MIC Panels Research Articles

A-292 Validation of Aztreonam-Avibactam MIC Antimicrobial Susceptibility Test for MicroScan Dried Gram-Negative MIC Panels from a Multicenter Assessment of Enterobacterales, Pseudomonas species, and Stenotrophomonas maltophilia

Abstract Background Aztreonam-avibactam (AZA) is a novel antibiotic combination for treating Gram-negative bacterial infections, including metallo-β-lactamase-producing multidrug-resistant pathogens for which there are limited or no treatment options.1 Given the need for accurate antimicrobial susceptibility testing results, a study was conducted with clinical isolates of Enterobacterales, Pseudomonas species, and Stenotrophomonas maltophilia on an investigational MicroScan Dried Gram-negative MIC (MSDGN) panel with AZA.2 Methods Three clinical sites evaluated MSDGN MIC values to MICs from CLSI reference panels. The study included 602/671 Enterobacterales, 53/59 Pseudomonas species and 69/70 S. maltophilia isolates using Prompt or turbidity inoculation. MSDGN panels were incubated at 35 ± 1°C and read on the WalkAway, autoSCAN-4, and visually at 16-20 hours. Reference panels were prepared according to CLSI methodology, incubated 16-20 hours for Enterobacterales and Pseudomonas species, and 20-24 hours for S. maltophilia and read visually. Results Essential agreement was calculated comparing MSDGN panel MIC results against reference panel MIC results for all isolates (Table 1). Conclusions AZA MIC results for Enterobacterales, Pseudomonas species, and S. maltophilia from MSDGN panels correlate well with MICs obtained using reference panels in this study. 1Pending approval by US Food and Drug Administration (FDA); not available for in vitro diagnostic use in the US. Not for Distribution in the US. 2Pending submission and clearance by the US FDA; not yet available for in vitro diagnostic use in the US. For Investigational Use Only. The performance characteristics of this product have not been established. In development, pending achievement of CE compliance; not yet available for in vitro diagnostic use. © 2024 Beckman Coulter. All rights reserved. All other trademarks are the property of their respective owners. BEC, the stylized logo and the BEC product and service marks mentioned herein are trademarks or registered trademarks of BEC, Inc. in the US and other countries. 2023-12350

A-273 Multicenter Assessment of the Accuracy of MIC Results for Piperacillin/Tazobactam with MicroScan Dried Gram-Negative MIC Panels using CLSI Breakpoints

Abstract Background MIC data from MicroScan Dried Gram-negative MIC (MSDGN) Panels with piperacillin/tazobactam were evaluated with CLSI-M100-ED32 breakpoints for Acinetobacter, Enterobacterales, Other-Non-Enterobacterales, and proposed CLSI breakpoints for Pseudomonas aeruginosa from a multicenter clinical study. MIC results were compared to results obtained with CLSI frozen broth microdilution panels. Materials/Methods The study included a total of 683 clinical isolates tested using Prompt and turbidity during efficacy and challenge phases. MSDGN panels were evaluated at three clinical sites, comparing MIC values obtained using MSDGN panels to MICs utilizing CLSI reference panel. MSDGN panels were incubated at 35 ± 1°C and read on WalkAway System, autoSCAN-4 instrument, and read visually at 16–20 h. Frozen reference panels were prepared according to CLSI methodology, incubated for 16–20 h for Enterobacterales, Other Non-Enterobacterales, and Pseudomonas aeruginosa and for 20–24 h for Acinetobacter and read visually. CLSI breakpoints(mg/L) used for interpretation of MIC results were: ≤16/4 S, 32/4–64/4 I, ≥128/4 R for Acinetobacter and Other Non Enterobacterales, ≤8/4 S, 16/4 SDD, ≥32/4 R for Enterobacterales, and ≤16/4 S, 32/4 I, >64/4 R for Pseudomonas aeruginosa. Results When compared to frozen reference panel results, essential and categorical agreements for all isolates tested are as follows with these recommendations: Due to elevated major error rates for S. marcescens and WalkAway reads with Prompt, results should be confirmed visually prior to reporting. Due to performance with P. rettgeri and S. liquefaciens complex, do not report drug, therapy, or MIC. Conclusion Piperacillin/tazobactam MIC results for gram-negative clinical isolates obtained with the MSDGN panel correlate with MICs obtained using frozen reference panels with updated CLSI interpretive criteria.

A-274 Validation of Cefepime-Taniborbactam MIC Antimicrobial Susceptibility Test for MicroScan Dried Gram-Negative MIC Panels from a Multicenter Assessment of Enterobacterales and Pseudomonas aeruginosa

Abstract Background Cefepime-taniborbactam is an investigational agent with activity against carbapenem and multidrug-resistant Enterobacterales and Pseudomonas aeruginosa.1 Given the need for accurate antimicrobial susceptibility testing results to support patient care decisions, a multicenter study was conducted with Enterobacterales and Pseudomonas aeruginosa clinical isolates on investigational MicroScan Dried Gram-negative MIC (MSDGN) panels with cefepime-taniborbactam.2 Materials/Methods MSDGN panels were evaluated at three clinical sites by comparing MIC values obtained using MSDGN panels to MICs utilizing CLSI broth microdilution reference panels. The study included 490/491 Enterobacterales and 65 Pseudomonas aeruginosa clinical isolates tested using Prompt® and turbidity methods of inoculation during the combined efficacy and challenge phases. MSDGN panels were incubated at 35 ± 1°C and read on the WalkAway System, the autoSCAN-4 instrument, and visually at 16–20 h. Frozen reference panels were prepared according to CLSI/ISO methodology, incubated for 16–20 h and read visually. Results Essential agreement was calculated compared to MIC results from frozen reference panels for isolates tested in efficacy and challenge and found in the following table. Conclusion Cefepime-taniborbactam MIC results for Enterobacterales and Pseudomonas aeruginosa obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels in this multicenter study.Pending approval by the US Food and Drug Administration; not available for in vitro diagnostic use in the US. Not for Distribution in the US.Pending submission and clearance by the US Food and Drug Administration; not yet available for in vitro diagnostic use in the US.For Investigational Use Only. Performance characteristics of this product have not been established.Read methodEnterobacterales Essential agreement (EA) % (n/N)Pseudomonas aeruginosaEssential agreement (EA) % (n/N)PromptTurbidityPromptTurbidityWalkAway90.0 (441/490)99.2 (487/491)100.0 (65/65)100.0 (65/65)autoSCAN-494.3 (462/490)99.0 (486/491)98.5 (64/65)98.5 (64/65)Visually92.7 (454/490)99.2 (487/491)100.0 (65/65)100.0 (65/65)Abbreviations: Prompt, Prompt inoculation method, Turbidity, Turbidity inoculation method.

Direct inoculation method for identification and antimicrobial susceptibility testing using matrix-assisted laser desorption ionization-time of flight mass spectrometry and both the Vitek 2 and MicroScan Walkaway 96 Plus systems

The aim of our study was to evaluate a protocol utilizing serum separator tubes (SST) to facilitate a faster, cost-effective, direct method for rapid sensitivity testing and identification of positive blood cultures. Spiked cultures were inoculated into either Becton Dickinson (BD) BACTECTM Aerobic Plus or Anaerobic/F bottles containing sterile human blood. Bottles were immediately processed when positive. A parallel study using patient isolates was used in which bacteria were pelleted by SST from positive blood cultures. For identification, a portion of the pellet was tested by matrix-assisted laser desorption/ionization as described by the manufacturer. MicroScan panels and Vitek 2 results were compared. Categorical agreement was used as comparison to standard subculture and/or polymerase chain reaction methods. No discordant identifications were observed, and 86% generated a successful identification when compared to subculture methods. For the Vitek 2, we observed a 99% essential agreement when compared to the subculture method. For the MicroScan Walkaway, we observed 94.9%, 97.4%, and 100% categorical agreement for MIC panels 53, 38, and MICroSTREP Plus 2, respectively. Turnaround times were reduced from 4 hours for identification and 11 hours for antimicrobial sensitivity testing. We conclude that the SST method results in timelier, actionable results for antimicrobial stewardship initiatives.

230. Multicenter Assessment of the Accuracy of MIC Results for Colistin with MicroScan Dried Gram Negative MIC Panels using CLSI Breakpoints

Abstract Background A multicenter study was performed to evaluate the accuracy of MIC results for colistin on a MicroScan Dried Gram Negative MIC (MSDGN) Panel when compared to results obtained with frozen broth microdilution panels prepared according to CLSI/EUCAST methodology. Note: Colistin is not available in all countries. Methods MSDGN panels were evaluated at three clinical sites (including Beckman Coulter) by comparing MIC values obtained using the MSDGN panels to MICs obtained utilizing a CLSI/EUCAST broth microdilution reference panel. The study included 407 clinical isolates tested using the turbidity and Prompt® methods of inoculation. MSDGN panels were incubated in the WalkAway System (35 ± 1°C) and read on the WalkAway System, the autoSCAN-4 instrument, and read visually at 16-20 hours. Frozen reference panels were prepared and inoculated according to CLSI/EUCAST Joint Working Group Recommendations for MIC determination of Colistin (Polymyxin E) and incubated for 16-20 hours and read visually. CLSI M100 ED32 breakpoints (µg/mL) used for interpretation of MIC results were: Enterobacterales ≤ 2 I, ≥ 4 R; P. aeruginosa ≤ 2 I, ≥ 4 R. Results Essential, categorical agreement, and categorical errors were calculated using MIC results from WalkAway reads for MSDGN panels in Table 1. All other read methods yielded similar results. Categorical agreement was not calculated for Acinetobacter spp. as MIC only is reported. Table 1- Results Conclusion This multicenter study showed that colistin MIC results for Gram Negative bacteria obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels with CLSI interpretive criteria. © 2022 Beckman Coulter. All rights reserved. All other trademarks are the property of their respective owners. Beckman Coulter, the stylized logo, and the Beckman Coulter product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the U.S. and other countries. Disclosures Stefan Riedel, M.D., PhD., D(ABMM), FCAP, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Maria Traczewski, BS, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Denise Beasley, BS, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Regina Brookman, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Jose Diaz, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Zabrina Lockett, PhD, Beckman Coulter, Inc.: Employee of Beckman Coulter Jennifer Chau, PhD, Beckman Coulter, Inc.: Employee of Beckman Coulter.

520. Development of Cefepime-taniborbactam MIC Antimicrobial Susceptibility Test (AST) for Enterobacterales and Pseudomonas aeruginosa on MicroScan Dried Gram-negative MIC Panels

Abstract Background Automated AST devices are critical to inform appropriate care of patients with bacterial infections. Cefepime-taniborbactam is an investigational agent under development to treat infections due to multidrug-resistant bacteria, including carbapenem-resistant Enterobacterales and Pseudomonas aeruginosa. Development of a cefepime-taniborbactam antimicrobial susceptibility test was completed for the MicroScan Dried Gram-negative MIC (MSDGN) Panel when compared to CLSI broth microdilution reference panels. Methods Development was conducted by comparing MICs obtained using the MSDGN panel to MICs using a CLSI broth microdilution reference panel. The concentration range of cefepime-taniborbactam evaluated was 0.12/4-64/4 µg/mL. A total of 1376 isolates (1256 Enterobacterales and 120 P. aeruginosa) were tested at 16, 18, and 20 hours incubation times (for visual read and autoSCAN-4). A total of 917 isolates (837 Enterobacterales and 80 P. aeruginosa) were tested at 16 and 18 hours incubation time for the WalkAway System. All isolates were tested using turbidity and Prompt® methods of inoculation. MSDGN panels were incubated at 35 ± 1°C. Reference panels, prepared according to ISO methodology, were inoculated using the turbidity inoculation method. All frozen reference panels were incubated at 35 ± 2°C and read visually. Rates of essential agreement (MicroScan MIC within ± 1 doubling dilution of reference MIC) were determined for each combination of inoculation method and read method. Results Essential agreement rates ranged from 93.0% to 98.8% for all isolates tested during development. Essential agreement rates for each inoculation and read method are presented in Table 1. Table 1- Results Conclusion Cefepime-taniborbactam MIC results obtained with the MSDGN panel correlated well with MIC results obtained using reference panels. Rates of essential agreement were ≥93.0% for all inoculation and read methods. These development data support the continued evaluation of MSDGN panel with cefepime-taniborbactam in a multicenter trial. Pending submission and clearance by the United States Food and Drug Administration; not yet available for in vitro diagnostic use in the US. For Investigational Use Only. The performance characteristics of this product have not been established. Disclosures Enrique J. Fernandez, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Robert L. Williams, PhD, Beckman Coulter, Inc.: Employee of Beckman Coulter Vasna Carr, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Vasna Carr, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Miller Renae, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter.

342. Multicenter Evaluation of Fosfomycin MIC Results for Enterobacterales Using EUCAST V11 Breakpoints (i.v. and oral for uncomplicated UTI only, E. coli) on MicroScan Dried Gram Negative MIC Panels

Abstract Background EUCAST V11 fosfomycin breakpoints for Enterobacterales (i.v. and oral for uncomplicated UTI only, E. coli) were evaluated against data from a multicenter clinical study on a MicroScan Dried Gram Negative MIC (MSDGN) Panel. MIC results were compared to results obtained with agar dilution reference prepared according to CLSI methodology. Methods A total of 344 Gram negative clinical isolates including 191 Enterobacterales were tested using the turbidity and Prompt® methods of inoculation during the efficacy phase at three clinical sites. An evaluation was conducted by comparing MIC values obtained using the MSDGN panels to MICs utilizing the CLSI agar dilution reference. MSDGN panels were incubated at 35 ± 1°C and read on the WalkAway System, the autoSCAN-4 instrument, and read visually at 16-20 hours. Agar dilution plates were prepared according to CLSI methodology, incubated for 16-20 hours and read visually. EUCAST v11.0 fosfomycin breakpoints (mg/L) used for interpretation of MIC results were: i.v. for Enterobacterales ≤ 32 S, > 32 R and oral for uncomplicated UTI only, E. coli ≤ 8 S, > 8 R. Results Essential agreement, categorical agreement and categorical errors were calculated compared to MIC results from agar dilution plates. Results for all efficacy isolates with turbidity inoculation and manual read are found in Table 1. Table 1- Results Conclusion This multicenter study showed that fosfomycin MIC results for i.v. for Enterobacterales and E. coli (oral, for uncomplicated UTI only) obtained with the MSDGN panel correlate well with MICs obtained using CLSI agar dilution reference using EUCAST interpretive criteria. © 2022 Beckman Coulter. All rights reserved. All other trademarks are the property of their respective owners. Beckman Coulter, the stylized logo, and the Beckman Coulter product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the United States and other countries. Disclosures Omai Garner, PhD, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Amanda Harrington, PhD, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc.|bioMeriuex/BioFire: Grant/Research Support Sharon DesJarlais, BS, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Maria Traczewski, BS, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Denise Beasley, BS, Beckman Coulter, Inc.: Clinical trial data collection funded by Beckman Coulter, Inc. Jose Diaz, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Regina Brookman, BS, Beckman Coulter, Inc.: Employee of Beckman Coulter Zabrina Lockett, PhD, Beckman Coulter, Inc.: Employee of Beckman Coulter Jennifer Chau, PhD, Beckman Coulter, Inc.: Employee of Beckman Coulter.

Validation of Three MicroScan® Antimicrobial Susceptibility Testing Plates Designed for Low-Resource Settings.

Easy and robust antimicrobial susceptibility testing (AST) methods are essential in clinical bacteriology laboratories (CBL) in low-resource settings (LRS). We evaluated the Beckman Coulter MicroScan lyophilized broth microdilution panel designed to support Médecins Sans Frontières (MSF) CBL activity in difficult settings, in particular with the Mini-Lab. We evaluated the custom-designed MSF MicroScan Gram-pos microplate (MICPOS1) for Staphylococcus and Enterococcus species, MSF MicroScan Gram-neg microplate (MICNEG1) for Gram-negative bacilli, and MSF MicroScan Fastidious microplate (MICFAST1) for Streptococci and Haemophilus species using 387 isolates from routine CBLs from LRS against the reference methods. Results showed that, for all selected antibiotics on the three panels, the proportion of the category agreement was above 90% and the proportion of major and very major errors was below 3%, as per ISO standards. The use of the Prompt inoculation system was found to increase the MIC and the major error rate for some antibiotics when testing Staphylococci. The readability of the manufacturer’s user manual was considered challenging for low-skilled staff. The inoculations and readings of the panels were estimated as easy to use. In conclusion, the three MSF MicroScan MIC panels performed well against clinical isolates from LRS and provided a convenient, robust, and standardized AST method for use in CBL in LRS.

Diarrhea-Causing Bacteria and Their Antibiotic Resistance Patterns Among Diarrhea Patients From Ghana.

Diarrheal disease remains a major global health problem particularly in children under 5 years and the emergence of antibiotic-resistant strains of causative pathogens could slow control efforts, particularly in settings where treatment options are limited. This surveillance study conducted in Ghana aimed to determine the prevalence and antimicrobial susceptibility profile of diarrhea-causing bacteria. This was a cross-sectional study carried out in five health facilities in the Ga West Municipality of Ghana between 2017 and 2021. Diarrheic stool samples from patients were collected and cultured on standard differential/selective media and isolates identified by standard biochemical tests, MALDI-TOF assay, and serological analysis. The antibiogram was determined using Kirby-Bauer disk diffusion and Microscan autoScan4 MIC panels which were used for extended-spectrum beta-lactamase (ESBL) detection. Bacteria were isolated from 97.5% (772/792) of stool samples, and 167 of the isolates were diarrheagenic and met our inclusion criteria for antimicrobial resistance (AMR) analysis. These included Escherichia coli (49.1%, 82/167), Salmonella species (23.9%, 40/167), Vibrio species (16.8%, 28/167), and Shigella species (10.2%, 17/167). Among 24 Vibrio species, we observed resistances to cefotaxime (21/24, 87.5%), ceftriaxone (20/24, 83.3%), and ciprofloxacin (6/24, 25%), including four multi-drug resistant isolates. All 13 Vibrio parahaemolyticus isolates were resistant to cefazolin. All 17 Shigella isolates were resistant to tetracycline with resistance to shigellosis drugs such as norfloxacin and ciprofloxacin. Salmonella isolates were highly susceptible to norfloxacin (40/40, 100%) and tetracycline (12/34, 35%). Two ESBL-producing E. coli were also identified with marked susceptibility to gentamicin (66/72, 91.7%) and amikacin (57/72, 79.2%) prescribed in the treatment of E. coli infections. This study showed the different bacteria implicated in diarrhea cases in Ghana and the need for differential diagnoses for better treatment outcomes. Escherichia coli, Shigella, Salmonella, and Vibrio have all been implicated in diarrhea cases in Ghana. The highest prevalence was E. coli and Salmonella with Shigella the least prevalent. Resistance to commonly used drugs found in these isolates may render bacteria infection treatment in the near future nearly impossible. Routine antimicrobial susceptibility testing, effective monitoring, and nationwide surveillance of AMR pathogens should be implemented to curb the increase of antimicrobial resistance in Ghana.

1079. Development of Tebipenem MIC Antimicrobial Susceptibility Test for Gram-negative Bacteria on MicroScan Dried Gram-negative MIC Panels

Abstract Background Development of a tebipenem antimicrobial susceptibility test was completed for the MicroScan Dried Gram-negative MIC (MSDGN) Panel when compared to CLSI broth microdilution reference panels. Methods Development was conducted by comparing MICs obtained using the MSDGN panel to MICs using a CLSI broth microdilution reference panel. A total of 669 Enterobacterales isolates were tested at 16, 18, and 20 hour incubation times using the turbidity and Prompt®* methods of inoculation. MSDGN panels were incubated at 35 ± 2ºC and read on the WalkAway System, the autoSCAN-4 instrument, and read visually. Frozen reference panels, prepared according to ISO/CLSI methodology, were inoculated using the turbidity inoculation method. All frozen reference panels were incubated at 35 ± 2ºC and read visually. Dilution sequence evaluated is 0.03-32 µg/mL. Results When compared to frozen reference panel results, essential agreement for all isolates tested during development are as follows: Conclusion The development data showed that tebipenem MIC results for Enterobacterales obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels. Essential agreement is > 90% for all inoculation and read methods. For Investigational Use Only. The performance characteristics of this product have not been established. * Prompt® is a registered trademark of 3M Company, St. Paul, MN USA. © 2021 Beckman Coulter. All rights reserved. Beckman Coulter, the stylized logo, and the Beckman Coulter product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the United States and other countries. Disclosures Jose Enrique Fernandez, n/a, Beckman Coulter (Employee) Vasna Carr, n/a, Beckman Coulter (Employee) Renae Miller, n/a, Beckman Coulter (Employee)

STRESS TOLERANCE AND ANTIBIOTIC SUSCEPTIBILITY OF CRONOBACTER SPP. ISOLATED FROM POWDERED INFANT FORMULA RETAILED IN NIGERIA

., is an emerging, opportunistic pathogen that causes infections such as , meningitis and in neonates and infants, and can sometimes lead to death. There is zero tolerance for the presence of . all powdered infant formulae because of the high mortality rate (80%) associated with . . Three . (CS14, CS17 and CS124) isolated from PIF retailed in Nigeria were exposed to different levels of stress (pH, osmotic, oxidative, heat, bile and desiccation). The production ability of the isolates was investigated and the susceptibility of the isolates to different antibiotics was carried out using the MIC panel. Variation in stress response was observed in the isolates with no consistent pattern. The CS 17 ( ) and CS 124 ( ) showed the highest tolerance to stress on the average. All the isolates exhibited the ability to produce ranging from 1.30 – 2.0 and were also sensitive to more than 95% of the antibiotics used in the MIC panel, with no resistance to any.

673. Updated CLSI Ciprofloxacin Breakpoints from a Multicenter Assessment for Enterobacterales, Salmonella spp. and Pseudomonas aeruginosa Using MicroScan Dried Gram Negative MIC Panels

BackgroundUpdated US FDA/CLSI ciprofloxacin breakpoints were evaluated against data from a multicenter clinical study with Enterobacterales, Salmonella spp. and P. aeruginosa on a MicroScan Dried Gram-negative MIC (MSDGN) Panel. MIC results were compared to results obtained with frozen broth microdilution panels prepared according to CLSI methodology.MethodsMSDGN panels were evaluated at three clinical sites by comparing MIC values obtained using the MSDGN panels to MICs utilizing a CLSI broth microdilution reference panel. Data from the combined phases of efficacy and challenge included 803 Enterobacterales, Salmonella spp. and P. aeruginosa clinical isolates tested using the turbidity and Prompt® methods of inoculation. To demonstrate reproducibility, a subset of 12 organisms were tested on MSDGN panels at each site during reproducibility. MSDGN panels were incubated at 35 ± 1ºC and read on the WalkAway System, the autoSCAN-4 instrument, and visually. Read times for the MSDGN panels were at 16-20 hours. Frozen reference panels were prepared and read according to CLSI methodology. FDA and CLSI breakpoints (µg/mL) used for interpretation of MIC results were: Enterobacterales ≤ 0.25 S, 0.5 I, ≥ 1 R; Salmonella spp. ≤ 0.06 S, 0.12-0.5 I, ≥ 1 R; P. aeruginosa ≤ 0.5 S, 1 I, ≥ 2 R.ResultsEssential and categorical agreement was calculated compared to frozen reference panel results. Results for isolates tested during efficacy and challenge with Prompt inoculation and manual read are as follows: Read Method Essential Agreement (EA) % Categorical Agreement (CA) % Very Major Error (VMJ) % Major Error (MAJ) % Enterobacterales 93.8(646/689)97.7(673/689)0.0(0/146)0.0(0/535) Salmonella spp. 100(21/21)95.2(20/21)0.0(0/1)0.0(0/18) P. aeruginosa 94.6(88/93)91.4(85/93)0.0(0/29)1.7(1/58)ConclusionCiprofloxacin MIC results for Enterobacterales, Salmonella spp., and P. aeruginosa obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels using updated FDA/CLSI interpretive criteria in this multicenter study.* PROMPT® is a registered trademark of 3M Company, St. Paul, MN USA.BEC, the stylized logo and the BEC product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the US and other countries.Disclosures Maria M. Traczewski, BS MT (ASCP), Beckman Coulter (Scientific Research Study Investigator) Denise Beasley, BS, Beckman Coulter (Other Financial or Material Support, Research personnel) Amanda Harrington, PhD, Beckman Coulter (Scientific Research Study Investigator) Sharon DesJarlais, BS, Beckman Coulter (Other Financial or Material Support, Research personnel) Omai Garner, PhD, D(ABMM), Beckman Coulter (Scientific Research Study Investigator) Christine Hastey, PhD, Beckman Coulter (Employee) Regina Brookman, BS, Beckman Coulter (Employee) Zabrina Lockett, MS, Beckman Coulter (Employee) Jennifer Chau, PhD, Beckman Coulter (Employee)

667. Multicenter Assessment of Enterobacterales, Salmonella spp. and Pseudomonas aeruginosa Using Updated CLSI Levofloxacin Breakpoints on MicroScan Dried Gram Negative MIC Panels

BackgroundData from a multicenter clinical study with Enterobacterales, Salmonella spp. and P. aeruginosa on a MicroScan Dried Gram-negative MIC (MSDGN) Panel was evaluated with updated US FDA/CLSI levofloxacin breakpoints. MIC results were compared to results obtained with frozen broth microdilution panels prepared according to CLSI methodology.MethodsA total of 839 Enterobacterales, Salmonella spp. and P. aeruginosa clinical isolates were tested at three clinical sites in efficacy and challenge combined. MSDGN panels were evaluated with turbidity and Prompt® methods of inoculation. MIC values obtained from the MSDGN panels were compared to MICs utilizing a CLSI broth microdilution reference panel. To assess reproducibility, a subset of 15 organisms were tested on MSDGN panels at each site. MSDGN panels were incubated at 35 ± 1ºC and read on the WalkAway System, the autoSCAN-4 instrument, and visually. Read times for the MSDGN panels were at 16-20 hours. Frozen reference panels were prepared and read according to CLSI methodology. FDA and CLSI breakpoints (µg/mL) used for interpretation of MIC results were: Enterobacterales ≤ 0. 5 S, 1 I, ≥ 2 R; Salmonella spp. ≤ 0.12 S, 0.25-1 I, ≥ 2 R; P. aeruginosa ≤ 1 S, 2 I, ≥ 4 R.ResultsEssential and categorical agreement were calculated compared to frozen reference panel results. Results for isolates tested during efficacy and challenge with Prompt inoculation and manual read are as follows: Read Method Essential Agreement (EA) % Categorical Agreement (CA) % Very Major Error (VMJ) % Major Error (MAJ) % Enterobacterales 96.2(638/663)96.7(641/663)1.5(2/133)0.0(0/515) Salmonella spp. 100(83/83)98.8(82/83)0.0(0/19)0.0(0/38) P. aeruginosa 94.6(88/93)93.6(87/93)0.0(0/34)1.9(1/54)ConclusionLevofloxacin MIC results for Enterobacterales, Salmonella spp., and P. aeruginosa obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels using updated FDA/CLSI interpretive criteria in this multicenter study.* PROMPT® is a registered trademark of 3M Company, St. Paul, MN USA.BEC, the stylized logo and the BEC product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the US and other countries.Disclosures Omai Garner, PhD, D(ABMM), Beckman Coulter (Scientific Research Study Investigator) Maria M. Traczewski, BS MT (ASCP), Beckman Coulter (Scientific Research Study Investigator) Denise Beasley, BS, Beckman Coulter (Other Financial or Material Support, Research personnel) Amanda Harrington, PhD, Beckman Coulter (Scientific Research Study Investigator) Sharon DesJarlais, BS, Beckman Coulter (Other Financial or Material Support, Research personnel) Christine Hastey, PhD, Beckman Coulter (Employee) Regina Brookman, BS, Beckman Coulter (Employee) Zabrina Lockett, MS, Beckman Coulter (Employee) Jennifer Chau, PhD, Beckman Coulter (Employee)

‘Breakpoint broth microdilution plate’ for susceptibility testing of Gram negative bacilli against colistin sulfate

The MIC method applicable to Gram negative bacilli including Acinetobacter spp. is broth microdilution (BMD). Cost and/or availability issues limit the use of commercial MIC panels in resource limited settings. ObjectivesTo design and implement an in-house breakpoint BMD panel (BBMD) for colistin against Gram negative bacilli. DesignBBMD panel was prepared in 96-well plate. MIC concentrations of 1, 2, & 4 ​μg/mL for test, and 0.25, 0.5, 1, 2 & 4 ​μg/mL for control strains were selected to accommodate 19 test and 3 quality control strains per plate. Plates were frozen at −80 ​°C until testing. Validation was performed using strains from a previously published study and compared with freshly prepared MIC panel of 16–0.03 ​μg/mL. ResultsValidation showed 100% agreement with the reference method and BBMD was introduced into routine laboratory practice for colistin susceptibility of carbapenem resistant Enterobacterales (CRE), Acinetobacter baumannii complex and Pseudomonas aeruginosa. From 2nd July-16th September 2018, a total of 1294 (mean 16.8 ​± ​5.5 isolates/day) clinical isolates were tested; 1157/1294 were reported (MIC ≤2 ​μg/mL) within 24-h, whereas 133 required resistance confirmation by full-range BMD. Resistance was confirmed for all but 24 isolates. These discrepancies were mostly due to contamination with bacterial genera inherently resistant to colistin. ConclusionThis BBMD plate is a high through-put and practical method that could reliably be utilized in a routine microbiology laboratory for colistin susceptibility testing of CRE, A. bauamanii complex and P. aeruginosa.

2132. Multicenter Evaluation of Eravacycline MIC Results for Enterobacteriaceae Using MicroScan Dried Gram-Negative MIC Panels

BackgroundA multicenter study was performed to evaluate the accuracy of eravacycline on a MicroScan Dried Gram-negative MIC (MSDGN) Panel when compared with a frozen CLSI broth microdilution reference panel.MethodsFor efficacy, an evaluation was conducted at three sites by comparing MIC values obtained using the MSDGN to MICs using a CLSI broth microdilution reference panel. A total of 414 Enterobacteriaceae clinical isolates were tested using the turbidity and Prompt®* methods of inoculation. For challenge, 79 Enterobacteriaceae isolates were tested on MSDGN panels at one site. For reproducibility, a subset of 11 organisms was tested on MSDGN panels at each site. MSDGN panels were incubated at 35 ± 2°C and read on the WalkAway System, the autoSCAN-4 instrument, and read visually. Read times for the MSDGN panels were at 16–20 hours. Frozen reference panels, prepared according to CLSI/ISO methodology, were inoculated using the turbidity inoculation method. All frozen reference panels were incubated at 35 ± 2°C and read visually. Frozen reference panels were read at 16–20 hours. FDA breakpoints (µg/mL) used for interpretation of MIC results were: Enterobacteriaceae ≤ 0.5 S. Potential major and very major errors were calculated using the NS result in place of resistant (R).ResultsWhen compared with frozen reference panel results, essential and categorical agreements for isolates tested in the Efficacy and Challenge are as follows (see table). Reproducibility among the three sites were greater than 95% for all read methods for both the turbidity and Prompt inoculation methods.ConclusionThis multicenter study showed that eravacycline MIC results for Enterobacteriaceae obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels using FDA interpretive criteria. * PROMPT® is a registered trademark of 3M Company, St. Paul, MN USA. Beckman Coulter, the stylized logo and the Beckman Coulter product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the United States and other countries. Xerava™ (Eravacycline) is a registered trademark of Tetraphase Pharmaceuticals, Inc. Disclosures All authors: No reported disclosures.

2131. Multicenter Evaluation of Meropenem/Vaborbactam MIC Results for Enterobacteriaceae Using MicroScan Dried Gram-Negative MIC Panels

BackgroundA multicenter study was performed to evaluate the accuracy of meropenem/vaborbactam on a MicroScan Dried Gram-negative MIC (MSDGN) Panel when compared with a frozen CLSI broth microdilution reference panel.MethodsFor efficacy, an evaluation was conducted at three US sites by comparing MIC values obtained using the MSDGN to MICs using a CLSI broth microdilution reference panel. A total of 560 Enterobacteriaceae clinical isolates were tested using the turbidity and Prompt®* methods of inoculation. For challenge, 95 Enterobacteriaceae isolates were tested on MSDGN panels at one site. For reproducibility, a subset of 14 organisms was tested on MSDGN panels at each site. MSDGN panels were incubated at 35 ± 2°C and read on the WalkAway System, the autoSCAN-4 instrument, and read visually. Read times for the MSDGN panels were at 16–20 hours. Frozen reference panels, prepared according to CLSI/ISO methodology, were inoculated using the turbidity inoculation method. All frozen reference panels were incubated at 35 ± 2°C and read visually. Frozen reference panels were read at 16–20 hours. FDA/CLSI breakpoints (µg/ml) used for interpretation of MIC results were: Enterobacteriaceae ≤ 4/8 S, 8/8 I, and ≥ 16/8 R.ResultsWhen compared with frozen reference panel results, essential and categorical agreements for isolates tested in the Efficacy and Challenge are as follows (see table). Reproducibility among the three sites were greater than 95% for all read methods for both the turbidity and Prompt* inoculation methods.ConclusionThis multicenter study showed that meropenem/vaborbactam MIC results for Enterobacteriaceae obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels using FDA/CLSI interpretive criteria. * PROMPT® is a registered trademark of 3M Company, St. Paul, MN, USA. Beckman Coulter, the stylized logo and the Beckman Coulter product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the United States and other countries. Vabomere® (Meropenem/Vaborbactam) is a registered trademark of Melinta Therapeutics, Inc. Disclosures All authors: No reported disclosures.

Extended-spectrum β-lactamase-producing Proteus mirabilis with multidrug resistance isolated from raw chicken in Singapore: Genotypic and phenotypic analysis.

Proteus mirabilis is ubiquitous in soil and water. It is an important catheter-associated urinary tract pathogen and has reportedly been associated with antimicrobial-resistant infections. This study reports the draft genome of a multidrug-resistant P. mirabilis isolated from raw retail chicken meat in Singapore. The P. mirabilis strain was isolated on BrillianceTM ESBL Agar and was screened for antimicrobial susceptibility against 29 antimicrobial agents using a MicroScan® Neg MIC Panel Type 44. The double-disk synergy test (DDST) was used for confirmation of extended-spectrum β-lactamase (ESBL) production. Genomic DNA from the pure culture isolate was extracted and was sent for sequencing based on Illumina HiSeq 2500 technology. Further bioinformatics analysis was performed using online tools available at the Center for Genomic Epidemiology. Species identification of the isolate was performed by KmerFinder. Antimicrobial susceptibility testing of the isolate showed multidrug resistance to broad-spectrum β-lactams, fluoroquinolones and aminoglycosides, among others. ESBL production was confirmed by the DDST. A total of 29 antimicrobial resistance genes were detected by ResFinder. To the best of our knowledge, this is the first report of the whole-genome sequence of a multidrug-resistant P. mirabilis producing an ESBL from raw chicken meat in Singapore. This indicates that raw meat in Singapore can be a reservoir for drug-resistant pathogens.

Evaluation of MICROANAUT-S Anaerobes MIC broth microdilution panels for antibiotic susceptibility testing of anaerobes

Background Accurate and routine-friendly methods for MIC determination of anaerobes are demanded. Here, we evaluate the performance of a commercially available microdilution panel in comparison to a gradient MIC Strip test. Methods N=163 anaerobes clinical isolates (60 species, 23 genera) were tested with the MICRONAUT-S Anaerobes MIC panel (MERLIN Diagnostika, Germany). The same bacterial suspension was used for the panel inoculum, and for testing by MIC Strips (Liofilchem, Italy). The panels were incubated at 37 °C in anaerobic conditions for ≥24 h, and read visually. In case of no bacterial growth for the growth control, incubation was prolonged to 48-72 h. Results were interpreted according to EUCAST guidelines. Comparison was performed in terms of essential agreement, category agreement and error rates. Results Category agreement with MIC strips resulted overall 95% (from 95.6% to 100%). Essential agreement resulted 91.1% for piperacillin/tazobactam, and 95% for all the otherantibiotics.Overall, n=15 minor errors, n=2 major errors and n=5 very major errors were observed. For doxycycline, tigecycline and moxifloxacin (for which no breakpoints are available), MICRONAUT results diverged for ≤1 dilution fold from MIC Strips results. For most isolates (117/163) the panels were readable after overnight incubation, in 42 cases after 48 h, in 4 cases after 72 h. Conclusions The MICRONAUT-S Anaerobes MIC panels proved to be a reliable microdilution method for antibiotic susceptibility testing of anaerobes, providing results consistent with gradient methodology, with both fast and slow growing species. The ease-of-handling and -result interpretation makes this method suitable for routine implementation.

A Study on the Review of Repair Methods and Repair Materials for the Prevention of Fire spread of Building Exterior Materials

국내의 경우 2018년도에 시행한 가연성 외장재 설치 건축물 현황조사결과 147,559동의 건축물이 이에 해당되는 것으로 조사되었으며, 상층부 및 인접건축물로의 화재확대사례는 연간 약 3,500건, 외장재에서 시작한 화재건수는 연간 약 1,500건 이상 발생하는 등 의정부 화재, 제천스포츠센터 화재와 같은 유사한 화재발생의 위험성이 내포되어 있다. 본 연구에서는 유사한 화재 재발방지를 위해 가연성 외장재가 시공된 건축물의 보수공법에 대해 조사하고 각 각의 보수재료 성능검증을 실시하였다. 보수방법의 경우 기존의 건축물 마감재를 제거한 뒤 보수재료로 보강하는 방법과 기존 마감재를 제거하지 않고 면고르기를 실시한 뒤 보수재료를 부착하는 방법을 제안했다. 또한 드라이비트 및 보수재료로서 방화석고보드, 미네랄 울, 경질우레탄 폼, 세라믹보드, ALC 패널 등 6가지 재료를 대상으로 콘 칼로리미터 시험을 실시하고 해당 재료들에 대한 기초 연소 성능을 조사하였다.In Korea, the results of a field survey on the construction of flammable exterior materials implemented in 2018 revealed that 14 7,559 buildings belong to this category. It was found that the fire spreading cases in upper and adjacent constructions are about 3,500 per year, the fires of starting in flammable exterior material are about 1,500 per year. In this study, we investigated the repair method of buildings constructed by flammable exterior material and conducted performance verification of each repair materials for prevention of similar fire. In the case of the repair method, a method of reinforcing with a repair material after removing the existing building finishing material and a method of attaching the repair material after performing the face finishing are proposed. In addition, we conducted cone calorimeter tests of 6 materials such as fireproof gypsum board, mineral wool, hard urethane foam, cera mic board and ALC panel as dryvit and repairing materials, and investigated basic combustion performance of that materials.

Compound design guidelines for evading the efflux and permeation barriers of Escherichia coli with the oxazolidinone class of antibacterials: Test case for a general approach to improving whole cell Gram-negative activity

Previously we reported the results from an effort to improve Gram-negative antibacterial activity in the oxazolidinone class of antibiotics via a systematic medicinal chemistry campaign focused entirely on C-ring modifications. In that series we set about testing if the efflux and permeation barriers intrinsic to the outer membrane of Escherichia coli could be rationally overcome by designing analogs to reside in specific property limits associated with Gram-negative activity: i) low MW (<400), ii) high polarity (clogD7.4 <1), and iii) zwitterionic character at pH 7.4. Indeed, we observed that only analogs residing within these limits were able to overcome these barriers. Herein we report the results from a parallel effort where we explored structural changes throughout all three rings in the scaffold for the same purpose. Compounds were tested against a diagnostic MIC panel of Escherichia coli and Staphylococcus aureus strains to determine the impact of combining structural modifications in overcoming the OM barriers and in bridging the potency gap between the species. The results demonstrated that distributing the charge-carrying moieties across two rings was also beneficial for avoidance of the outer membrane barriers. Importantly, analysis of the structure-permeation relationship (SPR) obtained from this and the prior study indicated that in addition to MW, polarity, and zwitterionic character, having ≤4 rotatable bonds is also associated with evasion of the OM barriers. These combined results provide the medicinal chemist with a framework and strategy for overcoming the OM barriers in GNB in antibacterial drug discovery efforts.