title: Relationship between cytotoxic necrotizing factor production and serotype in hemolytic Escherichia coli.
abstract: We examined the relationship between serotype and cytotoxic necrotizing factor (CNF) production in 123 hemolytic strains of Escherichia coli isolated from both stools and extraintestinal infections. Of 76 strains producing both hemolysin (Hly) and CNF, 66 (87%) belonged to one of six serogroups (O2, O4, O6, O22, O75, and O83). In contrast, 47 E. coli strains producing Hly only belonged to 21 different O serogroups, and only 2 of these (O6 and O18ac) were widely represented. Generally, CNF-positive and CNF-negative hemolytic isolates were assigned to different O serogroups, with the exception of O6, often present in both categories of isolates. Serogroups O4 and O18ac were significantly more prevalent among strains from extraintestinal infections than among those from stools. In contrast, the Hly-positive, CNF-negative isolates, belonging to numerous less common serogroups, were hardly ever isolated from extraintestinal infections. Serological typing further confirmed that hemolytic isolates of E. coli may grossly be divided into two main populations on the basis of the ability to produce CNF. Examination of hemolytic E. coli for this property may also be useful in achieving a more detailed characterization of pathogenic clones.
authors.affiliation: Laboratorio di Ultrastructure, Istituto Superiore di Sanità, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Caprioli
authors.forename: V
authors.initials: V
authors.lastname: Falbo
authors.forename: F M
authors.initials: FM
authors.lastname: Ruggeri
authors.forename: F
authors.initials: F
authors.lastname: Minelli
authors.forename: I
authors.initials: I
authors.lastname: Orskov
authors.forename: G
authors.initials: G
authors.lastname: Donelli
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000032:analysis; D001427:Bacterial Toxins / Q000096:biosynthesis*; D002648:Child; D003603:Cytotoxins / Q000096:biosynthesis*; D004926:Escherichia coli / Q000145:classification / Q000378:metabolism / Q000472:pathogenicity*; D029968:Escherichia coli Proteins; D005243:Feces / Q000382:microbiology; D006460:Hemolysin Proteins / Q000096:biosynthesis*; D006801:Humans; D012703:Serotyping; D014774:Virulence
chemical_list: D001425:Bacterial Outer Membrane Proteins; D001427:Bacterial Toxins; D003603:Cytotoxins; D029968:Escherichia coli Proteins; D006460:Hemolysin Proteins; C060296:cytotoxic necrotizing factor type 1