in cases of candidemia. METHODS: In March 2020, the hospital was prepared to receive patients with COVID-19, with cancellation of elective procedures, discharge of less sick patients and the activation of beds for COVID-19. We compared the incidence of candidemia in 2 periods: from January 2019 to February 2020 (period 1) and from March to September 2020 (period 2). RESULTS: We diagnosed 41 episodes of candidemia, 16 in period 1 and 25 in period 2 (9 COVID-19 patients). Compared with non-COVID-19 patients, COVID-19 patients with candidemia were more likely to be under mechanical ventilation (100% vs. 34.4%, P < .001). The median number of monthly admissions in period 1 and 2 was 723 (interquartile range 655-836) and 523 (interquartile range 389-574), respectively. The incidence of candidemia (per 1000 admissions) was 1.54 in period 1 and 7.44 in period 2 (P < .001). In period 2, the incidence of candidemia (per 1000 admissions) was 4.76 if we consider only cases of candidemia in non-COVID-19 patients, 2.68 if we consider only cases of candidemia in COVID-19 patients and 14.80 considering only admissions of patients with COVID-19. CONCLUSIONS: The increase in the incidence of candidemia in our hospital may be attributed to 2 factors: a reduction in the number of admissions (denominator) and the occurrence of candidemia in COVID-19 patients.

Pseudoflowers produced by Fusarium xyrophilum on yellow-eyed grass (Xyris spp.) in Guyana: A novel floral mimicry system?

Pseudoflower formation is arguably the rarest outcome of a plant-fungus interaction. Here we report on a novel putative floral mimicry system in which the pseudoflowers are composed entirely of fungal tissues in contrast to modified leaves documented in previous mimicry systems. Pseudoflowers on two perennial Xyris species (yellow-eyed grass, X. setigera and X. surinamensis) collected from savannas in Guyana were produced by Fusarium xyrophilum, a novel Fusarium species. These pseudoflowers mimic Xyris flowers in gross morphology and are ultraviolet reflective. Axenic cultures of F. xyrophilum produced two pigments that had fluorescence emission maxima in light ranges that trichromatic insects are sensitive to and volatiles known to attract insect pollinators. One of the volatiles emitted by F. xyrophilum cultures (i.e., 2-ethylhexanol) was also detected in the head space of X. laxifolia var. iridifolia flowers, a perennial species native to the New World. Results of microscopic and PCR analyses, combined with examination of gross morphology of the pseudoflowers, provide evidence that the fungus had established a systemic infection in both Xyris species, sterilized them and formed fungal pseudoflowers containing both mating type idiomorphs. Fusarium xyrophilum cultures also produced the auxin indole-3-acetic acid (IAA) and the cytokinin isopentenyl adenosine (iPR). Field observations revealed that pseudoflowers and Xyris flowers were both visited by bees. Together, the results suggest that F. xyrophilum pseudoflowers are a novel floral mimicry system that attracts insect pollinators, via visual and olfactory cues, into vectoring its conidia, which might facilitate outcrossing of this putatively heterothallic fungus and infection of previously uninfected plants.

Pathological profiles of systemic infections by Panton-Valentine leukocidin-positive, methicillin-resistant Staphylococcus aureus strains in a murine model.

AIMS: Staphylococcus aureus is one of the most common pathogens in hospital environment and community. Panton-Valentine leukocidin (PVL) production is clinically associated with skin abscesses, soft tissues infections, bacteraemia and sepsis. This study aimed to investigate the effects of the presence of genes lukF/S-PV coding for PVL, in histological and haematological features during systemic infection, using a Swiss mice experimental model. METHODS AND RESULTS: Experiments were performed using 25 mice distributed into five experimental groups, intravenously inoculated with 50 µl suspensions at density 1·0 × 107  CFU per ml of strains: methicillin-susceptible (MSSA) and pvl-negative strains isolated from nasal colonization; MSSA pvl-positive strains isolated from nasal colonization; methicillin-resistant (MRSA) and pvl-positive strains isolated from peripheral blood of a patient with severe pulmonary infection; and a MRSA pvl-positive strains isolated from a peripheral blood culture of a patient with bacteraemia. Haematological analysis was performed at 24, 48, 72 and 96 h post-infection. Morphoanatomy and histopathological analyses were performed at 96 h post-infection. For all S. aureus strains tested, the capability of intravenous dissemination and survival into mice tissues was demonstrated. Inflammatory processes at different levels were related to the presence of pvl genes, and included alterations in the format, size and colour of the organs. Staphylococcus aureus pvl-positive strains were detected in greater numbers in the organs of the infected animals. CONCLUSIONS: The pvl-positive strains isolated from blood cultures were capable to induce the greatest modifications in both haematological and histopathological profiles, and seemed to aggravate the systemic infections. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings are valuable in characterizing infections caused by S. aureus in humans and murine.

Effect of (-)-α-Bisabolol on the Inflammatory Response in Systemic Infection Experimental Model in C57BL/6 Mice.

(-)-α-Bisabolol (BISA) is an unsaturated monocyclic sesquiterpenes compound, mainly found in the essential oil of chamomile (Matricaria chamomilla). It has been reported that this compound has several biological activities, but there are few studies evaluating the activity of this compound in the systemic inflammatory response in infectious processes. The aim of this study was to evaluate the effect of BISA on the inflammatory response and survival rate in a systemic infection model, and in vitro neutrophils phagocytic activity. BISA at concentration of 3, 10, 30, and 90 µg/ml did not presented in vitro cytotoxicity in MTT assay, and at concentrations of 1 and 3 µg/ml the BISA treatment increased in vitro phagocytic neutrophil activity. For the inflammatory response study, we verified the BISA treatment effect in a cecal ligation and puncture (CLP)-induced systemic infection model in mice; in this model, we demonstrate that BISA at dose of 100 mg/kg reduced the leukocyte recruitment in peritoneal cavity; at dose of 200 mg/kg, the NO concentration was increased in the peritoneal cavity. The bacteria CFU number was reduced in mice blood in the BISA treatment, at doses of 100 and 200 mg/kg. The BISA treatment at doses of 50 and 100 mg/kg increased the myeloperoxidase activity and reduction NO production in lung tissue of mice in CLP model. At dose of 100 mg/kg, the BISA treatment was able to reduce the mortality rate of mice submitted to CLP-induced sepsis and observed for 7 days. The results suggest an effect of BISA on inflammatory response, with activity on leukocyte chemotactic and NO production, in addition to increasing the survival rate of animals submitted to CLP model.

Mucormycosis in South America: A review of 143 reported cases.

Mucormycosis is a rare but important invasive fungal disease that most often affects immunocompromised hosts. The incidence of mucormycosis appears to be increasing worldwide, as risk factors such as the use of immunosuppressive therapies become more common. We report the results of a literature review of 143 mucormycosis cases reported in South America between 1960 and 2018. The number of reported cases has increased by decade, from 6 in the 1960s to 51 in the 2010s. The most common underlying conditions associated with mucormycosis in South America were diabetes mellitus (42.0%) and penetrating trauma/burns (20.0%). Underlying conditions involving immunosuppression, including treatment of haematologic malignancy, solid organ transplant, and corticosteroid use, also accounted for a large proportion of cases (45.5%). Between 1960 and 2018, cases of mucormycosis associated with conditions involving immunosuppression accounted for the highest mortality rate (58.5%), followed by diabetes mellitus (45.0%), and penetrating trauma/burns (37.9%). Overall mortality decreased from 100% to 39.4% during this period, mainly driven by the increasing availability and use of antifungal therapies and surgical intervention. However, these treatments are not yet universally utilised across the region in the treatment of mucormycosis; efforts to improve availability of effective treatments would be likely to improve outcomes.

Inactivation of Streptococcus mutans genes lytST and dltAD impairs its pathogenicity in vivo.

Background: Streptococcus mutans orchestrates the development of a biofilm that causes dental caries in the presence of dietary sucrose, and, in the bloodstream, S. mutans can cause systemic infections. The development of a cariogenic biofilm is dependent on the formation of an extracellular matrix rich in exopolysaccharides, which contains extracellular DNA (eDNA) and lipoteichoic acids (LTAs). While the exopolysaccharides are virulence markers, the involvement of genes linked to eDNA and LTAs metabolism in the pathogenicity of S. mutans remains unclear. Objective and Design: In this study, a parental strain S. mutans UA159 and derivative strains carrying single gene deletions were used to investigate the role of eDNA (ΔlytS and ΔlytT), LTA (ΔdltA and ΔdltD), and insoluble exopolysaccharides (ΔgtfB) in virulence in a rodent model of dental caries (rats) and a systemic infection model (Galleria mellonella larvae). Results: Fewer carious lesions were observed on smooth and sulcal surfaces of enamel and dentin of the rats infected with ∆lytS, ∆dltD, and ΔgtfB (vs. the parental strain). Moreover, strains carrying gene deletions prevented the killing of larvae (vs. the parental strain). Conclusions: Altogether, these findings indicate that inactivation of lytST and dltAD impaired S. mutans cariogenicity and virulence in vivo.

Drosophila melanogaster as a model for the study of Malassezia pachydermatis infections.

Malassezia pachydermatis is a yeast that is commonly found in the skin of most animals. Changes in the physical, chemical or immunological processes of the skin may render the host more susceptible to the yeast, which then may cause otitis, dermatitis or, less often, systemic infection. We tested the pathogenicity of M. pachydermatis in wild-type (WT) and Toll-deficient Drosophila melanogaster. Flies were inoculated in the thorax with a needle previously dipped in inoculum concentrations ranging from 103 and 107 yeast cells/mL. After infection, flies were housed at 29 °C and mortality was evaluated daily until day seven. WT flies were resistant to the infection, whereas Toll-deficient flies showed inoculum-dependent mortality rates. Fungal burden, assessed by histopathological analysis and by counting the number of colony-forming units of dead flies, corroborated the results. The D. melanogaster model is a promising minihost model for future large-scale studies of virulence mechanisms and antifungal drug activity in malasseziosis.

Interleukin-10 Production by T and B Cells Is a Key Factor to Promote Systemic Salmonella enterica Serovar Typhimurium Infection in Mice.

Salmonella enterica serovar Typhimurium (S. Typhimurium) is a Gram-negative bacterium that produces disease in numerous hosts. In mice, oral inoculation is followed by intestinal colonization and subsequent systemic dissemination, which leads to severe pathogenesis without the activation of an efficient anti-Salmonella immune response. This feature suggests that the infection caused by S. Typhimurium may promote the production of anti-inflammatory molecules by the host that prevent efficient T cell activation and bacterial clearance. In this study, we describe the contribution of immune cells producing the anti-inflammatory cytokine interleukin-10 (IL-10) to the systemic infection caused by S. Typhimurium in mice. We observed that the production of IL-10 was required by S. Typhimurium to cause a systemic disease, since mice lacking IL-10 (IL-10-/-) were significantly more resistant to die after an infection as compared to wild-type (WT) mice. IL-10-/- mice had reduced bacterial loads in internal organs and increased levels of pro-inflammatory cytokines in serum at 5 days of infection. Importantly, WT mice showed high bacterial loads in tissues and no increase of cytokines in serum after 5 days of S. Typhimurium infection, except for IL-10. In WT mice, we observed a peak of il-10 messenger RNA production in ileum, spleen, and liver after 5 days of infection. Importantly, the adoptive transfer of T or B cells from WT mice restored the susceptibility of IL-10-/- mice to systemic S. Typhimurium infection, suggesting that the generation of regulatory cells in vivo is required to sustain a systemic infection by S. Typhimurium. These findings support the notion that IL-10 production from lymphoid cells is a key process in the infective cycle of S. Typhimurium in mice due to generation of a tolerogenic immune response that prevents bacterial clearance and supports systemic dissemination.