Extra-intestinal Salmonella infections: the significance of spv genes.
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Animals↗
Biomedical subjects
J Fierer
Publications and source records attributed to J Fierer.
The Salmonella spvB virulence gene encodes an enzyme that ADP-ribosylates actin and destabilizes the cytoskeleton of eukaryotic cells.
ADP-ribosylating enzymes, such as cholera and diphtheria toxins, are key virulence factors for a variety of extracellular bacterial pathogens but have not been implicated previously during intracellular pathogenesis. Salmonella strains are capable of invading epithelial cells and localizing in macrophages during infection. The spvB virulence gene of Salmonella is required for human macrophage cytotoxicity in vitro and for enhancing intracellular bacterial proliferation during infection. Here, we present evidence that spvB encodes an ADP-ribosylating enzyme that uses actin as a substrate and depolymerizes actin filaments when expressed in CHO cells. Furthermore, site-directed mutagenesis demonstrates that the ADP-ribosylating activity of SpvB is essential for Salmonella virulence in mice. As spvB is expressed by Salmonella strains after invasion of epithelial cells or phagocytosis by macrophages, these results suggest that SpvB functions as an intracellular ADP-ribosylating toxin critical for the pathogenesis of Salmonella infections.
ADP Ribose Transferases↗
High-fat, high-cholesterol diet increases the incidence of gastritis in LDL receptor-negative mice.
Transgenic and knockout mice are widely used as models for atherogenesis studies. While developing a Helicobacter infection model in LDL receptor-negative (LDLR(-/-)) mice, we noticed that mice fed a high-fat, high-cholesterol diet often contracted gastritis independent of infection. To further investigate this finding, we studied 27 male and 18 female LDLR(-/-) mice fed high-fat, 1% or 1.25% cholesterol diets for 3 to 4 months. The extent of atherosclerosis was morphometrically analyzed in the whole aorta, and the degree of gastric inflammation was scored histologically in hematoxylin-eosin-stained stomach sections. The autoantibody titers to epitopes of oxidized LDL were also measured. Mice fed high-fat, high-cholesterol diets had a significantly higher incidence of gastritis than mice fed normal chow, 62% versus 5%, respectively (P<0.0001). This effect was specific for LDLR(-/-) mice, because no difference in gastritis was found in wild-type mice fed either diet. Animals with gastritis showed slightly more atherosclerosis than animals without gastritis: 16.3+/-6.4% versus 12.8+/-3.4% in males and 9.4+/-3.5% versus 6.5+/-3.3% in females. Cholesterol-fed mice also had significantly higher IgG autoantibody titers against modified LDL than normal chow-fed animals, but no difference was seen between the gastritis and nongastritis groups. We conclude that the standard high-fat, high-cholesterol diet commonly used in many murine models to induce atherosclerosis increased the incidence of gastritis significantly in LDLR(-/-) mice.
Animals↗
Diverse virulence traits underlying different clinical outcomes of Salmonella infection.
Salmonella strains have evolved to infect a wide variety of reptiles, birds, and mammals resulting in many different syndromes ranging from colonization and chronic carriage to acute fatal disease. Adaptation to a large number of different evolutionary niches has undoubtedly driven the high degree of phenotypic and genotypic diversity in Salmonella strains. Differences in LPS and flagellar structure generate the antigenic variation that is reflected in the more than 2,000 known serotypes. Moreover, variations of LPS structure affect the virulence of the strain. The differential expression of various fimbriae by Salmonella is likely to be due to the wide variety of mucosal surfaces that are encountered by various strains, and the host immune response may select for a different expression pattern. As with these surface structures, a variety of other important virulence determinants show a variable distribution in Salmonella strains and also serve to delineate the divergence of the Salmonella lineage from E. coli. The acquisition of the SPI-1 region may have represented the defining genetic event in the separation of the Salmonella and E. coli lineages. The SPI-1 cell invasion function allowed Salmonella to establish a separate niche in epithelial cells. The mgtC locus on SPI-3 is also present in all lineages and facilitates the adaptation of the bacteria to the low Mg2+, low pH environment of the endosome that results from SPI-1-mediated invasion. Subsequent acquisition of SPI-2 allowed Salmonella to manipulate the sorting of the endosome or phagosome, altering the intracellular environment and facilitating bacterial growth within infected cells. The ability to disseminate from the bowel and establish extraintestinal niches is promoted by the spv locus. Since Salmonella proliferates within macrophages and must avoid phagocytosis by neutrophils to establish a systemic infection, the spv genes appear to promote the macrophage phase of the disease process. Here the polymorphism of the spv locus is clearly demonstrated, since the serovars that cause most cases of nontyphoid bacteremia contain the spv genes. The absence of the spv genes from S. typhi is particularly puzzling and is a strong indication that the pathogenesis of typhoid fever is fundamentally different from that of bacteremia due to nontyphoid Salmonella. There is currently no genetic explanation for the phenotype of host adaptation or for the finding that only a few serovars cause the majority of human infections. Based on recent findings that multiple individual virulence genes have a variable distribution in Salmonella, it is unlikely that a single locus will be found to be responsible for these complex biological traits. Instead, a complicated combination of genes are likely to contribute to the overall virulence phenotype.
Animals↗
Bursal sporotrichosis: case report and review.
We describe a patient whose prepatellar bursa was infected with Sporothrix schenckii. The infection persisted despite itraconazole therapy and cure was achieved only after surgical excision of the bursa. A review of treatments for bursal sporotrichosis is presented.
Bursa, Synovial↗
Genetic evidence for the role of the Lv locus in early susceptibility but not IL-10 synthesis in experimental coccidioidomycosis in C57BL mice.
Loci on chromosome 4 near Lv and on chromosome 6 near Tnfr1 are associated with resistance to coccidioidomycosis in mice. To assess the importance of the Lv locus, we compared C57BL/6 (B6) with C57BL/10 (B10), strains that are nearly congenic for the Lv locus. Fourteen days after intraperitoneal infection, B6 mice had nearly 100-fold more Coccidioides immitis in their lungs than did B10 mice (log 6.2 vs. log 4.8). Furthermore, the time to 50% deaths was 15 days for B6 and 22 days for B10. Nevertheless, 90% of B10 mice had died by day 28. In other mouse strains, we found a direct correlation between lung colony-forming units and levels of interleukin (IL)-10 and IL-4 mRNA, but B10 mice had 100-fold higher lung levels of IL-10 and 10-fold higher levels of IL-4 mRNA than did B6 mice, despite having less C. immitis. In the absence of IL-10, B10 mice are resistant to lethal infection. These results suggest that a locus near Lv is responsible for early resistance to coccidioidomycosis but not for modulating the IL-10 and IL-4 responses. This locus is not sufficient to make C57BL mice resistant to coccidioidomycosis.
Animals↗
Non-typhoid Salmonella: a review.
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Anti-Bacterial Agents↗
Extended-spectrum beta-lactamases: a plague of plasmids.
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Gram-Negative Bacteria↗
Genes influencing resistance to Coccidioides immitis and the interleukin-10 response map to chromosomes 4 and 6 in mice.
Coccidioidomycosis is a fungal infection that is endemic in the southwestern United States. Infection is more severe in blacks and Filipinos, which suggests that there is a genetic basis for susceptibility to this infection in humans. We found that there is also a difference in resistance to Coccidioides immitis infection among inbred mouse strains: B6 mice are susceptible, while DBA/2 mice are resistant (T. N. Kirkland and J. Fierer, Infect. Immun. 40:912-916, 1983). In this paper we report the results of our efforts to map the genes responsible for resistance to this infection in mice. Mice were infected by intraperitoneal inoculation, and 15 days later the numbers of viable fungi in their lungs and spleens were enumerated. We also determined the amounts of interleukin-10 mRNA made in the infected lungs. These three phenotypes were mapped as quantitative traits by using the 26 available lines of recombinant inbred mice derived from a cross between B6 and DBA/2 mice. The best associations were those between the regions near the Lv locus on chromosome 4 and the Tnfr1 locus on chromosome 6. We then infected backcross mice [(B6 x DBA/2) x B6] and confirmed these associations; 14 of 16 (87%) mice that were heterozygous at both Lv and Tnfr1 were resistant to infection, whereas only 4 of 16 (25%) mice that were homozygous B6 at both loci were resistant. These are the first genetic loci to be associated with susceptibility to C. immitis, but there may be additional genes involved in murine resistance to this infection.
Animals↗
The crucial role of polymorphonuclear leukocytes in resistance to Salmonella dublin infections in genetically susceptible and resistant mice.
Macrophages are considered to be the mediators of resistance to extra-intestinal Salmonella infections. Nevertheless, the initial cellular response to Salmonella infections consists primarily of polymorphonuclear leukocytes (PMN). To determine whether PMN serve an important function for the infected host, we made mice neutropenic with the rat mAb to RB6-8C5 and infected them i.v. with approximately 10(3) Salmonella dublin or an isogenic derivative that lacks the virulence plasmid (LD842). We infected BALB/c mice, which have a point mutation in the macrophage-expressed gene Nramp1 that makes them susceptible to Salmonella, and BALB/c.D2 congenic mice, which have the wild-type Nramp1 gene that makes them resistant to Salmonella. Both mouse strains were resistant to LD842, and neutropenia made only the BALB/c strain susceptible to this infection. Neutropenic congenic mice, however, were susceptible only to wild-type S. dublin (plasmid+). These results show a complex interplay between plasmid-virulence genes in Salmonella, host macrophages, and PMN. Mice with normal macrophages need PMN to defend against nontyphoid Salmonella that carry a virulence plasmid but not against Salmonella without virulence plasmids. Mice with a mutant Nramp1 gene need PMN to defend against all Salmonella, even those that lack virulence plasmids. These results, plus the evidence that PMN kill Salmonella efficiently in vitro, suggest that Salmonella have adapted to grow inside macrophages where they are relatively sheltered from PMN. The adaptations that allow Salmonella to survive in macrophages do not protect them from PMN.
Alleles↗
Importance of interleukin-10 in genetic susceptibility of mice to Coccidioides immitis.
Inbred strains of mice vary in their susceptibility to Coccidioides immitis. We infected resistant DBA/2 (D2) mice and three susceptible strains of mice (C57BL/6 [B6], BALB/c, and CAST/Ei) by intraperitoneal injection of arthroconidia and determined the severity of infection based on colony counts of fungus in the spleens and lungs 14 days after infection. We used quantitative reverse transcription-PCR to measure the amounts of cytokines made in the spleens and lungs of infected mice. Susceptible mice made 1, 000-fold more interleukin-10 (IL-10) than resistant D2 mice and about 10-fold more IL-4. In contrast, D2 mice had more IL-12 p40 in their lungs than did B6 mice. Resistant and susceptible mice made equivalent amounts of gamma interferon, IL-6, and IL-2. In order to determine whether IL-10 adversely affected the response to C. immitis, we infected IL-10-deficient mice, and they were found to be as resistant as D2 mice. This result indicates that IL-10 plays a crucial role in determining susceptibility to C. immitis in inbred mice. Because IL-4 mRNA levels were higher in most strains of susceptible mice, we also infected IL-4-deficient B6 mice. They were more resistant than B6 controls but not as resistant as IL-10-deficient mice. Thus, both IL-10 and IL-4 adversely affect the ability of C57BL mice to resist infection with C. immitis, but IL-10 has a larger effect and is the cytokine that is consistently associated with susceptibility in all strains of inbred mice.
Animals↗
D-myo-Inositol 1,4,5,6-tetrakisphosphate produced in human intestinal epithelial cells in response to Salmonella invasion inhibits phosphoinositide 3-kinase signaling pathways.
Several inositol-containing compounds play key roles in receptor-mediated cell signaling events. Here, we describe a function for a specific inositol polyphosphate, D-myo-inositol 1,4,5,6-tetrakisphosphate [Ins(1,4,5,6)P4], that is produced acutely in response to a receptor-independent process. Thus, infection of intestinal epithelial cells with the enteric pathogen Salmonella, but not with other invasive bacteria, induced a multifold increase in Ins(1,4,5,6)P4 levels. To define a specific function of Ins(1,4,5,6)P4, a membrane-permeant, hydrolyzable ester was used to deliver it to the intracellular compartment, where it antagonized epidermal growth factor (EGF)-induced inhibition of calcium-mediated chloride (Cl-) secretion (CaMCS) in intestinal epithelia. This EGF function is likely mediated through a phosphoinositide 3-kinase (PtdIns3K)-dependent mechanism because the EGF effects are abolished by wortmannin, and three different membrane-permeant esters of the PtdIns3K product phosphatidylinositol 3,4,5-trisphosphate mimicked the EGF effect on CaMCS. We further demonstrate that Ins(1,4,5,6)P4 antagonized EGF signaling downstream of PtdIns3K because Ins(1,4,5, 6)P4 interfered with the PtdInsP3 effect on CaMCS without affecting PtdIns3K activity. Thus, elevation of Ins(1,4,5,6)P4 in Salmonella-infected epithelia may promote Cl- flux by antagonizing EGF inhibition mediated through PtdIns3K and PtdInsP3.
Epidermal Growth Factor↗
Role of intestinal epithelial cells in the host secretory response to infection by invasive bacteria. Bacterial entry induces epithelial prostaglandin h synthase-2 expression and prostaglandin E2 and F2alpha production.
Increased intestinal fluid secretion is a protective host response after enteric infection with invasive bacteria that is initiated within hours after infection, and is mediated by prostaglandin H synthase (PGHS) products in animal models of infection. Intestinal epithelial cells are the first host cells to become infected with invasive bacteria, which enter and pass through these cells to initiate mucosal, and ultimately systemic, infection. The present studies characterized the role of intestinal epithelial cells in the host secretory response after infection with invasive bacteria. Infection of cultured human intestinal epithelial cell lines with invasive bacteria, but not noninvasive bacteria, is shown to induce the expression of one of the rate-limiting enzymes for prostaglandin formation, PGHS-2, and the production of PGE2 and PGF2alpha. Furthermore, increased PGHS-2 expression was observed in intestinal epithelial cells in vivo after infection with invasive bacteria, using a human intestinal xenograft model in SCID mice. In support of the physiologic importance of epithelial PGHS-2 expression, supernatants from bacteria-infected intestinal epithelial cells were shown to increase chloride secretion in an in vitro model using polarized epithelial cells, and this activity was accounted for by PGE2. These studies define a novel autocrine/paracrine function of mediators produced by intestinal epithelial cells in the rapid induction of increased fluid secretion in response to intestinal infection with invasive bacteria.
Animals↗
Secretion of proinflammatory cytokines by epithelial cells in response to Chlamydia infection suggests a central role for epithelial cells in chlamydial pathogenesis.
Chlamydia species infect epithelial cells at mucosal surfaces, and are major causes of sexually transmitted diseases. Infection is characterized by inflammation which is exacerbated upon reinfection, ultimately leading to tissue damage and scarring. Although central for the development of disease manifestations, little is known about the mechanisms that initiate and sustain the inflammatory response to Chlamydia. Infection of cervical and colonic epithelial cells with Chlamydia trachomatis and Chlamydia psittaci is shown in the present studies to upregulate mRNA expression and secretion of the proinflammatory cytokines IL-8, GRO alpha, GM-CSF, and IL-6. In contrast to the rapid, but transient, cytokine induction following infection with other invasive bacteria, the epithelial cytokine response to Chlamydia was delayed until 20-24 h after infection, persisted throughout the chlamydial growth cycle (2-4 d), and required bacterial protein synthesis. Moreover, epithelial cell lines and primary endocervical epithelial cells released IL-1alpha after Chlamydia infection, and increased secretion of the proinflammatory cytokines could be inhibited by anti-IL-1alpha. This suggests that IL-1alpha, released following lysis of infected epithelial cells, may amplify the inflammatory response by stimulating additional cytokine production by noninfected neighboring cells. These findings suggest a novel pathophysiologic concept wherein the acute host response to Chlamydia at mucosal surfaces is primarily initiated and sustained by epithelial cells, the first and major targets of chlamydial infection.
Actins↗
Pasteurella multocida epiglottitis.
Pasteurella multocida, a small gram-negative coccobacillus, colonizes the nasopharynx and gastrointestinal tract of many animals, including cats and dogs. Most human infections with P multocida are due to animal bites, but the respiratory tract is the second most common site of infection. We describe the third case report (to out knowledge) of acute P multocida epiglottitis. The mode of transmission in this case was inhalation of infectious nasopharyngeal secretions from cats. The patient responded well to treatment with penicillin, the drug of choice for P multocida infections. Therefore, infection with P multocida, though rare, should be considered in the differential diagnosis in any case involving acute epiglottitis and exposure to cats.
Acute Disease↗
Bactericidal effect of ADP and acetic acid on Bacillus subtilis.
Bacillus subtilis is a ubiquitous soil bacterium used for measuring the beta-lysin activity and in other bioassays. We observed a complete bactericidal effect of ADP on B. subtilis at concentrations of 50-100 microM at pH values <5.5, which disappeared at pH values above 6. The effect was also found for acetic acid at concentrations >17.4 microM and similar pH values. ATP, adenosine, and HCl were not bactericidal. We used BCECF-AM, a pH-sensitive probe, and found that the killing of B. subtilis was due to a change in the intracellular pH caused by the passage across the cell membrane of these weak organic acids when incubated with B. subtilis at pH values near the pK. More experiments are needed to determine the biological meaning of these in vitro findings.
Acetic Acid↗
Nosocomial infections in HIV-infected patients: preliminary results from a multicenter surveillance system (1989-1995).
OBJECTIVE: To describe the characteristics of and trends in nosocomial infection among human immunodeficiency virus (HIV)-infected patients. DESIGN: Multicenter prospective cohort study. SETTING/PATIENTS: HIV-infected patients were enrolled at time of first inpatient admission at five Veterans' Administration Medical Centers (VAMCs). RESULTS: As of March 1995, 2,541 patients with 6,625 inpatient admissions had been monitored in the five VAMCs. A total of 530 nosocomial infections were detected using standard Centers for Disease Control and Prevention definitions. Overall distribution by infection site was 31% for primary bloodstream infections (BSIs), 28% for urinary tract infections, 15% for pneumonia, and 26% for all other sites. Of BSIs, 63% were central line-associated bloodstream infections (CLABs). The rate of CLABs per 1,000 central line days was 6.5 (range, 2.3-8.3) for all patients from participating hospitals, similar to the median CLAB rate of 6.0 for patients in medical intensive-care units (ICUs) of National Nosocomial Infections Surveillance (NNIS) System hospitals from January 1990 through September 1994. For ICU-specific CLABs, the rate from hospitals reporting at least one ICU CLAB was 12.7 (range, 12.1-13.1), comparable to the 90th percentile of NNIS hospital medical ICUs (13.1). Staphylococcus aureus, associated with 35% of BSIs, was the most common nosocomial BSI pathogen. Our data demonstrated the following: 13 (10%) of 134 patients with CD4 counts > or = 200 cells/mm3 had a CLAB, compared with 61 (6%) of 1,011 patients with CD4 counts < 200 cells/mm3, P = .08; the per-day risk of CLABs did not change with increased duration of catheterization (P = .4); and the per-day risk of a temporary (ie, short-term) CLAB was greater than that of a permanent CLAB (P < .001). CONCLUSIONS: The data suggest that HIV-infected patients were at higher risk of acquiring a BSI than were patients in the NNIS population; patients with CD4 counts > or = 200 cell/mm3 and temporary central lines were at increased risk for BSI, perhaps reflecting widespread prophylaxis with trimethoprim-sulfamethoxazole among patients with CD4 counts < 200 cells/mm3, and, in contrast to most studies, S aureus, not coagulase-negative Staphylococcus, was the most common BSI pathogen.
AIDS-Related Opportunistic Infections↗
Role of alphabeta and gammadelta T cells in the host response to Salmonella infection as demonstrated in T-cell-receptor-deficient mice of defined Ity genotypes.
Salmonella spp. are facultative intracellular bacteria which enter the body through the intestinal tract. We studied the roles of T cells expressing either the alpha and beta chains or the gamma and delta chains of the T-cell receptor (alphabeta T cells or gammadelta T cells, respectively) in the host defense against Salmonella using mice genetically deficient in either alphabeta T cells, gammadelta T cells, or both T-cell subsets. These mutant strains of mice were infected orally or intraperitoneally with Salmonella dublin, and the progression of the disease was monitored by determining bacterial numbers in the feces, gut wall, Peyer's patches, mesenteric lymph nodes, spleen, and liver. Since susceptibility to Salmonella infection in mice is strongly affected by the alleles at the Ity locus, T-cell-mutant mice with either the Ity-sensitive or Ity-resistant phenotype were tested for resistance to S. dublin infection. We found that even though large numbers of intraepithelial and mucosal alphabeta and gammadelta T cells populate the normal intestine, they have no role in controlling the invasion of S. dublin into the intestine or the subsequent bacterial replication in the Peyer's patches or gut wall. Furthermore, systemic infections were equally severe for the first 6 days in normal, alphabeta T-cell-deficient, and gammadelta T-cell-deficient mice, and alphabeta but not gammadelta T cells were required for clearance of S. dublin, regardless of the Ity phenotype. However, mice that lacked both T-cell subsets had higher bacterial counts in their livers 15 to 18 days after infection than did alphabeta T-cell-deficient mice, suggesting that gammadelta T cells can contribute to acquired immunity to S. dublin.
Animals↗