In Vitro Activity of Eravacycline and comparator antimicrobials *Presenting Author: against 143 recent strains of Bacteroides species Diane M. Citron 1209 [email protected] Diane M. Citron, Kerin L. Tyrrell, and Ellie J. C. Goldstein R. M. Alden Research Laboratory, Culver City, CA 90230 Introduction Results Discussion Eravacycline (ERV) is a novel, fully-synthetic fluorocycline antibiotic in Resistance to tetracycline has become common among Bacteroides species and Table 1. In vitro activity (µg/ml) of eravacycline and comparators development for the treatment of serious infections, including those caused by the MIC90 for all of the strains was >32 µg/ml. Eravacycline was four- to eight- multidrug-resistant (MDR) pathogens. ERV recently completed phase 3 clinical against Bacteroides species. All results for the quality control fold more active than tigecycline against these strains with MIC at 1–4 µg/ml. strains were within acceptable CLSI ranges (4). 90 development for the treatment of complicated intra-abdominal infections (cIAI) Eravacycline was active against several strains that showed resistance to and is in phase 3 clinical development for complicated urinary tract infections piperacillin-tazobactam and meropenem. (cUTI), including pyelonephritis. Organism (no.) / Agent Range MIC MIC 50 90 Resistance to clindamycin was also common and all of these strains were ERV has potent activity against a broad range of Gram-positive, Gram- B. caccae (10) Eravacycline 0.25–4 0.5 2 susceptible to eravacycline. negative and anaerobic pathogens. Like other tetracyclines, ERV inhibits protein Tigecycline 0.25–16 4 16 Metronidazole resistance was not encountered in this group of isolates, although, synthesis by binding to the 30S ribosomal subunit. However, ERV retains activity Tetracycline 16–>32 32 >32 while still rare, it appears to be occurring with increased frequency (5). in the presence of common tetracycline-specific acquired resistance mechanisms Piperacillin-tazobactam 2–8 4 8 Meropenem 0.125–>32 0.25 0.25 (i.e. efflux, ribosomal protection) (1). Further, eravacycline is active against Clindamycin ≤0.06–>32 2 >32 MDR isolates, including those expressing extended spectrum β-lactamases and Metronidazole 0.25–2 0.5 1 carbapenemases and mechanisms conferring resistance to other classes of B. fragilis (25) Eravacycline 0.06–4 0.25 2 Conclusions antibiotics, including colistin-resistance (2). Tigecycline 0.25–8 2 8 To further explore its in vitro activity, we tested eravacycline against 143 Tetracycline 0.25–>32 32 >32 recent (within 3 years) clinical isolates of Bacteroides and included in the study Piperacillin-tazobactam ≤0.06–>128 0.25 1 Meropenem ≤0.06–>32 0.125 0.5 Eravacycline shows excellent activity against this important group of anaerobes tetracycline, tigecycline and other drugs frequently used to treat serious Clindamycin 0.125–>32 0.5 >32 infections. Metronidazole 0.5–2 1 1 that are often resistant to commonly used antimicrobials, and is a promising new B. ovatus (33) addition to our antimicrobial agent armamentarium. Eravacycline 0.06–16 1 4 Tigecycline 0.125–32 8 32 Eravacycline has completed two phase III clinical trials showing non-inferiority Tetracycline 0.25–>32 32 >32 to ertapenem and meropenem in the treatment of cIAI, where anaerobes are major MIC (1 mg/ml) <0.125 –1 2 >256 Rifaximin Total (n) n % n % n % Current Study Summary 394 365 92.64 2 0.51 27 6.85 By REA Type: BI 140 118 84.29 22 15.71 CF 6 6 100.00 G 32 32 100.00 J 28 27 96.43 1 3.57 K 13 10 76.92 1 7.69 2 15.38 Y 32 32 100.00 Non-specific 138 135 97.83 1 0.72 2 1.45 other 5 5 100.00 Piperacillin-tazobactam ≤0.06–16 4 8 causative pathogens (6). Meropenem ≤0.06–16 0.5 4 Methods Clindamycin 0.25–>32 >32 >32 Metronidazole 0.25–2 1 2 B. thetaiotaomicron (25) Eravacycline 0.125–4 0.5 4 Tigecycline 0.125–32 0.5 16 References The antimicrobial agents were reconstituted according to the manufacturers' Tetracycline 0.25–>32 32 >32 instructions or the guidelines in the CLSI M11-A8 document (3). Stock solutions Piperacillin-tazobactam 4–128 8 16 were prepared and stored at −70ºC. On the day of the test, two-fold dilutions of Meropenem 0.25–4 0.5 1 1. Xiao XY, Hunt DK, Zhou J, Clark RB, Dunwoody N, Fyfe C, Grossman TH, O'Brien WJ, Plamondon L, Ronn Clindamycin 2–>32 32 >32 M, Sun C, Zhang WY, Sutcliffe JA. 2012. Fluorocyclines. 1. 7-fluoro-9-pyrrolidinoacetamido-6-demethyl-6- the antimicrobial agents were prepared and added to molten Brucella agar to Metronidazole 0.25–2 1 1 deoxytetracycline: a potent, broad spectrum antibacterial agent. J Med Chem 55:597-605. prepare the plates. Piperacillin-tazobactam was tested at concentrations ranging Bacteroides spp. (25)a 2. Zhanel GG, Cheung D, Adam H, Zelenitsky S, Golden A, Schweizer F, Gorityala B, Lagace-Wiens PR, Walkty Eravacycline 0.06–4 0.125 1 A, Gin AS, Hoban DJ, Karlowsky JA. 2016. Review of Eravacycline, a Novel Fluorocycline Antibacterial Agent. from128 µg/ml to 0.06 µg/ml with tazobactam constant at 4 µg/ml, eravacycline Drugs 76:567-88. from 32 to 0.03 µg/ml and the remainder of the antibiotics from 32 to 0.06 µg/ml Tigecycline 0.25–16 0.5 4 Tetracycline 0.25–>32 16 >32 3. Clinical Laboratory Standards Institute. 2015. Methods for antimicrobial susceptibility testing of anaerobic bacteria; approved standard-8th edition. CLSI document M11-A8. CLSI, Wayne, Pa. (4). Piperacillin-tazobactam 0.125–8 4 8 4. Clinical Laboratory Standards Institute. 2017. Performance standards for antimicrobial susceptibility testing; 27th The isolates were subcultured from frozen stock by transferring twice on Meropenem 0.125–2 0.5 1 informational supplement. CLSI document M100-S27. CLSI, Wayne, Pa. Clindamycin ≤0.06–>32 0.5 >32 Brucella agar. On the day of the test, isolates were suspended in Brucella broth to 5. Merchan C, Parajuli S, Siegfried J, Scipione MR, Dubrovskaya Y, Rahimian J. 2016. Multidrug-Resistant Metronidazole 0.25–2 1 2 Bacteroides fragilis Bacteremia in a US Resident: An Emerging Challenge. Case Rep Infect Dis 2016:3607125. b equal the turbidity of the 0.5 McFarland standard and applied to the drug- Parabacteroides spp. (25) 6. Solomkin J, Evans D, Slepavicius A, Lee P, Marsh A, Tsai L, Sutcliffe JA, Horn P. 2017. Assessing the Efficacy containing plates using the Steers replicating device that delivers approximately 2 Eravacycline 0.125–4 0.5 1 and Safety of Eravacycline vs Ertapenem in Complicated Intra-abdominal Infections in the Investigating Gram- Tigecycline 0.5–16 1 8 Negative Infections Treated With Eravacycline (IGNITE 1) Trial: A Randomized Clinical Trial. JAMA Surg µl/spot for a final concentration of 105 CFU/spot. Drug-free plates were included Tetracycline 0.5–>32 16 >32 152:224-232. as growth controls. Piperacillin-tazobactam 1–16 4 8 Meropenem 0.125–4 0.25 1 After incubation in the anaerobic chamber at 36ºC, the plates were examined Clindamycin ≤0.06–>32 4 >32 for growth. The MIC was defined as the concentration of drug that completely Metronidazole 0.25–2 1 2 inhibited growth or resulted in a marked reduction from the drug-free growth Acknowledgment control. a Bacteroides vulgatus (22), B. dorei (3). QC strains included Bacteroides fragilis ATCC 25285 and B. thetaiotaomicron b Parabacteroides distasonis (22), P. goldsteinii (3). ATCC 29741. This study was sponsored by a grant from Tetraphase Pharmaceuticals, Inc. IDWEEK 2017 ♦ October 4–8 ♦ San Diego, CA, USA .