Effect of Penicillin on the Adherence of Streptococcus sanguis In Vitro and in the Rabbit Model of Endocarditis

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Abstract

The effect of penicillin treatment of Streptococcus sanguis in vitro, on subsequent bacterial density in the bloodstream and on cardiac valves in the rabbit model of endocarditis was studied. As experimental tools for this study, isogenic pairs of S. sanguis differing in resistance to streptomycin or rifampin were prepared by genetic transformation. Rabbits with traumatized heart valves received an intravenous inoculation of penicillin treated (1 μg/ml) and untreated S. sanguis, each marked by resistance to either streptomycin or rifampin. The number of penicillin-treated and untreated bacteria attached to the valvular surfaces was determined by differential counting on streptomycin or rifampin containing media. Penicillin pretreatment reduced cardiac valve colonization 5 min after inoculation (“adherence ratio” × 108 was 4.11 for the control and 3.66 for the penicillin-treated bacteria, P < 0.001). The results were not due to differences in serum killing or bacterial densities in the bloodstream. There was no difference in valvular bacterial densities 24 h after bacterial inoculation (adherence ratio × 108, 7.26 untreated vs. 6.34 penicillin-pretreated, P > 0.10).

Authors

Franklin D. Lowy, Daniel S. Chang, Ellen G. Neuhaus, Diane S. Horne, Alexander Tomasz, Neal H. Steigbigel