Mahmoud A. Ghannoum1,2 Janet Herrada1, Ahmed Gamal1,2, Lisa Long1,2, Thomas S. McCormick2, and Ayman Grada3 1University Hospital Cleveland Medical Center, Center for Medical Mycology, 2Case Western Reserve University, Department of Dermatology and 3R&D and Medical Affairs, Almirall US, Malvern, PA, USA *Corresponding author: Mahmoud Ghannoum, PhD, MBA, FAAM, FIDSA Table 1. Susceptibility Testing Results for sarecycline and minocycline Against Healthy Gut Microbes (µg/mL, n=28) • In this study, sarecycline demonstrated less activity against 79% of the microorganisms normally found in a healthy human gut, when compared to minocycline • Sarecycline is a narrow-spectrum antibiotic • Our data suggests that sarecycline may have less impact on disrupting commensal and symbiotic organisms residing in the gut and is less likely to promote dysbiosis. In vivo evaluation is ongoing • Sarecycline showed significantly less activity against E. coli compared to minocycline at all time points (P- values <0.05) • Sarecycline was significantly less active against C. tropicalis compared to minocycline at 20 and 22 hours post exposure (P-values <0.05) • Time kill study shows that with longer time exposure sarecycline has less inhibitory activity against Candida • Sarecycline showed significantly less activity against L. paracasei compared to minocycline after 24 hours of growth (P-value of 0.002) • Sarecycline showed significantly less activity against B. adolescentis compared to minocycline after 48 hours of growth (P-value of 0.042) Objective Evaluate the effect of sarecycline, a narrow spectrum antibiotic, compared to minocycline, a broad-spectrum antibiotic, against a panel of microorganisms that reflect the diversity of the gut microbiome using in vitro minimum inhibitory concentration (MIC) testing and time- kill kinetic assays. 1. Chose representative bacterial and fungal strains found in the Healthy Gut 2. Perform Antimicrobial Susceptibility Testing Minimum inhibitory concentration (MIC) testing was performed using modified Clinical Laboratory Standards Institute methodology 3. Establish Growth Curves E. coli and Candida tropicalis were selected as representative of aerobic bacteria and yeast, respectively. While Lactobacillus paracasei and Bifidobacterium adolescentis were selected as representative of anaerobic bacteria that colonize the gut. Methods Compared to minocycline, sarecycline showed significantly less antimicrobial activity against: • 10 of 12 isolates from the Bacteroidetes phylum • 3 out of 4 isolates from Actinobacteria phylum • 5 of 7 isolates from the Firmicutes phylum, E. coli • Propionibacterium freudenreichii (≥ 3 dilutions) • Sarecycline also showed less activity against 2 Candida species This study was supported by Almirall, LLC, Malvern, PA Higher fold difference indicates lower sarecycline activity 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0 2 4 6 20 22 A ve ra ge  O D  ± SD Hours Post Inoculation Escherichia coli Sarecycline Minocycline Growth Control * * * * * 0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0 2 4 6 20 22 A ve ra ge  O D  ± SD Hours Post Inoculation Candida tropicalis Sarecycline Minocycline Growth Control ** 4 4.5 5 5.5 6 6.5 7 0 2 4 8 24 A ve ra ge  L og  C FU  ± SD Hours Post Inoculation Lactobacillus paracesi Sarecycline Minocycline Growth Control * 4 4.5 5 5.5 6 6.5 7 7.5 8 0 2 4 8 24 48 A ve ra ge  L og  C FU  ± SD Hours Post Inoculation Bifidobacterium adolescentis Sarecycline Minocycline Growth Control * Figure 1. and 2. Effect of sarecycline vs. minocycline on the growth rates of Aerobic Microorganisms Figure 3. and 4. Effect of sarecycline vs. minocycline on the growth rates of Anaerobic Microorganisms Sarecycline Demonstrated Reduced Activity Against Representative Bacterial and Fungal Microflora Commonly Present in the Human Gastrointestinal Tract Phylum Genus Species Sarecycline Minocycline Fold Difference in MIC Actinobacteria Bifidobacterium Bifidobacterium adolescentis 1 1 1 Actinobacteria Collinsella Collinsella aerofaciens 1 0.5 2 Actinobacteria Eggerthella Eggerthella lenta 1 0.5 2 Actinobacteria Actinomycetales Propionibacterium freudenreichii 8 1 8 Bacteroidetes Bacteroides Bacteroides caccae 8 0.25 32 Bacteroidetes Bacteroides Bacteroides fragilis enterotoxigenic (ET) 2 4 0.5 Bacteroidetes Bacteroides Bacteroides fragilis nontoxigenic 1 0.25 4 Bacteroidetes Bacteroides Bacteroides ovatus 0.5 0.5 1 Bacteroidetes Bacteroides Bacteroides thetaiotaomicron 0.25 0.125 2 Bacteroidetes Bacteroides Bacteroides uniformis 2 0.5 4 Bacteroidetes Bacteroides Bacteroides vulgatus 0.125 0.016 7.8 Bacteroidetes Bacteroides Bacteroides xylanisolvens 1 0.25 4 Bacteroidetes Bacteroides Bifidobacterium subtile Biavati >8 8 Not Determined Bacteroidetes Odoribacter Odoribacter splanchnicus 8 4 2 Bacteroidetes Parabacteroides Parabacteroides distasonis 8 2 4 Bacteroidetes Parabacteroides Parabacteroides merdae 0.06 0.016 3.8 Firmicutes Blautia Blautia obeum 1 0.5 2 Firmicutes Clostridium Clostridium bolteae 4 0.5 8 Firmicutes Clostridium Clostridium ramosum 2 0.06 33.3 Firmicutes Clostridium Clostridium saccharolyticum 2 2 1 Firmicutes Dorea Dorea formicigenerans 0.25 0.06 4.2 Firmicutes Eubacterium Eubacterium eligens >8 4 Not Determined Firmicutes Lactobacillus Lactobacillus paracasei 1 0.25 4 Proteobacteria Escherichia Escherichia coli IAI1 16 8 2 Sac fungi Candida Candida albicans 32 16 2 Sac fungi Candida Candida glabrata 32 32 1 Sac fungi Candida Candida parapsilosis 32 16 2 Sac fungi Candida Candida tropicalis 16 16 1