Abstract
Abstract We have examined the effect of the antibiotic resistance plasmid, R100, on the complement (C) mediated killing of Escherichia coli K-12 strains. The viabilities, in dilute normal rabbit serum (NRS), of 5 such strains were compared with the viabilities of the same strains harboring R100. For 1 strain, J6-2, we also measured the effect of R100 on viability in normal human serum (NHS) and in guinea pig serum (GPS); in NRS, NHS,and GPS devoid of classical C pathway activity; and in NHS devoid of alternative pathway activity. Finally, we compared the depletion of individual complement components in sera exposed to J6-2 and J6-2 harboring R100. Our results demonstrate that 1) R100 renders E. coli K-12 resistant to killing by NRS, NHS, and GPS; 2) the level of resistance, which ranges from 30- to 10,000-fold, is strain dependent and serum dependent; 3) R100 inhibits killing by both the classical and alternative C pathway. Resistance appears to involve a disruption on the C pathway subsequent to the activation of C5.
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