In Vitro Activity of Antifungal Drugs Against Trichophyton rubrum and Trichophyton mentagrophytes spp. by E-Test Method and Non-supplemented Mueller–Hinton Agar Plates

Abstract Background Cefiderocol (CFDC) is a new siderophore cephalosporin with potent in vitro activity against a broad range of Gram-negative (GN) pathogens, including carbapenem-nonsusceptible (Carb-NS) strains. We evaluated the in vitro activity of CFDC and comparator agents against recent clinical Carb-NS GN respiratory isolates collected from North America and Europe as part of the multi-national SIDERO-WT surveillance program. Methods A total of 2831 Carb-NS GN respiratory isolates collected from 2014 to 2017 were tested centrally (IHMA, Inc., Schaumburg, IL). Minimum inhibitory concentrations (MIC) were determined for CFDC, cefepime (FEP), ceftazidime–avibactam (CZA), ceftolozane-tazobactam (C/T), ciprofloxacin (CIP), colistin (CST), and meropenem (MEM) by broth microdilution and interpreted according to the 2018 CLSI guidelines. CFDC MICs were tested in iron-depleted cation-adjusted Mueller–Hinton broth, and interpreted according to the 2018 CLSI provisional breakpoints. Carb-NS strains were defined as MEM MIC of ≥2 µg/mL for Enterobacteriaceae (ENB) and of ≥4 µg/mL for nonfermenters (NF). Results CFDC exhibited predictable in vitro activity against 2807 clinically relevant Carb-NS GN isolates (214 ENB, 1086 A. baumannii complex, 693 P. aeruginosa, 794 S. maltophilia, and 20 Burkholderia cepacia) isolated from respiratory infections. CFDC was the most active agent against Carb-NS ENB with 97.7% susceptibility followed by 78.0% CZA, 59.4% CST, and 16.4% CIP. Against Carb-NS A. baumannii complex, CFDC demonstrated 94% susceptibility vs. 83.7% for CST. CFDC was the most active agent against Carb-NS P. aeruginosa with 99.9% susceptibility followed by 97.8% CST, 77.6% C/T, and 77.5% CZA. 99.7% of S. maltophilia and 100% of B. cepacia isolates had CFDC MICs of ≤4 µg/mL. The MIC90s of tested compounds for clinically relevant pathogens are shown in the table. Conclusion In a multinational collection of Carb-NS GN respiratory isolates, CFDC demonstrated potent in vitro activity with MIC90 of ≤4 µg/mL for all clinically relevant ENB and NF. These findings suggest that CFDC can be a potential option for the treatment of respiratory infections caused by Carb-NS ENB, A. baumannii complex, P. aeruginosa, S. maltophilia, and B. cepacia. Disclosures All authors: No reported disclosures.

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1595. Comparative In Vitro Activity of Imipenem–Relebactam Against Drug-Resistant Gram-Negative Isolates from Pediatric Patients

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz360.1459 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S582-S582

Author(s):

Dithi Banerjee ◽

Christopher J Harrison ◽

Morgan Pence ◽

Rangaraj Selvarangan

Keyword(s):

Klebsiella Oxytoca ◽

Multidrug Resistant ◽

Vitro Activity ◽

In Vitro Activity ◽

Gram Negative ◽

Mueller Hinton ◽

Thermo Fisher Scientific ◽

Spectrum Activity ◽

Fisher Scientific

Abstract Background Drug resistance in Gram-negative bacteria is of particular concern in children. Relebactam, a novel diazabicyclooctane inhibitor, coupled with imipenem has broad-spectrum activity against β-lactamase producing organisms. Here, we compare the in vitro activity of imipenem-relebactam to 10 standard comparator drugs against resistant Gram-negative isolates from two US pediatric hospitals. Methods We tested 100 isolates (50 per site) from pediatric clinical specimens tested during 2015–2017. All isolates were extended-spectrum cephalosporin-resistant (ESC-R); more than half were multidrug resistant (67%). Selected ESC-R isolates included Escherichia coli (90), Klebsiella pneumoniae (8), Klebsiella oxytoca (1), and Enterobacter cloacae (1) that were resistant or intermediate to ≥1 cephalosporins and/or aztreonam. A 0.5 McFarland suspension was prepared from colonies grown on blood agar plates (Thermo Scientific) at 35 ± 1°C for 18–24 hours. A final inoculum of 5 × 105 CFU/mL was prepared in Mueller–Hinton broth. Sensititre plates (Thermo Fisher Scientific) containing graded concentrations of imipenem/relebactam and 10 comparator drugs were inoculated and incubated at 35 ± 1°C for 18–24 hours. The minimum inhibitory concentration (MIC) was determined using the Sensititre Vizion system (Thermo Fisher Scientific) and endpoints were interpreted using CLSI (2019) breakpoint criteria, with the exception of colistin (EUCAST 2019). Results Selected ESC-R isolates had high rates of resistance to cephalosporins (64%–97%), aztreonam (80%), and levofloxacin (61%). All isolates were susceptible to imipenem/relebactam, imipenem and meropenem (MIC, ≤1 μg/mL for all). The imipenem/relebactam MIC50 (0.06 μg/mL) and MIC90 (0.12 μg/mL) values for ESC-R isolates were within one dilution of MICs of imipenem alone (0.12 μg/mL and 0.25 μg/mL). Among the comparators, colistin, amikacin, and piperacillin/tazobactam demonstrated comparable activities with 100%, 99%, and 94% susceptibilities, respectively. Conclusion Meropenem, imipenem alone and in combination with relebactam exhibited 100% susceptibilities against ESC-R Enterobacteriaceae isolated from pediatric specimens, demonstrating the high potency of carbapenems. Disclosures All authors: No reported disclosures.

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