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Infectious Disease

DeFrancesco AS, Masloboeva N, Syed AK, DeLoughery A, Bradshaw N, Li G-W, Gilmore MS, Walker S, Losick R. Genome-wide screen for genes involved in eDNA release during biofilm formation by Staphylococcus aureus. Proc Natl Acad Sci U S A 2017;114(29):E5969-E5978.Abstract
Staphylococcus aureus is a leading cause of both nosocomial and community-acquired infection. Biofilm formation at the site of infection reduces antimicrobial susceptibility and can lead to chronic infection. During biofilm formation, a subset of cells liberate cytoplasmic proteins and DNA, which are repurposed to form the extracellular matrix that binds the remaining cells together in large clusters. Using a strain that forms robust biofilms in vitro during growth under glucose supplementation, we carried out a genome-wide screen for genes involved in the release of extracellular DNA (eDNA). A high-density transposon insertion library was grown under biofilm-inducing conditions, and the relative frequency of insertions was compared between genomic DNA (gDNA) collected from cells in the biofilm and eDNA from the matrix. Transposon insertions into genes encoding functions necessary for eDNA release were identified by reduced representation in the eDNA. On direct testing, mutants of some of these genes exhibited markedly reduced levels of eDNA and a concomitant reduction in cell clustering. Among the genes with robust mutant phenotypes were gdpP, which encodes a phosphodiesterase that degrades the second messenger cyclic-di-AMP, and xdrA, the gene for a transcription factor that, as revealed by RNA-sequencing analysis, influences the expression of multiple genes, including many involved in cell wall homeostasis. Finally, we report that growth in biofilm-inducing medium lowers cyclic-di-AMP levels and does so in a manner that depends on the gdpP phosphodiesterase gene.
Li H, Reksten TR, Ice JA, Kelly JA, Adrianto I, Rasmussen A, Wang S, He B, Grundahl KM, Glenn SB, Miceli-Richard C, Bowman S, Lester S, Eriksson P, Eloranta M-L, Brun JG, Gøransson LG, Harboe E, Guthridge JM, Kaufman KM, Kvarnström M, Cunninghame Graham DS, Patel K, Adler AJ, Farris DA, Brennan MT, Chodosh J, Gopalakrishnan R, Weisman MH, Venuturupalli S, Wallace DJ, Hefner KS, Houston GD, Huang AJW, Hughes PJ, Lewis DM, Radfar L, Vista ES, Edgar CE, Rohrer MD, Stone DU, Vyse TJ, Harley JB, Gaffney PM, James JA, Turner S, Alevizos I, Anaya J-M, Rhodus NL, Segal BM, Montgomery CG, Scofield HR, Kovats S, Mariette X, Rönnblom L, Witte T, Rischmueller M, Wahren-Herlenius M, Omdal R, Jonsson R, Ng W-F, for Registry UKPS's S, Nordmark G, Lessard CJ, Sivils KL. Identification of a Sjögren's syndrome susceptibility locus at OAS1 that influences isoform switching, protein expression, and responsiveness to type I interferons. PLoS Genet 2017;13(6):e1006820.Abstract
Sjögren's syndrome (SS) is a common, autoimmune exocrinopathy distinguished by keratoconjunctivitis sicca and xerostomia. Patients frequently develop serious complications including lymphoma, pulmonary dysfunction, neuropathy, vasculitis, and debilitating fatigue. Dysregulation of type I interferon (IFN) pathway is a prominent feature of SS and is correlated with increased autoantibody titers and disease severity. To identify genetic determinants of IFN pathway dysregulation in SS, we performed cis-expression quantitative trait locus (eQTL) analyses focusing on differentially expressed type I IFN-inducible transcripts identified through a transcriptome profiling study. Multiple cis-eQTLs were associated with transcript levels of 2'-5'-oligoadenylate synthetase 1 (OAS1) peaking at rs10774671 (PeQTL = 6.05 × 10-14). Association of rs10774671 with SS susceptibility was identified and confirmed through meta-analysis of two independent cohorts (Pmeta = 2.59 × 10-9; odds ratio = 0.75; 95% confidence interval = 0.66-0.86). The risk allele of rs10774671 shifts splicing of OAS1 from production of the p46 isoform to multiple alternative transcripts, including p42, p48, and p44. We found that the isoforms were differentially expressed within each genotype in controls and patients with and without autoantibodies. Furthermore, our results showed that the three alternatively spliced isoforms lacked translational response to type I IFN stimulation. The p48 and p44 isoforms also had impaired protein expression governed by the 3' end of the transcripts. The SS risk allele of rs10774671 has been shown by others to be associated with reduced OAS1 enzymatic activity and ability to clear viral infections, as well as reduced responsiveness to IFN treatment. Our results establish OAS1 as a risk locus for SS and support a potential role for defective viral clearance due to altered IFN response as a genetic pathophysiological basis of this complex autoimmune disease.
Inomata T, Ono K, Matsuba T, Shiang T, Di Zazzo A, Nakatani S, Yamaguchi M, Ebihara N, Murakami A. Pre-banking microbial contamination of donor conjunctiva and storage medium for penetrating keratoplasty. Jpn J Ophthalmol 2017;Abstract
PURPOSE: The aims of this study were to investigate the incidence of positive donor tissue cultures before transfer to preservation medium (Optisol™-GS) for penetrating keratoplasty, to verify the efficacy of antibiotics contained in Optisol™-GS by examining the drug susceptibility and to assess the relationship between the results of our microbial assessments as well as donor factors and the incidence of contamination. METHODS: We conducted a retrospective, cross-sectional study using Juntendo Eye Bank records for all corneal transplantations. Two hundred donor conjunctiva harvestings and storage medium (EP-II(®)) cultures were performed between July 2008 and June 2011. We analyzed the associations between donor factors (age, gender, history of cataract surgery, death-to-preservation interval, cause of death) and contamination rates using multivariate analysis by the generalized estimating equation model. RESULTS: We obtained positive bacterial cultures from 154 of the 200 eyes (77.0%). The isolated bacteria were indigenous, such as coagulase-negative Staphylococci, Corynebacterium sp., and methicillin-resistant Staphylococcus aureus (MRSA). There was significant resistance to levofloxacin (18 eyes, 9.0%) and gentamicin (12 eyes, 6.0%), and no vancomycin-resistant bacteria were detected. The donor factors did not correlate with the prevalence of bacterial contamination in our criteria. CONCLUSIONS: Pre-banking microbial assessment allows for microbial detection, bacterial susceptibility and resistance testing. This is useful for developing preservation mediums containing effective spectrum antibiotic agents for high quality control of corneal banking.
Ibberson CB, Stacy A, Fleming D, Dees JL, Rumbaugh K, Gilmore MS, Whiteley M. Co-infecting microorganisms dramatically alter pathogen gene essentiality during polymicrobial infection. Nat Microbiol 2017;2:17079.Abstract
Identifying genes required by pathogens during infection is critical for antimicrobial development. Here, we use a Monte Carlo simulation-based method to analyse high-throughput transposon sequencing data to determine the role of infection site and co-infecting microorganisms on the in vivo 'essential' genome of Staphylococcus aureus. We discovered that co-infection of murine surgical wounds with Pseudomonas aeruginosa results in conversion of ∼25% of the in vivo S. aureus mono-culture essential genes to non-essential. Furthermore, 182 S. aureus genes are uniquely essential during co-infection. These 'community dependent essential' (CoDE) genes illustrate the importance of studying pathogen gene essentiality in polymicrobial communities.
Lebreton F, Manson AL, Saavedra JT, Straub TJ, Earl AM, Gilmore MS. Tracing the Enterococci from Paleozoic Origins to the Hospital. Cell 2017;169(5):849-861.e13.Abstract
We examined the evolutionary history of leading multidrug resistant hospital pathogens, the enterococci, to their origin hundreds of millions of years ago. Our goal was to understand why, among the vast diversity of gut flora, enterococci are so well adapted to the modern hospital environment. Molecular clock estimation, together with analysis of their environmental distribution, phenotypic diversity, and concordance with host fossil records, place the origins of the enterococci around the time of animal terrestrialization, 425-500 mya. Speciation appears to parallel the diversification of hosts, including the rapid emergence of new enterococcal species following the End Permian Extinction. Major drivers of speciation include changing carbohydrate availability in the host gut. Life on land would have selected for the precise traits that now allow pathogenic enterococci to survive desiccation, starvation, and disinfection in the modern hospital, foreordaining their emergence as leading hospital pathogens.
Durand ML. Bacterial and Fungal Endophthalmitis. Clin Microbiol Rev 2017;30(3):597-613.Abstract
Endophthalmitis is a severe eye infection that may result in permanent loss of useful vision in the affected eye. Most cases are exogenous and occur as a complication of cataract surgery, an intravitreal injection, or penetrating ocular trauma. Endogenous endophthalmitis results from hematogenous seeding of the eye by bacteria or fungi, but bacteremia or fungemia may be transient and patients may present without symptoms of systemic infection. Nearly all endophthalmitis patients present with decreased vision, and some also have eye pain. Eye examination usually reveals a hypopyon and intraocular inflammation. Diagnosis is clinical, supported by cultures of the vitreous and/or aqueous or by blood cultures in some endogenous cases. Molecular diagnostic techniques have been used in research laboratories for pathogen identification in endophthalmitis and offer the possibility of rapid diagnosis, including in culture-negative cases. Intravitreal injection of antibiotics is the most important component of treatment; some cases also benefit from surgical debridement of the vitreous by a vitrectomy. The visual outcome depends partly on the pathogen: coagulase-negative staphylococcal endophthalmitis has a better prognosis than does streptococcal endophthalmitis, for example. Endophthalmitis is a medical emergency, and prompt diagnosis and treatment are essential for saving vision.
Van Tyne D, Gilmore MS. Raising the Alarmone: Within-Host Evolution of Antibiotic-Tolerant Enterococcus faecium. MBio 2017;8(1)Abstract

Enterococci are ancient commensal bacteria that recently emerged as leading causes of antibiotic-resistant, hospital-acquired infection. Vancomycin-resistant enterococci (VRE) epitomize why drug-resistant enterococcal infections are a problem: VRE readily colonize the antibiotic-perturbed gastrointestinal (GI) tract where they amplify to large numbers, and from there, they infect other body sites, including the bloodstream, urinary tract, and surgical wounds. VRE are resistant to many antimicrobials and host defenses, which facilitates establishment at the site of infection and confounds therapeutic clearance. Having evolved to colonize the GI tract, VRE are comparatively ill adapted to the human bloodstream. A recent study by Honsa and colleagues (E. S. Honsa et al., mBio 8:e02124-16, 2017, https://doi.org/10.1128/mBio.02124-16) found that a strain of vancomycin-resistant Enterococcus faecium evolved antibiotic tolerance within the bloodstream of an immunocompromised host by activating the stringent response through mutation of relA Precisely how VRE colonize and infect and the selective pressures that led to the outgrowth of relA mutants are the subjects of ongoing research.

Sadaka A, Durand ML, Sisk R, Gilmore MS. Staphylococcus aureus and its Bearing on Ophthalmic Disease. Ocul Immunol Inflamm 2017;25(1):111-121.Abstract

PURPOSE: To review antibiotic resistance associated with S. aureus endophthalmitis and the virulence of S. aureus. METHODS: Review of the current and prospective approaches for treating S. aureus endophthalmitis. RESULTS: Bacterial endophthalmitis remains to be a major threat for vision. S. aureus endophthalmitis specifically, carries a poor visual prognosis making early diagnosis and treatment crucial. Methicillin resistant Staphylococcus aureus (MRSA) endophthalmitis represents a significant number of S. aureus endophthalmitis cases. MRSA with reduced susceptibility to glycopeptide antibiotics such as vancomycin (vancomycin intermediate S. aureus, VISA) have also emerged in the ocular infections, and there has been a rise in S. aureus resistance to new and old generation fluoroquinolones that are commonly used for prophylaxis after intravitreal injections and intraocular surgeries. CONCLUSIONS: With the rise in the number of penetrating procedures in the ophthalmology practice and the parallel rise in antibiotic resistance, prophylaxis and awareness of the antimicrobial resistance profiles remain crucial and the identification of novel antimicrobials is essential.

Woods SE, Lieberman MT, Lebreton F, Trowel E, de la Fuente-Núñez C, Dzink-Fox J, Gilmore MS, Fox JG. Characterization of Multi-Drug Resistant Enterococcus faecalis Isolated from Cephalic Recording Chambers in Research Macaques (Macaca spp.). PLoS One 2017;12(1):e0169293.Abstract

Nonhuman primates are commonly used for cognitive neuroscience research and often surgically implanted with cephalic recording chambers for electrophysiological recording. Aerobic bacterial cultures from 25 macaques identified 72 bacterial isolates, including 15 Enterococcus faecalis isolates. The E. faecalis isolates displayed multi-drug resistant phenotypes, with resistance to ciprofloxacin, enrofloxacin, trimethoprim-sulfamethoxazole, tetracycline, chloramphenicol, bacitracin, and erythromycin, as well as high-level aminoglycoside resistance. Multi-locus sequence typing showed that most belonged to two E. faecalis sequence types (ST): ST 4 and ST 55. The genomes of three representative isolates were sequenced to identify genes encoding antimicrobial resistances and other traits. Antimicrobial resistance genes identified included aac(6')-aph(2"), aph(3')-III, str, ant(6)-Ia, tetM, tetS, tetL, ermB, bcrABR, cat, and dfrG, and polymorphisms in parC (S80I) and gyrA (S83I) were observed. These isolates also harbored virulence factors including the cytolysin toxin genes in ST 4 isolates, as well as multiple biofilm-associated genes (esp, agg, ace, SrtA, gelE, ebpABC), hyaluronidases (hylA, hylB), and other survival genes (ElrA, tpx). Crystal violet biofilm assays confirmed that ST 4 isolates produced more biofilm than ST 55 isolates. The abundance of antimicrobial resistance and virulence factor genes in the ST 4 isolates likely relates to the loss of CRISPR-cas. This macaque colony represents a unique model for studying E. faecalis infection associated with indwelling devices, and provides an opportunity to understand the basis of persistence of this pathogen in a healthcare setting.

Torkildsen G, Abelson MB, Gomes PJ, McLaurin E, Potts SL, Mah FS. Vehicle-Controlled, Phase 2 Clinical Trial of a Sustained-Release Dexamethasone Intracanalicular Insert in a Chronic Allergen Challenge Model. J Ocul Pharmacol Ther 2017;33(2):79-90.Abstract

PURPOSE: To evaluate the efficacy and safety of a sustained-release dexamethasone intracanalicular insert (Dextenza™) in a model of allergic conjunctivitis. METHODS: This was a randomized, double-masked, vehicle-controlled, Phase 2 study. Subjects had to have a positive conjunctival allergen challenge (CAC) reaction to allergen (bilateral +2 itching and redness on 5-point, 0-4 scales) at Visit 1, and for 2 of 3 time points on subsequent visits. Subjects who met entry criteria were randomized to receive Dextenza or PV (vehicle insert). Challenges occurred over 42 days, with efficacy assessed at 14 (primary endpoint visit), 28, and 40 days postinsertion. Outcome measures included the evaluation of ocular itching, redness, tearing, chemosis, eyelid swelling, rhinorrhea, and congestion. RESULTS: Twenty-eight subjects completed the study in the Dextenza group and 31 in the vehicle group. At 14 days postinsertion, Dextenza was statistically superior to PV, with least square mean differences for ocular itching of -0.76, -0.97, and -0.87 at 3, 5, and 7 min post-CAC, and for conjunctival redness of -0.46, -0.66, and -0.68 at 7, 15, and 20 min post-CAC. Clinical significance, defined as a 1-U decrease from PV, was not met for primary efficacy. Secondary endpoints, including number of subjects reporting itching and conjunctival redness, indicated superior performance of Dextenza compared with vehicle. Eleven Dextenza-treated (35.5%) and 10 vehicle-treated (30.3%) subjects each experienced a single adverse event. CONCLUSION: This Phase 2 study demonstrated preliminary efficacy and safety data of Dextenza for treatment of allergic conjunctivitis.

Drokhlyansky E, Göz Aytürk D, Soh TK, Chrenek R, O'Loughlin E, Madore C, Butovsky O, Cepko CL. The brain parenchyma has a type I interferon response that can limit virus spread. Proc Natl Acad Sci U S A 2017;114(1):E95-E104.Abstract

The brain has a tightly regulated environment that protects neurons and limits inflammation, designated "immune privilege." However, there is not an absolute lack of an immune response. We tested the ability of the brain to initiate an innate immune response to a virus, which was directly injected into the brain parenchyma, and to determine whether this response could limit viral spread. We injected vesicular stomatitis virus (VSV), a transsynaptic tracer, or naturally occurring VSV-derived defective interfering particles (DIPs), into the caudate-putamen (CP) and scored for an innate immune response and inhibition of virus spread. We found that the brain parenchyma has a functional type I interferon (IFN) response that can limit VSV spread at both the inoculation site and among synaptically connected neurons. Furthermore, we characterized the response of microglia to VSV infection and found that infected microglia produced type I IFN and uninfected microglia induced an innate immune response following virus injection.

Zhou X, Ramke M, Chintakuntlawar AV, Lee JY, Rajaiya J, Chodosh J. Role of MyD88 in adenovirus keratitis. Immunol Cell Biol 2017;95(1):108-116.Abstract

Pattern recognition receptors (PRRs) are critical to the early detection and innate immune responses to pathogens. In particular, the toll-like receptor (TLR) system and its associated adaptor proteins have essential roles in early host responses to infection. Epidemic keratoconjunctivitis, caused by the human adenovirus, is a severe ocular surface infection associated with corneal inflammation (stromal keratitis). We previously showed that adenovirus capsid was a key molecular pattern in adenovirus keratitis, with viral DNA having a lesser role. We have now investigated the role of the adaptor molecule MyD88 in a mouse model of adenovirus keratitis in which there is no viral replication. In MyD88(-/-) mice infected with human adenovirus type 37, clinical keratitis was markedly reduced, along with infiltration of CD45(+) cells, and expression of inflammatory cytokines. Reduction of inflammatory cytokines was also observed in infected primary human corneal fibroblasts pretreated with a MyD88 inhibitory peptide. Keratitis similar to wild type mice was observed in TLR2, TLR9 and IL-1R knockout mice, but was reduced in TLR2/9 double knockout mice, consistent with synergy of TLR2 and TLR9 in the response to adenovirus infection. MyD88 co-immunoprecipitated with Src kinase in mice corneas and in human corneal fibroblasts infected with adenovirus, and MyD88 inhibitory peptide reduced Src phosphorylation, linking MyD88 activation to inflammatory gene expression through a signaling cascade previously shown to be directed by Src. Our findings reveal a critical role for the PRRs TLR2 and 9, and their adaptor protein MyD88, in corneal inflammation upon adenovirus infection.

Hodges RR, Li D, Shatos MA, Bair JA, Lippestad M, Serhan CN, Dartt DA. Lipoxin A4 activates ALX/FPR2 receptor to regulate conjunctival goblet cell secretion. Mucosal Immunol 2017;10(1):46-57.Abstract

Conjunctival goblet cells play a major role in maintaining the mucus layer of the tear film under physiological conditions as well as in inflammatory diseases like dry eye and allergic conjunctivitis. Resolution of inflammation is mediated by proresolution agonists such as lipoxin A4 (LXA4) that can also function under physiological conditions. The purpose of this study was to determine the actions of LXA4 on cultured rat conjunctival goblet cell mucin secretion, intracellular [Ca(2+)] ([Ca(2+)]i), and identify signaling pathways activated by LXA4. ALX/FPR2 (formyl peptide receptor2) was localized to goblet cells in rat conjunctiva and in cultured goblet cells. LXA4 significantly increased mucin secretion, [Ca(2+)]i, and extracellular regulated kinase 1/2 (ERK 1/2) activation. These functions were inhibited by ALX/FPR2 inhibitors. Stable analogs of LXA4 increased [Ca(2+)]i to the same extent as LXA4. Sequential addition of either LXA4 or resolvin D1 followed by the second compound decreased [Ca(2+)]i of the second compound compared with its initial response. LXA4 activated phospholipases C, D, and A2 and downstream molecules protein kinase C, ERK 1/2, and Ca(2+)/calmodulin-dependent kinase to increase mucin secretion and [Ca(2+)]i. We conclude that conjunctival goblet cells respond to LXA4 to maintain the homeostasis of the ocular surface and could be a novel treatment for dry eye diseases.

Yu Z, Zeng Z, Zhang J, Pan Y, Chen M, Guo Y, Yu N, Chodosh J, Fu N, Che X, Zhang Q. Fatal Community-acquired Pneumonia in Children Caused by Re-emergent Human Adenovirus 7d Associated with Higher Severity of Illness and Fatality Rate. Sci Rep 2016;6:37216.Abstract

Human adenoviruses (HAdVs) are highly contagious pathogens causing acute respiratory disease (ARD), such as community-acquired pneumonia. HAdV-7d, a re-emergent genomic variant, has been recently reported in Asia and the United States after a several-decade absence. However, whether HAdV-7d is associated with higher severity than other types is currently unclear. In this study, the clinical and epidemiological investigation showed that fever, cough, and sore throat were the three most common respiratory symptoms of HAdV infections. HAdV-7 caused longer duration of fever, higher morbidity of tachypnea/dyspnea, pleural effusion, diarrhea, hepatosplenomegaly, consciousness alteration, as well as higher rates of pneumonia, mechanical ventilation and higher fatality rate (28.6%) than other types, particularly HAdV-3 and HAdV-2. The genomes of seven HAdV-7d isolates from mild, severe, and fatal cases were sequenced and highly similar with each other. Surprisingly, two isolates (2011, 2012) had 100% identical genomes with an earlier strain from a fatal ARD outbreak in China (2009), which elucidates the virus origin and confirms the unexpected HAdV genomic conservation and stability. Phylogenetic analysis indicated that L1 52/55-kDa DNA packaging protein may be associated with the higher severity of illness and fatality rate of HAdV-7. Clinicians need to be aware of HAdVs in children with ARD.

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