Puyuan Li1, Yong Huang2, Lan Yu3, Yannan Liu1, Wenkai Niu1, Dayang Zou4, Huiying Liu1, Jing Zheng1, Xiuyun Yin5, Jing Yuan6, Xin Yuan7, Changqing Bai8. 1. Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China. 2. State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, Beijing 100071, China. 3. Department of Gastroenterology, Navy General Hospital, 6 Fucheng Road, Beijing 100048, China. 4. Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China. 5. Department of Clinical Laboratory, 307th Hospital of PLA, Beijing 100071, China. 6. Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing 100071, China. Electronic address: yuanjing6216@163.com. 7. Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China. Electronic address: xinyuannatile@sina.com. 8. Department of Respiratory and Critical Care Diseases, 307th Hospital of PLA, Beijing 100071, China. Electronic address: mlp1604@sina.com.
Abstract
OBJECTIVES: Heteroresistance is a phenomenon in which there are various responses to antibiotics from bacterial cells within the same population. Here, we isolated and characterised an imipenem heteroresistant Acinetobacter baumannii strain (HRAB-85). METHODS: The genome of strain HRAB-85 was completely sequenced and analysed to understand its antibiotic resistance mechanisms. Population analysis and multilocus sequence typing were performed. RESULTS: Subpopulations grew in the presence of imipenem at concentrations of up to 64μg/mL, and the strain was found to belong to ST208. The total length of strain HRAB-85 was 4,098,585bp with a GC content of 39.98%. The genome harboured at least four insertion sequences: the common ISAba1, ISAba22, ISAba24, and newly reported ISAba26. Additionally, 19 antibiotic-resistance genes against eight classes of antimicrobial agents were found, and 11 genomic islands (GIs) were identified. Among them, GI3, GI10, and GI11 contained many ISs and antibiotic-resistance determinants. CONCLUSIONS: The existence of imipenem heteroresistant phenotypes in A. baumannii was substantiated in this hospital, and imipenem pressure, which could induce imipenem-heteroresistant subpopulations, may select for highly resistant strains. The complete genome sequencing and bioinformatics analysis of HRAB-85 could improve our understanding of the epidemiology and resistance mechanisms of carbapenem-heteroresistant A. baumannii.
OBJECTIVES: Heteroresistance is a phenomenon in which there are various responses to antibiotics from bacterial cells within the same population. Here, we isolated and characterised an imipenem heteroresistant Acinetobacter baumannii strain (HRAB-85). METHODS: The genome of strain HRAB-85 was completely sequenced and analysed to understand its antibiotic resistance mechanisms. Population analysis and multilocus sequence typing were performed. RESULTS: Subpopulations grew in the presence of imipenem at concentrations of up to 64μg/mL, and the strain was found to belong to ST208. The total length of strain HRAB-85 was 4,098,585bp with a GC content of 39.98%. The genome harboured at least four insertion sequences: the common ISAba1, ISAba22, ISAba24, and newly reported ISAba26. Additionally, 19 antibiotic-resistance genes against eight classes of antimicrobial agents were found, and 11 genomic islands (GIs) were identified. Among them, GI3, GI10, and GI11 contained many ISs and antibiotic-resistance determinants. CONCLUSIONS: The existence of imipenem heteroresistant phenotypes in A. baumannii was substantiated in this hospital, and imipenem pressure, which could induce imipenem-heteroresistant subpopulations, may select for highly resistant strains. The complete genome sequencing and bioinformatics analysis of HRAB-85 could improve our understanding of the epidemiology and resistance mechanisms of carbapenem-heteroresistant A. baumannii.