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New Approaches to Colonization Screening in Response to Emerging Antimicrobial Resistance
- Karen Anderson, Maria Karlsson, Sandra Boyd, Natashia Reese, Uzma Ansari, Davina Campbell, Amelia Bhatnagar, Paige Gable, Stephanie Swint, Cynthia Longo, Sarah Gilbert, Lori Spicer, Jake Cochran, David Lonsway
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 41 / Issue S1 / October 2020
- Published online by Cambridge University Press:
- 02 November 2020, p. s330
- Print publication:
- October 2020
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Background: The capacity to monitor the emergence of carbapenemase-producing organisms (CPO) is critical in limiting transmission. CPO-colonized patients can be identified by screening rectal specimens for carbapenemase genes and the Cepheid GeneXpert Carba-R (XCR), the only FDA-approved test, is limited to 5 carbapenemase genes and cannot identify the bacterial species. Objective: We describe the development and validation of culture-based methods for the detection of CPO in rectal cultures (RCs) and nonrectal cultures (NRCs) of tracheal aspirate and axilla-groin swabs. Methods: Colonization screening was performed at 3 US healthcare facilities; specimens of RC swabs and NRC ESwabs were collected. Each specimen was inoculated to a MacConkey broth enrichment tube for overnight incubation then were subcultured to MacConkey agar with meropenem and ertapenem 10 µg disks (BEMA) and CHROMagar KPC (KCHR) or CHROMagar Acinetobacter (ACHR). All media were evaluated for the presence of carbapenem-resistant organisms; suspect colonies were screened by real-time PCR for the most common carbapenemase genes. MALDI-TOF was performed for species identification. BEMA, a previously validated method, was the comparator for 52 RCs; clinical culture (CC) served as the comparator method for 66 NRCs. Select CPO-positive and -negative specimens underwent reproducibility testing. Results: Among 56 patients undergoing colonization screening, 12 (21%) carried a CPO. Only 1 patient had CPO solely from RC. Also, 6 patients had both CPO-positive RC and NRC, and 5 patients only had a CPO-positive NRC. Of the latter, 4 had a CPO-positive tracheal specimen, and 1 had a positive culture from both tracheal and axilla-groin specimens. Sensitivity of BEMA (70%) for NRC was lower than for KCHR (96%) and ACHR (88 %) for all specimens. All methods showed a specificity of 100% and reproducibility of 92%. The detected CPO included OXA-23–positive Acinetobacter baumannii, NDM-positive Escherichia coli, KPC-positive Pseudomonas aeruginosa and 4 genera of KPC-positive Enterobacteriaceae. Conclusions:The addition of nonrectal specimens and use of selective media contributed to increased sensitivity and enhanced identification of CPO-colonized patients. Positive cultures were equally distributed among the 3 specimen types. The addition of the nonrectal specimens resulted in the identification of more colonized patients. The culture-based method was successful in detecting an array of different CPOs and target genes, including genes not detected by the Carba-R assay (eg, blaOXA-23-like). Enhanced isolation and characterization of CPOs will be key in aiding epidemiologic investigations and strengthening targeted guidance for containment strategies.
Funding: None
Disclosures: We discuss the drug combination aztreonam-avibactam and acknowledge that this drug combination is not currently FDA approved.
In Vitro Activity of Cefiderocol Against Multidrug-Resistant Gram-Negative Clinical Isolates
- Sandra Boyd, Karen Anderson
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- Journal:
- Infection Control & Hospital Epidemiology / Volume 41 / Issue S1 / October 2020
- Published online by Cambridge University Press:
- 02 November 2020, pp. s291-s292
- Print publication:
- October 2020
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Background: New antimicrobials are being developed as a response to the global threat of multidrug-resistant and panresistant bacterial pathogens. Cefiderocol (FDC; Shionogi & Co) is a novel parenteral siderophore cephalosporin with activity against gram-negative rods. Here, we report on the in vitro activity of FDC against multidrug-resistant gram-negative isolates collected by the CDC, including isolates available through the CDC and FDA Antibiotic Resistance Isolate Bank (AR Isolate Bank). Methods: The challenge set of gram-negative isolates (n = 339), most of which were obtained from the AR isolate bank (n = 258), comprised 188 Enterobacteriaceae (ENT), 72 Pseudomonas aeruginosa (PSA), and 79 Acinetobacter baumannii (ACB). Minimum inhibitory concentrations (MICs) for FDC in iron-depleted cation-adjusted Mueller-Hinton broth were determined using frozen reference broth microdilution panels (IHMA, Schaumburg, IL) according to CLSI guidelines. Isolates displaying nonsusceptibility to FDC (MIC >4 µg/mL) underwent additional testing with β-lactamase inhibitors (FDC with 4 µg/mL avibactam, FDC with 100 µg/ml dipicolinic acid (DPA), and FDC with both 100 µg/mL dipicolinic acid (DPA) and 4 µg/mL avibactam). Results: Cefiderocol MICs ranged from ≤0.03 to >64 µg/mL, and 313 (92.3%) isolates displayed susceptibility to FDC (MIC ≤4 μg/mL). The proportions of susceptible ENT, PSA, and ACB were 93.1%, 94.4%, and 88.6%, respectively. Among isolates harboring Ambler class A, class B, or class D carbapenemases, the proportions of susceptible isolates were 96.5%, 79.5%, and 94.0%, respectively. Overall, 26 (7.7%) isolates were categorized as FDC nonsusceptible (MIC ≥ 8 µg/mL); 65% of these were NDM producers. We selected 23 isolates for testing with β-lactamase inhibitors. The combination FDC-avibactam reduced the MIC to susceptible for all isolates harboring an Ambler class A or D carbapenemase, except for 1 OXA-71–producing ACB and 1 KPC-producing Citrobacter farmeri. The combination FDC-DPA reduced the MIC to susceptible for 9 of 13 (69.2%) NDM-producing and 4 of 4 (100%) OXA-23–producing ACB. By combining FDC with both DPA and avibactam, the MIC was reduced to susceptible (91%) for all but 1 KPC-producing and 1 NDM-producing Enterobacteriaceae isolate. Conclusions: Cefiderocol (FDC) demonstrated potent activity against a diverse collection of multidrug-resistant, gram-negative isolates, including producers of Ambler class A, B, and D carbapenemases. Among the 26 FDC nonsusceptible isolates, 65% were NDM positive. Our data indicate that FDC combined with β-lactamase inhibitors may restore susceptibility in FDC nonsusceptible isolates. Additional studies are needed to understand the underlying mechanism(s) of FDC resistance and to further explore the use of β-lactamase inhibitors in combination with FDC.
Funding: None
Disclosures: None
Focused abdominal ultrasound for blunt trauma in an emergency department without advanced imaging or on-site surgical capability
- Michael Shuster, Riyad B. Abu-Laban, Jeff Boyd, Charles Gauthier, Sandra Mergler, Lance Shepherd, Chris Turner
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 6 / Issue 6 / November 2004
- Published online by Cambridge University Press:
- 21 May 2015, pp. 408-415
- Print publication:
- November 2004
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Objectives:
To determine whether focused abdominal sonogram for trauma (FAST) in a rural hospital provides information that prompts immediate transfer to a tertiary care facility for patients with blunt abdominal trauma who would otherwise be discharged or held for observation.
Methods:Prior to the study, participating emergency physicians underwent a minimum of 30 hours of ultrasound training. All patients who presented with blunt abdominal trauma to our rural hospital between Mar. 1, 2002, and Apr. 30, 2003, were eligible for study. Following a history and physical examination, the emergency physician documented his or her disposition decision. A FAST was then performed, and the disposition reconsidered in light of the FAST results.
Results:Sixty-seven FAST exams were performed on 65 patients. Three examinations (4.5%) were true-positive (95% confidence interval [CI] 0.9%–12.5%); 60 (89.6%) were true-negative (95% CI 79.7%–95.7%), 4 (6%) were false-negative (95% CI 1.7%–14.6%) and none (0%) were false-positive (95% CI 0%–5.4%). These values reflect sensitivity, specificity, negative predictive value and positive predictive values of 43%, 100%, 94% and 100% respectively. FAST results did not alter the decision to transfer any patient (0%: 95% CI 0.0%–5.4%), although one positive FAST may have led to an expedited transfer. One of 38 patients who was discharged after a negative FAST study returned 24 hours later because of worsening symptoms, and was ultimately found to have splenic and pancreatic injuries.
Conclusions:This study failed to demonstrate that FAST improves disposition decisions for patients with blunt abdominal trauma who are evaluated in a hospital without advanced imaging or on-site surgical capability. However, the study is not sufficiently powered to rule out a role for FAST in these circumstances, and our data suggest that up to 5.4% of transfer decisions could be influenced by FAST. Rural emergency physicians should not allow a negative FAST study to override a clinical indication for transfer to a trauma centre; however, positive FAST studies can be used to accelerate transfer for definitive treatment.
Prospective evaluation of clinical assessment in the diagnosis and treatment of clavicle fracture: Are radiographs really necessary?
- Michael Shuster, Riyad B. Abu-Laban, Jeff Boyd, Charles Gauthier, Sandra Mergler, Lance Shepherd, Chris Turner
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- Journal:
- Canadian Journal of Emergency Medicine / Volume 5 / Issue 5 / September 2003
- Published online by Cambridge University Press:
- 21 May 2015, pp. 309-313
- Print publication:
- September 2003
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Introduction:
Current recommended treatment for middle-third clavicle fractures is limited to the use of ice, analgesics, a sling, and rest. Radiography for these fractures would be superfluous if physicians could accurately identify them by clinical examination alone. The primary purpose of this study was to determine whether emergency physicians can accurately diagnose clavicle fractures, and whether they can differentiate middle-third fractures from medial- or lateral-third fractures by clinical assessment alone.
Methods:We enrolled a convenience sample of patients who presented to our rural emergency department with possible clavicle fracture between Nov. 1, 2001, and Apr. 30, 2002. Prior to viewing radiographs, physicians scored their clinical certainty of diagnosis on a 10-cm visual analogue scale. When certain of fracture, physicians determined the location of the fracture, the nature of the fracture and their hypothetical comfort in treating the injury without radiography.
Results:In 51 of 77 enrolled patients (66%; 95% confidence interval [CI], 54.6%–76.6%), treating physicians were certain of the diagnosis of clavicle fracture prior to radiography. In these 51 cases, radiography revealed a fracture in 50 cases (98.0%; 95%CI, 89.6%–99.9%). The physicians were 100% accurate for 4 fractures clinically identified as lateral-third fractures (95% CI, 39.7%–100%) and for 41 fractures identified as middle-third fractures (95% CI, 91.4%–100%). They were correct on only 1 of 5 injuries (20%; 95% CI: 1%–72%) they clinically identified as medial-third fractures. Despite high clinical accuracy with middle-third fractures, they stated in 27 of 42 cases (64%; 95%CI, 48.0%–78.5%) that they would have been uncomfortable treating the patient without a radiograph.
Conclusions:This study provides evidence that experienced emergency physicians are highly accurate when they are clinically certain of clavicle fracture. Further, when emergency physicians do clinically diagnose clavicle fracture, they can accurately identify the patient subgroup that will be responsive to conservative treatment. Routine radiography of obvious middle-third clavicle fractures does not appear to improve diagnostic accuracy or treatment decisions.