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Background: Mice do not get diarrhea when orally infected with S. enterica, but pre-treatment with oral aminoglycosides makes them susceptible to Salmonella colitis. However, genetically susceptible ItyS mice (Nramp1G169D allele) die from systemic infection before they develop diarrhea, so a new model is needed to study the pathogenesis of diarrhea. We pretreated ItyR mice (Nramp1G169) with oral kanamycin prior to infecting them with virulent S. Typhimurium strain 14028s in order to study Salmonella-induced diarrhea. We used both a visual scoring system and the measurement of fecal water content to measure diarrhea. BALB/c.D2Nramp1 congenic started losing weight 5 days post-infection and they began to die from colitis 10-14 days after infection. A SPI-1 (invA) mutant caused cecal, but not colonic inflammation and did not cause diarrhea. A phoP- mutant did not cause manifestations of diarrhea in either normal or NADPH-deficient (gp91phox) mice. However, strain 14028s caused severe colitis and diarrhea in gp91phox-deficient mice on an ItyR background. pmr A and F mutants, which are less virulent in orally infected BALB/c mice, were fully virulent in this model of colitis. Conclusions: S. enterica must be able to invade the colonic epithelium and to persist in the colon in order to cause colitis with manifestations of diarrhea. The NADPH oxidase is not required for diarrhea in Salmonella colitis. Furthermore, a Salmonella phoP mutant can be cleared from the colon by non-oxidative host defenses. [ABSTRACT FROM AUTHOR]

The Salmonella SpvB protein possesses ADP-ribosyl transferase activity. SpvB, acting as an intracellular toxin, covalently modifies monomeric actin, leading to loss of F-actin filaments in Salmonella-infected human macrophages. Using defined Salmonella mutants, different functional components of the SPI-2 type three secretion system (TTSS), ssaV, spiC, sseB, sseC, and sseD, were found to be required for SpvB-mediated actin depolymerization in human macrophages. Expression of SpvB protein in Salmonella was not affected by any of the SPI-2 mutants and the effects of these loci were not due to reduced numbers of intracellular bacteria. Interestingly, the major SPI-2 virulence effector, SifA, is not required for SpvB action. Further, caspase-3 activation is an additional marker of cytotoxicity in Salmonella-infected human macrophages. Caspase-3 activity depended on SpvB and SPI-2 TTSS function, but not on SifA. These human macrophage cell culture results were corroborated by virulence studies in mice. Using competitive infection of mice with mixed inocula of single and double mutants, spvBmut1 mutation did not have an effect independent of ssaJ mutation, essential for SPI-2 TTSS function. In contrast, competitive infection studies in mice confirmed that SpvB and SifA have independent virulence effects, as predicted by the macrophage studies. [ABSTRACT FROM AUTHOR]

The pathology of human coccidioidomycosis is granulomatous inflammation with many neutrophils surrounding ruptured spherules, but the chemotactic pathways that draw neutrophils into the infected tissues are not known. We previously showed that formalin-killed spherules (FKS) stimulate mouse macrophages to secret macrophage inflammatory protein 2 (MIP-2), which suggested that CXC ELR+ chemokines might be involved in neutrophil recruitment in vivo To test that hypothesis, we intranasally infected interleukin-8R2 (IL-8R2) ( Cxcr2 )-deficient mice on a BALB/c background with Coccidioides immitis RS. IL-8R2-deficient mice had fewer neutrophils in infected lungs than controls, but unexpectedly the IL-8R2-deficient mice had fewer organisms in their lungs than the control mice. Infected IL-8R2-deficient mouse lungs had higher expression of genes associated with lymphocyte activation, including the Th1 and Th17-related cytokines Ifnγ and Il17a and the transcription factors Stat1 and Rorc Additionally, bronchial alveolar lavage fluid from infected IL-8R2-deficient mice contained more IL-17A and interferon-γ (IFN-γ). We postulate that neutrophils in the lung directly or indirectly interfere with the development of a protective Th1/Th17 immune response to C. immitis at the site of infection., (Copyright © 2020 American Society for Microbiology.)

Coccidioidomycosis is a systemic fungal infection caused by the inhalation of the arthroconidia of either of two closely related dimorphic fungi, Coccidioides immitis and C. posadasii , that are endemic in the southwestern United States and other areas in the Western Hemisphere. Chronic cavitary pulmonary infections and extrapulmonary sites of infection are very difficult to treat and often require lifelong azole therapy. APX001A is the first in a new class of broad-spectrum antifungal agents that inhibit Gwt1, an enzyme which is required for cell wall localization of glycosylphosphatidylinositol (GPI)-anchored mannoproteins in fungi. APX001A and several analogs were highly active against clinical isolates of Coccidioides , inhibiting hyphal growth at low nanogram/ml concentrations. APX001 is the N-phosphonooxymethyl prodrug of APX001A, currently in clinical trials for the treatment of invasive fungal infections. Mice were treated orally once daily with 26 mg/kg/day of APX001 and the prodrug analog APX2097, 2 h after administration of the pan-cytochrome P450 inhibitor 1-aminobenzotriazole, which was used to enhance drug half-life and exposures to more closely mimic human pharmacokinetics of APX001A. Five days of treatment reduced lung colony counts by nearly 3 logs and prevented dissemination, similar to the efficacy of fluconazole dosed orally at 25 mg/kg twice daily. In a survival experiment, both APX001- and APX2097-treated mice survived significantly longer than control and fluconazole-treated mice. APX001 and other members of this new class of antifungal agents may offer great promise as effective therapies for coccidioidomycosis., (Copyright © 2019 Viriyakosol et al.)

Rodents are a natural host for the dimorphic pathogenic fungi Coccidioides immitis and Coccidioides posadasii , and mice are a good model for human infection. Humans and rodents both express Dectin-1 and Toll-like receptor 2 (TLR2) on myeloid cells, and those receptors collaborate to maximize the cytokine/chemokine responses to spherules (the tissue form of the fungi) and to formalin-killed spherules (FKS). We showed that Dectin-1 is necessary for resistance to pulmonary coccidioidomycosis, but the importance of TLR2 in vivo is uncertain. Myeloid differentiation factor 88 (MyD88) is the adapter protein for TLR2 and -4, interleukin-1R1 (IL-1R1), and IL-18R1. MyD88/TRIF -/- and MyD88 -/- mice were equally susceptible to C. immitis infection, in contrast to C57BL/6 (B6) controls. Of the four surface receptors, only IL-1R1 was required for resistance to C. immitis , partially explaining the susceptibility of MyD88 -/- mice. We also found that FKS stimulated production of IL-1Ra by bone marrow-derived dendritic cells (BMDCs), independent of MyD88 and Dectin-1. There also was a very high concentration of IL-1Ra in the lungs of infected B6 mice, supporting the potential importance of this regulatory IL-1 family protein in the largely ineffective response of B6 mice to coccidioidomycosis. These results suggest that IL-1R1 signaling is important for defense against C. immitis infection., (Copyright © 2018 American Society for Microbiology.)

We investigated the roles of Salmonella pathogenicity island 2 (SPI-2) and two SPI-2 effectors in Salmonella colitis and diarrhea in genetically resistant BALB/c.D2(Slc11a1) congenic mice with the wild-type Nramp1 locus. Wild-type Salmonella enterica serovar Typhimurium 14028s caused a pan-colitis, and the infected mice developed frank diarrhea with a doubling of the fecal water content. An ssaV mutant caused only a 26% increase in fecal water content, without producing the pathological changes of colitis, and it did not cause weight loss over a 1-week period of observation. However, two SPI-2 effector mutants, the spvB and sifA mutants, and a double spvB sifA mutant caused diarrhea and colitis, even though the sifA mutant was sensitive to killing by bone marrow-derived macrophages from BALB/c.D2 mice and was severely impaired in extraintestinal growth but not in growth in the cecum. These results demonstrate that systemic S. enterica infection and diarrhea/colitis are distinct pathogenic processes and that only the former requires spvB and sifA.

Background: Mice do not get diarrhea when orally infected with S. enterica, but pre-treatment with oral aminoglycosides makes them susceptible to Salmonella colitis. However, genetically susceptible ItyS mice (Nramp1(G169D) allele) die from systemic infection before they develop diarrhea, so a new model is needed to study the pathogenesis of diarrhea. We pretreated ItyR mice (Nramp1(G169)) with oral kanamycin prior to infecting them with virulent S. Typhimurium strain 14028s in order to study Salmonella-induced diarrhea. We used both a visual scoring system and the measurement of fecal water content to measure diarrhea. BALB/c.D2(Nramp1) congenic started losing weight 5 days post-infection and they began to die from colitis 10-14 days after infection. A SPI-1 (invA) mutant caused cecal, but not colonic inflammation and did not cause diarrhea. A phoP- mutant did not cause manifestations of diarrhea in either normal or NADPH-deficient (gp91(phox)) mice. However, strain 14028s caused severe colitis and diarrhea in gp91(phox)-deficient mice on an ItyR background. pmr A and F mutants, which are less virulent in orally infected BALB/c mice, were fully virulent in this model of colitis., Conclusions: S. enterica must be able to invade the colonic epithelium and to persist in the colon in order to cause colitis with manifestations of diarrhea. The NADPH oxidase is not required for diarrhea in Salmonella colitis. Furthermore, a Salmonella phoP mutant can be cleared from the colon by non-oxidative host defenses.