Polymicrobial Blood Cultures Research Articles

Antibiotic utilization trends in Veterans Affairs patients with Stenotrophomonas maltophilia bloodstream infections.

Stenotrophomonas maltophilia is a multidrug-resistant gram-negative bacillus that can cause serious infections but has limited treatment options. This study aims to establish trends in the treatment of S. maltophilia bloodstream infections (BSI) across the United States in Department of Veterans Affairs (VA) facilities. Data was evaluated over a 10-year timeframe (2012 to 2021) in this retrospective cohort study. Veterans with ≥ 1 blood culture with S. maltophilia within a VA medical encounter were included. Microbiology, pharmacy, and patient information were collected through national VA data sources and chart review. Descriptive statistics and Poisson regression were used to summarize patient demographics, facility characteristics, microbiologic data, and treatment trends. A total of 374 blood cultures positive for S. maltophilia were identified across 75 VA facilities. Of 282 unique patients with BSI, the majority were male (93.6%), white (67.4%), with a mean age of 64 ± 13.1 years. Of those patients, 78% received treatment, 12.8% had a polymicrobial blood culture, and 5.3% had a documented sulfa allergy. Susceptibility results were most reported for trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin, and ceftazidime, with 4.5%, 4.3%, and 44.4% resistant isolates, respectively. Antibiotics most prescribed included TMP-SMX (41.5%) and levofloxacin (39.4%), followed by ciprofloxacin (13.8%) and ceftazidime (12.4%). Combination therapy was prescribed in 33% of patients. No significant trends were found with antibiotic utilization over time. TMP-SMX and levofloxacin were the most prescribed antibiotics for S. maltophilia BSI treatment. No significant changes were seen with antibiotic prescribing trends in Veterans from 2012 to 2021.

866. A new protocol for bacterial identification and carbapenemases by MALDI-TOF and lateral flow assay directly from positive blood culture: MALDI-FAST

Abstract Background Infectious diseases are a global public health problem, accounting for more than 20% of the mortality burden. Klebsiella pneumoniae and Pseudomonas aeruginosa caused more than 1.3 million deaths globally in 2019. Antimicrobial resistance (AMR) is a major factor in this mortality. Rapid molecular test for the detection of the blaKPC gene improves treatment time and mortality in patients with bacteremia caused by carbapenem-resistant Enterobacterales, however, the use of molecular biology techniques may not be optimal in multiple resourced care settings limited. Our goal is to perform rapid identification of Gram-negative bacilli and detection of carbapenemases directly from blood cultures using the combination of mass spectrometry (MALDI-TOF) and the lateral flow immunochromatography test.4 Methods We analyzed 97 bottles of positive blood cultures detected by the BACT/Alert 3D system (BioMérieux®). Our new method (MALDI-FAST) uses 0.5ml of blood obtained from the positive blood culture bottle for Gram-negative bacilli, from which a pellet is obtained by rapid centrifugation in 3 minutes. This material is processed both for bacterial identification by MALDI-TOF mass spectrophotometry (Bruker®), and rapid detection of carbapenemases by NG Test Carba 5 lateral flow immunochromatography (NG Biotech®). The results obtained were compared with the gold standard RT-PCR FilmArray Panel BCID 2.0 (BioMérieux®) Results Of the 97 blood culture bottles, 94/97 (96.9%) were correctly identified to the species level and 3/97 (3.1%) were polymicrobial blood cultures. Klebsiella pneumoniae was detected in 39 samples, E. coli in 24, and 34 other microorganisms including non-fermenting bacteria. Excellent concordance (kappa index 1,000) was achieved in 31/97 blood cultures (31.9%) that presented carbapenemases, 18/31 KPC (18.6%) and 13/31 with KPC and NDM coproduction (13.4%). 66/97(68.15%) bottles did not present carbapenemase. Conclusion Our protocol presents very good results for bacterial identification by mass spectrometry and carbapenemase detection by lateral flow immunoassay in a few minutes directly from the positive blood culture, becoming a fast and cost-effective tool to contribute to patient management. Disclosures All Authors: No reported disclosures

Oritavancin vs Standard of Care for Treatment of Nonendovascular Gram-Positive Bloodstream Infections.

Data is limited comparing oritavancin (ORT) to the standard-of-care (SOC) for the treatment gram-positive blood stream infections (BSI). This was a retrospective study of all patients in the Veteran's Affairs Health Care System treated with at least 1 dose of oritavancin or at least 5 days of vancomycin, daptomycin, ceftaroline, ampicillin, ampicillin-sulbactam, nafcillin, oxacillin, or cefazolin for a documented gram-positive BSI from 1 January 2015 to 30 June 2021. Patients with polymicrobial blood cultures or positive cultures from other sites were included if the organisms were sensitive to the incident antimicrobial; no concomitant antimicrobials could be used once the incident agent was started. Individuals were also excluded if they were diagnosed with endocarditis, had a neutrophil count 96-hours of treatment before the incident antimicrobial was started.The primary composite outcome was clinical failure, defined as all-cause mortality within 30-days from the end of therapy, or blood cultures positive for the incident organisms ≥72 hours after administration of the first dose and ≤30 days after the administration of the final dose of the study antimicrobial, or any drug or line-related readmissions within 30-days of hospital discharge. Two hundred-forty patients were identified for screening with 96 meeting criteria (27 in ORT and 69 in SOC groups). Baseline characteristics were generally balanced between groups except more patients in the ORT group received >96-hours of treatment before the incident antimicrobial was started (70.3% (19/27) vs 13.04% 9/69); P < .001). The pathogen most prevalent was methicillin susceptible Staphylococcus aureus (MSSA) (ORT 33.3% (9/27) vs SOC 46.4% (32/69)). Clinical failure occurred in 7.4% (2/27) in the ORT group and 17.4% (12/69) in SOC (P = .34). No components of the primary outcome were significantly different between groups, but AKI did occur more commonly in the SOC group (27.5% (19/69) vs 3.7% (1/27); P = .01). ORT appears to be a safe and effective option when directly compared to the SOC for non-endocarditis BSIs.

Evaluation of InTray Cassettes Directly from Blood Cultures for the Diagnosis of Sepsis in Clinical Bacteriology Laboratories as an Alternative to Classic Culture Media.

Culture media is fundamental in clinical bacteriology for the detection and isolation of bacterial pathogens. However, in-house media preparation could be challenging in low-resource settings. InTray® cassettes (Biomed Diagnostics) could be a valid alternative as they are compact, ready-to-use media preparations. In this study, we evaluate the use of two InTray media as a subculture alternative for the diagnosis of bloodstream infections: the InTray® Müller-Hinton (MH) chocolate and the InTray® Colorex™ Screen. The InTray MH chocolate was evaluated in 2 steps: firstly, using simulated positive blood cultures (reference evaluation study), and secondly, using positive blood cultures from a routine clinical laboratory (clinical evaluation study). The Colorex Screen was tested using simulated poly-microbial blood cultures. The sensitivity and specificity of the InTray MH chocolate were respectively 99.2% and 90% in the reference evaluation study and 97.1% and 88.2% in the clinical evaluation study. The time to detection (TTD) was ≤20 h in most positive blood cultures (99.8% and 97% in the two studies, respectively). The InTray® MH Chocolate agar showed good performance when used directly from clinical blood cultures for single bacterial infections. However, mixed flora is more challenging to interpret on this media than on Colorex™ Screen, even for an experienced microbiologist.

Cytokine profile in critically ill patients and/or injured persons with secondary sepsis – influence of different pathogens

Background/Aim. The role of the complex sepsis-related immune response has not been fully clarified and remains a subject matter of investigation. Nowadays, sepsis is considered a dynamic syndrome characterized by many, often antagonistic phenomena, ranging from hyperinflammation to anergy and immunoparalysis. The aim of the study was to determine, based on the level of pro- and anti-inflammatory mediators in critically ill patients with secondary sepsis, whether the cytokine profile differs according to the type of bacterial causative agent, as well as to assess the prognostic value regarding the outcome. The outcome measure was in-hospital mortality. Methods. Blood serum samples were taken from 125 critically ill patients admitted to the Surgical Intensive Care Unit with severe secondary sepsis as a consequence of peritonitis, pancreatitis, or trauma. The average age of the patients was 57.7 ? 17.3 years. Of the total number of patients, 84 (67.2%) were males, and 41 (32.8%) were females. The levels of pro-inflammatory interleukin (IL)-1?, IL-1?, IL-6, IL-8, IL-12?70, IL-17?, tumor necrosis factor (TNF)-?, interferon (IFN)-?, IFN-?-inducible protein-10 (IP-10), monocyte chemoattractant protein-1(MCP-1), macrophage inflammatory protein (MIP)-1? and MIP-1?, as well as anti-inflammatory mediators IL-4, IL-10, IL-13, IL-27, IL- 31, and IL-33, were determined at three time intervals ? on the day of admission (the first day) and then on the third and fifth day. The type of the bacterial causative agent was determined using standard microbiological analyses. Results. On the third day of measurement, significant differences in the cytokine levels regarding the nature of bacteremia were determined in all pro- and anti-inflammatory cytokines, except for IL-8. In general, the lowest levels were observed in patients with polymicrobial blood cultures. On the first and fifth days of measurement, no significant differences in the cytokine levels regarding the nature of bacteremia were found. The only significant predictor of the fatal outcome on the first measurement day was IL-17?, Area Under the Receiver Operating Characteristic (ROC) Curve (AUC) of 0.665 (95% confidence interval 0.519?0.791; ? = 0.034) in the patients with secondary sepsis as a complication of peritonitis. Conclusion. According to the type of bacterial causative agent, the lowest levels of cytokines have been observed in patients with the polymicrobial blood culture. The low level of IL-17? on the first day of measurement is a good predictor of a fatal outcome in patients with peritonitis as an underlying condition of secondary sepsis. On the other hand, the levels of other cytokines correlated with the out-come only on the fifth day of measurement, and they were higher in survivors than in non-survivors.

Laboratory diagnosis of community-acquired bloodstream infection in therapeutic pathology.

Community-acquired bloodstream infections (CBSIs) occur in the out-of-hospital setting (44%) and increase the overall mortality from bloodstream infections (BSIs) by 7.2% per year. The development of CBSIs depends on both comorbid and polymorbid diseases and the patients' age. The causes of CBSIs are: respiratory, hepatobiliary gastrointestinal and urogenital tracts and dental interventions. The etiology of CBSIs is characterized by the isolation of coagulase-negative staphylococci (CNS) (32%), E. coli (27%). To investigate community-acquired bloodstream infection in therapeutic patients. The study included out-of-hospital patients (n=382). 4.5 ml of blood were taken intravenously into a closed vacuum system in order to obtain a buffy coat of blood, which was put on glasses for microscopy and Petri dishes with blood agar for cultivating under aerobic and anaerobic conditions. Microorganisms were identified by mass spectrometry. Microscopy of blood smears was used for rapid diagnosis of infection in the bloodstream. BSI was diagnosed in 183 (48.0%) out of 382 out-of-hospital patients. The etiology of CBSIs was studied on 297 isolated strains of microorganisms. CBSIs rather often complicated the underlying disease in women and young people. The spectrum of CBSI pathogens included aerobic and anaerobic bacteria and fungi. Gram-positive cocci with the leadership of S.epidermidis (25.7%) were more often isolated among bacteria. 70% of all isolated pathogens grew under anaerobic conditions. CBSIs were characterized by polymicrobiality (33.5%) of two to four different microorganisms in one blood culture; the species of associates of polymicrobial blood cultures are shown. Microscopic examination of blood smears revealed microorganisms in 97.1% of cases, including associations of bacteria with fungi (66.9%). CBSIs occurred after contour plastic, in diseases of the respiratory system, genitourinary system, oral cavity, skin and subcutaneous tissue. Microbiological examination of the buffy coat is an alternative microbiological method of CBSIs diagnosis, which includes microscopy and blood cultivating and has a high diagnostic efficiency (97.1% and 48% respectively). It can become an option for replacing imported blood culture automated systems.

1845. Oritavancin Compared to the Standard-of-Care for the Treatment of Gram-positive Blood Stream Infections

Abstract Background Data is limited comparing oritavancin (ORT) to the standard-of-care (SOC) for the treatment gram-positive blood stream infections (BSI). Methods This was a retrospective study of all patients in the Veteran’s Affairs Health Care System treated with at least 1 dose of oritavancin or at least 5 days of vancomycin, daptomycin, ceftaroline, ampicillin, ampicillin-sulbactam, nafcillin, oxacillin, or cefazolin for a documented gram-positive BSI from 1 January 2015 to 30 June 2021. Patients with polymicrobial blood cultures or positive cultures from other sites were included if the organisms were sensitive to the incident antimicrobial; no concomitant antimicrobials could be used once the incident agent was started. Individuals were also excluded if they were diagnosed with endocarditis, had a neutrophil count &amp;lt; 500 cells/mm3, or had a diagnosis of Human Immunodeficiency Virus (HIV) on their problem list. The primary composite outcome was clinical failure, defined as all-cause mortality within 30-days from the end of therapy, or blood cultures positive for the incident organisms ≥72 hours after administration of the first dose and ≤30 days after the administration of the final dose of the study antimicrobial, or any drug or line-related readmissions within 30-days of hospital discharge. Secondary outcomes included all-cause 30-day readmission and rates of acute kidney injury (AKI). Results Two hundred-forty patients were identified for screening with 96 meeting criteria (27 in ORT and 69 in SOC groups). Baseline characteristics were generally balanced between groups except more patients in the ORT group received &amp;gt; 96-hours of treatment before the incident antimicrobial was started (70.3% (19/27) vs. 13.04% (9/69); p&amp;lt;0.001). The pathogen most prevalent was methicillin-susceptible Staphylococcus aureus (MSSA) (ORT 33.3% (9/27) vs. SOC 46.4% (32/69)). Clinical failure occurred in 7.4% (2/27) in the ORT group and 17.4% (12/69) in SOC (p=0.34). No components of the primary outcome were significantly different between groups, but AKI did occur more commonly in the SOC group (27.5% (19/69) vs. 3.7% (1/27); p=0.01). Conclusion ORT appears to be a safe and effective option when directly compared to the SOC for non-endocarditis BSIs. Disclosures Ryan P. Moenster, Pharm.D., FIDSA, Melinta Therapeutics: Grant/Research Support|Melinta Therapeutics: Honoraria.

186. Klebsiella aerogenes: Are there implications to taxonomic accuracy?

Abstract Background With advances in genomics, microbiologists can accurately rename existing bacteria which may cause confusion among clinicians familiar with prior names. Limited investigation is available on the clinical impact of these name changes. University of Alabama at Birmingham Hospital microbiology updated Klebsiella aerogenes in the electronic medical record (EMR) to "Klebsiella (Enterobacter) aerogenes" to reflect change in nomenclature. Therapy selection differs between Klebsiella pneumoniae and Enterobacter spp. due to differences in Ambler Class C (AmpC) beta-lactamase production. Our Antimicrobial Stewardship Program previously implemented selective and cascaded susceptibility reporting for E. aerogenes to guide antibiotic selection which remained after nomenclature change. The goal of this study is to determine if the change led to inappropriate antibiotic use. Methods We reviewed blood culture data from May 2016-2020 which grew Enterobacter aerogenes or Klebsiella "Enterobacter" aerogenes. We excluded polymicrobial blood cultures, patients aged 18 and under, and patients who died within 48 hours of drawing blood cultures. Appropriate therapy was defined as an antibiotic with reported susceptibility with consideration of AmpC induction for a duration appropriate to clinical syndrome with minimum of 7 days. We recorded patient demographics, nature of therapy, and clinical outcomes. We performed comparative analysis with descriptive statistics to compare the two groups. Results There were 38 patients with K. aerogenes bacteremia, 21 patients prior to name change and 17 afterwards. None were ESBL. Cefepime was most often used directed inpatient therapy while oral ciprofloxacin was the most common outpatient regimen with no use of ceftriaxone. Prior to name change, there was one case (4.76%) that did not receive targeted AmpC therapy while there were two afterwards (11.8%), one of which decided by the ID consult team. Table 1 Demographics (Data presented as No. (%)) Table 2 Microbiology and Outcomes (Data presented as No. (%)) Table 3 Antimicrobial Selection. One patient that received 72 hours of appropriate therapy but died prior to completion of therapy. This was labeled labelled as appropriate therapy. Conclusion Care must be taken when taxonomic changes of clinically relevant bacteria may potentially affect optimization of antibiotics. As the ID consultants, we must be aware of these name changes and provide up to date recommendations. Cascade reporting and documentation in the EMR may be helpful to reduce morbidity related to changes in nomenclature. Disclosures Sixto M. Leal, Jr., MD, PhD, GenMark Dx: Grant/Research Support|GenMark Dx: Honoraria.

Performance evaluation of the FAST™ System and the FAST-PBC Prep™ cartridges for speeded-up positive blood culture testing.

ObjectivesAs time to appropriate antimicrobial therapy is major to reduce sepsis mortality, there is great interest in the development of tools for direct identification (ID) and antimicrobial susceptibility testing (AST) of positive blood cultures (PBC). Very recently, the FAST™ System (Qvella) has been developed to isolate and concentrate microorganisms directly from PBCs, resulting in the recovery of a Liquid Colony™ (LC) within 30 min. The LC can be used as equivalent of an overnight subcultured colony for downstream testing. We aimed to evaluate the performances of the FAST™ System and FAST-PBC Prep™ cartridges by testing the resulting LC for direct ID, AST and rapid resistance detection.Materials and methodsProspectively, FAST™ System testing was carried out on each patient’s first PBC with a monomicrobial Gram-stain result. In the second arm of the study, FAST™ System testing was carried out on blood cultures spiked with multidrug-resistant bacteria. Downstream testing using the LC included MALDI-TOF MS ID with the Bruker Biotyper® smart system, rapid resistance detection testing including the Abbott Diagnostics Clearview™ PBP2a SA Culture Colony Test (PBP2a) and the Bio-Rad βLACTA™ Test (βLT). AST was performed using the Becton Dickinson Phoenix™ System or by Bio-Rad disk diffusion using filter paper disk following EUCAST 2020 breakpoint criteria.ResultsFAST™ System testing was completed on 198 prospective PBCs and 80 spiked blood cultures. After exclusion of polymicrobial blood cultures, performance evaluation compared with standard of care results was carried out on 266 PBCs. Concordant, erroneous and no ID results included 238/266 (89.5%), 1/266 (0.4%), 27/266 (10.2%) PBCs, respectively. Sensitivity and specificity for PBP2a were 100% (10/10) and 75% (15/20), respectively. Sensitivity and specificity for βLT were 95.8% (23/24) and 100% (42/42), respectively. Categorical agreement for all 160 tested strains was 98% (2299/2346) with 1.2% (8/657) very major errors and 0.7% (10/1347) major errors.ConclusionFAST™ System testing is a reliable approach for direct downstream testing of PBCs including MALDI-TOF MS ID, BD Phoenix™ and Bio-Rad disk diffusion AST as well as rapid resistance testing assays. Next steps include optimal integration of the FAST™ System in the PBC workflow with a view toward clinical studies.

Performance of the BioFire Blood Culture Identification 2 panel for the diagnosis of bloodstream infections

BackgroundConventional blood cultures methods are associated with long turnaround times, preventing early treatment optimization in bloodstream infections. The BioFire Blood Culture Identification 2 (BCID2) Panel is a new multiplex PCR applied on positive blood cultures, reducing time to pathogen identification and resistant markers detection. MethodsWe conducted a prospective observational study including positive blood cultures from Intensive Care Units and Emergency Departments and performed BCID2 in addition to conventional testing. Concordance between the two methods was assessed and BCID2 performance characteristics were evaluated. Resistance markers detected by BCID2 were confirmed by in-house PCR. Whole genome sequencing was performed in discordant cases. ResultsAmong 60 monomicrobial blood cultures, BCID2 correctly identified 55/56 (91.7%) on-panel pathogens, showing an overall concordance of 98%. In 4/60 cases BCID2 did not detect any target and these all grew BCID2 off-panel bacteria. Only one discordant case was found. Sensitivity and specificity for Gram-positive bacteria on monomicrobial samples were 100% (95% CI 85.8–100%) and 100% (95% CI 90.3–100%) respectively, while for Gram-negatives 100% (95% CI 87.7–100) and 96.9% (95% CI 83.8–99.9%), respectively. Among two polymicrobial blood cultures, full concordance was observed in one case only. BCID2 identified antimicrobial resistance genes in 6/62 samples, all confirmed by in-house PCR (3 mecA/C S. epidermidis, 3 blaCTX-ME. coli). Estimated time to results gained using BCID2 as compared to conventional testing was 9.69 h (95% CI: 7.85–11.53). ConclusionsBCID2 showed good agreement with conventional methods. Studies to assess its clinical impact are warranted.

Clinical and microbiological characterization of Aerococcus urinae bacteraemias at Helsinki metropolitan area, Finland

Our objective was to assess the incidence of bacteraemic Aerococcus urinae cases at Helsinki metropolitan area, Finland, from a 6-year study period (2013 to 2018) and to further characterize available cases. The study evaluates the outcome of commonly used cefuroxime treatment and determinate a set of A. urinae in vitro antimicrobial susceptibilities for benzylpenicillin, cefuroxime, and ceftriaxone. Clinical records of A. urinae bacteraemic patients were reviewed retrospectively. Antimicrobial susceptibility testing was performed by disk diffusion, gradient test, and broth microdilution for 139–141 clinical A. urinae isolates. Clinical data of 72/77 patients were combined with the in vitro susceptibilities. We found an increasing number of bacteraemic A. urinae cases within 6-year study period (p = 0.01). The patients were mainly elderly males, and all suffered from underlying conditions. A total of 27.3% of cases (21/77) showed polymicrobial blood cultures. Thirty-day mortality was 22.1%. Cefuroxime was the initial empiric antimicrobial agent given for 66/76 of the patients and treatment outcome was favorable for 20/22 patients who received cefuroxime at least up to day 5. All isolates were susceptible to benzylpenicillin and cefuroxime interpreted by EUCAST breakpoints for Aerococci and PK-PD breakpoints, respectively. MIC determinations gave variable results for ceftriaxone, 2.1–2.9% of the isolates were resistant. To conclude, it seems that the number of bacteraemic Aerococcus urinae cases is increasing at Helsinki metropolitan area, Finland, reflecting the growing blood culture sampling. Clinical A. urinae isolates were susceptible to cefuroxime in vitro. Treatment data indicate that empirical cefuroxime started for possibly urinary tract -derived community-acquired bacteraemia covers A. urinae.

Morbidity and Mortality of Necrotizing Fasciitis and Their Prognostic Factors in Children.

This is a prospective study of the clinico-etiologic profile and factors affecting outcomes in 40 children managed for necrotizing fasciitis (NF). Demographic details, clinical characteristics, and laboratory parameters were recorded, and the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score was calculated. Primary outcome (survival vs. nonsurvival) was noted, and prognostic factors were identified. Initiating factors included boils (45%), i.v. cannula extravasations (22.5%), and blunt trauma (17.5%). Lesion (s) were predominantly on the lower limbs (35%) and trunk (25%). Twenty-two patients (55%) had <5% body surface area (BSA) involved. Severely deranged clinical and laboratory parameters were common. Ultrasound localized fluid collections. Pus cultures showed methicillin-resistant Staphylococcus aureus (52.5%), methicillin-sensitive S. aureus [27.5%], and polymicrobial growth (20%). Blood culture was positive in 24 patients (60%). Most isolates were sensitive to clindamycin and amoxy-clavulanate. Prognostic factors for mortality (n = 6; 15%) included categorization as "Sick," BSA involvement >10%, thrombocytopenia, raised serum creatinine, late debridement, and polymicrobial blood culture isolates. All six nonsurvivors had a LRINEC score of ≥8 and positive blood cultures. Six patients (20.7%) developed unsightly scars and 5 (17.24%) contractures across joints. Pediatric NF has significant morbidity and mortality. Patients with adverse prognostic factors can benefit from early referral to a facility with a critical care unit. Adequate wound management is essential to minimize residual deformity.

988. Is There Value of Infectious Diseases Consultation in Candidemia? A Single Center Retrospective Review From 2016-2019

BackgroundCandidemia is the second most common cause of healthcare-associated bloodstream infections in the US with mortality of approximately 25%. Studies demonstrate lower candidemia mortality with infectious diseases consultation (IDC). We evaluated effects of IDC on mortality and guideline-adherence at our institution to determine if mandatory IDC was warranted.MethodsWe retrospectively reviewed adults hospitalized with candidemia (≥ 1 blood culture positive for Candida) between 1/1/2016-12/31/2019. Exclusion criteria included age < 19 years, polymicrobial blood culture, or death or hospice within 48 hours. Primary outcome was all-cause 30-day mortality. Secondary outcomes included guideline-adherence and treatment choice. Guideline-adherence was assessed with a modified EQUAL Candida score (Table 1). Descriptive statistics were performed.Table 1. Original vs Modified EQUAL Candida Score Abbreviations. CVC: central venous catheter, BCx: blood cultureResultsOf 187 patients reviewed, 92 episodes of candidemia with 94 species of Candida were included. Patient characteristics are shown in Table 2. Central venous catheters (CVCs) were present in 66 (71.7%) patients and were the most common infection source (N=38 [41.3%]) followed by intra-abdominal (N=23 [25%]). The most isolated species were Candida glabrata (40/94 [42.6%]) and C. albicans/dublienensis (35/94 [37.2%]). 30-day mortality was 21.7%. IDC was performed in 84 (91.3%) cases. Outcomes are in Table 3. Mortality was not different between IDC vs no IDC (18 [21.4%] vs 2 [25%]); other comparisons were numerically different but not significant: repeat blood culture (98.8% vs 87.5%), echocardiography (70.2% vs 50%), CVC removal (91.7% vs 83.3%), and initial treatment echinocandin (67.9% vs 50%). All patients received antifungal therapy. IDC resulted in more ophthalmology consultations (77.4% vs 12.5%, p< 0.01). Mean modified EQUAL Candida score was higher with IDC (17.4 vs 13.9, p< 0.01).Table 2. Patient Characteristics Abbreviations. TPN: total parenteral nutrition, ICU: intensive care unit, AIDS: acquired immunodeficiency syndromeTable 3. Outcomes Abbreviations. NS: non-significant, CVC: central venous catheterConclusionIDC was common in candidemic patients and not associated with significant differences in outcomes. Current antimicrobial stewardship and consultation practices at our center do not warrant mandated IDC for candidemia.Disclosures Trevor C. Van Schooneveld, MD, FACP, BioFire (Individual(s) Involved: Self): Consultant, Scientific Research Study Investigator; Insmed (Individual(s) Involved: Self): Scientific Research Study Investigator; Merck (Individual(s) Involved: Self): Scientific Research Study Investigator; Rebiotix (Individual(s) Involved: Self): Scientific Research Study Investigator

More than Just Contaminants: Frequency and Characterization of Polymicrobial Blood Cultures from a Central Clinical Microbiology Laboratory Serving a Large Healthcare System.

Polymicrobial blood stream infection is often considered uncommon, and corresponding cultures may be assumed to represent contamination. Here we characterized the prevalence and epidemiology of these cultures submitted to a central clinical microbiology laboratory. Blood cultures from 2017 to 2018 (n = 104 547) were evaluated. Polymicrobial blood cultures were defined by the presence of more than one organism in a blood culture set (set = one aerobic and one anaerobic bottle). Data were stratified by patient location and characteristics of the microbiota detected. Of all blood culture sets, 14 600 (14.0%) were positive. Among these, 1651 sets (11.3% of positive cultures; 1.6% of total cultures) were polymicrobial. Most cultures (85.2%) grew two microorganisms; the greatest number of microorganisms in a culture was 6. The most common microorganism pairs were (a) two coagulase-negative staphylococci (CoNS), (b) Corynebacterium and CoNS, and (c) S. aureus and CoNS. Microorganisms in polymicrobial cultures represented microbiota from skin (46.1%), the gastrointestinal (GI) tract (33.9%), strict anaerobes (1.4%), and "other" microorganisms (18.6%). Most cultures with GI microbiota originated from an adult academic medical center compared to community or pediatric settings (40.5% of polymicrobial cultures vs 27.2% and 25.8%, P < 0.0001). Within the academic medical center, patients in an intensive care unit (ICU) or who had bone marrow transplants (BMT) had more cultures suggestive of GI microbiota compared to those from the emergency department (ED) (50.8% and 52.8% vs 31.2%, P < 0.0001). Polymicrobial blood cultures are common in a variety of healthcare settings and the recovered microorganisms can be clinically relevant.

48. Association of Rapid Pathogen Identification and Pharmacist Intervention on Time to Optimal Antimicrobial Therapy for Bloodstream Infections at Two Community Hospitals

BackgroundAs many as 1 in 3 patients with bloodstream infections at community hospitals receive inappropriate empiric antimicrobial therapy. Studies have shown that the coupling of real-time intervention with rapid pathogen identification improves patient outcomes and decreases health-system costs at large, tertiary academic centers. The aim of this study was to assess if similar outcomes could be obtained with the implementation of real-time pharmacist intervention to rapid pathogen identification at two smaller, rural community hospitals.MethodsThis was a pre-post implementation study that occurred from September of 2019 to March 2020. This study included patients ≥18 years of age admitted with one positive blood culture. Patients were excluded if they were pregnant, had a polymicrobial blood culture, known culture prior to admission, hospice consulted prior to admission, expired prior to positive blood culture, or transferred to another hospital within 24 hours of a positive blood culture. Endpoints of patients prior to intervention were compared to patients post-implementation. The primary endpoint was time to optimal antimicrobial therapy. Secondary endpoints included time to effective antimicrobial therapy, in-hospital mortality, length of hospital stay, and overall cost of hospitalization.ResultsOf 212 patients screened, 88 patients were included with 44 patients in each group. Both groups were similar in terms of comorbidities, infection source, and causative microbial. No significant difference was seen in the mean time to optimal antimicrobial therapy (27.3±35.5 hr vs 19.4± 30 hr, p=0.265). Patients in the post-implementation group had a significantly higher mean hospitalization cost ($24,638.87± $11,080.91 vs $32,722.07±$13,076.73, p=0.013). There was no significant difference in time to effective antimicrobial therapy, in-hospital mortality, or length of hospital stay.ConclusionThere were no between-group differences in the primary outcome of time to optimal therapy, with a higher mean hospitalization cost after implementation. These results suggest further antimicrobial stewardship interventions are needed, along with larger studies conducted in the community hospital settings.Disclosures All Authors: No reported disclosures

Direct Identification of Microorganisms from Positive Blood Cultures by MALDI-TOF MS Using an in-House Tween® 80 Method: Experimental and Clinical Study

It has been reported that direct identification from blood culture bottles with positive signals and reporting the results to the clinics earlier has positive effects on mortality and morbidity. Extraction methods especially using detergents are used for the direct identification from the bottles which give positive signal. For this purpose, in-house methods developed based on the usage of saponin are widely available in the literature. In this study, it was aimed to develop a simple, easy-to-apply and reliable protocol for identifying the agent directly from the blood culture bottle that gives positive signal with the use of detergent Tween® 80, and to study the obtained protocol in clinical samples in a routine microbiology laboratory and to evaluate the results. The study was carried out in two stages, the experimental stage where the method was developed and the clinical stage where the method was applied. In the experimental stage, blood culture bottles were created with standard strains and isolates previously diagnosed with the 16S rRNA method. 10% solution of Tween® 80 was prepared with distilled water. 1 ml sample was transferred from the bottle that gave positive signal to the microcentrifuge tube, 100 µl of 10% solution of Tween® 80 was added, vortexed for 10 seconds and then incubated for 5 minutes at room temperature. The tubes were centrifuged for 5 min at 14.000 rpm, the supernatant was discarded and the pellet was washed with 1 ml of distilled water and centrifuged at 14.000 rpm for 5 minutes in three times. Samples taken from the pellets were rubbed on the slide and dried on air. Firstly, 1 µl of 70% formic acid, then 1 µl, of matrix solution was added and it was used after drying. In the second stage of the study, the method was applied to the 502 vials giving positive signal in the Microbiology Laboratory of Ankara University Faculty of Medicine Ibni Sina Hospital between 17 April 2018-31 August 2018 and the results were compared with the subculture results. The results obtained at the end of extraction in the experimental stage were compared with the subculture results and no statistical difference was found. In 383 (82.9%) bottles among 462 (92.1%) bottles with monomicrobial positive cultures, compatible results with the subculture results were obtained. Of the microorganisms correctly identified, 350 (91.3%) were bacteria and 33 (8.7%) were fungi. On the other hand, 216 (56.4%) of the bacteria were gram positive and 134 (34.9%) of them were gram negative bacteria. At least one microorganism was correctly identified in 19 (47.5%) of 40 (7.9%) bottles with polymicrobial blood cultures. Their distribution was gram negative (n= 10) and gram positive (n= 8) and yeast (n= 1). No microorganisms were identified in six bottles with polymicrobial cultures. According to the results, we believe that this in-house method developed using Tween® 80 will be a routinely applicable method for blood culture bottles that give positive signal in microbiology laboratories and it will contribute to the early diagnosis.

Method for obtaining blood culture while diagnosing bloodstream infection.

Diagnosing of bloodstream infection (BSI) in outpatients is essential. A large blood volume is required to obtain blood culture (CLSI): 2 sets, 40ml of blood for diagnosing in 95% cases of bacteremia. Molecular-genetic methods can not replace blood culture method, but they accelerate the identification of any pathogen. Culturomics gives a combination of different conditions for isolating microorganisms from a sample and along with their genetic identification. We used the patent method for direct inoculation of buffy-coat from 4,5ml of a venous blood sample and MALDI-ToF identification method. In 382 outpatients examined there were received 183 blood cultures (48,0%), more often among women (65,6%) and young people (74,9%). The causative agents of community-acquired bloodstream infection were aerobes (73,4%), anaerobes (24,2%), fungi (2,4%). The gram-positive cocci were prevailing (51,4%) and the gram-negative rods were isolated rather seldom (9,6%). BSI was monomicrobial (66,5%) and polymicrobial (33,5%). Polymicrobial blood cultures had 2, 3, 4 agents in one blood sample (75,4%, 18,8%, 5,8%, respectively). There were also found combinations of different species of aerobes (47,8%), aerobes with anaerobes (42%). BSI caused complications of the primary disease of the respiratory system, urogenital system and in 100% of cases after plastic surgery. A small blood volume is required for buffy-coat inoculation, the direct agar culture reduces the response time to 2 days, so it makes genetic identification possible on the 2nd day from the moment of blood collection.

Applicability of an in-house saponin-based extraction method in Bruker Biotyper matrix-assisted laser desorption/ionization time-of-flight mass spectrometry system for identifying bacterial and fungal species in positively flagged pediatric VersaTREK blood cultures

Early identification of pathogens causing bloodstream infection (BSI) is critical for prompt administration of appropriate antimicrobial therapy. We used an in-house saponin-based extraction method to evaluate the performance of Bruker Biotyper MALDI-TOF MS system (MALDI Biotyper) for bacterial and fungal identification in 2013 positively-flagged VersaTREK blood culture bottles. A total of 180 monomicrobial and 23 polymicrobial positive blood cultures were investigated. Among monomicrobial positive blood cultures, the MALDI Biotyper recognized 90.6% and 81.7% of organisms directly from the flagged blood culture bottles to the genus and species levels, respectively. The MALDI Biotyper also correctly characterized one of the polymicrobial organisms to the species level in 20 (87%) bottles and to the genus level in 21 (91.3%) bottles. The overall identification rate using our protocol was 90.6% (184/203) and 82.3% (167/203) for genus and species levels, respectively. Identification accuracy was higher for Gram-positive than Gram-negative organisms and was the lowest for yeasts. Score values of identification were ≥1.500 for 200 (98.5%) bottles, ≥1.700 for 195 (96.1%) bottles and ≥2.000 for 182 (89.7%) bottles. Moreover, 83.5% and 92% of the isolates were identified precisely to species and genus level with the lower cutoff score of 1.500. Using our protocol also helped identifying BSI pathogens 18-24h earlier compared to the sub-cultured colonies. Using Bruker MALDI Biotyper for identification of isolates directly from positive VersaTREK blood culture bottles, our in-house saponin-based protocol provided a more rapid turn-around time for correct identification of BSI pathogens than the conventional methods.

A new culture-based method for rapid identification of microorganisms in polymicrobial blood cultures by MALDI-TOF MS

BackgroundThe application of matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) to microbial identification has allowed the development of rapid methods for identification of microorganisms directly in positive, blood cultures (BCs). These methods can yield accurate results for monomicrobial BCs, but often fail to identify multiple microorganisms in polymicrobial BCs. The present study was aimed at establishing a rapid and simple method for identification of bacteria and yeast in polymicrobial BCs from patients with bloodstream infection.ResultsThe rapid method herein proposed is based on short-term culture in liquid media allowing selective growth of microorganisms recovered from polymicrobial BCs, followed by rapid identification by MALDI-TOF MS. To evaluate the accuracy of this method, 56 polymicrobial BCs were comparatively analyzed with the rapid and routine methods. The results showed concordant identification for both microbial species in 43/50 (86%) BCs containing two different microorganisms, and for two microbial species in six BCs containing more than two different species. Overall, 102/119 (85.7%) microorganisms were concordantly identified by the rapid and routine methods using a cut-off value of 1.700 for valid identification. The mean time to identification after BC positivity was about 4.2 h for streptococci/enterococci, 8.7 h for staphylococci, 11.1 h for Gram-negative bacteria, and 14.4 h for yeast, allowing a significant time saving compared to the routine method.ConclusionsThe proposed method allowed rapid and reliable microbial identification in polymicrobial BCs, and could provide clinicians with timely, useful information to streamline empirical antimicrobial therapy in critically ill patients.

1022. Is it Time to Re-Evaluate Oral Β-Lactam Antibiotics for Step-Down Therapy of Uncomplicated Gram-Negative Bacteremia?

BackgroundBloodstream infections (BSI) due to Enterobacteriaceae often require empiric intravenous (IV) antibiotics. Oral antibiotics for the definitive treatment of these infections have been reserved to antibiotics with “high” oral bioavailability, mainly fluoroquinolones (FQ). Safety concerns and increasing resistance associated with FQ has modified clinical practice to identify alternative oral therapies. Select β-lactam (BL) antibiotics are well-tolerated, have moderately high bioavailability, and possess in-vitro activity against Escherichia coli (E. coli), Klebsiella pneumoniae (K. pneumoniae), and Proteus mirabilis (P. mirabilis). Limited evidence exists for oral BL step-down therapy for definitive treatment of BSI due to these organisms.MethodsThis retrospective cohort study compares clinical outcomes of patients treated with oral BL antibiotics to those who received oral FQ or trimethoprim/sulfamethoxazole (TS) for the treatment of BSI due to E. coli, K. pneumoniae, and P. mirabilis. The primary outcome is a composite of 30-day all-cause mortality, 30-day readmission due to recurrence, and/or change in oral antibiotic therapy. Secondary endpoints include 90-day development of Clostridium difficile infection, 90-day all-cause readmission, hospital length of stay (LOS), and 90-day recovery of a multi-drug-resistant organism.ResultsNine hundred eighty-one patients were screened and 397 adult patients were included. Excluded patients: IV only (n = 291), polymicrobial blood culture (n = 112), immunocompromised (n = 61), other (n = 120). Two-hundred patients received oral step-down therapy with a BL, and 197 with either an FQ or TS. E. coli was the causative organism for most patients in both groups, and urinary tract was the most common source of BSI. The median total duration of therapy was 14 days in both groups. There was no significant difference in the primary composite endpoint (7% vs. 5.6%, P = 0.561). There was no mortality or differences in secondary outcomes, except LOS (6 vs. 5 days, P = 0.043).ConclusionUtilization of oral BL for the step-down therapy of uncomplicated BSI due to E. coli, K. pneumoniae, and P. mirabilis did not result in worse outcomes compared with those receiving oral FQ or TS.Disclosures All authors: No reported disclosures.