The Journal of Medical Microbiology, Vol 27, Issue 1 17-22, Copyright © 1988 by Society for General Microbiology
Penicillin tolerance among oral streptococci
W. P. Holbrook, D. Olafsdottir, H. B. Magnusson and E. Benediktsdottir
Faculty of Odontology, University of Iceland, Reykjavik.
Penicillin tolerance was elicited in 18 of 46 strains of viridans
streptococci isolated from the mouths of 19 of 20 healthy subjects and in
31 of 54 consecutive blood-culture isolates of streptococci. Enterococci
and Streptococcus sanguis were the organisms most frequently tolerant but
the property was also common among isolates of S. mutans, S. mitior and
Lancefield Group G streptococci. Pneumococci and S. salivarius were rarely
tolerant. When incubated with penicillin at 5 x MIC in batch or continuous
cultures, both tolerant and sensitive strains of oral streptococci declined
in number less rapidly than S. pyogenes. However, combinations of
penicillin and gentamicin killed tolerant and sensitive oral streptococci.
