bluuebunny/crossref_metadata_2025_split huggingface dataset:
2599. Studying the Effects of Altering Histone Modification on Aspergillus fumigatus Virulence
Authors: Lee Pam , Liu Hong , Filler Scott 
Published: October 2019

Abstract

Background
As there are few drugs for treating invasive aspergillosis, there is an urgent need for new antifungal agents. Enzymes involved in histone modification are possible antifungal drug targets. We set out to investigate whether genes whose products are involved in histone modifications influence the virulence of Aspergillus fumigatus (Af).

Methods
Genes whose products were likely involved in histone modification were deleted in strain Af293 using CRISPR-Cas9. Virulence was assessed in a triamcinolone-treated mouse model of invasive pulmonary aspergillosis. The extent of Af-induced damage to the A549 pulmonary epithelial cell line was determined by Cr51 release assay.

Results
Af genes were selected for investigation based on their homology to genes encoding known histone modifying proteins and their high expression level in vivo. The genes were predicted to encode members of the COMPASS histone methyltransferase complex (cclA/bre2, set2/Afu5g06000), the SAGA histone acetyltransferase complex (spt3, spt8), and the RPDL histone deacetylase complex (hosA). The ΔcclA and Δset2 mutants had significant growth defects on rich media and were not tested further. The Δspt3 and Δspt8 mutants grew normally and had mild conidiation defects. The ΔhosA mutant had wild-type (WT) growth and conidiation in vitro. Mice infected with the WT strain had 100% mortality within 9 days whereas mice infected the Δspt3, Δspt8, and ΔhosA mutants had only 40% mortality by 21 days. The ΔhosA mutant also had impaired capacity to damage pulmonary epithelial cells in vitro.

Conclusion
Ccla and Set2, components of the COMPASS complex, are required for normal growth in vitro. Spt3 and Spt8, members of the SAGA complex, are required for normal conidiation and virulence. HosA, part of the RPD3L complex, is necessary for maximal virulence and induction of host cell damage. Our results suggest that the HosA histone deacetylase may be a promising drug target for treating invasive aspergillosis.

Disclosures
All authors: No reported disclosures.
2604. Changes in a Fatty Acid Kinase Associated with Daptomycin (DAP) Resistance Lead to Increased Collagen Binding and Biofilm Formation in Enterococcus faecalis
Authors: Miller William R , Singh Kavindra V , Reyes Jinnethe , Murray Barbara E , Arias Cesar A 
Published: October 2019

Abstract

Background
Enterococci are a major cause of healthcare-associated infections with limited treatment options. We previously identified that mutations in dak (a gene encoding a putative fatty acid kinase), ace (a collagen adhesin) and the YxdJK stress response system are associated with DAP resistance (DAP-R) in E. faecalis (Efs) in the absence of a functional LiaFSR system. Here, we examined the role of DAK in pathogenesis by examining the ability of the mutants to produce biofilm and bind to collagen, an important protein of the extracellular matrix.

Methods
Previously, the Efs strain OG1RFΔliaR (inactive LiaFSR system, DAP susceptible) was adapted to make a DAP-R derivative (mutations in yxdK, dak, and ace), and the mutant OG1RFΔliaRΔc-dak, lacking the C-terminal domain of dak, and its complement OG1RFΔliaRΔc-dak::c-dak were constructed to study the dak mutation in isolation. Biofilm formation (BF) for the above strains was assayed after growth in tryptic soy broth with glucose in 96-well plates at 37° C for 24 hours. Bacteria were fixed with Bouin’s fixative, stained with crystal violet, and biofilm was quantitated by absorbance at 570 nm. For collagen adherence, 96-well plates were coated with 10 μg/well type I collagen, with 2% bovine serum albumin (BSA) as a control. Bacteria grown at 46° C (to induce ace expression) were added at OD 600 nm of 1.0 and allowed to bind for 2 hours. Non-adherent bacteria were removed by washing, cells were fixed, stained, and quantified as above.

Results
When compared with OG1RFΔliaR, the DAP-R derivative exhibited a significant increase in BF (4.6 vs. 2.4, P < 0.001). This enhanced biofilm phenotype was also seen in the OG1RFΔliaRΔc-dak mutant (6.1 vs. 2.4, P < 0.001), and reverted on complementation of the full-length dak in its native chromosomal location (2.4 vs. 2.6, p = 0.72). DAK was also found to impact adherence to collagen, with OG1RFΔliaRΔc-dak showing increased binding to collagen when compared with OG1RFΔliaR (7.9 vs. 3.4, P < 0.001), a phenotype which reverted on complementation (7.9 vs. 1.2, P < 0.001).

Conclusion
Changes in an enzyme involved in DAP adaptation lead to biofilm formation and adherence to extracellular matrix proteins, potentially enhancing virulence in the setting of DAP-R.

Disclosures
All authors: No reported disclosures.
2607. Establishment of a Novel High-Throughput Fungal Infection Model in Zebrafish Larvae by Controlled Ablation of Epithelial Cells
Authors: Wurster Sebastian , Ruiz Oscar E , Tatara Alexander M , Samms Krystin M , Kim Nguyen Anh , D. Albert Nathaniel , H. Kahan Philip , Mikos Antonios G , Eisenhoffer George T , Kontoyiannis Dimitrios P 
Published: October 2019

Abstract

Background
Efficient animal models are needed in order to investigate fungal pathogenicity and antifungal therapy in the context of epithelial injury, e.g., due to anticancer chemotherapy. Using a Gal4 enhancer trap (GET) zebrafish line facilitating metronidazole (MTZ)-inducible ablation of epithelial (periderm) cells, we aimed to establish a mucositis model predisposing larvae for fungal invasion.

Methods
4 days post-fertilization Et(Gal4-VP16)zc1044A;Tg(UAS-1b:nfsB-mCherry)c264 zebrafish larvae were exposed to 10 mM MTZ in E3 medium for 5 h. After washing, larvae were incubated in Candida albicans or Rhizopus arrhizus spore suspensions (5 × 105–5 × 107/mL) for 16 h. Thereafter, larvae were washed again and survival was monitored until 72 h post-infection. Fungal burden was assessed by 18S qPCR and histopathology. For drug protection studies, 5 µg/mL amphotericin B (AMB) or posaconazole (PCZ) was added to the medium of R. arrhizus-infected larvae at 16 h post-infection.

Results
In MTZ-treated GET larvae, inoculum-dependent mortality was found for both R. arrhizus (panel A) and C. albicans (panel B). High inter-experiment reproducibility of survival rates was seen (CV < 0.3). Using a GFP-expressing R. arrhizus strain, fungal invasion of the larval tissue was verified by fluorescence microscopy (panel C). PCZ and AMB improved survival rates of R. arrhizus-infected (5 × 106/mL) larvae from 46% to 85% and 51% to 86%, respectively (P < 0.001). Similarly, significantly reduced fungal burden in AMB and PCZ-treated larvae was documented by qPCR (panel D) and histopathology. In additional validation experiments, the hypo-virulent phenotypes of a CotH-depleted R. arrhizus strain and filamentation-defective C. albicans mutants (Δefg1 and Δcph1) were recapitulated in zebrafish larvae with epithelial cell loss.

Conclusion
We have established a robust and reliable model of invasive mycoses by controlled ablation of epithelial cells in zebrafish larvae, allowing for rapid immersion-based interrogation of different infection and treatment options. Our proof-of-concept experiments suggest that GET zebrafish larvae are positioned as an appealing high-throughput in vivo system for antifungal drug screening or comparative virulence studies.

Disclosures
All authors: No reported disclosures.
2628. Nasopharyngeal Microbiome in the First Weeks of Life Distinguishes Infants Who Subsequently Develop Lower Respiratory Tract Infections
Authors: Lapidot Rotem , Faits Tyler , Arshad Ismail , Mushal Allam , Macleod William , Kwenda Geoffrey , Mupila Zacharia , Murphy Caitriona , Nakazwe Ruth , Johnson Evan , Thea Donald M , Mwananyanda Lawrence , Gill Christopher 
Published: October 2019

Abstract

Background
Colonization of the nasopharynx (NP) is the initial event in the pathogenesis of lower respiratory tract infections (LRTI). Evidence is accumulating that the NP microbiome influences host immune responses and whether colonization progresses to disease or not. We hypothesized that infants who experience LRTI early in life display distinct NP microbiome characteristics prior to infection, and potentially as early as the newborn period.

Methods
As part of the “Southern Africa Mother Infant Pertussis Study” in Zambia, NP samples were prospectively collected approximately every 2 weeks beginning at birth, through 3 months of age, in conjunction with clinical data. Samples were also collected when an infant experienced respiratory symptoms. We identified infants from the cohort with LRTI and matched with asymptomatic controls. We performed 16S ribosomal DNA amplicon sequencing on DNA extracted from the NP samples using Illumina MiSeq, and analyzed the data using Qiime2 and PathoScope2. We described the NP microbiome characteristics of asymptomatic infants and infants with LRTI and their changes over time and compared between the two populations at each 2-week interval using the R package DESeq2.

Results
Ten infants who had LRTI during the study period were matched with 17 healthy asymptomatic controls, together contributing 183 samples with high-quality reads. In asymptomatic infants, Dolosigranulum, Haemophilus and Moraxella’s relative abundance increased over the first 3 months of life, while Corynebacterium and Staphylococcus relative abundance decreased in the NP microbiome (Figure 1). In contrast, infants who developed LRTI had increased abundance of Staphylococcus, Anaerobacillus, and Bacillus, and decreased relative abundance of Dolosigranulum and Moraxella compared with asymptomatic controls (Figure 2). These differences were already present at the time of first sample collection (age 1 week).

Conclusion
Infants who develop LRTI early in life demonstrate altered NP microbial composition as early as the first week of life. These differences could potentially lead to early identification of at-risk infants. If confirmed, interventions to prevent LRTI in infancy could be evaluated to reduce respiratory mortality and morbidity.

Disclosures
All authors: No reported disclosures.
159. Comparing Clinical Cure and Patient Outcomes Between Intravenous Therapy and Intravenous (IV)-to-Oral (PO) Step-down Therapy for Treatment of Gram-Negative Bloodstream Infections
Authors: Williams Kelsey , Ghamrawi Riane , Takieddine Sheila , Grubbs Peter , Powers-Fletcher Maggie , Liao Siyun 
Published: October 2019

Abstract

Background
There is a paucity of evidence surrounding optimal prescribing practices for the treatment of Gram-negative bloodstream infections (GNBSI). This study aimed to assess the appropriateness of IV-to-PO step-down therapy in the treatment of GNBSI.

Methods
A retrospective cohort study was conducted at the University of Cincinnati Medical Center and West Chest Hospital and included subject’s ≥18 years of age with GNBSI caused by Enterobacteriaceae spp. or Pseudomonas aeruginosa. The primary objective was to compare clinical cure rates between IV-only and IV-to-PO therapy, and to further assess differences in clinical cure rates amongst oral antibiotics of high, moderate, and low bioavailability. The study also aimed to identify factors associated with clinical cure, hospital length of stay, and emergence of multi-drug-resistant organisms (MDRO).

Results
Amongst 215 subjects screened, 99 subjects were included and 64 subjects met criteria for clinical cure. In the univariate analysis, the IV-to-PO group had a higher percentage of clinical cure than IV only therapy (82% vs. 48%, P = 0.001). Of note, the two study groups were significantly different in regards to intensive care status, Pitt bacteremia score, and primary site of infection. Upon further analysis, data from the multivariate logistic regression revealed that critical illness was the only significant factor that negatively impacted clinical cure (OR = 0.208; 95% CI 0.04–0.99; P = 0.049). A total of 49 subjects received oral antibiotics. Majority of patients (82%) in the IV-to-PO group received a moderately bioavailable oral antibiotic. No difference in respect to clinical cure rate was found between the three PO antibiotic bioavailability groups (P = 0.346). The median duration of hospital stay was shorter in the IV-to-PO compared with IV alone group (4 days vs. 9.5 days, respectively, P ≤ 0.001). There was a trend in emergence of MDROs with IV therapy compared with IV-to-PO therapy (10% vs. 2%, P = 0.204).

Conclusion
IV-to-PO stepdown therapy compared with IV therapy alone was noninferior in clinical cure rates in the treatment of GNBSI and may result in fewer hospital days and less emergence of multidrug-resistant organisms. These conclusions are limited by significant differences in severity of illness between groups in this study.

Disclosures
All authors: No reported disclosures.
2676. Effect of β-Lactam Allergy on Appropriateness of Antibiotic Use in Patients with Febrile Neutropenia
Authors: Yetmar Zachary A , Vijayvargiya Prakhar , Tosh Pritish , Kasten Mary J 
Published: October 2019

Abstract

Background
Over 80% of patients with hematologic malignancies develop some form of infectious complication, most commonly febrile neutropenia. Patients with febrile neutropenia have 10% mortality, which increases if antibiotic administration is delayed past 30 minutes. Studies have suggested β-lactam allergy may delay administration of antibiotic while putting patients at greater risk for inappropriate antibiotic choice and adverse effects stemming from this. We sought to describe the risks associated with β-lactam allergy in the neutropenic population.

Methods
We conducted a retrospective, descriptive study from January 2016 to December 2017 identifying patients with febrile neutropenia and a reported history of β-lactam allergy. Baseline characteristics, allergy data, treatment data, and outcomes were collected and analyzed.

Results
We identified 31 patients with febrile neutropenia and β-lactam allergy during this time period. Etiologies of neutropenia were hematologic malignancy (61.2%), stem cell transplantation (12.9%), solid-organ malignancy (22.6%), and autoimmune (3.3%). Reported reactions to β-lactams were rash (41.9%), hives (9.7%), anaphylaxis (3.2%), other (9.7%), and unknown (35.5%). Average time to antibiotic administration was 142.5 minutes. Antibiotic choice was cefepime (61.3%), piperacillin–tazobactam (6.5%), carbapenem (22.6%), fluoroquinolone (6.5%), cefepime and fluoroquinolone (3.2%), and vancomycin (58.1%). 51.6% received initial antibiotics consistent with the 2010 IDSA guidelines. Six patients underwent penicillin skin testing, all negative. 1 patient developed C. difficile infection, 1 developed MRSA colonization, and 3 developed VRE colonization. Mortality was 3.2% at 30 days and 16.1% at 90 days.

Conclusion
Our study estimated the antibiotic usage patterns and outcomes in patients with febrile neutropenia and reported β-lactam allergy. This showed low adherence to an established guideline for antibiotic choice in these patients. With rising antimicrobial resistance, there is a need to develop strategies to reduce inappropriate antimicrobial use, especially in patients with febrile neutropenia. Preemptive β-lactam allergy evaluation warrants further evaluation in the neutropenic population.

Disclosures
All authors: No reported disclosures.
2677. Infection-Related Outcomes in Patients With Malignancy-Related Febrile Neutropenia: A National Perspective
Authors: Noor Arish , Desai Aakash , Tandon Varun , Siddappa Pradeep K , Balakumaran Kathir , Diez-morales Luis F 
Published: October 2019

Abstract

Background
Febrile neutropenia (FBN) is a life-threatening oncological emergency requiring hospitalization and early treatment with broad-spectrum antibiotics. We aimed to study differences in infection-related outcomes for febrile neutropenia in various malignancies.

Methods
The National Inpatient Sample (NIS) data set was queried from 2007 to 2014 to identify all patients with a diagnosis of neutropenic fever (ICD-9: 780.6x and 288.5x or 288.0x or 284.1x). Diagnoses for various cancers were determined via their respective Clinical Classification Software (CCS) codes. Diagnoses of pneumonia (481.x, 482x), bacterial meningitis (320.x), Clostridium difficile (008.45), infectious colitis due to neoplastic agents (009.x), urinary tract infection (599.0x), pyelonephritis (590.1x, 590.80), skin and soft-tissue infection (682.x, 684.x, 686.8x, 686.9x), mucositis (528.01), influenza (CCS 487), sepsis (995.91), severe sepsis (995.92), septic shock (785.52), E. coli septicemia (038.42), Pseudomonas septicemia (038.43), MRSA septicemia (038.12) and Streptococcal septicemia (038.0) were identified using their respective ICD/CCS codes. Variables were analyzed via multivariate analysis using the program SAS.

Results
We studied 381,043 patients with FBN. Leukemia was the most common malignancy associated with FBN (140,190, patients, 36.8%). Meningitis was found to be significantly associated with brain cancer, while other infections were associated with a range of malignancies. (Table.1) Methicillin-resistant Staphylococcus aureus was associated with cancers of the bone, breast, uterus and non- hodgkins lymphoma, while other microorganisms varied across different malignancies (Table 2). Septic Shock was associated with cancer of the pancreas, lung, bone, breast, leukemia, bladder, kidney, thyroid, myeloma, prostate, testis, cervix, brain, melanoma, non-hodgkins lymphoma, compared with other malignancies (Table 3).

Conclusion
Pathogen-specific and targeted antibiotic therapy is the cornerstone of treatment in FBN. Our study provides evidence of specific presentations and organisms causing infections in various malignancies. We hope that further outcomes-based research will provide objective evidence of certain high-risk infections, improving patient outcomes and minimizing redundant testing.

Disclosures
All authors: No reported disclosures.
2689. Stenotrphomonas maltophilia, The Hidden Threat Among Pediatric Cancer Patients
Authors: Madney. Said Youssef , Abdelaziz Riham , Samir Shimaa , Elanany Mervat 
Published: October 2019

Abstract

Background
Stenotrophomonas maltophilia is an emerging nosocomial pathogen in immunocompromised patients. Although S. maltophilia exhibits limited pathogenicity in immunocompetent hosts, it has been shown to cause fatal infections in patients with malignancies. The objective of this study to analyze the clinical characteristics, susceptibility pattern, and treatment outcome of S. maltophilia among pediatric cancer patients.

Methods
Retrospective analysis including all pediatric cancer patients treated at children cancer hospital Egypt (CCHE) with S. maltophilia bloodstream infection from June 2013 till June 2018.

Results
281 isolates among 135 pediatric cancer patients. Most are hematological malignancies 67(50%), solid tumors 55 (40%) and post-transplant 13(10%). Most common hematological malignancies were acute lymphoblastic leukemia 34 patients (25%) while brain tumor was the most common solid tumors 20 patients (15%). The spectrum of infections includes bacteremia in 61 patients (45%) catheter-related in 34 (25%), pneumonia in 22 (16%), skin and soft-tissue infection in 11(8%) meningitis in 5 (3%) and disseminated infections with multiorgan involvement in 4(3%) patients. 46 patients (34%) was admitted in intensive care unit (ICU), 67 inpatient (50%), 11 (8%) stem cell transplant unit and 11 patient (8%) from emergency and outpatient department. The isolates revealed 80% susceptibility to Trimethoprim-Sulfamethoxazole (TMP-SMX), 77% to ciprofloxacin, 50% to cefepime and ceftazidime, 63% to amikacin, 48% to piperacillin–tazobactam, 93% to colistin, 97% to tigecycline. Day 30 mortality (Crude mortality rate) 33 patients (25%) while S. maltophilia attributable mortality (died within 7 days of culture isolation) was 17 patients (13%). Patients with pneumonia, (TMP-SMX) resistance and ICU admission were associated with a significant risk of mortality.

Conclusion
Stenotrphomonas bloodstream is a serious pathogen and hidden threat among pediatric cancer patients associated with high mortality rate.

Disclosures
All authors: No reported disclosures.
2703. Pneumococcal Carriage of 13-Valent Pneumococcal Conjugate Vaccine (PCV13) and Non-PCV13 Serotypes among Greek Children Vaccinated with PCV13 in a 3 + 1 Schedule During the First 6 years after the Fourth Dose of PCV13
Authors: Syrogiannopoulos George A , Grivea Ioanna N , Moriondo Maria , Nieddu Francesco , Michoula Aspasia N , Azzari Chiara 
Published: October 2019

Abstract

Background
We evaluated the long-term impact of full PCV13 vaccination in a 3 + 1 schedule on pneumococcal colonization patterns of children in order to clarify PCV13 serotype persistence/enhancement and re-colonization.

Methods
From January 18 to August 29, 2017, consecutive children who had received the 4-dose course of PCV13, as per the National Immunization Program recommendations, were prospectively enrolled through 45 general pediatric practice facilities in 30 municipalities in Greece. A single oropharyngeal sample was obtained from each subject in a standardized manner (questionnaire, procedure). Based on the time interval since the fourth dose of PCV13, the children sampled were grouped for analysis in 6 groups: 26 days to 11 months; 12–23 months; 24–35 months; 36–47 months; 48–59 months, and 60–71 months. Carriage and distribution of Streptococcus pneumoniae serotypes was detected by RT–PCR.

Results
A total of 1212 children aged 14–83 months were investigated. S. pneumoniae was identified in the pharyngeal swab of 617 children (50.9%); 172/617 (27.9%) children carried > 1 pneumococcal serotypes. As a consequence of co-colonization, a total number of 718 S. pneumoniae (belonging to 28 serotypes) was identified. The carriage rate of non-PCV13 serotypes escalated within 3 years after the fourth dose and plateaued during the fourth and fifth year. The carriage rate of PCV13 serotypes escalated during the 4 years after the fourth dose and declined thereafter. 22/305 children (7.2%) carried one or more PCV13 serotypes in the first year after the fourth vaccine dose, 27/201 (13.4%) in the second year, 34/207 (16.4%) in the third year, 48/224 (21.4%) in the fourth year, 40/191 (20.9%) in the fifth year and 13/84 (15.5%) in the sixth year (P < 0.0001) (Figure 1). The colonization frequency of serotypes 3 and 19A increased with the rise of the vaccination time interval (Figure 2). Changes in the frequency of other PCV13 serotypes were not significant. Serotypes 7F, 14 and 23F were not recovered.

Conclusion
Our study suggests that S. pneumoniae is present in the pharynx of children 26 days to 71 months after the completion of PCV13 vaccination, and that non-PCV13 serotypes predominate throughout this period. The carriage rate of PCV13 serotypes 3 and 19A increases significantly as the time interval from the fourth dose of PCV13 increases.

Disclosures
All authors: No reported disclosures.