Stefanie Gerson1, Jennifer Nowak1, Esther Zander1, Julia Ertel1,2, Yurong Wen3,4, Oleg Krut1,5, Harald Seifert1,2, Paul G Higgins1,2. 1. Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstraße 19-21, 50935 Cologne, Germany. 2. German Center for Infection Research (DZIF), partner site Bonn-Cologne, Cologne, Germany. 3. Center for Translational Medicine, The Key Laboratory of Biomedical Information Engineering of Ministry of Education, School of Life Science and Technology, Xi'an Jiaotong University, Xi'an 710061, China. 4. Department of Biochemistry and Molecular Biology, The Key Laboratory of Environment and Genes Related to Disease of Ministry of Education, Health Science Center, Xi'an Jiaotong University, Xi'an 710061, China. 5. Paul-Ehrlich-Institute, Federal Institute for Vaccines and Biomedicines, Paul-Ehrlich-Straße 51-59, 63225 Langen, Germany.
Abstract
Objectives: To investigate the mechanisms of tigecycline resistance in isogenic Acinetobacter baumannii isolate pairs as well as 65 unique clinical A. baumannii isolates obtained during the MagicBullet clinical trial from Greece, Italy and Spain. Methods: A. baumannii isolates were subjected to WGS and the regulatory genes of resistance-nodulation-cell division (RND)-type efflux pumps were analysed. MICs were determined by agar dilution and the expression of RND-type efflux pumps was measured by semi-quantitative RT-PCR. Results: In isolate pairs, disruption of adeS or adeN by ISs increased adeB or adeJ expression and conferred increased resistance to at least three antimicrobial classes, respectively. The insertion of ISAba1 in adeN was observed in more than 30% of tested isolates and was the most prevalent IS. Furthermore, the insertion of ISAba125 and ISAba27 into adeN was observed for the first time in A. baumannii isolates. Besides ISs, several different mutations were observed in adeN (e.g. deletions and premature stop codons), all of which led to increased tigecycline MICs. Moreover, several amino acid substitutions were detected in AdeRS, AdeN and AdeL. Of note, the substitutions D21V, G25S and D26N in AdeR were found in multiple sequences and suggest a mutational hotspot. Conclusions: This study provides an insight into the different mechanisms associated with tigecycline resistance using a genomic approach and points out the importance of considering adeRS and adeN as markers for tigecycline-resistant A. baumannii isolates.
Objectives: To investigate the mechanisms of tigecycline resistance in isogenic Acinetobacter baumannii isolate pairs as well as 65 unique clinical A. baumannii isolates obtained during the MagicBullet clinical trial from Greece, Italy and Spain. Methods:A. baumannii isolates were subjected to WGS and the regulatory genes of resistance-nodulation-cell division (RND)-type efflux pumps were analysed. MICs were determined by agar dilution and the expression of RND-type efflux pumps was measured by semi-quantitative RT-PCR. Results: In isolate pairs, disruption of adeS or adeN by ISs increased adeB or adeJ expression and conferred increased resistance to at least three antimicrobial classes, respectively. The insertion of ISAba1 in adeN was observed in more than 30% of tested isolates and was the most prevalent IS. Furthermore, the insertion of ISAba125 and ISAba27 into adeN was observed for the first time in A. baumannii isolates. Besides ISs, several different mutations were observed in adeN (e.g. deletions and premature stop codons), all of which led to increased tigecycline MICs. Moreover, several amino acid substitutions were detected in AdeRS, AdeN and AdeL. Of note, the substitutions D21V, G25S and D26N in AdeR were found in multiple sequences and suggest a mutational hotspot. Conclusions: This study provides an insight into the different mechanisms associated with tigecycline resistance using a genomic approach and points out the importance of considering adeRS and adeN as markers for tigecycline-resistant A. baumannii isolates.
Authors: K Lucaßen; S Gerson; K Xanthopoulou; J Wille; T Wille; H Seifert; P G Higgins Journal: Antimicrob Agents Chemother Date: 2021-07-16 Impact factor: 5.191
Authors: Jaime E Zlamal; Semen A Leyn; Mallika Iyer; Marinela L Elane; Nicholas A Wong; James W Wamsley; Maarten Vercruysse; Fernando Garcia-Alcalde; Andrei L Osterman Journal: mBio Date: 2021-06-22 Impact factor: 7.867