The presence of K54 capsular polysaccharide increases the pathogenicity of Escherichia coli in vivo.
Proven isogenic capsule-negative derivatives (CP9.29, CP9.108, CP9.137, CP9.171, CP9.443, and CP9.C56), generated from an O4/K54/H5 blood isolate (CP9) of Escherichia coli by IS50L::phoA (TnphoA)-mediated transposon mutagenesis, were used to assess the function of a non-K1 capsule in three animal models. Intraperitoneal injection of CP9 (K54+) into mice resulted in an LD50 at 24 h of 5.5 x 10(6) cfu compared with LD50s of 2.6 x 10(7) cfu and 3.8 x 10(7) cfu for CP9.108 (K54-) and CP9.C56 (K54-) (P < .001). CP9 was cleared less rapidly from the bloodstream, after intravascular injection, than was CP9.108 (P < .01). In the rat granuloma pouch model, CP9 could proliferate from starting inocula as low as 1.0 x 10(3) cfu/mL. In contrast, capsule-deficient derivatives underwent transient log kills with starting inocula as high as 1.0 x 10(6) cfu/mL. Because proven isogenic strains were evaluated, a clear contribution of the K54 capsular polysaccharide to virulence in vivo is demonstrated.
Russo
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Bacterial Pathogenesis Unit, National Institute of Allergy and Infectious Disease, National Institutes of Health, Bethesda, Maryland 20892.
Liang
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Cross
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D000818:Animals; D000942:Antigens, Bacterial / Q000378:metabolism / Q000502:physiology*; D000954:Antigens, Surface / Q000378:metabolism / Q000502:physiology*; D004251:DNA Transposable Elements / Q000276:immunology; D004195:Disease Models, Animal; D004926:Escherichia coli / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D004927:Escherichia coli Infections / Q000382:microbiology*; D005260:Female; D006801:Humans; D007122:Immunoelectrophoresis; D007928:Lethal Dose 50; D008099:Liver / Q000382:microbiology; D008297:Male; D008657:Metabolic Clearance Rate; D051379:Mice; D008813:Mice, Inbred ICR; D016254:Mutagenesis, Insertional; D051381:Rats; D017208:Rats, Wistar; D013154:Spleen / Q000382:microbiology; D013997:Time Factors; D014774:Virulence / Q000235:genetics
D000942:Antigens, Bacterial; D000954:Antigens, Surface; D004251:DNA Transposable Elements; C030659:K antigens