Penicillin Sensitivity of Streptococci Isolated from Root Canal Infections and the Normal Mouth

Abstract

Penicillin sensitivity tests were made on streptococci isolated from normal mouths and infected root canals. Tests were made in either beef infusion broth, or tryptose broth, to which was added 0.2% glucose and 5% ascitic fluid. Broths containing 0.03 U., 0.5 U., and 8 U. of penicillin per ml. in 3 separate tubes were inoculated with 0.2 ml. of an 18 to 24-hour broth culture of the organism being tested. Negative and positive controls were also made. Results of the tests were read after 18-24 hrs. incubation at 37.5 C. 89% of the strains of Streptococcus viridans from both infected root canals, and salivas of normal mouths were sensitive to penicillin. The anhemolytic and hemolytic streptococci from infected root canals were resistant to penicillin while the same types of streptococci isolated from saliva were sensitive to penicillin. The results of the expts. lead one to doubt that the anhemolytic and hemolytic streptococci from infected root canals are the same as those found predominating in the mouth.