Members of the alpha hemolytic (viridans) group of streptococci, hereinafter referred to as alpha streptococci, are the commonest cause of subacute bacterial endocarditis and are also normal inhabitants of the human throat and gastrointestinal tract. Consequently, they are inevitably exposed to penicillin each time it is used in the treatment of any infection. It would seem, therefore, that, irrespective of the mechanisms involved, conditions favorable to the emergence of drug-resistant strains of alpha streptococci have been continuously operative for the past decade. In fact, the tentative acceptance of the idea that alpha streptococci have become less susceptible to penicillin is responsible in part for the present practice of using large doses of penicillin in the treatment of bacterial endocarditis.1 Indeed, the apparently widespread loss of effectiveness of penicillin with respect to the micrococci has presented the grave question of whether this drug is losing its effectiveness in other infections.
Berntsen CA. UNALTERED PENICILLIN SUSCEPTIBILITY OF STREPTOCOCCISTUDY OF ALPHA HEMOLYTIC STREPTOCOCCI CAUSING ENDOCARDITIS, 1944 TO 1954. JAMA. 1955;157(4):331-333. doi:10.1001/jama.1955.02950210027008