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Infect. Immun., Dec 1995, 4764-4769, Vol 63, No. 12
S Takahashi, Y Nagano, N Nagano, O Hayashi, F Taguchi and Y Okuwaki
Type III group B streptococci (GBS) can be subdivided into three subtypes,
RDP III-1, III-2, and III-3, on the basis of numerical analysis of HindIII
restriction endonuclease digestion patterns (HindIII RDP) with their
chromosomal DNAs. In the present study, the effect of C5a on
opsonophagocytic killing of a representative strain from each RDP type was
investigated by using a novel optical method for determining
opsonophagocytic killing, and the effect of C5a-ase treatment of C5a on
opsonophagocytic killing was also investigated. Pre- stimulation of
polymorphonuclear leukocytes (PMNs) with C5a significantly increased
opsonophagocytic killing of all three strains. The increase in killing was
abolished by pretreating the C5a with GBS that express C5a-ase, a treatment
that also destroyed the chemoattractant activity of the C5a. The kinetics
of killing of the RDP III-2 strain differed from those of the other two
strains. The survival of the RDP III-2 bacteria continued to decline over
the entire 60-min incubation of the opsonophagocytic assay when PMNs were
prestimulated with C5a or with C5a that had been inactivated with GBS
C5a-ase (dC5a). In contrast, killing of the RDP III-1 and III-3 strains
almost ceased after 20 or 60 min when PMNs were prestimulated with dC5a or
C5a, respectively. A difference in bacterial killing between the III-2
strain and the III-1 and III-3 strains therefore became increasingly
apparent with prolonged incubation time. The percentage of bacteria
surviving in the extracellular fluid was approximately the same as the
percentages of bacteria surviving in both intracellular and extracellular
locations when PMNs were prestimulated with either C5a or dC5a. These data
imply that the majority of bacterial killing occurred following
phagocytosis and suggest that the enhanced killing of GBS following
prestimulation of PMNs with C5a resulted from increased ingestion of the
bacteria.
Copyright © 1995, American Society for Microbiology
Role of C5a-ase in group B streptococcal resistance to opsonophagocytic killing
Department of Microbiology, Joshi-Eiyoh University, Saitama, Japan.
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