Chien-Hao Tseng1, Jan-Fang Cheng2, Shi-Yu Chen3, Wen-Huei Chen3, Zhi-Yuan Shi4, Yu-Hui Lin1, Che-An Tsai1, Shih-Ping Lin1, Yung-Chun Chen5, Yu-Chia Lin6, Yao-Ting Huang7, Po-Yu Liu8. 1. Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan. 2. Department of Energy, Joint Genome Institute, Walnut Creek, CA, USA. 3. Department of Computer Science and Information Engineering, National Chung Cheng University, Chia-Yi, Taiwan. 4. Infection Control Center, Taichung Veterans General Hospital, Taichung, Taiwan. 5. Department of Critical Care Medicine, Taichung Veterans General Hospital, Taichung, Taiwan. 6. Division of Infectious Diseases, Chiayi Branch, Taichung Veterans General Hospital, Chia-Yi, 600, Taiwan. 7. Department of Computer Science and Information Engineering, National Chung Cheng University, Chia-Yi, Taiwan. Electronic address: ythuang@cs.ccu.edu.tw. 8. Division of Infectious Diseases, Department of Internal Medicine, Taichung Veterans General Hospital, Taichung, Taiwan; Rong Hsing Research Center for Translational Medicine, National Chung Hsing University, Taichung, Taiwan; Ph.D. Program in Translational Medicine, National Chung Hsing University, Taichung, Taiwan. Electronic address: liupoyu@gmail.com.
Abstract
BACKGROUND: Shewanella algae is a zoonotic pathogen that poses a serious health threat to immunocompromised hosts. Treatment of S. algae infections is challenging due to the pathogen's intrinsic resistance to a variety of β-lactam antibiotics. Therapeutic options have become further limited by the emergence of quinolone-resistant strains. Currently, there are few studies concerning the genetic and molecular mechanisms underlying acquired quinolones resistance in S. algae. qnrA was once proposed as the candidate gene related to quinolones resistance in S. algae. However, recent studies demonstrated qnrA are highly conservative and does not confer resistance to quinolones in S. algae. METHODS: A total of 27 non-duplicated isolates of S. algae strains were examined. MICs of ciprofloxacin were determined using Vitek 2. Whole genome sequencing was performed using MiSeq platform. Comprehensive Antibiotic Resistance Database and ResFinder were used for annotation of quinolones resistance genes. Multiple sequence alignment by EMBOSS Clustal Omega were used to identified mutation in quinolone resistance-determining regions. To investigation of the alteration of protein structure induced by mutation, in silico molecular docking studies was conducted using Accryl Discovery studio visualizer. RESULTS: All S. algae harbored the quinolone-resistance associated genes (qnrA, gyrA, gyrB, parC, and parE) regardless its resistance to ciprofloxacin. Comparison of these genomes identified a nonsynonymous mutation (S83V) in chromosome-encoded gyrase subunits (GyrA) in quinolone-resistant strain. We found this mutation disrupts the water-metal ion bridge, reduces the affinity of the quinolone-enzyme complex for the metal ions and therefore decrease the capability of quinolones to stabilize cleavage complexes. CONCLUSIONS: The study provides insight into the quinolone resistance mechanisms in S. algae, which would be helpful for the evolution of antibiotic resistance in this bacterium.
BACKGROUND: Shewanella algae is a zoonotic pathogen that poses a serious health threat to immunocompromised hosts. Treatment of S. algae infections is challenging due to the pathogen's intrinsic resistance to a variety of β-lactam antibiotics. Therapeutic options have become further limited by the emergence of quinolone-resistant strains. Currently, there are few studies concerning the genetic and molecular mechanisms underlying acquired quinolones resistance in S. algae. qnrA was once proposed as the candidate gene related to quinolones resistance in S. algae. However, recent studies demonstrated qnrA are highly conservative and does not confer resistance to quinolones in S. algae. METHODS: A total of 27 non-duplicated isolates of S. algae strains were examined. MICs of ciprofloxacin were determined using Vitek 2. Whole genome sequencing was performed using MiSeq platform. Comprehensive Antibiotic Resistance Database and ResFinder were used for annotation of quinolones resistance genes. Multiple sequence alignment by EMBOSS Clustal Omega were used to identified mutation in quinolone resistance-determining regions. To investigation of the alteration of protein structure induced by mutation, in silico molecular docking studies was conducted using Accryl Discovery studio visualizer. RESULTS: All S. algae harbored the quinolone-resistance associated genes (qnrA, gyrA, gyrB, parC, and parE) regardless its resistance to ciprofloxacin. Comparison of these genomes identified a nonsynonymous mutation (S83V) in chromosome-encoded gyrase subunits (GyrA) in quinolone-resistant strain. We found this mutation disrupts the water-metal ion bridge, reduces the affinity of the quinolone-enzyme complex for the metal ions and therefore decrease the capability of quinolones to stabilize cleavage complexes. CONCLUSIONS: The study provides insight into the quinolone resistance mechanisms in S. algae, which would be helpful for the evolution of antibiotic resistance in this bacterium.