title: Isolation and characterization of cytotoxic, aggregative Citrobacter freundii.
abstract: Citrobacter freundii is an infrequent but established cause of diarrhea in humans. However, little is known of its genetic diversity and potential for virulence. We analyzed 26 isolates, including 12 from human diarrheal patients, 2 from human fecal samples of unknown diarrheal status, and 12 from animals, insects, and other sources. Pulsed field gel electrophoresis using XbaI allowed us to divide the 26 isolates into 20 pulse types, while multi-locus sequence typing using 7 housekeeping genes allowed us to divide the 26 isolates into 6 sequence types (STs) with the majority belonging to 4 STs. We analyzed adhesion and cytotoxicity to HEp-2 cells in these 26 strains. All were found to adhere to HEp-2 cells. One strain, CF74, which had been isolated from a goat, showed the strongest aggregative adhesion pattern. Lactate dehydrogenase (LDH) released from HEp-2 cells was evaluated as a measure of cytotoxicity, averaging 7.46%. Strain CF74 induced the highest level of LDH, 24.3%, and caused >50% cell rounding, detachment, and death. We named strain CF74 "cytotoxic and aggregative C. freundii." Genome sequencing of CF74 revealed that it had acquired 7 genomic islands, including 2 fimbriae islands and a type VI secretion system island, all of which are potential virulence factors. Our results show that aggregative adherence and cytotoxicity play an important role in the pathogenesis of C. freundii.
authors.affiliation: State Key Laboratory for Infectious Disease Prevention and Control, National Institute for Communicable Disease Control and Prevention, Chinese Center for Disease Control and Prevention, Beijing, China.
authors.forename: Li
authors.initials: L
authors.lastname: Bai
authors.forename: Shengli
authors.initials: S
authors.lastname: Xia
authors.forename: Ruiting
authors.initials: R
authors.lastname: Lan
authors.forename: Liyun
authors.initials: L
authors.lastname: Liu
authors.forename: Changyun
authors.initials: C
authors.lastname: Ye
authors.forename: Yiting
authors.initials: Y
authors.lastname: Wang
authors.forename: Dong
authors.initials: D
authors.lastname: Jin
authors.forename: Zhigang
authors.initials: Z
authors.lastname: Cui
authors.forename: Huaiqi
authors.initials: H
authors.lastname: Jing
authors.forename: Yanwen
authors.initials: Y
authors.lastname: Xiong
authors.forename: Xuemei
authors.initials: X
authors.lastname: Bai
authors.forename: Hui
authors.initials: H
authors.lastname: Sun
authors.forename: Jin
authors.initials: J
authors.lastname: Zhang
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.forename: Jianguo
authors.initials: J
authors.lastname: Xu
mesh_terms: D000818:Animals; D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002448:Cell Adhesion; D002460:Cell Line; D016971:Citrobacter freundii / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism / Q000472:pathogenicity*; D016000:Cluster Analysis; D003967:Diarrhea / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D005243:Feces / Q000382:microbiology; D006041:Goats; D006801:Humans; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D037521:Virulence Factors; D007770:L-Lactate Dehydrogenase