Repeated Blood Cultures Research Articles

F-18 FDG PET/CT scan in recurrent prosthetic valve endocarditis without detectable abnormality on echo: a case report

BackgroundInfective endocarditis poses many clinical and diagnostic challenge. The diagnosis of infective endocarditis is made by high index of clinical suspicion based on the American Heart Association modified Duke’s criteria, and the main imaging modality of choice is echocardiography.Case presentationHere, we reported a case of recurrent infective endocarditis revealed by FDG PET/CT study despite completion of antibiotics and negative on echocardiography. A 38-year-old female with history of double-valve replacement for aortic stenosis presented with 1-week history of chest pain, dyspnea and intermittent fever. She was treated with 5 weeks of antibiotic with IV Cephalexin for prosthetic valve endocarditis. The repeated blood culture after IV antibiotic was negative for infection. She represented again with episodes of palpitation. Post-treatment blood investigation showed normal leukocyte level with increasing CRP and Troponin T level. The repeated blood culture and transesophageal echo was negative. The F-18 FDG PET/CT showed a mild hypermetabolic focus at the inferior basal myocardial wall adjacent to the prosthetic valve, however not involving the paraaortic region which is likely secondary to ongoing inflamed myocardium. As the fear of another relapse of endocarditis, oral suppression antibiotic therapy was continued for another 6 months.ConclusionsThis case report illustrates a patient with a prosthetic valve replacement detected by F-18 FDG PET/CT, which one could have overlooked an endocarditis if one had relied on transesophageal echo (TEE) alone. F-18 FDG PET/CT is a promising adjunctive tool in the diagnostic workup of patients with suspected IE, particularly prosthetic device endocarditis where the TEE sensitivity is lower. In our patient, the positive F-18 FDG PET/CT governs the subsequent therapeutic consequences which include adjustment of antibiotic and length of treatment, and it prevents unnecessary intervention.

Is It Useful to Repeat Blood Cultures in Endocarditis Patients? A Critical Appraisal.

Previous guidelines for endocarditis have suggested repeating blood cultures until they become negative, with limited evidence. Literature reviews were conducted (1) on the incidence of persistent bacteremia and association with outcome and (2) on timing of valve culture negativization to examine the claim for prolongation of antibiotic therapy starting from negative blood cultures. Persistent bacteremia and fever may be present in the first 3 days of endocarditis, despite treatment, and are more common in Staphylococcus (especially MRSA) and Enterococcus species. Persistent bacteremia (48-72 h), persistent infection (day 7), and new onset septic shock are related and predict in-hospital mortality. It is, however, persistent infection at day 7 and septic shock that primarily determine the infectious course of endocarditis, and not persistent bacteremia. Valve cultures at surgery become negative in most cases (>85-90%) after 14-21 days of antibiotic therapy, with no calculated benefit for prolonging therapy after 21 days. Persistent infection at 7 days after appropriate antibiotic therapy is a better key event for prognosis then positive or negative blood cultures at 48-72 h. Therapy prolongation from the day of negative blood cultures is not reasonable. There is no need to survey blood cultures in endocarditis patients after starting therapy.

Yield of repeat blood cultures in acute myeloid leukemia patients with febrile neutropenia and bacteremia following allogeneic hematopoietic stem cell transplant.

This study explored the efficacy of repeat blood cultures in bacteremic acute myeloid leukemia (AML) patients following allogeneic hematopoietic stem cell transplantation (HSCT). This was a retrospective study of AML patients who experienced febrile neutropenia (FN) and bacteremia following HSCT at the Taussig Cancer Center from January 1, 2019, to December 31, 2022. The primary endpoint was the rate of positive repeat blood cultures following initial positive blood culture. Fifty patients were included in the study. There were 50 occurrences of FN with positive initial blood cultures that were diagnosed following HSCT. Fifty initial sets of blood cultures and 96 sets of repeat blood cultures were drawn between the 50 occurrences of FN. Twelve of 96 (12.5%) repeat blood culture sets were positive for a pathogen, which occurred over nine of 50 (18.0%) episodes of FN. Three of 96 (3.2%) repeat blood culture sets grew a pathogen that differed from the pathogen that grew in the preceding positive blood culture. Among bacteremic AML patients in the post-HSCT period, the yield of repeat blood cultures for detecting previously detected and new pathogens was low.

Ruthenibacterium lactatiformans isolated from a human blood culture: a first report

BackgroundRuthenibacterium lactatiformans, a Gram-stain-negative, rod-shaped, obligate anaerobic bacterium of the Oscillospiraceae family, has not been previously reported in human infections. This study reports the first case of bacteraemia and potential vertebral osteomyelitis caused by Ruthenibacterium lactatiformans.Case presentationAn 82-year-old man with a history of diabetes, chronic renal failure, and prior spinal surgery for spondylolisthesis and spinal stenosis presented with fever and lower back pain. Magnetic resonance imaging revealed multiple vertebral osteomyelitis lesions. Initial blood cultures identified methicillin-resistant Staphylococcus aureus (MRSA), which prompted vancomycin treatment. However, repeated blood cultures not only confirmed persistent MRSA, but also detected Gram-negative bacilli (GNB). Despite surgical removal of the spinal hardware and antimicrobial therapy, the patient’s osteomyelitis worsened, necessitating transfer for further management. Subsequent analysis using 16S rRNA gene sequencing identified the GNB as Ruthenibacterium lactatiformans.ConclusionsThis is the first documented instance of human infection with Ruthenibacterium lactatiformans, signifying its pathogenic potential in vertebral osteomyelitis. The involvement of anaerobic bacteria and the possibility of polymicrobial infections complicate the diagnosis and treatment of vertebral osteomyelitis. This report underscores the need for caution when identifying the causative organism and selecting an appropriate treatment.

Nontubercular Primary Spinal Epidural Abscess – A Retrospective Study of 11 Culture-Positive Cases

Abstract Background: An epidural abscess that occurs in the absence of contiguous spread from vertebral osteomyelitis or following spinal surgery, spinal anesthesia, or open spinal injuries is considered to be a primary spinal epidural abscess (SEA). The triad of back pain, fever, and progressive neurological dysfunction has long been considered to be the hallmark of primary SEA. Objective: The vast majority of epidural abscesses in our country are either tubercular or associated with pyogenic spondylitis. Primary non tubercular spinal epidural abscesses are rare and also need a different paradigm of management in terms of need for stabilization and duration of antibiotic treatment that we wish to highlight. Material and Methods: Eleven consecutive cases of nontubercular primary SEA were operated by the corresponding author between 2010 and 2019. Their clinical presentation, magnetic resonance imaging (MRI) findings, blood investigations, bacteriological profile, and outcomes were extracted from the patient files and follow-up visits to the outpatient clinic and analyzed 5 years after the last case. Results: All patients had spinal pain at presentation. Seven patients had fever and ten had neurological deficits at presentation. Diabetes and renal failure were the most common comorbidities. All patients had elevated erythrocyte sedimentation rate and C-reactive protein at presentation. The total leukocyte count was not uniformly elevated. One patient who was human immunodeficiency virus positive with a low cell count could not be operated. Diagnosis in his case was established by computed tomography-guided aspirate of the pus. Of the remainder, one patient had no recovery following surgery and two patients had residual deficits. Gram-positive coverage was started empirically in all patients who were operated and based on cultures changed and later extended orally for 4 weeks after discharge till repeat MRI and blood cultures were satisfactory. Conclusions: SEA is a surgical emergency. The majority of cases are caused by Gram-positive bacteria, and many of the patients have comorbidities that need to be addressed. Patients with better preoperative neurological status and those with lumbar location of abscess tend to have a better recovery. Antibiotic treatment must be continued till postoperative radiological and hematological parameters are satisfactory.

Brucella Prostatitis: A Rare Manifestation of Fever of Unknown Origin, Detected by FDG PET/CT.

FDG PET/CT is a well-documented imaging investigation to evaluate fever of unknown origin (FUO). Brucellosis is one of the causes of FUO, which can be missed as it requires a longer incubation period for growth on culture media. Rarely, it can involve the prostate. Here, we present a case of FUO with initial negative blood and urine cultures and no localizing signs or symptoms. 18F-FDG PET/CT revealed hypermetabolism in the prostate and seminal vesicles. A repeat blood and urine culture showed the growth of Brucella species after 5 days of incubation, and the patient responded to Brucella-directed antibiotic therapy.

PROSTHETIC GRAFT INFECTION: WHEN ECHOCARDIOGRAPHY IS NOT ENOUGH!

Abstract A 68–year–old Caucasian male, post–Bentall procedure with a bioprosthetic valve following extensive aortic dissection involving the ascending aorta and aortic arch, presented to the Emergency Department with persistent fever for over a month. During his hospitalization, he experienced ventricular fibrillation in the setting of hypokalemia, successfully managed with Advanced Cardiovascular Life Support (ACLS) and DC shock, leading to the restoration of sinus rhythm. Subsequently, he was admitted to the Cardiovascular Intensive Care Unite. Blood tests revealed neutrophilic leukocytosis with elevated inflammatory markers, anemia, and a troponin curve consistent with myocardial injury in the context of sepsis and anemia. Echocardiography demonstrated a left ventricle of normal dimensions with globally depressed function (EF 45%), attributed to apical akinesia. The prosthetic valve was functioning normally, and there were no signs of endocarditic vegetations or pericardial involvement. A transesophageal echocardiogram confirmed the absence of vegetations. Given echocardiographic signs of myocardial ischemia, coronary angiography was performed, revealing a coronary circulation free from significant stenosis. Cultural exams showed positivity for Enterococcus faecalis. A PET–CT revealed the presence of radioisotope uptake around the vascular prosthesis situated in the aortic arch. An Infectious Disease specialist recommended antibiotic therapy with Piperacillin/Tazobactam and Teicoplanin. At the one–month follow–up, the patient remained asymptomatic, free from new febrile episodes. The follow–up echocardiogram indicated improved global systolic function, and inflammatory markers remained consistently negative. Repeat blood cultures were negative. This case illustrates a suspected endocarditis on a prosthetic valve where both transthoraci and transesophageal echocardiography yielded negative results. The use of PET–CT, on the other hand, revealed the presence of vascular graft infection, proving to be a valuable method in this clinical setting.

Make Modern Microbiology Matter More in the 2023 European Society of Cardiology Guidelines for the Management of Infective Endocarditis.

The European Society of Cardiology (ESC) 2023 guidelines for the management of infective endocarditis (IE) stress that a multidisciplinary approach is needed to manage patients with IE. In our view, the guidelines do not include the relevant perspectives from modern microbiology. The diagnostic criteria for IE were changed in the ESC 2023 guidelines, and many IE-causing pathogens are either not clearly defined. Moreover, an improved understanding of the relationship between bacterial species and the risk for IE has not been implemented. The guidelines give detailed and, in our view, incorrect instructions about diagnostic testing in blood culture-negative IE without presenting proper evidence. Other important diagnostic aspects, such as the value of repeated blood cultures and incubation time for blood cultures, are not discussed. We believe that a multidisciplinary collaboration that include microbiologists would have improved these guidelines, and we hope for a future harmonization of diagnostic criteria for IE.

Axillary necklace graft salvage of a locally infected Haemodialysis with Reliable Outflow (HeRO®) graft.

A 48-year-old patient presented 4 months after insertion of a right sided Haemodialysis with Reliable Outflow (HeRO®, Merit Medical) graft with a discharging abscess at the site of the brachial artery anastomosis. There was localised involvement of the arterial Gore® Acuseal inflow graft that necessitated its removal. The venous outflow component was thought salvageable as infection was well localised to the region of the antecubital fossa. Alternative access options were limited so we sought to preserve the venous outflow portion of the patient's original graft - minimising tissue damage and avoiding the need for a dialysis line. The infected arterial graft was excised, leaving behind the original SuperHero® connector and venous graft. A left sided tunnelled axillary necklace technique was utilised to restore arterial inflow. After a four-day recovery, the patient went on to successfully resume their usual haemodialysis regimen without any complications. Convalescent imaging, repeat blood cultures, and monitoring of inflammatory markers showed no signs of residual infection at 6 weeks. The originality of this case was the way in which an axillary necklace inflow graft was connected to the pre-existing venous outflow portion of the HeRO® haemodialysis graft system, allowing the excision of the infected inflow graft at the brachial anastomosis. This technique could be viewed as an effective salvage procedure as it allowed the venous outflow portion of the original graft to remain in situ, minimised tissue damage and enabled the patient to swiftly resume haemodialysis without the need for a line.

A case report of lactobacillus bacteremia in a patient on chronic parenteral nutrition

Short bowel syndrome is a malabsorption disorder typically caused by the physical loss of a portion of the intestine, whereafter the body is unable to adequately absorb nutrients, fluids, and electrolytes. Many patients with short bowel syndrome are reliant on home parenteral nutrition through a tunneled or peripherally inserted central catheter to ensure sufficient hydration and nutrition. Central venous catheters are a nidus for bacteria, and patients are at risk for infections associated with high levels of morbidity and mortality. Lactobacillus is a ubiquitous microorganism that most frequently colonizes mucosal surfaces such as the gastrointestinal tract. Lactobacillus bacteremia is rare, with limited occurrence in current medical literature. Our patient is a 60-year-old female with a past medical history significant for multiple abdominal surgeries resulting in short bowel syndrome, with subsequent dependence on home parenteral nutrition via peripherally inserted central catheter. She had type III chronic intestinal failure, category D2, and stage 1 moderate malnutrition. She was originally admitted to the hospital for a presumed pulmonary embolism and was found to have a deep vein thrombosis in the setting of her peripherally inserted central catheter. On admission her abdominal exam was unremarkable, she denied abdominal pain, and her only gastrointestinal complaint was chronic stable diarrhea. During the hospitalization she developed severe left lower quadrant abdominal pain and noted decreased frequency of her bowel movements. A computed tomography scan of her abdomen revealed chronic stable intestinal distension and was concerning for obstruction. Clinically she remained without symptoms of acute obstruction or ileus. During the admission she became febrile, with blood cultures from her peripherally inserted central catheter and peripheral IV growing out gram negative rods determined to be lactobacillus bacteremia. The infectious disease team recommended removal of her peripherally inserted central catheter given their concern for a line infection. The patient was treated with broad-spectrum antibiotics, did well clinically, and was ultimately discharged following reinsertion of her peripherally inserted central catheter after negative repeat blood cultures. Though she initially did well in the outpatient setting, she ultimately passed away ten months later after re-presenting to the hospital in septic shock, secondary to bowel ischemia and suspected fungemia of her peripherally inserted central catheter. In this case report, we describe an unusual case of a patient with short bowel syndrome on chronic parenteral nutrition who developed catheter-associated lactobacillus bacteremia - the first reported case in an adult patient on parenteral nutrition.

Rapid formation of aortoesophageal fistula complicated by mycotic thoracic aortic aneurysm secondary to infective endocarditis.

A 73-year-old man was admitted with four weeks of intermittent fever. He had a history of total aortic arch replacement for aortic arch aneurysm four years prior. CT scans showed no abnormalities before admission. Repeated blood cultures yielded Streptococcus anginosus and Prevotella melaninogenica, suggesting infective endocarditis (IE). Transesophageal echocardiography revealed a vegetation on the aortic valve, confirming IE. He suddenly presented with massive hematemesis and hypotension. Endoscopy revealed an elevated lesion with a laceration but no active bleeding in the esophagus. CT scans showed a thoracic aneurysm involving the esophagus. A diagnosis of aortoesophageal fistula (AEF) complicated by mycotic thoracic aortic aneurysm (MTAA) was made, and he underwent stent graft interpolation followed by minimally invasive esophagectomy. MTAAs are more prone to rupture than arteriosclerotic aneurysms as they are usually not true but pseudoaneurysms. Antecedent infection, including endocarditis, sepsis, predisposes to MTAA. AEF is a rare but life-threatening cause of gastrointestinal bleeding characterized by Chiari's triad. There have been no reports of such rapid formation of AEF after the graft replacement, as shown here. A recent article reported a rapid formation (16 days) of AEF after thoracic endovascular aortic repair, emphasizing prosthetic infection as the most important risk factor. Our case underscores the importance of suspecting AEF and conducting repeated appropriate examinations even if initial examinations do not reveal any aneurysms.

Successful Endovascular Management of Juxta Internal Iliac Vessel Pseudoaneurysm with Allograft Preservation in Post-Renal Transplant

Vascular complications following renal transplant surgery are extremely uncommon, and pseudoaneurysm is even rarer, with an incidence of 0.3%. The presentation can vary from acute blood loss to chronic dull aching pain, anorexia, etc. Majority of pseudoaneurysms are associated with allograft loss. We present a case of an anastomotic pseudoaneurysm successfully managed with an endovascular approach. A 54-year-old female, post cadaveric renal transplant (end-to-end anastomosis between the renal artery and right internal iliac artery) presented on post-operative day 159 with complaint of fever with chills. On treating conservatively with antibiotics, the fever subsided, only to recur after 5-days. On further investigation, c-reactive protein (CRP) was found to be persistently elevated. Patient’s fever of unknown origin was further investigated with repeat blood culture and fluoro-D-glucose (FDG) positron emission tomography (PET)/computed tomography (CT). Blood culture was positive for Klebsiella pneumoniae sensitive to colistin and tigecycline and FDG-PET showed a 5 cm aneurysm of the juxta anastomotic segment of the right internal iliac vessels, a possible pseudoaneurysm. After a multidisciplinary discussion, the patient underwent renal angiography, an aneurysm was delineated, and a covered stent was placed which partially excluded the aneurysm. The patient responded well to the intervention. Pseudoaneurysm formation is a rare and potentially life-threatening complication and can present even in the late post-operative period. Endovascular management can be a safe approach in carefully selected cases with allograft preservation being of paramount importance.

Yield of Repeat Blood Cultures in Acute Myeloid Leukemia Patients Following Allogeneic Hematopoietic Stem Cell Transplantation

Introduction: Unnecessary repeat blood culture collection has been demonstrated to increase health care costs, length of stay, duration of antimicrobial exposure, and risk of anemia and result in unnecessary removal of vascular catheters. The aim of this study was to characterize the yield of new pathogen identification in acute myeloid leukemia (AML) patients with known bacteremia in the post-allogeneic hematopoietic stem cell transplant (HSCT) period. Methods: This was a retrospective study of AML patients who underwent allogeneic HSCT at Taussig Cancer Center from January 1 st 2019 to December 31 st 2022. Patients who experienced an occurrence of febrile neutropenia (FN) within 35 days of date of HSCT and had positive initial blood cultures within 24 hours of diagnosis of FN were included in the study. Patients who had at least 1 additional set of repeat cultures drawn following initial blood cultures were included in the study. Blood cultures were collected through a peripheral site via venipuncture or through a central line. The study was approved by the Institutional Review Board. Data were collected on baseline patient characteristics, AML disease characteristics, HSCT characteristics, and infection characteristics. Febrile neutropenia was defined as recorded temperature ≥ 100.4°F with concurrent ANC <1500 cells/uL. Each patient day with a recorded temperature ≥100.4°F and ANC <1500 cells/μL was considered as a day of FN. An episode of FN was considered to be resolved following 72 hours of defervescence. Cultures drawn within 24 hours of onset of FN were considered the initial blood cultures. All subsequent sets of blood cultures were considered repeat blood cultures. A positive set of blood culture was defined as >50% of all blood cultures in that set growing an organism. Cultures drawn from all peripheral and central sites on the same day of FN were considered as one set of blood cultures. All patients received post-HSCT anti-bacterial prophylaxis with bactrim or ciprofloxacin. Results: A total of 154 AML patients who underwent HSCT at Taussig Cancer Center were screened for the study. 50/154 (32.5%) of those patients met inclusion criteria and were included in the study. Among the 50 patients included in the study, there were 50 episodes of FN with positive initial blood cultures that were diagnosed within 35 days of HSCT. There were 120 total days of FN among the 50 episodes of FN with an average of 2.4 days per episode. 50 initial sets of blood cultures and 96 sets of repeat blood cultures were drawn between the 50 episodes of FN with an average of 2.9 total sets of blood cultures per episode. 12/96 (12.5%) of repeat blood cultures sets were positive for a pathogen. 3/96 (3.1%) of repeat blood cultures sets grew a pathogen that differed from the pathogen which grew in the preceding positive blood culture. The median duration of febrile neutropenia at time of repeat positive culture was 3.5 days. 30-day mortality rate from infection was 6.0% (3/50). Conclusion: Even amongst bacteremic AML patients in the post-HSCT period, the yield of repeat blood cultures was low for detecting new pathogen identification. Repeat blood cultures should be guided by thorough evaluation of emerging clinical signs and symptoms.

2270. Dealing with an old foe –Assessment of Knowledge, Attitude, and Practices: A survey on management of Staphylococcus aureus bacteraemia among Indian Physicians

Abstract Background Staphylococcus aureus bacteraemia (SAB) is associated with high morbidity, mortality, and healthcare costs. Effective management of SAB significantly improves outcome. There is significant gap in the guidelines and clinical practice. This survey was conducted with aim to assess opinions and practice patterns in management of SAB among Indian clinicians. Methods We conducted a cross-sectional respondent-driven survey, using a 45-item, anonymous, voluntary, multiple-choice google form questionnaire among clinicians in India, after obtaining ethical approval from the institute. We distributed survey via social media, WhatsApp, and E-mail. Survey responses were analysed using SPSS, Version 25.0. Results The total of 125 practicing clinicians responded to this survey. Questions where systematically divided into treatment of choice for MSSA, MRSA, additional investigations, persistent bacteraemia, and adjunctive anti-toxin therapy. Around 57% of the respondents have 1-10 episodes of SAB every month. For suspected SAB, most respondents (74%) preferred vancomycin as empiric therapy. If MSSA was identified, 66.7% initiated on Anti staphylococcal penicillin, while in MRSA vancomycin was selected by majority (80%) (Figure 1 & 2). Most clinicians (74%) perceived 1st generation cephalosporins non-inferior to ASPs. Infectious diseases referral for SAB was undertaken in only in about 56% of the cases, with 25% respondents citing non-availability of ID specialist in the institute. Repeat blood cultures and echocardiography was performed by most respondents. Lack of consensus was apparent in diagnosis and management of persistent bacteraemia and oral switch of therapy (Figure 1 & 2).Most respondents managed SAB with at least 14 days of parenteral antibiotics in several scenarios. But, in patients with complicated SAB there was significant practice variation (Figure 3). Figure - 1 Drug of choice in MSSA, MRSA and management of persistent bacteraemia according to the respondents Figure 2 Persistent bacteraemia definition according to the respondents along with the additional tests performed Conclusion There were some areas of consensus, but this survey highlights considerable practice variation among clinicians. Although the value of ID consultation in SAB management has been established by multiple studies, this survey demonstrates that there remains ample opportunity to further define best practices and optimize management of this complex disease. Disclosures All Authors: No reported disclosures

2232. Comparison of Empiric Vancomycin Prescribing in Response to Gram Positive Cocci Alerts on Blood Cultures Between Primary and Overnight Physicians on General Medicine Services: A Retrospective Study

Abstract Background Blood culture contamination is associated with unnecessary antibiotic use, increased length of stay, and increased costs. Assessing the likelihood of true bacteremia versus contamination requires consideration of clinical context and microbiologic data. This may be more difficult for covering physicians overnight, who typically cover more patients and may not know patients’ clinical history as well. We compared rates of vancomycin (VAN) initiation in response to microbiology alerts for gram-positive cocci (GPC) in blood cultures during primary team shifts versus overnight. Methods We queried the University of Virginia Clinical Data Repository for blood culture results positive for GPC from 07/01/2021 to 12/30/2022 in inpatient general medicine patients. Cultures were stratified by time of the initial positive gram stain alert, which is called as a critical result to the team. All new positive blood cultures are run on a rapid molecular diagnostic (ePlex GenMark Diagnostics) with speciation results passively entered into the chart 2 hours after gram stain. Results were excluded if the patient was already on VAN or daptomycin at the time of gram stain or if the gram stain resulted during hours when the physician coverage (primary vs covering) was not consistent. The primary outcome was the rate of VAN initiation within 2 hours of gram stain with GPCs. Secondary outcomes were number of repeat blood cultures, length of stay (LOS), and incidence of acute kidney injury (AKI). Results 320 instances of positive blood cultures were reviewed. 141 were excluded. Of 179 included instances, there was no significant difference in VAN initiation by overnight physicians compared to primary teams (21% vs 26%; p=0.418). There was no significant difference in repeat cultures or incidence of AKI. Comparison of primary and overnight physicians Blood culture speciation Conclusion There was no difference in VAN use, repeat blood cultures, or AKI when positive gram stain alerts were received by overnight physicians versus primary teams. Stewardship interventions targeting VAN prescribing in the setting of a rapid diagnostic workflow may not need to be specifically adapted to covering physicians or teams. Disclosures Amy Mathers, MD, D(ABMM), Merck: Advisor/Consultant

591. Positivity of Blood Culture on Automated Incubation System After 72 Hours and Clinical Significance from the Large United States Tertiary Care Center

Abstract Background Hospitals commonly use automated blood culture incubation systems that provide continuous monitoring for routine blood cultures. Detecting microorganisms early on can help optimize the utilization of antibiotics (ABx) and enable clinicians to de-escalate or discontinue ABx as necessary, making it an important aspect of antimicrobial stewardship. The BD BACTEC Fx, an automated system for blood culture incubation, holds blood culture bottles until growth is demonstrated or for five days unless an extended incubation period is requested by the infectious disease physician. We conducted a clinical evaluation of the significance of positive blood cultures after 72 hours of incubation time. Methods After receiving approval from the institutional review board (IRB), we obtained positive blood cultures from July 2017 to June 2020, which we then stratified based on positivity from day one to day five. To evaluate clinical significance, we retrospectively reviewed charts for positive blood culture results on day four and day five. An Infectious Diseases subspecialty team determined the clinical significance of each case. Results During the time frame of July 2017 to June 2020, there were 120,320 blood cultures taken. Out of these, 7,558 were determined to be positive, with 76 being positive on day 4 and 22 being positive on day 5. Upon further inspection of patients with positive blood cultures, it was discovered that repeat blood cultures continued to be positive due to either untreated sources or a high burden of bacteremia. It was also found that bottles containing fungus, particularly candida glabrata and candida albicans, tested positive on day 4 requiring treatment. Table 1 and Table 2 contain more detailed results. Blood cultures positive on day 4 Blood cultures positive on day 4 and clinical significance Blood cultures positive on day 5 Blood cultures positive on day 5 and clinical significance Conclusion In our study we have found that not all positive blood cultures at 72 hours translate into clinical scenarios requiring antibiotic therapy. In fact, prolonged antimicrobial treatment in such cases may lead to unnecessary exposure to antibiotics and increased risk of antibiotic resistance. It is important to consider the full context of clinical and laboratory findings when interpreting blood culture results, as well as any potential sources of contamination. Disclosures All Authors: No reported disclosures

2795. Cefepime Versus Meropenem for Infections Due to HECCcK-YeS-MAm Organisms with Cefepime MICs of 4-8 mCg/mL (S-DD)

Abstract Background Recent guidance from IDSA recommends meropenem for treatment of organisms at moderate-high risk for inducible chromosomal AmpC β-lactamase hyperproduction (AmpC organisms) with a cefepime minimum inhibitory concentration (MIC) of 4-8 mCg/mL (susceptible dose-dependent or S-DD).1 This runs contrary to pharmacokinetic/pharmacodynamic data and Clinical and Laboratory Standards Institute (CLSI) M100 guidance, which considers organisms ≥ 16 mCg/mL resistant.2 The purpose of this study is to evaluate the clinical efficacy of cefepime versus meropenem for the treatment of infections caused by AmpC organisms with a S-DD cefepime MIC. Methods This was a retrospective study evaluating patients treated within Indiana University Health from 2015-2022. All cefepime S-DD AmpC isolates were included. Exclusion criteria were < 48 hours of treatment, multiple days of therapy with another active agent, inadequate dosing, extended spectrum β-lactamase (ESBL) co-production, and carbapenem resistance. The primary endpoint of this study was a composite of in-hospital all-cause mortality and antibiotic escalation due to clinical worsening. Secondary endpoints include positive repeat blood cultures within 7 days of treatment initiation, and ESBL or carbapenem resistant organism isolation during or following treatment. Results 355 isolates were screened. 71 patients were included in the final analysis, 43 in the cefepime group and 28 in the meropenem group. Baseline characteristics were not significantly different. Enterobacter cloacae made up 79% of cases. The primary endpoint occurred in 13/43 (30%) of patients on cefepime and 7/28 (25%) of patients on meropenem (P=0.63). Treatment escalation and escalation due to clinical worsening was higher in the cefepime group with 7 (16%) and 6 (14%) incidents respectively compared to none in the meropenem group (P=0.03; P=0.04). No other endpoints, including all-cause mortality, were significantly different between groups. Conclusion Cefepime remains a viable treatment option for ESBL-negative, AmpC organisms with MICs in the S-DD range. Disclosures All Authors: No reported disclosures

186. The Role of Repeated Blood Cultures in Hematologic Malignancy Patients with Neutropenic Fever due to Gram-Negative Bacterial Bloodstream Infections

Abstract Background Several observational studies and a recent meta-analysis suggest there is a mortality benefit associated with acquiring repeat blood cultures for gram-negative bacterial bloodstream infections (GNBSI). However, limited data are available among patients with febrile neutropenia. We sought to evaluate the utility of obtaining follow-up blood cultures (FUBC) in GNBSI among neutropenic hematological malignancy patients. Methods A retrospective chart review was conducted to identify all patients with a hematologic malignancy admitted with a diagnosis of neutropenic fever due to gram-negative rod bacteremia (GNRB) from 2018-2021 at a large urban academic medical center. We collected demographics, cancer diagnosis and treatment data, microbiology and antibiotic information, and death at discharge, 30 days, and 90 days. Descriptive statistics and chi-square tests were used. Results A total of 47 episodes of GNBSI among 43 patients were included. Mean age was 57 years, 61% were male, 49% were White, and 14% were Latino. Most patients had AML (47%), and most common chemotherapy regimen was R-CHOP (19%). 32% of GNRB were due to K. pneumoniae, in the setting of long-term central venous catheter (53%), and from a gastrointestinal source (49%). FUBC were collected among most patients (87%), but only two patients (5%) had positive FUBC. ESBL resistance profiles were uncommon (6%), and most were treated with beta-lactams (55%). Patients who died at discharge were less likely to have FUBC collected (p< 0.001). We also found an association between acquiring FUBC and mortality at 30 (p=0.01) and 90 days (p=0.02). However, there was no association between having a positive FUBC and mortality at discharge (p=0.47), 30 days (p=0.93), and 90 days (p=1.00). Conclusion Among patients with neutropenic fever found to have GNBSI, acquiring repeat blood cultures was associated with decreased mortality. Due to their immunocompromised status, patients with neutropenic fever and GNRB should have repeat blood cultures collected. Disclosures All Authors: No reported disclosures

Abstract 15982: Management and Follow-Up of Inpatients With Cardiac Implantable Electronic Devices and Bacteremia With and Without Electrophysiology Consultation

Introduction: Transvenous cardiac implantable electronic device (CIED) infection is a significant cause of morbidity and mortality. Expert consensus recommends a multidisciplinary approach to bacteremia in the context of CIED incorporating both infectious disease (ID) and electrophysiology (EP) consultation to balance the risks of infection with those of CIED removal. Hypothesis: Not all patients with CIEDs and bacteremia are evaluated with EP consultation, and this difference is associated with variability in management. Methods: Using the EMR, we retrospectively identified inpatients with a CIED and a positive blood culture across three hospitals: one academic, one specialty and one community. True infection versus contaminant was determined by an EP or ID attending at the time of presentation or adjudicated retrospectively by an EP who performs extractions. We examined the rates of EP consultation based on hospital site, CIED removal and appropriate follow-up in those without CIED removal. Fisher’s exact test was used to compare the rates of follow up. Results: We identified 88 inpatients with a CIED and positive blood culture between January 2020 - February 2023. True bacteremia was adjudicated in 48 patients (55%). Of these patients, 24 were seen by EP (50%), 22 were seen by EP and ID (46%), and 14 were seen by neither (29%). Patients admitted to an academic hospital were more likely to be seen by EP (22/38, 57%) than those admitted to a specialty or community hospital (2/10, 20%). CIED removal was performed in 15 of 24 patients seen by EP (63%). Patients seen by EP were significantly more likely to have documented plans, repeat blood cultures after antibiotic completion, and appropriate follow up than those not seen by EP (24/24 100% vs. 3/24, 8%, p<0.001). Conclusion: Even at a high-volume extraction center, EP consultation for patients with true bacteremia in the context of CIED only occurred 50% of the time. Patients admitted to an academic hospital were more likely to be seen by EP than at a community or subspecialty hospital. EP consultation is important for all bacteremic patients with CIEDs, not only to recommend extraction if appropriate, but also to ensure timely follow-up and management of treatment failure, consistent with expert consensus.

Infective endocarditis of the aortic valve in an 85-year-old man due to translocation of the intestinal flora

Infective endocarditis (IE) is an infectious and inflammatory disease of the endocardium that is associated with a high incidence of complications and mortality. Elderly patients are the most vulnerable age group for the IE. Infective endocarditis caused by E. coli is a rare disease due to both bacteria life-cycle and human immune system protection. Nevertheless, recent years the incidence of IE associated with E. coli has been increasing in the group of elderly patients. It seems important to reassess the indications for antibiotic prophylaxis in certain categories of patients (including the elderly patients with an unobvious but increased risk of IE). This clinical case demonstrates a native valve endocarditis caused by E. coli developed after bowel preparation with osmotic laxatives and endoscopic procedure in an 85 year-old male without significant chronic diseases. Despite the fact that the patient did not belong to the category of increased risk of IE, he had the predisposing conditions for the development of IE (weaked immune system, bacteremia, heart valve sclerosis), that realized in the active manifest disease. Treatment with antibiotics led to an improvement in the patient’s condition and regression of infectious vegetations on the valve. Repeat blood cultures were negative. When planning endoscopic procedure for patients at risks (elderly person, weakened immune system, minimal aortic valve lesions), antibacterial prophylaxis should be considered. Additional research is required to develop clear algorithms for antibacterial prophylaxis.