Recurrent Bloodstream Infections Research Articles

In vivo selection of carbapenem resistance during persistent Klebsiella pneumoniae sequence type 395 bloodstream infection due to OmpK36 deletion.

Non-carbapenemase-producing carbapenem-resistant Enterobacterales (non-CP CRE) may be associated with a grave outcome. The common underlying mechanism is beta-lactamases and mutations in outer membrane porins. We report a case of a deep-seated infection caused by Klebsiella pneumoniae ST395 not amenable to source control, involving recurrent bloodstream infection, resulting in in vivo selection of carbapenem resistance under therapy. Three consecutive K. pneumoniae blood isolates were studied using short- and long-read sequencing. The genomes were subject to resistome and virulome, phylogenetic, and plasmid analyses. ompK36 porins were analyzed at the nucleotide and amino acid levels. Genomes were compared to 297 public ST395 K. pneumoniae genomes using cgMLST, resistome, and porin analyses and the EuSCAPE project. Relevant ompK36 and micF sequences were extracted and analyzed as above. The three sequential K. pneumoniae blood isolates belonged to the same clone. Subsequent CR isolates revealed a new large deletion of the ompK36 gene also involving the upstream region (deletion of micF). Comparison with public ST395 genomes revealed the study isolates belonged to clade B, representing a separate clone. N-terminal large ompK36 truncations were uncommon in both public data sets. In vivo selection of non-CP CRE K. pneumoniae could have substantial clinical implications. Such selection should be scrutinized through repeated cultures and frequent susceptibility testing during antimicrobial treatment, especially in the context of persistent or recurrent bloodstream infections and when adequate source control cannot be achieved. The occurrence of an unusually large deletion involving the ompK36 locus and upstream micF should be further studied.

Antibiotic duration and route for treatment of adults with uncomplicated streptococcal bloodstream infections: a retrospective study in a large healthcare system.

Data guiding the duration and route of streptococcal bloodstream infection (BSI) treatment are lacking. We conducted a retrospective cohort study of adults hospitalized with uncomplicated streptococcal BSI in a large integrated healthcare system from 2013 to 2020. The exposures of interest were antibiotic duration (5-10 days vs. 11-15 days) and antibiotic route (oral switch vs. entirely intravenous). The primary outcome was a composite 90-day outcome comprised of all-cause mortality, recurrent streptococcal BSI, or readmission. We performed non-inferiority analyses for each exposure. Separate multivariable Cox proportional hazards regression models were constructed for each exposure. The antibiotic duration analysis included 1,407 patients (5-10 days, n = 246; 11-15 days, n = 1,161). We found that 5-10-day courses were non-inferior to 11-15-day courses (P = 0.047). The antibiotic route analysis included 1,461 patients (oral switch, n = 1,112; entirely intravenous, n = 349). Oral step-down therapy did not meet the criteria for non-inferiority (P = 0.06). In the adjusted models, no significant difference was found in the primary outcome rate by antibiotic duration or antibiotic route at discharge. We found that 5-10-day courses were non-inferior to longer courses, and thus may be a safe and effective treatment option in the treatment of uncomplicated streptococcal bacteremia. Randomized controlled trials are needed to confirm the equivalent outcomes with shorter regimens and to definitively determine the optimal antibiotic route on discharge.

Efficacy of short- versus prolonged-courses of antimicrobial therapy for carbapenem-resistant Klebsiella pneumoniae bloodstream infections: A propensity score-matched cohort study

BackgroundAs limited antibiotic options are available for the treatment of carbapenem-resistant Klebsiella pneumoniae (CRKP) bloodstream infections (BSIs), the optimal treatment duration for CRKP BSIs is unclear. Our objective was to investigate whether short courses (6–10 days) are as effective as prolonged courses (≥11 days) of active antibiotic therapy for CRKP BSIs. MethodsA retrospective cohort study comprising adults with monomicrobial CRKP BSI receiving a short or prolonged course of in vitro active therapy at a medical center was conducted between 2010 and 2021. Comparisons of two therapeutic strategies were assessed by the logistic regression model and propensity score analysis. The primary endpoint was 30-day crude mortality. Secondary outcomes included recurrent BSIs, the emergence of multidrug-resistant organisms and candidemia during hospitalization after completing antibiotic therapy for CRKP BSIs. ResultsOf 263 eligible adults, 160 (60.8%) were male, and the median (interquartile range) age was 69.0 (53.0–76.0) years. Common comorbidities included diabetes (143 patients, 54.4%), malignancy (75, 28.5%), cerebrovascular accident (58, 22.1%), and hemodialysis (49, 18.6%). The 30-day mortality rate was 8.4% (22 patients). Of 84 propensity score well-balanced matched pairs, the 30-day mortality was similar in the short-course and prolonged-course group (6.0% and 7.1%, respectively; P = 1.00). However, there were less episodes candidemia in the short-course group (1.2% versus 13.1%; odds ratio, 0.08; 95% confidence interval, 0.01–0.63; P = 0.005). ConclusionShort courses of active therapy for CRKP BSIs demonstrate comparable clinical outcomes to prolonged courses and are associated with a lower risk of subsequent candidemia.

Persistent Gram-negative Bloodstream Infection Increases the Risk of Recurrent Bloodstream Infection With the Same Species.

The association between persistent gram-negative bloodstream infection (GN-BSI), or ongoing positive cultures, and recurrent GN-BSI has not been investigated. Among 992 adults, persistent GN-BSI was associated with increased recurrent GN-BSI with the same bacterial species and strain (6% vs 2%; P = .04). Persistent GN-BSI may be a marker of complicated infection.

Characterization of Prescribing Practices for Uncomplicated Streptococcal and Enterococcal Bacteremias: The NARRATE Study.

Bloodstream infections (BSIs) rank among the top causes of death in North America. Despite the prevalence of these infections, there remain significant practice variations in the prescribing of antibiotics. To investigate current prescribing practices for management of uncomplicated streptococcal and enterococcal BSIs. A retrospective cohort study was conducted using charts for patients admitted to an acute care centre in British Columbia between November 16, 2019, and October 20, 2020. Adult patients (≥ 18 years of age) with a diagnosis of uncomplicated streptococcal or enterococcal BSI were included. Patients were excluded if they had polymicrobial bacteremia or deep-seated infection or had been admitted for no more than 48 hours. The primary outcomes were duration of antibiotic therapy (IV and oral) and time to appropriate oral therapy for treatment of BSI. The secondary outcomes were observed rates of re-initiation of antibiotics and readmission with recurrent BSI. Descriptive statistics were calculated and regression analysis was performed for the primary and secondary outcomes. A total of 96 patients met the inclusion criteria. The median total duration of therapy for uncomplicated streptococcal and enterococcal BSI was about 2 weeks. Streptococcus pneumoniae BSIs were associated with a significantly shorter duration of IV therapy and were more likely to be associated with transition to oral antibiotics. No recurrent BSIs were observed in patients for whom therapy was transitioned to oral antibiotics. Further study is warranted to explore shorter duration of antibiotic therapy and transition to oral therapy as treatment approaches for uncomplicated streptococcal and enterococcal BSI. Other outcomes of interest for future research include determining the optimal time for transition to oral therapy.

Mortality, hospital length of stay, and recurrent bloodstream infections associated with extended-spectrum beta-lactamase-producing Escherichia coli in a low prevalence region: A 20-year population-based large cohort study

ObjectivesThis population-based study aimed to investigate the risk factors and effect of extended-spectrum beta-lactamase (ESBL) production on clinical outcomes in Escherichia coli bloodstream infection (BSI) patients. MethodsThe study population was defined as patients aged ≥15 years with E. coli BSI in Queensland, Australia, from 2000 to 2019. Outcomes were defined as 30-day case fatality, hospital length of stay (LOS), and recurrent E. coli BSI. ResultsA total of 27,796 E. coli BSIs were identified, of which 1112 (4.0%) were ESBL-producers. Patients with ESBL-Ec BSI were more frequently older, male, with comorbidity, recurrent E. coli BSI, and less likely with community-associated community-onset infections as compared to non-ESBL-Ec BSI patients. The standardized mortality rate of ESBL-Ec BSI increased 8-fold from 2000 to 2019 (1 to 8 per million residents) and case fatality was 12.8% (n = 142) at 30 days from positive blood culture. Patients with ESBL-Ec BSI were not at higher risk of 30-day case fatality (adjusted hazard ratio [HR] = 0.98, 95% CI: 0.83-1.17), but had higher risk of recurring episodes (adjusted subdistribution HR = 1.58, 95% CI: 1.29-1.92) and observed 14% longer LOS (adjusted incidence rate ratio = 1.14, 95% CI: 1.10-1.18) than non-ESBL-Ec BSI patients. ConclusionIn this large patient cohort, ESBL-Ec BSI did not increase case fatality risk but observed higher hospital LOS and recurrent E. coli BSI than non-ESBL-Ec BSI. Clinical resources are warranted to account for the higher morbidity risk associated with ESBL production and incidence.

Short-Course Versus Prolonged-Course Antimicrobial Therapy in Adults With Catheter-Related Septic Thrombosis: A Propensity-Weighted Retrospective Study

Abstract Background Optimal duration of antimicrobial therapy (AT) for catheter-related septic deep venous thrombosis (DVT) is unknown. We aimed to compare the outcomes of patients receiving short-course AT (≤21 days) versus prolonged-course AT (>21 days). Methods This was a monocentric retrospective study comparing adults with catheter-related septic DVT from 2015 to 2020 treated with short- or prolonged-course AT. A propensity score–weighted analysis was used to mitigate potential bias. The primary outcome was a composite of all-cause mortality or recurrent bloodstream infection 30 days after AT discontinuation. Results Of 172 patients with catheter-related septic DVT, 104 were treated with prolonged-course AT and 68 with short-course AT. In the propensity score analysis, we found no significant difference in 30-day all-cause mortality or relapse between the 2 groups (inverse probability of treatment weighted hazard ratio [wHR], 2.16 [95% confidence interval {CI}, .68–6.88]; P = .192). No differences in 90-day all-cause mortality and 90-day relapse were observed between the treatment groups (wHR, 1.01 [95% CI, .49–2.05], P = .987 and 1.13 [95% CI, .08–15.62], P = .928, respectively). Conclusions A 21-day AT could be an effective and safe option to treat catheter-related septic DVT. Further randomized studies are needed to establish the optimal duration of AT for patients with catheter-related septic DVT.

Management and outcomes of heart transplant candidates with bloodstream infection on temporary mechanical circulatory support

The outcomes and management of bloodstream infection (BSI) in patients on temporary mechanical circulatory support (TMCS) awaiting heart transplant (HT) are poorly understood. We present outcomes of patients on TMCS with BSI (TMCS-I) relative to matched uninfected patients (TMCS-U) and discuss their management. Between 1/1/2013-4/30/2023, N=136 patients were bridged to transplant with TMCS at Emory Transplant Center. Twenty-one (15.4%) were TMCS-I. Two (9.5%) had infective endocarditis. Median duration of antimicrobial treatment was 24 days (IQR 28.3). All TMCS-I were re-activated for transplant within 48-72 hours of negative blood cultures. None developed recurrent BSI. Post-transplant survival did not differ between TMCS-I and TMCS-U (P=0.38). HT for TMCS-I may be safe as soon as blood cultures clear. Duration of antimicrobial therapy is individualized and depends on the organism, duration of bacteremia, presence of endocarditis, and timing of HT. Additional research is needed to determine optimal duration of treatment.

Temporal dynamics of genetically heterogeneous extended-spectrum cephalosporin-resistant Escherichia coli bloodstream infections.

Extended-spectrum cephalosporin-resistant Escherichia coli (ESC-R-Ec) is an urgent public health threat with sequence type clonal complex 131 (STc131), phylogroup B2 strains being particularly concerning as the dominant cause of ESC-R-Ec infections. To address the paucity of recent ESC-R-Ec molecular epidemiology data in the United States, we used whole-genome sequencing (WGS) to fully characterize a large cohort of invasive ESC-R-Ec at a tertiary care cancer center in Houston, Texas, collected from 2016 to 2020. During the study time frame, there were 1,154 index E. coli bloodstream infections (BSIs) of which 389 (33.7%) were ESC-R-Ec. Using time series analyses, we identified a temporal dynamic of ESC-R-Ec distinct from ESC-susceptible E. coli (ESC-S-Ec), with cases peaking in the last 6 months of the calendar year. WGS of 297 ESC-R-Ec strains revealed that while STc131 strains accounted for ~45% of total BSIs, the proportion of STc131 strains remained stable across the study time frame with infection peaks driven by genetically heterogeneous ESC-R-Ec clonal complexes. bla CTX-M variants accounted for most β-lactamases conferring the ESC-R phenotype (89%; 220/248 index ESC-R-Ec), and amplification of bla CTX-M genes was widely detected in ESC-R-Ec strains, particularly in carbapenem non-susceptible, recurrent BSI strains. Bla CTX-M-55 was significantly enriched within phylogroup A strains, and we identified bla CTX-M-55 plasmid-to-chromosome transmission occurring across non-B2 strains. Our data provide important information regarding the current molecular epidemiology of invasive ESC-R-Ec infections at a large tertiary care cancer center and provide novel insights into the genetic basis of observed temporal variability for these clinically important pathogens. IMPORTANCE Given that E. coli is the leading cause of worldwide ESC-R Enterobacterales infections, we sought to assess the current molecular epidemiology of ESC-R-Ec using a WGS analysis of many BSIs over a 5-year period. We identified fluctuating temporal dynamics of ESC-R-Ec infections, which have also recently been identified in other geographical regions such as Israel. Our WGS data allowed us to visualize the stable nature of STc131 over the study period and demonstrate a limited but genetically diverse group of ESC-R-Ec clonal complexes are detected during infection peaks. Additionally, we provide a widespread assessment of β-lactamase gene copy number in ESC-R-Ec infections and delineate mechanisms by which such amplifications are achieved in a diverse array of ESC-R-Ec strains. These data suggest that serious ESC-R-Ec infections are driven by a diverse array of strains in our cohort and impacted by environmental factors suggesting that community-based monitoring could inform novel preventative measures.

Outcomes associated with empiric cefepime for bloodstream infections caused by ceftriaxone-resistant, cefepime-susceptible Escherichia coli and Klebsiella pneumoniae

BackgroundCefepime is a first-line agent for empiric sepsis therapy; however, cefepime use may be associated with increased mortality for extended-spectrum beta-lactamase-producing Enterobacterales (ESBL-E) in an MIC-dependent manner. This study aimed to compare the efficacy of empiric cefepime versus meropenem for bloodstream infections (BSI) caused by ceftriaxone-resistant Escherichia coli and Klebsiella pneumoniae with cefepime MICs ≤ 2 mg/L. MethodsThis single-center retrospective cohort study included patients admitted from October 2010 to August 2020 who received cefepime or meropenem empirically for sepsis with a blood culture growing ceftriaxone-resistant Escherichia coli or Klebsiella pneumoniae. The primary outcome was 30-day mortality; secondary endpoints included 14-day mortality, recurrent BSI, readmission and recurrent infection within 90 days, time to clinical resolution of infection, time to clinical stability, and clinical stability at 48 hours. ResultsFifty-four patients met inclusion criteria: 36 received meropenem and 18 received cefepime. The median (IQR) treatment durations of cefepime and meropenem were 3 (2–6) days and 7 (5–10) days, respectively. Thirty-day and 14-day mortality were similar between cefepime and meropenem (11.1% vs. 2.8%; P = 0.255 and 5.6% vs. 2.8%; P = 1.00, respectively). Cefepime was associated with longer time to clinical stability compared with meropenem (median 38.48 hours vs. 21.26; P = 0.016). ConclusionMortality was similar between groups, although most patients who received cefepime empirically were ultimately transitioned to a carbapenem to complete the full treatment course. Empiric cefepime was associated with a delay in achieving clinical stability when compared with meropenem to treat BSI caused by ceftriaxone-resistant Enterobacterales, even when cefepime-susceptible.

Recurrent bloodstream infections after allogeneic hematopoietic cell transplantation

ABSTRACT Background Although colonization is an established risk factor for bloodstream infection (BSI) due to identical strain, prior infection with resistant bacteria should also be considered during the management of febrile neutropenia. This study aimed to analyze the rate and etiology of recurrent BSI in allogeneic hematopoietic cell transplant (allo-HCT) recipients to determine its potential impact on decision-making. Materials and methods The retrospective study included 284 allo-HCT recipients. Recurrent BSI was defined as a new BSI episode occurring in a period of more than 72 hours after antibiotic withdrawal. Results Overall, 104 patients (36.6%) developed at least one BSI, and 23 of them (22.1%) experienced recurrent BSI episodes (n = 30). Median time to recurrent BSI was 41 days (range 5–526 days). Recurrent BSI was associated with second allo-HCT (p < 0.0001), primary (p = 0.021), and secondary graft failure (p = 0.024). Carbapenem-resistant gram-negative bacteria were more common during recurrent BSI episodes (23.7% vs. 6.0%; p = 0.003). In only 17.5% patients experiencing recurrent BSI episode and in only 3.9% of patients with at least one BSI episode phenotypically identical recurring pathogen was isolated. Conclusions In view of low rate of recurrent BSI due to identical pathogen, empirical antimicrobial therapy should not be based on data on previous BSI episodes.

1857. Risk factors for recurrent bacteremia in children undergoing chemotherapy or hematopoietic stem cell transplantation

Abstract Background Sepsis is a complication frequently encountered in children with underlying malignancies, especially due to a majority of patients having indwelling venous catheters. Indications for catheter removal among children with central-line associated blood stream infection (CLABSI) should follow the recommendations for adults, however, difficulties in vascular access often leads to attempting treatment without catheter removal. Therefore, the primary aim of this study was to find risk factors for recurrent sepsis in children undergoing chemotherapy of HSCT and examine whether more aggressive catheter removal after CLABSI in children is necessary. Methods In the Pediatric Bone Marrow Transplant Center of Seoul St. Mary’s Hospital, positive blood cultures were prospectively monitored to control and prevent outbreaks. The date of culture, culture results, symptoms presented, category of blood stream infections (by the CDC/NHSN surveillance definition (2021) of Bloodstream infections), and central-line associated blood stream infection (CLABSI) events were monitored. Results During September 2016 to February 2021, a total 280 cases of laboratory confirmed bloodstream infections (LCBI) or Mucosal Barrier Injury LCBI (MBI-LCBI) were diagnosed in children &amp;lt; 18 years old with underlying malignancies. Of these, 52.9% (n=148) were male, and the mean age was 9.7 (SD±6.1) years old. CLABSI was diagnosed in 51.8% (n=145), and the most common pathogens cultured were S. mitis/oralis (24.0%, n=67), E. coli (15.4%, n=43), and coagulase negative Staphylococci (CNS) (10.4%, n=29). Recurrent sepsis occured in 17.1% (n=48), and 9.6% (n=27) had two indwelling catheters . Multivariable analysis showed that factors associated with recurrent blood stream infections were as follows: duration of indwelling catheter (OR, 1.002; 95% CI, 1.001-1.004; P&amp;lt; 0.001) and no removal of central lines after previous episode (OR, 51.143; 95% CI, 6.6-395.0; P&amp;lt; 0.001). Conclusion Permanent central lines should be removed as soon as possible, and more aggressive approach in permanent catheter removal after LCBSIs in children is necessary to reduce recurrent infections. Disclosures All Authors: No reported disclosures.

1992. Risk of Infective Endocarditis in Streptococcal mitis Bloodstream Infections Among Patients with Neutropenia from Hematologic Malignancies

Abstract Background Streptococcus mitis is a common colonizer of the human oral and gastrointestinal tract. Patients with neutropenia due to hematologic malignancy (HM), particularly those prescribed fluoroquinolone prophylaxis are at increased risk of a S. mitis bloodstream infection (BSI). Risk of infective endocarditis (IE) in this patient population remains unclear. Methods This was a multicenter, retrospective study of neutropenic (ANC &amp;lt; 500 K/uL) patients with HM from November 2016 - February 2022. Patients were included if they had S. mitis isolated in at least 1 blood culture bottle. The primary outcome was number of patients who developed IE based on cardiac imaging. Secondary outcomes included number of patients who underwent IE workup via cardiac imaging and BSI recurrence within 12 weeks. Results Among 171 patients who met the inclusion criteria, 101 (59%) were male and median age was 60 years old (range 19-86). Patient demographics, microbiologic information and outcomes are shown in Table 1. All patients in the cohort had native cardiac valves. Acute leukemia/myelodysplastic syndrome was the most common HM (n=129, 75%), followed by lymphoma (n=27, 16%), multiple myeloma (n=10, 6%) and chronic leukemia (n=5, 3%). Most patients had a transthoracic echocardiogram (TTE) (n=97, 56.7%) within 7 days of BSI. Of these patients, 1 had suspected valvular vegetations on TTE, but transesophageal echocardiogram (TEE) was negative. Two patients had negative TTEs, but there was a high clinical suspicion, so cardiac computed tomography was performed and showed no valvular vegetations. Despite negative cardiac imaging, 1 patient completed 6 weeks of empiric treatment for IE based on radiographic findings in the torso suggesting visceral infarcts. One patient had S. mitis BSI recurrence within 12 weeks of first positive culture. Median duration of antimicrobial therapy for BSI was 15 days (range 8-43). Conclusion IE is uncommon in neutropenic HM patients with native cardiac valves and S. mitis BSI. In this cohort where approximately half had a TTE after bacteremia and median duration of BSI therapy was 15 days, recurrent BSI was rare, suggesting that IE cases were not underdiagnosed in those without cardiac imaging. Cardiac imaging such as TTE to rule out IE may not be necessary for all patients in this population. Disclosures Ramy H. Elshaboury, PharmD, Eli Lilly: Honoraria|Gilead Sciences: Grant/Research Support David W. Kubiak, PharmD, BCPS, BCIDP, FIDSA, Astellas Pharma, Inc.: Advisor/Consultant|AVIR Pharma Inc: Advisor/Consultant|Cidara Therapeutics: Advisor/Consultant Sarah P. Hammond, MD, F2G: Advisor/Consultant|F2G: Grant/Research Support|GSK: Grant/Research Support|Scynexis: Grant/Research Support.

152. Molecular Epidemiological Analysis of Relapsed Gram-negative Bloodstream Infection Isolates

Abstract Background Gram-negative bacterial bloodstream infections (GNB-BSI) are common and frequently lethal. Many patients experience multiple episodes of GNB-BSI for unclear reasons. This study examines the genetic differences between initial and subsequent isolates of recurrent GNB-BSI. Methods We used a prospective cohort of patients with GNB-BSI at Duke Hospital to identify patients with &amp;gt;1 episode of GNB-BSI due to the same bacterial species. We performed pulsed field gel electrophoresis (PFGE) on paired isolates to determine if the events were Reinfection (paired isolates different) or Relapse (paired isolates genetically identical). We then used whole genome sequencing (WGS) to verify the PFGE findings and explore the genetic similarity between initial and relapsed GNB-BSI isolates. Results Among 1,423 unique patients with GNB-BSI, 60 (4%) experienced recurrent GNB-BSI with the same bacterial species. We performed genotyping (PFGE, followed by WGS) on the paired bacterial isolates from the index and recurrent bloodstream infections for the four most common species in our study population (Escherichia coli, Klebsiella species, Pseudomonas aeruginosa, and Serratia marcescens) (n=48 pairs). We determined that 63% (30/48) of recurrent GNB-BSI episodes were due to relapse and 37% (18/48) were due to reinfection. PFGE correctly identified relapse versus reinfection in 98% (47/48) of cases. The WGS data illustrated the microevolution of relapsed GNB-BSI isolates within patients. When comparing initial to relapsed isolates, we calculated a median of 5 single-nucleotide polymorphisms (SNPs) in relapsed E. coli isolates and 2 SNPs in Klebsiella spp. isolates. Of these SNPs, 37% (E. coli) and 12% (Klebsiella) were non-synonymous changes in coding regions, most commonly genes associated with antimicrobial resistance (AMR), energy metabolism and stress response. Alterations in the AMR profile was common, with 20/30 relapsed isolates demonstrating either loss or acquisition of AMR. Figure 1:Time from initial to recurrent episode of gram-negative bloodstream infection. Relapse (i.e., same bacterial strain noted by green circle) versus reinfection (i.e., different bacterial strain noted by red circle) was determined by pulse field gel electrophoresis followed by WGS. Whole genome sequencing was performed on the initial and recurrent isolate from patients with relapsed GNB-BSI. We identified single nucleotide polymorphisms (SNPs) present in the recurrent isolate, which were not present in the initial isolate. We identified the function of genes containing SNPs in E. coli (n=28 SNPs) and Klebsiella spp. (n=13 SNPs). Synonymous mutations, insertions, deletions, and non-synonymous mutations in hypothetical proteins were excluded. Conclusion Most recurrent GNB-BSI with same species are due to relapse. PFGE has comparable accuracy to WGS to determine reinfection versus relapse. Multiple mutations in genes involved in stress response, AMR and metabolism were identified in relapsed isolates. Disclosures Vance G. Fowler, Jr, MD, MHS, Affinergy: Grant/Research Support|Affinergy: Honoraria|Affinium: Honoraria|Amphliphi Biosciences: Honoraria|ArcBio: Stocks/Bonds|Basilea: Grant/Research Support|Basilea: Honoraria|Bayer: Honoraria|C3J: Honoraria|Cerexa/Forest/Actavis/Allergan: Grant/Research Support|Contrafect: Grant/Research Support|Contrafect: Honoraria|Cubist/Merck: Grant/Research Support|Debiopharm: Grant/Research Support|Deep Blue: Grant/Research Support|Destiny: Honoraria|Genentech: Grant/Research Support|Genentech: Honoraria|Integrated Biotherapeutics: Honoraria|Janssen: Grant/Research Support|Janssen: Honoraria|Karius: Grant/Research Support|Medicines Co.: Honoraria|MedImmune: Grant/Research Support|MedImmune: Honoraria|NIH: Grant/Research Support|Novartis: Grant/Research Support|Novartis: Honoraria|Pfizer: Grant/Research Support|Regeneron: Grant/Research Support|Regeneron: Honoraria|Sepsis diagnostics: Sepsis diagnostics patent pending|UpToDate: Royalties|Valanbio: Stocks/Bonds.

Short Course of Antifungal Therapy in Patients With Uncomplicated Candida Bloodstream Infection: Another Case of Less Is More in the Clinical Setting?

The objective of this study was to compare the clinical outcomes of patients receiving a short course (SC) vs a prolonged course (PC) of antifungal therapy for uncomplicated Candida bloodstream infections (BSIs). All episodes of uncomplicated Candida BSI from September 1, 2018, to August 31, 2020, were reviewed. We compared the primary (all-cause 90-day mortality) and secondary study end points (1-year recurrent Candida BSI and all-cause 1-year mortality) among patients who underwent SC (5-11 days) or PC (12-24 days) therapy using propensity score analysis with the inverse probability of treatment weighting (IPTW) method. A total of 114 patients with uncomplicated Candida BSI were included: 35 (30.7%) were classified into the SC group (median [interquartile range {IQR}], 9 [7-11] days) and 79 (69.3%) into the PC group (median [IQR], 14 [14-16] days). Patients in the SC group compared with the PC group had a higher rate of hospitalization in the surgical ward (40.0% vs 19.0%; P = .02) or septic shock at the time of Candida BSI onset (11.4% vs 1.3%; P = .03). The risk of 90-day mortality was not different between the SC and PC groups (n = 8 [22.9%] vs 17 [21.5%], respectively; IPTW-adjusted subdistribution hazard ratio [sHR], 0.67; 95% CI, 0.31-1.47; P = .20). The risk for recurrent Candida BSI within 1 year of completing therapy (IPTW-adjusted sHR, 1.07; 95% CI, 0.20-5.80; P = .94) or for all-cause 1-year mortality (IPTW-adjusted HR, 0.72; 95% CI, 0.35-1.50; P = .38) did not differ between groups. Receiving a short vs prolonged course of antifungal therapy did not affect mortality or BSI recurrence in patients with uncomplicated candidemia.

Highly versus less bioavailable oral antibiotics in the treatment of gram-negative bloodstream infections: a propensity-matched cohort analysis

ObjectivesIn this study, we evaluated the clinical outcomes associated with the use of highly bioavailable oral antibiotics (fluoroquinolones and trimethoprim-sulfamethoxazole) compared with the less-bioavailable oral antibiotics (β-lactams) in gram-negative bloodstream infections (BSIs). MethodsAmong hospitalized older adult patients in Ontario, Canada, discharged home on oral treatment for gram-negative BSI between 1 January 2017 and 31 December 2019, we used a matched cohort design to compare outcomes among those receiving highly versus less-bioavailable agents; hard-matching 1:1 on sex, BSI pathogen (Escherichia coli vs. non–E. coli), and infection source (urinary vs. non-urinary/unknown source) along with a propensity score, incorporating specific pathogen, patient, and infection characteristics. The primary outcome was the composite of 90-day all-cause mortality, recurrent BSI with the same pathogen (genus and species), and re-admission to any Ontario hospital. ResultsA total of 2012 patients were included in the study (1006 in each bioavailability category). Those who received highly (compared with less) bioavailable antibiotics at discharge had lower rates of the composite outcome (171/1006 [17.0%] vs. 216/1006 [21.5%]), adjusted odds ratio being 0.74 (95% CI, 0.60–0.92). Recurrent BSI at 90 days was the main driver for the composite outcome occurring in 64 (5.4%) and 107 (9.4%) patients of the highly and less-bioavailable groups, respectively (p < 0.001) (adjusted odds ratio, 0.56; 95% CI, 0.40–0.78). DiscussionUse of highly (compared with less) bioavailable antibiotics at discharge was associated with significantly better clinical outcomes among patients with gram-negative BSIs.

Phenotypic and genotypic characterisation of thymine auxotrophy in Escherichia coli isolated from a patient with recurrent bloodstream infection.

IntroductionThymine auxotrophic in vitro mutants of Escherichia coli were first reported in the mid-20th century. Later, thymine-dependent clinical strains of E. coli as well as other Enterobacterales, Enterococcus faecalis and Staphylococcus aureus have been recognized as the cause of persistent and recurrent infections.ObjectivesThe aim of this study was to characterize the phenotype and investigate the molecular basis of thymine auxotrophy in ten E. coli isolates obtained at different time points from a patient with recurrent bloodstream infection (BSI) due to a chronic aortic graft infection treated with Trimethoprim/sulfamethoxazole (TMP-SMX).MethodsClinical data was obtained from hospital records. Growth characterization and antimicrobial susceptibility testing to TMP-SMX was performed on M9 agar and in MH broth with different thymine concentrations (0.5, 2, 5, 10 and 20 μg/mL), on Mueller-Hinton (MH) and blood agar. Whole genome sequencing (WGS) was performed on all E. coli isolates.ResultsE. coli were isolated from ten consecutive BSI episodes from a patient with chronic aortic graft infection. Six of these isolates were resistant to TMP-SMX when assayed on blood agar. Growth experiments with added thymine confirmed that these isolates were thymine-dependent (thy-), and revealed growth defects (slower growth rate and smaller colony size) in these isolates relative to thy+ isolates (n = 4). WGS indicated that all isolates were of the same clonal lineage of sequence type 7358. Genomic analysis revealed a G172C substitution in thyA in all TMP-SMX resistant isolates, while mutations affecting genes involved in the deoxyribose salvage pathway (deoB and deoC) were identified in eight isolates.ConclusionThis case highlights the risk of resistance development to TMP-SMX, especially for long-term treatment, and the possible pitfalls in detection of growth-deficient subpopulations from chronic infections, which could lead to treatment failure.

Improving patient outcomes by promoting antimicrobial stewardship for patients with positive blood cultures: Investigation of patients with gram negative bacterium.

In this study, changes in patient outcomes were analysed to evaluate the effects of prospective audit and feedback (PAF), which was promoted under a new system of antimicrobial stewardship (AS), in patients with gram-negative rod (GNR)-positive blood cultures. This study included patients with positive blood cultures treated at Kagawa University Hospital between 2019 and 2020. The effects of PAF, as promoted in 2020 and performed within a few days of treatment initiation, were examined in terms of patient prognosis and estimated cost of extra hospital stay associated with GNR infection. As AS activities under the new system, proposals were made for targeted therapy based on susceptibility results and for the duration of antimicrobial therapy, escalation and dose increases, and imaging evaluation. Between 2019 and 2020, there was no difference in the rate of de-escalation in the form of switching to a narrower-spectrum intravenous antimicrobial, the rate of image inspection, but the rate of switching to oral therapy after receiving culture results increased from 19.7% to 31.3%, the rate of sensitivity-based treatment increased from 76.4% to 92.2%. Regarding patient outcomes, the 90-day mortality rate and the duration of hospital stay were similar between the groups. The rate of recurrent bloodstream infections decreased from 8.7% to 0.9%. Most of the changes in the indicators related to patient outcomes analysed in this study suggest that the increased use of PAF in AS activities improved patient outcomes.

Recurrent Group B Streptococcus Septicemia Secondary to Portal Hypertensive Colopathy

Background Group B streptococcal infections (GBSs) in nonpregnant adults have become an increasingly recognized entity. Bacteremia without focus has consistently been demonstrated as the second leading cause of infection. Recurrent bacteremia, however, remains a significantly rarer phenomenon, and underlying mechanisms and risk factors are poorly elucidated in the literature. Case Report We report the first case of 3 independent episodes Streptococcus agalactiae bacteremia without focus, in 56-year-old woman with Child-Pugh B cirrhosis and the uncommon finding of portal hypertensive colopathy. Results We propose bowel hemorrhage secondary to portal hypertensive colopathy, facilitated recurrent bacterial translocation and blood stream infection in this immunocompromised host, presenting as recurrent bacteremia without focus. We discuss the disease epidemiology of GBS infections, antibiotic sensitivity, and risk factors for infection relating to this theory in a literature review. Conclusions Portal hypertensive colopathy in liver cirrhosis may contribute to underlying risk for recurrent GBS bacteremia without focus that necessitates prolonged penicillin class antibiotic therapy.

219. Outcomes with Low- vs. High-bioavailability Oral Antibiotics in Treatment of Uncomplicated Gram-Negative Bacteremia

BackgroundHigh-bioavailability (HIGH-BIO) oral agents (i.e. trimethoprim-sulfamethoxazole, fluoroquinolones) are increasingly utilized for definitive treatment of uncomplicated gram-negative (UGN) bloodstream infections (BSI). Literature supports use of HIGH-BIO agents as step-down therapy, but few studies have assessed use of low-bioavailability (LOW-BIO) agents (i.e. beta-lactams). Increased recurrence of BSI has been associated with LOW-BIO agents; suboptimal dosing of beta-lactam agents may have impacted outcomes. Trials have not assessed whether high-dose beta-lactams (HD-BL) improve clinical outcomes over low-dose beta-lactams (LD-BL) for UGN BSI.MethodsThis retrospective cohort study conducted between December 2016 and December 2020 included adults with UGN BSI administered oral step-down therapy for at least 1/3rd the total antibiotic duration. The primary outcome was incidence of treatment failure of HIGH-BIO compared to LOW-BIO agents within 90 days of completing oral therapy. Treatment failure was a composite of all-cause mortality, recurrent BSI, reinfection of the primary site, or transition to IV antibiotics after initiating oral therapy. Secondary outcomes were incidence of treatment failure of HIGH-BIO compared to HD-BL agents, and of HD-BL compared to LD-BL agents.ResultsOf 225 patients, 67 (29.8%) received a HIGH-BIO and 158 (70.2%) a LOW-BIO agent; of those in the LOW-BIO arm 126 (79.7%) received a HD-BL. The most common source of BSI was urinary (202 [89.8%]); transition to oral therapy occurred after a mean of 5 ± 2.39 days. No difference in treatment failure was observed (8 [11.9%] HIGH-BIO vs. 25 [15.8%] LOW-BIO, P = 0.45). A numerically higher number of patients in the LOW-BIO arm had recurrent BSI (4 [2.5%] LOW-BIO vs. 0 [0%] HIGH-BIO, P = 0.18). No difference in treatment failure was observed between HIGH-BIO and HD-BL agents (8 [11.9%] vs. 20 [15.9%], P = 0.46), or HD-BL and LD-BL agents (20 [15.9%] vs. 5 [15.6%], P = 0.97). ConclusionNo difference in treatment failure was observed between groups; further study is needed due to failure to reach statistical power. A numerical trend towards increased recurrence of BSI was observed with LOW-BIO agents. Beta-lactams may be reasonable for step-down therapy of UGN BSI if HIGH-BIO agents are contraindicated. Disclosures All Authors: No reported disclosures