Virulence factors of bacteraemic Escherichia coli with particular reference to production of cytotoxic necrotising factor (CNF) by P-fimbriate strains.
Thirty-seven strains of Escherichia coli isolated from bacteraemia and 40 faecal strains isolated from healthy individuals were O serogrouped and investigated for the production of colicins, haemolysin (Hly), cytotoxic necrotising factor (CNF), lethal activity for mice, the expression of P fimbriae, mannose-resistant (MRHA) and mannose-sensitive (MSHA) haemagglutination, and relative cell surface hydrophobicity. Virulence factors significantly associated with bacteraemic strains were: serogroups O2, O4, O6, O7, O8 and O75 (54% versus 10%, p less than 0.001), production of Hly (32% versus 8%, p less than 0.02) and CNF (38% versus 10%, p less than 0.01), expression of P fimbriae (27% versus 5%, p less than 0.02), MRHA types III, IVa and IVb (51% versus 8%, p less than 0.001), and possession of a moderate cell surface hydrophobic charge (35% versus 13%, p less than 0.05). Virulence factors were strongly associated with strains expressing defined MRHA types. Thus, all strains belonging to MRHA types III and IVa were toxigenic, whereas only 11% of strains belonging to MRHA types IVb, V or VI were toxigenic (p less than 0.001). Virulence factors were concentrated in strains belonging to O serogroups usually found in E. coli that cause extra-intestinal infections, especially in strains of O4 and O6 groups. The most interesting result of this study was that all 12 P-fimbriate strains expressed the MRHA type IVa and 11 of them synthesised CNF.
Blanco
J
J
Departamento de Microbiología y Parasitología, Facultad de Veterinaria, Universidad de Santiago, Lugo, Spain.
Alonso
M P
MP
González
E A
EA
Blanco
M
M
Garabal
J I
JI
D000293:Adolescent; D000328:Adult; D000368:Aged; D001427:Bacterial Toxins / Q000032:analysis / Q000096:biosynthesis*; D002648:Child; D002675:Child, Preschool; D003603:Cytotoxins / Q000032:analysis / Q000096:biosynthesis*; D004768:Enterotoxins / Q000096:biosynthesis; D004926:Escherichia coli / Q000145:classification / Q000302:isolation & purification / Q000472:pathogenicity*; D029968:Escherichia coli Proteins; D005243:Feces / Q000382:microbiology; D010861:Fimbriae, Bacterial / Q000378:metabolism*; D006386:Hemagglutination Tests; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008358:Mannose / Q000494:pharmacology; D008875:Middle Aged; D018805:Sepsis / Q000382:microbiology*; D012703:Serotyping; D022622:Shiga Toxin 1; D013045:Species Specificity; D014774:Virulence
D001427:Bacterial Toxins; D003603:Cytotoxins; D004768:Enterotoxins; D029968:Escherichia coli Proteins; D022622:Shiga Toxin 1; C034151:heat stable toxin (E coli); C060296:cytotoxic necrotizing factor type 1; C027538:heat-labile enterotoxin, E coli; D008358:Mannose