Tande, Aaron J.

Metagenomic shotgun sequencing has the potential to transform how serious infections are diagnosed by offering universal, culture-free pathogen detection. This may be especially advantageous for microbial diagnosis of prosthetic joint infection (PJI) by synovial fluid analysis since synovial fluid cultures are not universally positive and since synovial fluid is easily obtained preoperatively.

Abstract Background Detection and identification of microorganism(s) involved in periprosthetic joint infection (PJI) can inform surgical management and directed antibiotic therapy. Metagenomic shotgun sequencing is a powerful tool with the potential to change how many PJIs are diagnosed as it allows direct detection and identification of pathogens in clinical specimens. In the largest series to date, we utilized a metagenomics-based approach applied to SF to define potential microbial etiologies of failed total knee arthroplasties (TKAs). Methods Synovial fluid was collected from 112 failed TKAs [74 PJI and 38 aseptic implant failure (AF)] via preoperative arthrocentesis. Cell count and differential, standardized culture and DNA-based metagenomic shotgun sequencing were performed. Human DNA was depleted using the MolYsis basic kit prior to DNA extraction, whole genome amplification, and sequencing. Taxonomic assignment of reads and pathogen identification was achieved using a pipeline incorporating k-mer- and marker gene-based classification software. A scheme for analysis and filtration of false-positives was created and applied, incorporating cut-offs for the number of reads, quality scores, and coverage across a reference genome. Patients were classified as having PJI using the IDSA criteria and expert review. Analyses were recorded as percent agreement, with 95% confidence intervals (CI), of metagenomics to SF culture. Results Metagenomic analysis identified the known pathogen in 54 (90%) (CI, 79.5%–96.2%) of the 60 culture-positive PJIs analyzed and one (2%) (CI, 0.0%–8.9%) potential polymicrobial infection not detected by culture. For the 14 culture-negative PJIs tested, metagenomics showed 79% (CI, 49.2%–95.3%) agreement for negative findings; potential pathogens were identified in three (21%) (CI, 4.7%–50.8%) culture-negative PJI cases, with one being polymicrobial. Of the 37 culture-negative AF cases, metagenomics showed 97% (CI, 85.8%–99.9%) agreement with negative culture and identified one (3%) (CI, 0.0%–14.2%) potential pathogen. For the one culture-positive AF case, metagenomic results were negative, suggesting possible culture contamination. Conclusion Metagenomic shotgun sequencing performed on SF can be used to diagnose PJI and may be particularly useful for culture-negative PJI. Disclosures R. Patel, ASM: Board Member, None; CD Diagnostics, BioFire, Curetis, Merck, Hutchison Biofilm Medical Solutions, Accelerate Diagnostics, Allergan, and The Medicines Company: Grant Investigator, Grant recipient; Curetis: Consultant, Monies paid to my employer; A patent on Bordetella pertussis/parapertussis PCR issued, a patent on a device/method for sonication with royalties paid by Samsung to Mayo Clinic, and a patent on an anti-biofilm substance issued: Patents, Patents, any money is paid to my employer; Actelion: DSMB, Money paid to my employer; ASM and IDSA: Editor’s stipends, Editor’s stipends; NBME, Up-to-Date and the Infectious Diseases Board Review Course: NBME, Up-to-Date and the Infectious Diseases Board Review Course, Honoraria; Roche, ASM, and IDSA: Travel reimbursement, Travel reimbursement

Abstract Background While several studies have identified risk factors for PJI using insurance claims data, these data sets have been limited to a single regional insurance dataset or to the Medicare population. We sought to investigate risk factors for early PJI among patients undergoing total hip or knee arthroplasty (THKA). Methods All patients who underwent primary THKA between January 1, 2004 and July 31, 2014 with 12 months of continuous preceding medical and pharmacy insurance coverage were included in the study. The primary outcome of PJI required both a compatible procedure code and a diagnostic code during an inpatient stay from the time of THKA through 90 days after discharge. Comorbidities were based on ICD-9 codes in the preceding 12 months and patients with a prior diagnosis of PJI during that time period were excluded. Univariate and multivariate analysis was performed using logistic regression. Results A total of 147,053 patients underwent THKA during the study period, including 97,448 patients with TKA and 49,605 with THA. PJI occurred in 754 (0.5%) patients. Female gender was independently associated with lower odds of PJI (Figure). A number of biologically plausible factors were associated with increased risk, including chronic skin ulcer, obesity, substance use disorders, joint sarcoma, and malnutrition. The adjusted odds of PJI increased in a stepwise fashion with each increase in the Charlson comorbidity index (CCI), with those with a score of 4 or more having a nearly 2-fold adjusted odds of PJI compared with a score of 0 (OR 1.91; 95% CI 1.29 −2.82). Previously observed risk factors diabetes mellitus, rheumatoid arthritis, and chronic renal failure were associated with increased odds of PJI on univariate analysis, but not after adjustment. Conclusion These data identify several potentially modifiable risk factors for preoperative optimization, including obesity, malnutrition, chronic skin ulcers, and substance-use disorders. The level of comorbidity as assessed by the CCI provides a rough estimate of the increasing risk of PJI. The pathobiology of additional risk factors observed here deserves further study. Disclosures All authors: No reported disclosures.

ABSTRACT While posaconazole prophylaxis decreases the risk of invasive fungal infection compared to fluconazole, low bioavailability of the oral-suspension formulation limits its efficacy. A new delayed-release tablet formulation demonstrated an improved pharmacokinetic profile in healthy volunteers. However, serum levels for the two formulations have not been compared in clinical practice. This study compared achievement of therapeutic posaconazole levels in patients taking the delayed-release tablet to those taking the oral suspension. This retrospective cohort study included 93 patients initiated on posaconazole between 2012 and 2014 and had at least one serum posaconazole level measured. The primary measure was the proportion of patients achieving an initial therapeutic level (>700 ng/ml). An initial therapeutic posaconazole level was seen in 29 of 32 (91%) patients receiving tablets and 37 of 61 (61%) patients receiving suspension ( P = 0.003). Among patients with a steady-state level measured 5 to 14 days after initiation, a therapeutic level was observed in 18 of 20 (90%) patients receiving tablets and 25 of 43 (58%) patients receiving suspension ( P = 0.01). In these patients, the median posaconazole level of the tablet cohort (1655 ng/ml) was twice that of the suspension cohort (798 ng/ml) ( P = 0.004). In this cohort study, the improved bioavailability of delayed-release posaconazole tablets translates into a significantly higher proportion of patients achieving therapeutic serum levels than in the cohort receiving the oral suspension. The results of this study strongly support the use of delayed-release tablets over suspension in patients at risk for invasive fungal infection.

Abstract A 68-year-old avid deer hunter with ischemic cardiomyopathy underwent left ventricular assist device (LVAD) implantation for destination therapy two years ago. He was living an active lifestyle, tracking deer and fishing in a Midwestern forest in November. His wife removed an engorged tick on his thorax. A few days later, he experienced fever, confusion, and ataxia and was hospitalized with septic shock and ventricular fibrillation. The LVAD site had no signs of trauma, drainage, warmth, or tenderness. A peripheral blood smear revealed intraleukocytic anaplasma microcolony inclusions. After completing 14 days of doxycycline, he recovered. Typical non-device-associated infections in LVAD recipients include pneumonia, urinary tract infection, or Clostridium difficile colitis. Human granulocytic anaplasmosis (HGA) is a very atypical non-LVAD infection, and the incidence of tickborne illnesses in LVAD recipients is unknown.