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Infect. Immun., Apr 1995, 1263-1269, Vol 63, No. 4
TA Russo, G Sharma, CR Brown and AA Campagnari
The O-specific antigen in extraintestinal isolates of Escherichia coli is
believed to be an important virulence factor. To assess its role in the
pathogenic process, proven isogenic derivatives with either a complete
(CP921) or nearly complete (CP920) deficiency of the O4 antigen were
obtained by TnphoA'1-mediated transposon mutagenesis of an O4/K54/H5 blood
isolate (CP9). By utilizing a previously reported isogenic K54
capsule-deficient derivative (CP9.137), additional isogenic derivatives
deficient in both the K54 capsular antigen and either all (CP923) or nearly
all (CP922) of the O4 antigen were also constructed. These strains and
their wild-type parent were evaluated in vitro for serum sensitivity and in
vivo by intraperitoneal challenge of outbred mice. The complete or nearly
complete loss of the O4 antigen (CP920 and CP921) resulted in only a minor
increase in serum sensitivity. In contrast, CP9.137 had a significant
increase in serum sensitivity, and CP922 and CP923 were extremely serum
sensitive. When tested in vivo, the complete or nearly complete loss of the
O4 antigen resulted in a small but significant increase (P < or = 0.05),
not the expected decrease, in virulence compared with its wild-type parent.
In contrast, CP9.137 and CP922 were significantly less virulent (P < or
= 0.05). These studies do not exclude a role for the O4 antigen moiety of
lipopolysaccharide in the pathogenesis of extraintestinal E. coli
infection; however, they demonstrate that the O4 antigen plays only a minor
role in serum resistance in vitro and that its loss does not diminish and
perhaps enhances the virulence of CP9 in vivo after intraperitoneal
challenge.
Copyright © 1995, American Society for Microbiology
Loss of the O4 antigen moiety from the lipopolysaccharide of an extraintestinal isolate of Escherichia coli has only minor effects on serum sensitivity and virulence in vivo
Department of Medicine, State University of New York at Buffalo 14215.
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