Anna Cristina Garza-Mayers

Bacterial subversion of host innate immune pathways.

Defense and Counter-Defense Provided a pathogen can enter the body and survive coughing and spluttering, peristalsis, and mucus, the first active responses the host evokes to an invading organism will be at the level of the first cell encountered, well before classical cellular immunity and antibody responses are initiated. Randow et al. (p. 701) review the range of intracellular defenses against incoming pathogens and describe how compartmental boundaries within the cell provide multiple levels at which pathogens can be thwarted in their attempts to subjugate the cell to do their bidding. Baxt et al. (p. 697) review the range of evasion tactics that bacterial pathogens can summon to counter host repulsion and establish a niche in which to replicate and ensure onward transmission. The pathogenesis of infection is a continuously evolving battle between the human host and the infecting microbe. The past decade has brought a burst of insights into the molecular mechanisms of innate immune responses to bacterial pathogens. In parallel, multiple specific mechanisms by which microorganisms subvert these host responses have been uncovered. This Review highlights recently characterized mechanisms by which bacterial pathogens avoid killing by innate host responses, including autophagy pathways and a proinflammatory cytokine transcriptional response, and by the manipulation of vesicular trafficking to avoid the toxicity of lysosomal enzymes.

Shigella flexneri Regulation of ARF6 Activation during Bacterial Entry via an IpgD-Mediated Positive Feedback Loop

ABSTRACT Entry into cells is critical for virulence of the human bacterial pathogens Shigella spp. Shigella spp. induce membrane ruffle formation and macropinocytic uptake, but the events instigating this process are incompletely understood. The host small GTPase ADP-ribosylation factor 6 (ARF6) functions in membrane trafficking at the plasma membrane and activates membrane ruffle formation. We demonstrate that ARF6 is required for efficient Shigella flexneri entry, is activated by S. flexneri dependent on the phosphatase activity of the type III secreted effector IpgD, and depends on cytohesin guanine nucleotide exchange factors (GEFs) for recruitment to entry sites. The cytohesin GEF ARF nucleotide binding site opener (ARNO) is recruited to these sites, also dependent on IpgD phosphatase activity. ARNO recruitment is independent of ARF6, indicating that, in addition to the described recruitment of ARNO by ARF6, ARNO is recruited upstream of ARF6. Our data provide evidence that ARF6, IpgD, phosphoinositide species, and ARNO constitute a previously undescribed positive feedback loop that amplifies ARF6 activation at bacterial entry sites, thereby promoting efficient S. flexneri uptake. IMPORTANCE Shigella spp. cause diarrhea and dysentery by infection of epithelial cells in the human colon. Critical to disease is the ability of Shigella to enter into cells, yet the mechanisms involved in entry are incompletely understood. We demonstrate that the small GTPase ADP-ribosylation factor 6 (ARF6) is required for efficient cellular entry of Shigella flexneri and that activation of ARF6 depends on the phosphatase activity of the Shigella protein IpgD, which is introduced into cells via the bacterial type III secretion system. We further show that IpgD phosphatase activity is required for recruitment of the ARF6 guanine nucleotide exchange factor (GEF) ARF nucleotide binding site opener (ARNO) to bacterial entry sites and that ARNO lies upstream of ARF6 activation. These relationships define a positive feedback loop that contributes to activation of ARF6 at S. flexneri entry sites and leads to local amplification of signals that promote bacterial entry. Shigella spp. cause diarrhea and dysentery by infection of epithelial cells in the human colon. Critical to disease is the ability of Shigella to enter into cells, yet the mechanisms involved in entry are incompletely understood. We demonstrate that the small GTPase ADP-ribosylation factor 6 (ARF6) is required for efficient cellular entry of Shigella flexneri and that activation of ARF6 depends on the phosphatase activity of the Shigella protein IpgD, which is introduced into cells via the bacterial type III secretion system. We further show that IpgD phosphatase activity is required for recruitment of the ARF6 guanine nucleotide exchange factor (GEF) ARF nucleotide binding site opener (ARNO) to bacterial entry sites and that ARNO lies upstream of ARF6 activation. These relationships define a positive feedback loop that contributes to activation of ARF6 at S. flexneri entry sites and leads to local amplification of signals that promote bacterial entry.

Review of treatment for discoid lupus erythematosus

Discoid lupus erythematosus (DLE) is a chronic cutaneous disease characterized by inflammatory plaques that, in the absence of prompt diagnosis and treatment, may lead to disfiguring scarring and skin atrophy. However, there is limited evidence for which treatments are most effective. Currently, no medications have been approved specifically for the treatment of DLE. Many of the drugs described in the literature were developed for use in other immune disorders. This review will summarize current therapeutic options for DLE and their supporting evidence with discussion of prevention, topical measures, physical modalities, and systemic therapies, including newer potential therapies.

Effect of Dermatology Consultation on Outcomes for Patients With Presumed Cellulitis: A Randomized Clinical Trial

Importance Each year, cellulitis leads to 650 000 hospital admissions and is estimated to cost

Location of skin lesions in Henoch-Schönlein purpura and its association with significant renal involvement

3.7 billion in the United States. Previous literature has demonstrated a high misdiagnosis rate for cellulitis, which results in unnecessary antibiotic use and health care cost. Objective To determine whether dermatologic consultation decreases duration of hospital stay or intravenous antibiotic treatment duration in patients with cellulitis. Design, Setting, and Participants This randomized clinical trial was conducted in a large urban tertiary care hospital between October 2012 and January 2017, with 1-month follow-up duration. Patients were randomized to the control group, which received the standard of care (ie, treatment by primary medicine team), or the intervention group, which received dermatology consultation. Medical chart review of demographic information and hospital courses was performed. Adult patients hospitalized with presumed diagnosis of cellulitis were eligible. A total of 1300 patients were screened, 1125 were excluded, and 175 were included. Statistical analysis was employed to identify significant outcome differences between the 2 groups. Interventions Dermatology consultation within 24 hours of hospitalization. Main Outcomes and Measures Length of hospital stay and duration of intravenous antibiotic treatment. Results Of 175 participants, 70 (40%) were women and 105 (60%) were men. The mean age was 58.8 years. Length of hospital stay was not statistically different between the 2 groups. The duration of intravenous antibiotic treatment (<4 days: 86.4% vs 72.5%; absolute difference, 13.9%; 95% CI, 1.9%-25.9%; P = .04) and duration of total antibiotic treatment was significantly lower in patients who had early dermatology consultation (<10 days: 50.6% vs 32.5%; absolute difference, 18.1%; 95% CI, 3.7%-32.5%; P = .01). Clinical improvement at 2 weeks was significantly higher for those in the intervention group (79 [89.3%] vs 59 [68.3%]; absolute difference, 21.0%; 95% CI, 9.3%-32.7%; P < .001). There was no significant difference in 1-month readmission rate between the groups (4 [4.5%] vs 6 [6.9%]; absolute difference, −2.4%; 95% CI, −9.3% to 4.5%; P = .54). In the intervention group, the rate of cellulitis misdiagnosis was 30.7% (27 of 88 participants). Among the entire cohort, 101 (57.7%) patients were treated with courses of antibiotics longer than what is recommended by guidelines. Conclusions and Relevance Early dermatologic consultation can improve outcomes in patients with suspected cellulitis by identifying alternate diagnoses, treating modifiable risk factors, and decreasing length of antibiotic treatment. Trial Registration clinicaltrials.gov Identifier: NCT01706913

Clinical Usefulness of Imaging and Blood Cultures in Cellulitis Evaluation

Background: Henoch‐Schönlein purpura (HSP) is a small vessel IgA‐predominant vasculitis. Objective: To describe adult patients with HSP and determine if the distribution of skin lesions (ie, purpura above the waist or purpura below the waist only), is a predictor of significant renal involvement at the time of the skin biopsy and the months following. Methods: A retrospective study on renal function from 72 adult patients with skin‐biopsy proven HSP. Longitudinal renal data were analyzed after HSP diagnosis by using baseline renal function for comparison. Results: Statistical analysis adjusted for sex, age, and baseline creatinine revealed a trend between HSP lesions only on the upper and lower extremities and long‐term renal involvement (4.767, P = .067). Moreover, in another analysis adjusted for age and baseline creatinine, lesions located only on the upper and lower extremities significantly increased the odds of having long‐term significant renal involvement (6.55, P = .049) in men. Limitations: This retrospective study used patient information that was subject to selection bias. Conclusion: In patients with HSP, skin lesion distribution on the extremities might be predictive of significant long‐term renal involvement and might be critical for risk stratification and development of personalized diagnostics and therapeutics.

The Successful Use of Apixaban in Dialysis Patients with Calciphylaxis Who Require Anticoagulation: A Retrospective Analysis

volve a shorter duration of antibiotic exposure.6 Our study has limitations. First, we were not able to account for underlying conditions or other indicators for longer courses of antibiotic therapy. Second, by excluding visits with a diagnosis of unspecified sinusitis from our analysis, we may have excluded some cases of acute sinusitis. However, the findings of a sensitivity analysis that included cases of both acute and unspecified sinusitis were similar (median duration of therapy, 10.0 days; 88.1% [95% CI, 85.1%-91.0%] of nonazithromycin antibiotic courses were 10 days or longer in duration). Outpatient antibiotic stewardship programs can optimize infection management by ensuring guideline-concordant treatment, including the use of minimum effective durations of antibiotic therapy. The durations of most courses of antibiotic therapy for adult outpatients with sinusitis exceed guideline recommendations, which represents an opportunity to reduce the unnecessary use of antibiotics when therapy with antibiotics is indicated.

Identification of interactions among host and bacterial proteins and evaluation of their role early during Shigella flexneri infection

Calciphylaxis is a disease of dermal arteriolar calcification that results in necrosis. It commonly occurs in individuals with end-stage renal disease (ESRD) on hemodialysis and is associated with a high morbidity and mortality. Warfarin use is an identified risk factor. Twenty patients with ESRD on dialysis with calciphylaxis who were treated with apixaban for indications of deep vein thrombosis or atrial fibrillation were identified. There were no reports of thrombosis. Three individuals experienced bleeding requiring a transfusion, and anticoagulation was resumed without further event. Findings suggest that apixaban may be a safe and effective alternative to warfarin in patients with ESRD on dialysis with calciphylaxis.

Skin Surface Temperatures Measured by Thermal Imaging Aid in the Diagnosis of Cellulitis

Shigella species cause diarrhoea by invading and spreading through the epithelial layer of the human colon. The infection triggers innate immune responses in the host that the bacterium combats by translocating into the host cell cytosol via a type 3 secretion system bacterial effector proteins that interfere with host processes. We previously demonstrated that interaction of the Shigella type 3 secreted effector protein IcsB with the host protein Toca-1 inhibits the innate immune response microtubule-associated protein light-chain 3 (LC3)-associated phagocytosis, and that IcsB interaction with Toca-1 is required for inhibition of this host response. Here, we show that Toca-1 in vitro precipitated not only IcsB, but also the type 3 secreted proteins OspC3, IpgD and IpaB. OspC3 and IpgD precipitation with Toca-1 was dependent on IcsB. Early during infection, most of these proteins localized near intracellular Shigella. We examined whether interactions among these proteins restrict innate host cell responses other than LC3-associated phagocytosis. In infected cells, OspC3 blocks production and secretion of the mature pro-inflammatory cytokine IL-18; however, we found that interaction of OspC3 with IcsB, either directly or indirectly via Toca-1, was not required for OspC3-mediated restriction of IL-18 production. These results indicate that interactions of the host protein Toca-1 with a subset of type 3 effector proteins contribute to the established function of some, but not all involved, effector proteins.