Empiric Antibiotic Coverage Research Articles

Clinical Approach to Nosocomial Bacterial Sepsis.

Bacterial sepsis and septic shock are associated with a high mortality, and when clinically suspected, clinicians must initiate broad-spectrum antimicrobials within the first hour of diagnosis. Thorough review of prior cultures involving multidrug-resistant (MDR) pathogens along with other likely pathogens should be performed to provide an appropriate broad-spectrum empiric antibiotic coverage. The appropriate antibiotic loading dose followed by individualized modification of maintenance dose should be implemented based on the presence of hepatic or renal dysfunction. Use of procalcitonin is no longer recommended to determine need for initial antibacterial therapy and for de-escalation. Daily reevaluation of appropriateness of treatment is necessary based on the culture results and clinical response. All positive cultures should be carefully screened for possible contamination or colonization, which may not represent the true organism causing the sepsis. Culture negative sepsis accounts for one-half of all cases, and de-escalation of initial antibiotic regimen should be done gradually in these patients with close monitoring.

A patient with fever and umbilicated papules

A patient with fever and umbilicated papules

Personalized antibiograms for machine learning driven antibiotic selection

BackgroundThe Centers for Disease Control and Prevention identify antibiotic prescribing stewardship as the most important action to combat increasing antibiotic resistance. Clinicians balance broad empiric antibiotic coverage vs. precision coverage targeting only the most likely pathogens. We investigate the utility of machine learning-based clinical decision support for antibiotic prescribing stewardship.MethodsIn this retrospective multi-site study, we developed machine learning models that predict antibiotic susceptibility patterns (personalized antibiograms) using electronic health record data of 8342 infections from Stanford emergency departments and 15,806 uncomplicated urinary tract infections from Massachusetts General Hospital and Brigham & Women’s Hospital in Boston. We assessed the trade-off between broad-spectrum and precise antibiotic prescribing using linear programming.ResultsWe find in Stanford data that personalized antibiograms reallocate clinician antibiotic selections with a coverage rate (fraction of infections covered by treatment) of 85.9%; similar to clinician performance (84.3% p = 0.11). In the Boston dataset, the personalized antibiograms coverage rate is 90.4%; a significant improvement over clinicians (88.1% p < 0.0001). Personalized antibiograms achieve similar coverage to the clinician benchmark with narrower antibiotics. With Stanford data, personalized antibiograms maintain clinician coverage rates while narrowing 69% of empiric vancomycin+piperacillin/tazobactam prescriptions to piperacillin/tazobactam. In the Boston dataset, personalized antibiograms maintain clinician coverage rates while narrowing 48% of ciprofloxacin to trimethoprim/sulfamethoxazole.ConclusionsPrecision empiric antibiotic prescribing with personalized antibiograms could improve patient safety and antibiotic stewardship by reducing unnecessary use of broad-spectrum antibiotics that breed a growing tide of resistant organisms.

A Fatal Case of Nocardia Bacteremia in a Lung Transplant Recipient

<h3>Introduction</h3> <i>Nocardia</i> bacteremia is an extremely rare disease. Although closely associated with immunocompromised states, only a few cases have been reported after lung transplant (LT). <h3>Case Report</h3> We present a case of <i>Nocardia</i> bacteremia in a 75-year-old man after bilateral LT (11/2017) for combined pulmonary fibrosis and emphysema. Nearing 3 years posttransplant, pulmonary function tests (PFTs) revealed an obstructive pattern with downtrending FEV₁ from baseline; work-up for acute cellular rejection, infection, and antibody-mediated rejection was unremarkable. Serial PFTs ultimately suggested CLAD-BOS phenotype, and he received photopheresis with some stabilization. However, over the next 2 months, he required 2 hospital admissions with need for high-dose intravenous steroids given hypercapnia in the setting of underlying rejection. At 38 months posttransplant, he developed lower extremity cellulitis and new-onset anorexia, generalized weakness, and rapid decline in mental status with need for a third hospitalization and mechanical ventilation with vasopressor support. Infectious work-up and empiric broad-spectrum antibiotic coverage were initiated. Within 12 hours, both blood cultures were positive for <i>Nocardia cyriacigeorgica</i> (Gram stain, <b>Figure A</b>). Meropenem and trimethoprim/sulfamethoxazole were substituted without clinical improvement over the next several days. Brain MRI ruled out cerebral nocardiosis; chest CT showed bibasilar consolidations with air space opacities. An echocardiogram estimated a left ventricular ejection fraction between 20-25% with severe diffuse hypokinesis, likely stress-induced cardiomyopathy, with no evidence of vegetations. Bronchoscopy revealed superinfection with pan-sensitive <i>Pseudomonas</i> spp, without isolation of <i>Nocardia</i> spp. The patient deteriorated and died 39 months after transplant. <h3>Summary</h3> <i>Nocardia</i> bacteremia, scarcely reported in LT recipients, portends a poor prognosis despite aggressive combination antimicrobial therapy.

Preterm Infant with Respiratory Distress, Hypotonia, and Hypoglycemia.

Preterm Infant with Respiratory Distress, Hypotonia, and Hypoglycemia.

Necrotizing Soft Tissue Infections (NSTI): Pearls and Pitfalls for the Emergency Clinician

BackgroundSkin and soft tissue infections are common emergency department (ED) presentations. These infections cover a wide spectrum of disease, from simple cellulitis to necrotizing fasciitis. Despite the commonality, a subset of skin and soft tissue infections known as necrotizing soft tissue infections (NSTIs) can cause significant morbidity and mortality. ObjectiveThis review evaluates the current evidence regarding the presentation, evaluation, and management of NSTI from the ED perspective. DiscussionNSTIs are commonly missed diagnoses. History and physical examination findings are inconsistent, and the risk factors for this high mortality disease are common amongst ED populations. Laboratory evaluation and the Laboratory Risk in Necrotizing Fasciitis (LRINEC) score is helpful but is insufficient to rule out the disease. Imaging modalities including ultrasound, computed tomography, and magnetic resonance imaging are highly sensitive and specific, but may delay definitive management. The gold standard for diagnosis includes surgical exploration. Surgical intervention and empiric broad-spectrum antibiotic coverage are the foundations of treatment. Adjuvant therapies including hyperbaric oxygen and intravenous immunoglobulin have not yet been proven to be beneficial or to improve outcome. ConclusionNSTIs are associated with significant morbidity and mortality. Knowledge of the history, examination, evaluation, and management is vital for emergency clinicians.

1317. Prevalence of Pseudomonas aeruginosa as the Causative Organism for Community Acquired Pneumonia

BackgroundIDSA/ATS guidelines regarding pneumonia diagnosis and treatment changed in 2019. Guidelines recommend determining local prevalence of MRSA and P. aeruginosa to help guide empiric antibiotic coverage. The aim of our study was to determine the prevalence of P. aeruginosa as the causative organism for adult patients admitted to a large urban academic medical center with community acquired pneumonia (CAP).MethodsA report of urine streptococcus antigen tests collected January 1st-December 31st in 2019 was generated. Six hundred charts were reviewed and two hundred subjects met inclusion criteria (figure 1). Inclusion criteria were age >18, hospital admission, and documented suspicion of pneumonia by a physician.ResultsThe average age was 70 and half of the cases were women. The causative organism was identified in 60/200 cases (table 1). No cases of P. aeruginosa were identified. The most commonly isolated organisms were Influenza A and pneumococcus. 66% of cases had age >65yo, 25% were from long term care facilities, 34% had structural lung disease, 20% had dementia, 15% were hospitalized in the prior 90 days and received IV antibiotics, and 30% of cases met severe CAP criteria (table 2). Figure 1. WorkflowTable 1. Organisms Identified Table 2. Risk Factors ConclusionLimitations include a low prevalence of renal failure in the study population, and lack of a standardized respiratory infection evaluation. Our results suggest that empiric coverage for P. aeruginosa may not be needed at our center in this cohort of older patients with clinical characteristics sometimes thought to be risk factors for P. aeruginosa.Disclosures Wendy Szymczak, PhD, Premier, Inc (Consultant)Qiagen (Consultant, Scientific Research Study Investigator) Gregory Weston, MD MSCR, Allergan (Grant/Research Support)

S2896 Encysted Empyema: An Uncommon Complication of Pyogenic Liver Abscess

Introduction: Pyogenic liver abscess (PLA) is uncommon in the U.S. with an estimated incidence of 8-15 cases per 100,000 persons and has a mortality rate between 15% and 20%. Despite being a rare complication, PLA has been found to increase 18 times the risk of pleural empyema. Case Description/Methods: A 36-year-old woman with presented to the emergency department with intractable right hypochondrial and shoulder pain. HPI: 2 weeks before the presentation the patient developed right hypochondrium and epigastric pain, radiating to the right shoulder, dull aching, gradually worsening, associated with nausea, vomiting. PMH: Hypertension, Asthma, and Lactose intolerance. Physical Exam : The patient was found to be afebrile, Elevated blood pressure, mildly distressed due to severe abdominal pain. Abdomen: Normoactive bowel sounds. soft, non distended, tender to palpation in RUQ, No rebound tenderness, No gardening. Clinical Course: • CT of the abdomen demonstrated right hepatic lobe abscess. • The patient was started on empiric antibiotic coverage with cefepime and metronidazole. • CT-guided liver abscess drainage and pig tail catheter placement resulted in drainage of 200 cc of foul-smelling, thick, maroon-brown fluid. • Fluid culture was positive for K. pneumoniae sensitive to ceftriaxone. • Despite drainage of the abscess and appropriate antibiotic coverage the patient’s condition deteriorated as she developed signs of sepsis with worsening right sided chest pain and leukocytosis. • Repeat CT of the chest showed a newly formed right-sided large multiloculated pleural effusion concerning for empyema. • Patient underwent video-assisted thoracoscopic surgery decortication and laparoscopic liver abscess drainage and marsupialization. • The patient improved after these interventions and was discharged one week after the procedure with a plan to continue oral ciprofloxacin for 10 days. Discussion: PLA of the right hepatic lobe with exophytic extension to the posterior thoracic wall is a risk factor for the development of an encysted pleural effusion complicated by empyema. Image guided percutaneous drainage is the most reliable method for both diagnosis and treatment of a single, unilocular liver abscess. However, this procedure may increase the risk of developing a pleural effusion and subsequent empyema suggesting that these cases may benefit from early surgical intervention rather than image guided drainage.Figure 1.: Triphasic CT abdomen and pelvis; Liver: There is a 7.0 x 6.8 x 8.0 cm peripherally enhancing lesion in the posterior RIGHT hepatic lobe., with exophytic extension to involve the posterior wall of the lower thorax and adjacent retroperitoneum.

NEUROFIBROMATOSIS-ASSOCIATED LUNG DISEASE: A CASE REPORT

TOPIC: Genetic and Developmental Disorders TYPE: Fellow Case Reports INTRODUCTION: Neurofibromatosis type I (NF-1) is a rare disorder that affects multiple organs, with cutaneous findings being the most well-known. It is an autosomal dominant disease caused by dysplasia of ectoderm and mesoderm with variable expression[1]. NF is characterized by a collection of neurofibromas, café au lait spots, and Lisch nodules. Neurofibromatosis is a rare disease and only 10-20% of the cases have associated diffuse lung disease (NF-DLD). Thus, many of the specific characteristics have yet to be elucidated[2]. CASE PRESENTATION: A 50-year-old white man with NF-1 diagnosed by skin biopsy 2 years ago was seen by his PCP due to worsening shortness of breath associated with a productive cough. Levofloxacin was ordered, but 5 days later symptoms persisted so he was referred to the ED.He reported a prior tube thoracostomy after spontaneous right-sided pneumothorax.Family history was remarkable for neurofibromatosis in his mother and spontaneous pneumothorax in his brother. However, his brother does not have any of the cutaneous findings consistent with NF.He is a former smoker with a 20 pack-year history, quitting a month before admission. He works in a furniture company with exposure to wood dust and chemical fumes for more than 30 years.He denies any fever, chills, chest pain, or weight change. Denies any sick contacts.Physical examination demonstrated no respiratory distress. He had mild bibasilar crackles and multiple neurofibromas throughout his body, more so on his back. SARS-CoV-2, influenza A, influenza B, RSV PCR were all negative. Chest x-ray demonstrated peripheral interstitial opacities. He was started on empiric antibiotic coverage for community-acquired pneumonia. Chest CT showed evidence of upper lobe predominant cystic disease and pulmonary reticular abnormalities in the lower lobes consistent with neurofibromatosis associated diffuse lung disease. Centrilobular emphysema and mild bronchiectatic changes were also noted. He was started on bronchodilators with a 5-day course of prednisone. Respiratory status returned to baseline and he was discharged with a LABA+LAMA inhaler and follow-up with the pulmonary clinic. DISCUSSION: The exact prevalence of NF-DLD is unknown. Based on the limited case reports, NF-DLD is more predominant in men, occurring during the third or fourth decade of life with dyspnea being the more common presenting symptom. Whether smoking plays a role in NF-DLD is still unknown. The typical HRCT finding in NF-DLD is upper-lobe cystic and bullous disease with basilar interstitial lung disease. HRCT results demonstrate bibasilar reticular opacities 50%, bullae 50%, ground-glass opacities 37%, cysts, and emphysema 25%[3]. CONCLUSIONS: NF-DLD is considered one of the rare etiologies of cystic lung disease characterized by upper lobe cystic and bullous disease and lower lobe interstitial changes. REFERENCE #1: V. M. Riccardi, "Von Recklinghausen Neurofibromatosis," https://doi.org/10.1056/NEJM198112313052704, Jan. 19, 2010. https://www.nejm.org/doi/pdf/10.1056/NEJM198112313052704 REFERENCE #2: J. H. Ryu, J. G. Parambil, P. S. McGrann, and G. L. Aughenbaugh, "Lack of Evidence for an Association Between Neurofibromatosis and Pulmonary Fibrosis," Chest, vol. 128, no. 4, pp. 2381–2386, Oct. 2005, doi: 10.1378/chest.128.4.2381. REFERENCE #3: A. C. Zamora, H. R. Collard, P. J. Wolters, W. R. Webb, and T. E. King, "Neurofibromatosis-associated lung disease: a case series and literature review," European Respiratory Journal, vol. 29, no. 1, pp. 210–214, Jan. 2007, doi: 10.1183/09031936.06.00044006. DISCLOSURES: No relevant relationships by Susanti Ie, source=Web Response No relevant relationships by seyed pourshahid, source=Web Response No relevant relationships by Seyedmohammad Pourshahid, source=Web Response No relevant relationships by Edmundo Rubio, source=Web Response

Efficacy of Empiric Antibiotic Coverage in Community-Acquired Pneumonia Associated with Each Atypical Bacteria: A Meta-Analysis.

The benefit of empiric coverage for community-acquired pneumonia (CAP) for atypical bacteria is controversial. This meta-analysis purpose was to compare the clinical failure rate between adults who empirically received atypical coverage versus those who did not. We searched PubMed and EMBASE for randomized controlled trials (RCTs), comparing the clinical failure rate of CAP associated with individual atypical bacteria between adults who received empiric atypical coverage versus those who did not. Risk differences (RDs) with 95% confidence intervals (CIs) were calculated using random-effects models. Eight double-blind RCTs (65 patients with Legionella spp., 176 patients with M. pneumoniae, and 78 patients with C. pneumoniae) were included in the meta-analysis. The rate of clinical failure was significantly lower with empiric atypical coverage in CAP associated with Legionella spp. (RD, −42.6%; 95% CI, −69.8% to −15.4%; p-value = 0.002; I2 = 0%) and Mycoplasma pneumoniae (RD, −9.5%; 95% CI, −18.9% to −0.1%; p-value = 0.048; I2 = 0%), but not with Chlamydia pneumoniae (RD, 7.1%; 95% CI, −9.0% to 23.1%; p-value = 0.390; I2 = 0%). This meta-analysis of RCTs found that empiric atypical coverage decreased the clinical failure rate of CAP associated with Legionella spp. and M. pneumoniae, but not with C. pneumoniae.

A Practical Approach to Antibiotic Use in Critically Ill Obstetric Patients.

In recent years, several new antimicrobials have become available that are safer and more effective compared with older agents commonly used in obstetrics. Basic knowledge of these agents is of paramount importance to obstetricians and maternal fetal medicine specialists, as administration of early adequate broad-spectrum empiric antibiotic coverage plays a pivotal role in the management of septic patients. Of particular importance is the critically ill pregnant patient with life-threatening infectious processes in whom poor initial antibiotic selection may result in higher mortality and significant side effects from antibiotics themselves. In this article we aim to provide a guide for clinicians to select an adequate empirical antibiotic regimen for the most common severe infections that may affect pregnant individuals.

Listeriosis in infants: Prospective surveillance studies in Canada and Switzerland.

International data on listeriosis during infancy from large populations are essential to guide evidence-based empiric antibiotic guidelines for sepsis in infancy. We aimed to determine the incidence, clinical manifestations, and outcome of listeriosis in infants <6 months of age in Canada and Switzerland. Prospective, active surveillance of listeriosis in infants <6 months of age was conducted through the Canadian Paediatric Surveillance Program (May 2015 to April 2017) and the Swiss Paediatric Surveillance Unit (April 2017 to March 2018). Confirmed and probable cases were included. In Canada, eight sporadic listeriosis cases were reported (incidence, 1.1/100,000 live births/year). In Switzerland, four cases were reported (incidence, 4.5/100,000 live births/year) of which three were part of a confirmed outbreak with an unclear source. In the two countries, eight of the 12 cases (66.6%) presented as early-onset disease (within the first 7 days of life) and none presented after 28 days life. Neonatal listeriosis is rare. Infants presenting with sepsis, especially after 4 weeks of life, may not routinely require empiric antibiotic coverage for listeriosis. Outbreak-related cases still occur. Continued surveillance is important.

Secular trends of Blood stream infections in allogeneic hematopoietic cell transplant recipients 72 hours prior to death.

Blood stream infections (BSI) frequently cause morbidity and mortality in allogeneic (allo) hematopoietic cell transplant (HCT) recipients. Characteristics of causative organisms shortly before death have not been previously described. Early treatment with antimicrobial agents targeting the recent surge in multidrug-resistant (MDR) pathogens may lead to better outcomes. This is retrospective study including 529 allo HCT recipients who died between 2000 and 2013. All patients who had BSI that happened 72hours before death were included. BSI and criteria for antimicrobial resistance were defined according to the Centers for Disease Control and Prevention and the National Healthcare Safety Network surveillance criteria. Overall, 104 BSI were identified from 91 patients. Bacterial infections accounted for 87% of the infections which were comprised by 37% gram-negative organisms and 50% gram-positive bacteria. The most common species were Enterococcus (30%), Staphylococcus (16%), and Pseudomonas (16%). Most enterococci were vancomycin resistant (87%), 100% of staphylococci were resistant to methicillin, and 64% of Pseudomonas were MDR. Over time there was a significant increase in vancomycin-resistant enterococcal (P=.01) and gram-negative BSI (P=.01). Blood stream infections were either the primary or secondary cause of death in 53% of patients. In allo HCT recipients, vancomycin-resistant enterococcal infections caused the majority of BSI 72hours prior to death. Our findings provide information that may guide empiric antibiotic coverage in critically ill HCT recipients.

EFFECT OF EMPIRICAL ANTIBIOTIC THERAPY ON THE CLINICAL OUTCOME OF ACUTE CALCULOUS CHOLECYSTITIS

Abstract INTRODUCTION Acute calculous cholecystitis (ACC) is the second surgical cause of emergency consultation in the Western world. According to the Tokyo International Guidelines 2018 (TIG18), the treatment of choice is laparoscopic cholecystectomy in patients with mild or moderate cholecystitis. However, in severe cases there is a great variability of therapeutic options. We analyzed the adequacy of antibiotic therapy by studying intraoperative cultures (bile and peritoneal fluid) and preoperative blood cultures, to identify the effect of this antibiotic therapy on complication and mortality rates. MATERIAL AND METHODS A retrospective unicentric study on a prospective database of 725 ACCs between 2012 and 2016. More than 200 general, clinical, postoperative and microbiological variables are collected, including the antibiogram of the isolated germs in order to determine the adequacy of each administered antibiotic. RESULTS Cultures were performed in 76.1% of the cases, with a greater tendency to cultivate in older patients, men or with greater severity according to TIG18 (p &amp;lt; 0.001). Cultured patients had a higher rate of postoperative complications (p = 0.001). Patients who received adequate empirical antibiotic therapy had a lower rate of complications (50% vs 64%;p=0.037) and lower mortality (2.8% vs 11.8%;p=0.003) compared to patients with resistant germs to the antibiotic therapy given, especially important in severe ACC (3.7% vs 15.7%;p=0.022). CONCLUSIONS Adequate empirical antibiotic therapy is associated with fewer complications, as well as a lower mortality rate, especially in severe ACCs. Patients with severe ACC will probably require empirical broad-spectrum antibiotic coverage.

Local audit of empiric antibiotic therapy in bacteremia: A retrospective cohort study.

It is unclear if a local audit would be useful in providing guidance on how to improve local practice of empiric antibiotic therapy. We performed an audit of antibiotic therapy in bacteremia to evaluate the proportion and risk factors for inadequate empiric antibiotic coverage. This retrospective cohort study included patients with positive blood cultures across 3 hospitals in Hamilton, Ontario, Canada during October of 2019. Antibiotic therapy was considered empiric if it was administered within 24 hours after blood culture collection. Adequate coverage was defined as when the isolate from blood culture was tested to be susceptible to the empiric antibiotic. A multivariable logistic regression model was used to predict inadequate empiric coverage. Diagnostic accuracy of a clinical pathway based on patient risk factors was compared to clinician's decision in predicting which bacteria to empirically cover. Of 201 bacteremia cases, empiric coverage was inadequate in 56 (27.9%) cases. Risk factors for inadequate empiric coverage included unknown source at initiation of antibiotic therapy (adjusted odds ratio (aOR) of 2.76 95% CI 1.27-6.01, P = 0.010) and prior antibiotic therapy within 90 days (aOR of 2.46 95% CI 1.30-4.74, P = 0.006). A clinical pathway that considered community-associated infection as low risk for Pseudomonas was better at ruling out Pseudomonas bacteremia with a negative likelihood ratio of 0.17 (95% CI 0.03-1.10) compared to clinician's decision with negative likelihood ratio of 0.34 (95% CI 0.10-1.22). An audit of antibiotic therapy in bacteremia is feasible and may provide useful feedback on how to locally improve empiric antibiotic therapy.

Which Type of Empiric Antibiotic Therapy is Appropriate? A 20-Year Retrospective Study of Bloodstream Infections in Childhood Cancer.

IntroductionSufficient empirical antimicrobial therapy in febrile patients with cancer is challenging, owing to the limited arsenal of available antibiotics in an era of growing resistance. Because of the emergence of gram-negative bacteria resistant to ceftazidime and piperacillin, a combination antibiotic therapy was employed that uses meropenem combined with gentamicin and/or vancomycin if the patient further deteriorates.MethodsA retrospective cohort analysis was performed including all patients with catheter-associated bloodstream infections (BSIs) and treated for childhood cancer in a tertiary single centre between 1 January 2000 and 31 June 2018. We calculated the prevalence and the risk for BSIs and compared the in vitro susceptibility to various antimicrobial agents. ResultsOf 653 patients with childhood cancer, 113 patients (17.3%) were identified with a total of 139 BSIs, most of them occurring in patients with leukaemia (n = 90, 64.7%) and were associated with gram-positive bacteria (60.5%). In our cohort, all BSIs with gram-negative bacteria exhibited in vitro susceptibility against meropenem alone without any signs of resistance development. The antibiotic coverage of our meropenem-based combination therapy was also highly effective for gram-positive and non-fermenting bacteria. Thus, BSI-related mortality in all 139 BSI episodes was 1.4%. Clostridium difficile infections (CDIs), as main adverse event of carbapenem usage, occurred in only 16 (2.5%) patients.ConclusionOur meropenem-based combination therapy showed sufficient empirical antibiotic coverage in the majority of BSIs (96.4%) and did not result in an increased rate of unwanted side effects or development of antibiotic resistance.Supplementary InformationThe online version contains supplementary material available at 10.1007/s40121-021-00427-5.

Impact of a vancomycin-resistant Enterococcus (VRE) screening result on appropriateness of antibiotic therapy.

Vancomycin-resistant Enterococcus (VRE) infections have been associated with increased mortality and poor outcomes. VRE screening has been used to identify colonized patients to prevent transmission; however, little is known about the utility of screening results to guide antibiotic therapy. A retrospective review was performed at a tertiary-care center between June 1, 2015, and May 31, 2018. All patients who underwent VRE polymerase chain reaction assay (PCR) screening and had a bacterial culture from 7 days before to 90 days after the screening test were included. In total, 1,374 patients who had a VRE screening test met inclusion criteria. Sensitivity, specificity, and positive and negative predictive values of VRE screening for VRE infection were calculated. The appropriateness of the antibiotic therapy for each patient based on screening results was also assessed. We detected no difference in the appropriateness of antibiotic therapy between patients with a positive screen and those with a negative screen (59.3% vs 61.0%; P = .8657). The VRE PCR demonstrated 54% sensitivity, 89% specificity, a positive predictive value (PPV) of 13% and a negative predictive value (NPV) of 98%. The high NPV and specificity indicate that patients with a negative VRE screening results may not require empiric antibiotic coverage for VRE. Although VRE screening may have utility to detect colonization in high-risk patients, a positive VRE screen is of limited value in determining the need for an antibiotic with VRE culture-directed coverage.

1026. Is Empiric Coverage Necessary? Incidence of Pseudomonas aeruginosa and Methicillin-Resistant Staphylococcus aureus in Foot Infections

BackgroundEmpiric antibiotics for foot infections often include coverage of Pseudomonas aeruginosa (PA) and Methicillin-resistant Staphylococcus aureus (MRSA) due to their presumed frequency and ability to cause severe infection. The purpose of this study was to: 1) determine the incidence of PA and MRSA in foot infections; 2) identify variables associated with the presence of PA or MRSA; and 3) examine empiric antibiotic trends for foot infections to determine if empiric coverage of PA and MRSA is warranted.MethodsRetrospective study of foot infections at five large urban hospitals in San Diego during 2018. Data were collected from the medical records including demographics, host factors, laboratory data, pathology and imaging data, culture results, and empiric antibiotics. Patients with a foot infection treated as an inpatient in our healthcare system who had a culture collected were included.Results310 patients with foot infections were included. Mean age was 61.6 years; 220 (71%) were male; 248 (80%) had diabetes; 40 (13%) had end-stage renal disease (ESRD), and 122 (39%) had peripheral arterial disease (PAD). PA was present in 28 (9%) cases. No patient had a positive blood culture for PA. MRSA was present in 55 (18%) cases. Only one patient had a positive blood culture for MRSA. On univariate analysis, wound location not in the forefoot (p=0.047) and presence of PAD (p=0.048) were associated with PA. These failed to remain significant in multivariate analysis (OR=0.42, p=0.074 and OR=2.54, p=0.0504, respectively). Factors associated with MRSA included shallower depth of wound (OR=0.36; p=0.043). 199/310 patients (64%) received empiric antibiotic coverage for PA while 262/310 patients (85%) received empiric MRSA coverage. Of those who received empiric anti-PA coverage, 174 were overtreated (87%). Of those who received empiric anti-MRSA coverage, 218 (83%) were overtreated.ConclusionThe incidence of PA in foot infections was overall low, and none had positive blood cultures. MRSA was more often present, however, most patients did not have bacteremia or severe infections. In our study, the majority of empiric anti-PA, as well as anti-MRSA, antibiotic coverage for foot infections was unnecessary questioning the need for upfront, empiric coverage for these pathogens in foot infections.Disclosures All Authors: No reported disclosures

103. Empiric Antibiotic Susceptibility Using a Traditional vs. Syndromic Antibiogram-Implications for Antimicrobial Stewardship Programs

BackgroundA primary tenet of antimicrobial stewardship programs (ASPs) is to establish empiric antibiotic treatment recommendations. While traditional antibiograms are useful, intrinsic variability in susceptibility exists when stratifying by source and/or location. In contrast, a syndromic antibiogram displays the likelihood of adequate coverage for a specific infection syndrome, considering the weighted incidence of pathogens causing that syndrome. The aim of the study was to compare antibiotic susceptibilities using a traditional versus syndromic antibiogram.MethodsBetween 2016–2019, 20 US institutions per year submitted up to 250 consecutive targeted gram-negative pathogens from hospitalized patients as part of the Study for Monitoring Antimicrobial Resistance Trends (SMART). MICs were determined by broth microdilution and interpreted using 2020 CLSI breakpoints, except for imipenem/relebactam (I/R) for which FDA breakpoints were used. The traditional antibiogram included the 3 most common Gram-negative pathogens from all sources and represented critical organisms considered for empiric antibiotic coverage; the syndromic antibiogram included the 3 most commonly isolated Gram-negative pathogens from a respiratory source based on patient location.Results17,561 Gram-negative isolates, including 6,654 lower respiratory isolates were evaluated. The top 3 most common Gram-negative organisms included: E. coli (n=6095, 44%), Klebsiella spp. (n=4097, 30%), P. aeruginosa (n=3649, 26%). Cumulative susceptibilities were comparable using a traditional vs. syndromic antibiogram (Figure 1); however, cefepime (FEP), piperacillin/tazobactam (TZP), and meropenem (MEM) susceptibilities were 5 – 8% lower when stratified by patient location (Figure 2) and ≥10% for P. aeruginosa (Figure 3). Ceftolozane/tazobactam (C/T) and I/R demonstrated ≥90% susceptibility regardless of respiratory source or patient location.Figure 1. Cumulative susceptibility of E. coli, Klebsiella spp, and P. aeruginosa for traditional vs. syndromic antibiogram Figure 2. Syndromic antibiogram evaluating cumulative susceptibility of E. coli (n = 637), Klebsiella spp. (n = 1190) and P. aeruginosa (n = 1997) respiratory isolates stratified by patient location Figure 3. Syndromic antibiogram evaluating susceptibility of P. aeruginosa (n = 1997) respiratory isolates stratified by patient location ConclusionOur analysis demonstrated that susceptibilities were lower for first-line agents when stratified by ICU and P. aeruginosa. ASPs should consider syndromic antibiograms based on source and patient location to optimize empiric antibiotic therapy recommendations.DisclosuresKenneth Klinker, PharmD, Merck & Co, Inc (Employee) Karri A. Bauer, PharmD, Merck Research Laboratories (Employee) C. Andrew DeRyke, PharmD, Merck & Co., Inc. (Employee, Shareholder) Levita K. Hidayat, PharmD BCIDP, Merck & Co (Employee)

MEDIASTINAL ABSCESS: AN UNCOMMON CAUSE OF DYSPHAGIA

SESSION TITLE: Medical Student/Resident Cardiothoracic Surgery Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Endograft infection and abscess formation is a rare late complication of endovascular aortic aneurysm repair (EVAR) with an estimated incidence 0.05-4% [1]. Fever and weight loss are the most common presenting complaints secondary to systemic inflammatory response. Less frequently extension of the infection to adjacent structures such as the esophagus, left main bronchus, left atrium or vertebrae causes symptoms related to their compromised function. We report a patient with extrinsic dysphagia resulting from a mediastinal abscess complicating EVAR. CASE PRESENTATION: A 78-year-old female presented with a 16-day history of worsening dysphagia (solids and liquids) and upper back pain. Past history included a thoracic EVAR two years prior which was complicated by vertebral osteomyelitis successfully treated with intravenous antibiotics. On exam, afebrile, hemodynamically stable without any focal abnormalities. Initial labs were significant for a microcytic anemia and malnourishment suggestive of chronic inflammation. Blood cultures were obtained and negative. A computed tomography (CT) chest scan demonstrated 3.5 cm, ill-defined hypodensity along the anteromedial aspect of the thoracic aorta which was inseparable from the thoracic esophagus [Figure 1A]. Due to worsening dysphagia, an esophagram was ordered which revealed an anterior luminal filling defect of the esophagus [Figure 1B]. Esophagogastroduodenoscpy showed extrinsic compression along the length of the esophagus. During the admission, she developed worsening leukocytosis and was started on vancomycin and meropenem for empiric antibiotic coverage. A repeat CT chest demonstrated an enlarging complex loculated abscess in the posterior mediastinum, which extended around the thoracic aorta graft, thoracic vertebrae and compressed the esophageal lumen [Figure 2A-B]. Thoracic surgery consultation was obtained and given the patient’s age and complexity of the procedure; she was deemed a high-risk surgical candidate. Ultimately the patient decided to pursue comfort care and was discharged on hospice. DISCUSSION: The differential diagnosis of dysphagia can be divided into intrinsic and extrinsic etiologies [2]. Extrinsic causes include abscesses, thyroid masses, lung cancer, metastatic adenopathy, aortic aneurysm, dissection, or cardiomegaly. Clinicians should consider possible mediastinal abscess in patients with dysphagia and a history of EVAR as it is associated with a high mortality rate. One multicenter study observed a 30-day mortality rate of 38.4% and overall mortality of 50% in 26 cases [3]. In the study all infected grafts required open graft explantation and surgical revision. CONCLUSIONS: Mediastinal abscess is an uncommon extrinsic cause of dysphagia and rare complication following thoracic EVAR. Early recognition, broad empiric antibiotics, and early surgical intervention with graft explantation are the cornerstones of management. Reference #1: Hobbs SD, Kumar S., and Gilling-Simth GL. Epidemiology and diagnosis of endograft infection. The Journal of Cardiovascular Surgery. 2010 February; 51(1):5-14 Reference #2: Carucci LR, Turner MA. Dysphagia revisited: common and unusual causes. Radiographics. 2015 Jan-Feb;35(1):105-22. doi: 10.1148/rg.351130150. Reference #3: Capoccia L, Speziale F, Menna D et al. Preliminary results from a national enquiry of infection in abdominal aortic endovascular repair. Annals of vascular surgery. 2016 (30) 198-204. DISCLOSURES: No relevant relationships by Tamar Gubeladze, source=Web Response No relevant relationships by Zachary Holliday, source=Web Response No relevant relationships by Michael Nance, source=Web Response No relevant relationships by Tarang Patel, source=Web Response