title: In vivo evolution of tigecycline-non-susceptible Klebsiella pneumoniae strains in patients: relationship between virulence and resistance.
abstract: Tigecycline resistance among Klebsiella pneumoniae isolates has been increasingly reported. We aimed to investigate the relationship among in vivo acquisition of tigecycline resistance in K. pneumoniae clinical isolates, the underlying molecular mechanisms and bacterial virulence. Clinical isolates of K. pneumoniae from the same patient in a medical centre in Taiwan that were initially tigecycline-susceptible (TS) and then became tigecycline-non-susceptible (TNS) were identified. Clinical data were collected. All isolates were subjected to MIC determination by Etest, pulsed-field gel electrophoresis (PFGE), multilocus sequence typing (MLST), virulence factor determination, and growth rate and mouse lethality studies. Quantitative RT-PCR was performed to analyse acrA, oqxA, ramA and rarA expressions. The presence of mutations in acrR, ramR, oqxR and rpsJ were analysed by DNA sequencing. Five isogenic paired isolates were determined by PFGE fingerprinting. TNS K. pneumoniae appeared after treatment with a variety of antibiotics among patients infected with TS K. pneumoniae. TNS K. pneumoniae isolates were associated with upregulation of RamA and/or RarA and the corresponding AcrAB and/or OqxAB efflux pump(s), respectively. Various mutations in negative regulatory genes (ramR and oqxR) accounted for overexpression of ramA and rarA, respectively. Three of the five paired isolates showed similar growth rates and virulence between TS and TNS isolates. Two TNS K. pneumoniae strains belonging to capsular types K1 and K20 retained their high virulence. In conclusion, some TNS K. pneumoniae strains derived from TS isolates did not compromise their virulence. Dissemination of these highly pathogenic and resistant strains would be of major concern in the future.
authors: Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; Institute of Emergency and Critical Care Medicine, National Yang-Ming University, Taipei, Taiwan. Electronic address: ytlin8@vghtpe.gov.tw.
authors: Yi-Tsung
authors: YT
authors: Lin
authors: Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Yi-Wei
authors: YW
authors: Huang
authors: Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Hsin-Hui
authors: HH
authors: Huang
authors: Department of Biotechnology and Laboratory Science in Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Tsuey-Ching
authors: TC
authors: Yang
authors: Division of Infectious Diseases, Department of Medicine, Taipei Veterans General Hospital, Taipei, Taiwan; School of Medicine, National Yang-Ming University, Taipei, Taiwan.
authors: Fu-Der
authors: FD
authors: Wang
authors: Division of Infectious Diseases, Sijhih Cathy General Hospital, New Taipei City, Taiwan.
authors: Chang-Phone
authors: CP
authors: Fung
mesh_terms: D000368:Aged; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D004195:Disease Models, Animal; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D006801:Humans; D007710:Klebsiella Infections / Q000188:drug therapy / Q000382:microbiology*; D007711:Klebsiella pneumoniae / Q000145:classification / Q000187:drug effects* / Q000302:isolation & purification / Q000472:pathogenicity*; D008297:Male; D008810:Mice, Inbred C57BL; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D008911:Minocycline / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D058885:Multilocus Sequence Typing; D016019:Survival Analysis; D013624:Taiwan; D000078304:Tigecycline; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D037521:Virulence Factors; D000078304:Tigecycline; D008911:Minocycline
keywords: Antimicrobial resistance; Efflux pump; Klebsiella pneumoniae; Tigecycline; Virulence