Results from a 13-Year Prospective Cohort Study Show Increased Mortality Associated with Bloodstream Infections Caused by Pseudomonas aeruginosa Compared to Other Bacteria

ABSTRACT The impact of bacterial species on outcome in bloodstream infections (BSI) is incompletely understood. We evaluated the impact of bacterial species on BSI mortality, with adjustment for patient, bacterial, and treatment factors. From 2002 to 2015, all adult inpatients with monomicrobial BSI caused by Staphylococcus aureus or Gram-negative bacteria at Duke University Medical Center were prospectively enrolled. Kaplan-Meier curves and multivariable Cox regression with propensity score models were used to examine species-specific bacterial BSI mortality. Of the 2,659 enrolled patients, 999 (38%) were infected with S. aureus , and 1,660 (62%) were infected with Gram-negative bacteria. Among patients with Gram-negative BSI, Enterobacteriaceae (81% [1,343/1,660]) were most commonly isolated, followed by non-lactose-fermenting Gram-negative bacteria (16% [262/1,660]). Of the 999 S. aureus BSI isolates, 507 (51%) were methicillin resistant. Of the 1,660 Gram-negative BSI isolates, 500 (30%) were multidrug resistant. The unadjusted time-to-mortality among patients with Gram-negative BSI was shorter than that of patients with S. aureus BSI ( P = 0.003), due to increased mortality in patients with non-lactose-fermenting Gram-negative BSI generally ( P < 0.0001) and Pseudomonas aeruginosa BSI ( n = 158) in particular ( P < 0.0001). After adjustment for patient demographics, medical comorbidities, bacterial antibiotic resistance, timing of appropriate antibiotic therapy, and source control in patients with line-associated BSI, P. aeruginosa BSI remained significantly associated with increased mortality (hazard ratio = 1.435; 95% confidence interval = 1.043 to 1.933; P = 0.02). P. aeruginosa BSI was associated with increased mortality relative to S. aureus or other Gram-negative BSI. This effect persisted after adjustment for patient, bacterial, and treatment factors

A qualitative study exploring pre-hospital patient delays in seeking care for symptoms of sepsis

Delays in help-seeking among patients with bloodstream infection (BSI) impact the timeliness of appropriate treatment and contribute to poor outcomes. The purpose of this study was to identify psychosocial factors influencing help-seeking delays among patients with BSI using the Common-Sense Model of Self-Regulation. A qualitative descriptive study using in-depth, semi-structured interviews with 10 former patients diagnosed with BSI was conducted to identify factors influencing patient pre-hospital delay. Three main themes were identified in the qualitative analysis: Gathering Threads for a Tapestry, Weaving the Threads into a Tapestry for a Garment, and Being Clothed and in Their Right Mind. Four men and six women hospitalized at a university medical center with BSI were enrolled and completed all study components. An inability to recognize symptoms of BSI resulted in delayed help-seeking. Participants had difficulty recognizing their experienced symptoms as being related to BSI if they lacked experience with infection or could not differentiate them from symptoms of other chronic comorbid conditions. When reacting to symptoms of BSI, participants searched for their meaning to develop an action plan. Help-seeking is a coping strategy used by all participants, and they all delayed seeking care. Participants encountered facilitators and barriers to help-seeking. Patient-reported outcomes of BSI on their quality of life (QOL) varied widely, from none to major impact. Problems of symptom recognition and lack of awareness for BSI contributed to help-seeking delays in patients with BSI. Many patients with BSI reported enduring impacts on QOL

Transmission of MRSA between Companion Animals and Infected Human Patients Presenting to Outpatient Medical Care Facilities

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in both human and veterinary medicine. The importance of companion animals as reservoirs of human infections is currently unknown. The companion animals of 49 MRSA-infected outpatients (cases) were screened for MRSA carriage, and their bacterial isolates were compared with those of the infected patients using Pulsed-Field Gel Electrophoresis (PFGE). Rates of MRSA among the companion animals of MRSA-infected patients were compared to rates of MRSA among companion animals of pet guardians attending a “veterinary wellness clinic” (controls). MRSA was isolated from at least one companion animal in 4/49 (8.2%) households of MRSA-infected outpatients vs. none of the pets of the 50 uninfected human controls. Using PFGE, patient-pets MRSA isolates were identical for three pairs and discordant for one pair (suggested MRSA inter-specie transmission p-value = 0.1175). These results suggest that companion animals of MRSA-infected patients can be culture-positive for MRSA, representing a potential source of infection or re-infection for humans. Further studies are required to better understand the epidemiology of MRSA human-animal inter-specie transmission

Panton-Valentine Leukocidin Is Not the Primary Determinant of Outcome for Staphylococcus aureus Skin Infections: Evaluation from the CANVAS Studies

The impact of Panton-Valentine leukocidin (PVL) on the severity of complicated skin and skin structure infections (cSSSI) caused by Staphylococcus aureus is controversial. We evaluated potential associations between clinical outcome and PVL presence in both methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) isolates from patients enrolled in two large, multinational phase three clinical trials assessing ceftaroline fosamil for the treatment of cSSSI (the CANVAS 1 and 2 programs). Isolates from all microbiologically evaluable patients with monomicrobial MRSA or MSSA infections (n = 473) were genotyped by PCR for pvl and underwent pulsed-field gel electrophoresis (PFGE). Genes encoding pvl were present in 266/473 (56.2%) isolates. Infections caused by pvl-positive S. aureus were associated with younger patient age, North American acquisition, and presence of major abscesses (P<0.001 for each). Cure rates of patients infected with pvl-positive and pvl-negative S. aureus were similar overall (93.6% versus 92.8%; P = 0.72), and within MRSA-infected (94.5% vs. 93.1%; P = 0.67) and MSSA-infected patients (92.2% vs. 92.7%; P = 1.00). This finding persisted after adjustment for multiple patient characteristics. Outcomes were also similar when USA300 PVL+ and non-USA300 PVL+ infections were compared. The results of this contemporary, international study suggest that pvl presence was not the primary determinant of outcome in patients with cSSSI due to either MRSA or MSSA

Identifying barriers and facilitators to seeking care for symptoms of bacterial sepsis: A qualitative study

Abstract Aim Research suggests that early access to quality care is essential to improving bacteraemia outcomes and reducing the risk of developing sepsis because it allows for early intervention. Currently, there are limited data regarding the facilitators and barriers that alter the trajectory of arrival at the hospital when patients in the United States experience symptoms of bacteraemia and sepsis. This study sought to explore and describe the facilitators and barriers to seeking care for suspected bacteraemia and sepsis symptoms. Design A qualitative descriptive study. Methods Ten men and women were recruited using convenience sampling. The study used audio‐recorded semi‐structured interviews and the collection of socio‐demographic data as the data collection techniques. Thematic analysis was used, including inductive and deductive approaches, to analyse the data. Results During data analysis, the codes related to barriers and facilitators were collapsed into three themes—symptom recognition, psychosocial support and healthcare planning and coordination. Patient Contribution The patients' participation in the study has contributed to our understanding of patients' perspectives and experiences in the pre‐hospital phase and provides important insights into what barriers and facilitators are encountered. Study findings highlight the need to develop interventions to improve patient decision time, patient–provider interactions and knowledge of bacteraemia and sepsis through patient and provider education

Integrated transcriptomic analysis reveals immune signatures distinguishing persistent versus resolving outcomes in MRSA bacteremia.

INTRODUCTION: Staphylococcus aureus bacteremia (SAB) is a life-threatening infection particularly involving methicillin-resistant S. aureus (MRSA). In contrast to resolving MRSA bacteremia (RB), persistent MRSA bacteremia (PB) blood cultures remain positive despite appropriate antibiotic treatment. Host immune responses distinguishing PB vs. RB outcomes are poorly understood. Here, integrated transcriptomic, IL-10 cytokine levels, and genomic analyses sought to identify signatures differentiating PB vs. RB outcomes. METHODS: Whole-blood transcriptomes of propensity-matched PB (n=28) versus RB (n=30) patients treated with vancomycin were compared in one independent training patient cohort. Gene expression (GE) modules were analyzed and prioritized relative to host IL-10 cytokine levels and DNA methyltransferase-3A (DNMT3A) genotype. RESULTS: Differential expression of T and B lymphocyte gene expression early in MRSA bacteremia discriminated RB from PB outcomes. Significant increases in effector T and B cell signaling pathways correlated with RB, lower IL-10 cytokine levels and DNMT3A heterozygous A/C genotype. Importantly, a second PB and RB patient cohort analyzed in a masked manner demonstrated high predictive accuracy of differential signatures. DISCUSSION: Collectively, the present findings indicate that human PB involves dysregulated immunity characterized by impaired T and B cell responses associated with excessive IL-10 expression in context of the DNMT3A A/A genotype. These findings reveal distinct immunologic programs in PB vs. RB outcomes, enable future studies to define mechanisms by which host and/or pathogen drive differential signatures and may accelerate prediction of PB outcomes. Such prognostic assessment of host risk could significantly enhance early anti-infective interventions to avert PB and improve patient outcomes

307. Exploring HLA genotypes as contributing risk factors in Staphylococcus aureus bacteremia

Abstract Background The impact of host genetic variability on the outcome of S. aureus infection is unknown. HLA variation has evolved to ensure broad presentation of pathogen derived peptides to initiate protective adaptive immune responses. In genome-wide association studies we identified specific HLA class II variants (HLA-DRB1*04:01 & 04:02) that are positively associated with S. aureus infection. The goal of this study was to determine how HLA-DR variants may differ in their ability to bind and present S. aureus peptides to host T cells and impact protective immunity. Methods S. aureus (USA300) proteasome was obtained (UP000008816) and a dataset of 468,812 overlapping 15 amino acid peptides was created. Peptide binding predictions for seven HLA variant subgroups were performed using a machine learning framework (MixMHC2pred 2.0). Binding prediction score of ≤ 2.0 was used as a biological threshold and data was analyzed using R (4.2.2). HLA-DR expression was measured on HLA homozygous B cell lines using flow cytometry (BD Fortessa) and antibodies specific for HLA-DR (L243 APC) and CD69 (FN50-PE) and analyzed using FlowJo and Microsoft Excel. Results We observed different S. aureus peptide binding score distributions across HLA-DRB1 alleles representing unique peptide binding pockets (Fig 1A). Analysis revealed significantly higher proportions of peptides predicted to bind HLA-DRB1*04:01 and DRB1*04:02 compared to controls DRB1*15:01 and DRB1*01:01 (score ≤ 2.0). (Fig 1B). HLA-DR alleles also showed variable expression on HLA homozygous B cell lines, with DRB1*04:02 showing highest and DRB1*04:01 showing lowest expression (Fig 1C). HLA-DR expression was higher on B cells expressing activation marker CD69+ (p< 0.002) for all alleles except DRB1*04:01. In vitro T cell stimulation assays controlling for HLA genotype are in progress. Conclusion We provide evidence to suggest that variation in peptide binding and cell surface expression may explain the association of HLA class II haplotypes with S. aureus infection. Elucidating the genetic basis of susceptibility to S. aureus infection will improve our understanding, treatment, and prevention of this urgent unmet medical need. Disclosures Vance G. Fowler, MD, MHS, Amphliphi Biosciences, Integrated Biotherapeutics; C3J, Armata, Valanbio; Akagera, Aridis, Roche, Astra Zeneca: Advisor/Consultant|Genentech, Regeneron, Deep Blue, Basilea, Janssen;: Grant/Research Support|Infectious Diseases Society of America: Honoraria|MedImmune, Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Merck; Medical Biosurfaces; Locus; Affinergy; Contrafect; Karius;: Grant/Research Support|Novartis, Debiopharm, Genentech, Achaogen, Affinium, Medicines Co., MedImmune, Bayer, Basilea, Affinergy, Janssen, Contrafect, Regeneron, Destiny,: Advisor/Consultant|Sepsis diagnostic: Patent pending|UpToDate: Royalties|Valanbio and ArcBio: Stock Option

Escherichia coli ST131 Associated with Increased Mortality in Bloodstream Infections from Urinary Tract Source.

Escherichia coli sequence type 131 (ST131) is a globally dominant multidrug- resistant clone, although its clinical impact on patients with bloodstream infection (BSI) is incompletely understood. This study aims to further define the risk factors, clinical out- comes, and bacterial genetics associated with ST131 BSI. A prospectively enrolled cohort study of adult inpatients with E. coli BSI was conducted from 2002 to 2015. Whole-genome sequencing was performed with the E. coli isolates. Of the 227 patients with E. coli BSI in this study, 88 (39%) were infected with ST131. Patients with E. coli ST131 BSI and those with non-ST131 BSI did not differ with respect to in-hospital mortality (17/82 [20%] versus 26/145 [18%]; P = 0.73). However, in patients with BSI from a urinary tract source, ST131 was associated with a numerically higher in-hospital mortality than patients with non-ST131 BSI (8/42 [19%] versus 4/63 [6%]; P = 0.06) and increased mortality in an adjusted analysis (odds ratio of 5.85; 95% confidence interval of 1.44 to 29.49; P = 0.02). Genomic analyses showed that ST131 isolates primarily had an H4:O25 serotype, had a higher number of pro- phages, and were associated with 11 flexible genomic islands as well as virulence genes involved in adhesion (papA, kpsM, yfcV, and iha), iron acquisition (iucC and iutA), and toxin production (usp and sat). In patients with E. coli BSI from a urinary tract source, ST131 was associated with increased mortality in an adjusted analysis and contained a distinct repertoire of genes influencing pathogenesis. These genes could contribute to the higher mortality observed in patients with ST131 BSI

Complicated Staphylococcus aureus Bacteremia (SAB) Is Associated with Genetic Variation in GLS2

Abstract Background SAB is a serious, common infection. We used whole exome sequencing (WES) to examine the cumulative effect of coding variants in each gene on risk of complicated SAB in a discovery set of patients, and then evaluated the nominally significant genes in a replication set of patients using custom-capture sequencing. Methods The discovery set comprised 84 complicated SAB cases (endocarditis or bone/joint infection) frequency-matched by age (in deciles), sex, and bacterial clonal complex (CC5/30, CC8) to 84 uncomplicated SAB controls. All were white inpatients at Duke University. WES utilized Agilent SureSelect 72Mb capture kits, followed by sequencing on an Illumina HiSeq2000, alignment and base calling with a standard pipeline. The SKAT-O and EPACTS packages were used for gene-based association tests and logistic regression models with Firth bias correction, respectively. Both controlled for age, sex, and clonal complex as covariates. The replication set of 122 complicated SAB cases and 118 uncomplicated SAB controls was frequency matched by age, sex, and clonal complex. All were white Europeans collected by the Statens Serum Institute. An Agilent SureSelect 2Mb capture array captured genic sequence for 342 genes nominally associated with complicated SAB in discovery (SKAT-O P < 0.035). Sequencing and data analysis proceeded as for WES. A Bonferroni-corrected gene-based test P-value of 1.5×10–4 determined significance in the replication set. Results One gene, GLS2, was significantly associated with complicated SAB in the replication set (P = 1.2 x 10–4). The strongest single-variant association in all 342 genes was rs2657878 in GLS2 (p = 5×10−4). This variant is strongly correlated with a missense variant (rs2657879, p = 4.4x10-3) in which the minor allele (associated here with complicated SAB) has previously been shown to reduce circulating glutamine levels. Conclusion Comprehensive examination of the coding sequence for association with complicated SAB in a two-stage discovery/replication design identified a novel candidate gene. GLS2 is an interesting candidate for complicated SAB due to its role in regulating glutamine production, a key factor in activation of T-cell production. Disclosures V. Fowler Jr., Pfizer, Novartis, Galderma, Novadigm, Durata, Debiopharm, Genentech, Achaogen, Affinium, Medicines Co., Cerexa, Tetraphase, Trius, MedImmune, Bayer, Theravance, Cubist, Basilea, Affinergy, Janssen, xBiotech, Contrafect: Consultant, Consulting fee; NIH, Basilea, MedImmune, Cerexa/Forest/Actavis/Allergan, Pfizer, Advanced Liquid Logics, Theravance, Novartis, Cubist/Merck; Medical Biosurfaces; Locus; Affinergy; Contrafect; Karius: Grant Investigator, Research grant; Green Cross, Cubist, Cerexa, Durata, Theravance; Debiopharm: Consultant, Consulting fee; UpToDate: author on several chapters, Royaltie