Comparative in Vitro Activities of Omadacycline, Eravacycline and Tigecycline Against Non-ESBL- Producing ESBL- Producing and Carbapenem- Resistant Isolates of K. Pneumoniae

Abstract

Introduction. Extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae and carbapenem-resistant Enterobacte-riaceae are characterized by the World Health Organization as pathogens for which new antibiotics are urgently needed. Oma-dacycline and eravacycline are two novel antibacterials within the tetracycline class.Gap Statement. There are limited data regarding the comparison of the activities of omadacycline, eravacycline and tigecycline against K. pneumoniae isolates with different antimicrobial susceptibility profiles.Aim. Our objective was to compare the in vitro activities of omadacycline, eravacycline and tigecycline against a collection of K. pneumoniae isolates, including non- ESBL-producing, ESBL-producing and carbapenem-resistant strains.Methodology. Ninety-four K. pneumoniae isolates, including 30 non- ESBL-producing, 30 ESBL-producing and 34 carbapenem-resistant (22 carrying blaOXA-48, 12 carrying blaNDM) strains were included in the study. ESBL and carbapenemase genes were detected by conventional PCR. Omadacycline, eravacycline and tigecycline MICs were determined by the gradient diffusion method and interpreted using US Food and Drug Administration (FDA)-defined breakpoints.Results. Overall, the percentage of tigecycline-susceptible strains (97.9 %) was higher than the percentage of omadacyline-susceptible (75.5 %) and eravacycline-susceptible (72.3 %) strains. The omadacycline and eravacycline susceptibility rates were 83.3 % among non- ESBL-producing isolates and 66.7 % among ESBL-producing isolates. The most common ESBL gene detected was blaCTX-M (90 %), followed by blaTEM (50 %) and blaSHV (50 %). The omadacycline and eravacycline susceptibility rate among isolates carrying blaTEM was 33.3 %, whereas it was 100 % among isolates that do not carry blaTEM. The omadacycline and eravacycline susceptibility rates among carbapenem-resistant isolates were 76.5 and 67.6 %, respectively. The omadacycline susceptibility rates among blaOXA-48-positive and blaNDM-positive isolates were 77.3 and 75.0 %, respectively. The eravacycline susceptibility rates among blaOXA-48-positive and blaNDM- positive isolates were 68.2 and 66.7 %, respectively. One carbapenem-resistant isolate was intermediate and one ESBL-producing isolate was resistant to tigecycline.Conclusion. Overall, tigecycline was the most active tetracycline against isolates. Omadacycline and eravacycline showed excellent activity against ESBL-producing K. pneumoniae isolates that do not carry blaTEM. Omadacycline showed reasonable activity against carbapenem-resistant K. pneumoniae isolates carrying blaOXA-48 or blaNDM.