Cross Resistance Between Lincomycin and Erythromycin in Viridans Streptococci

Twenty-four (67%) of 36 patients who received either lincomycin (L) or erythromycin (E) had oropharyngeal viridans streptococcal populations, appreciable proportions of which were resistant to one or both antibiotics. Viridans streptococci resistant to both antibiotics were demonstrated in 22 of the aforementioned 24 patients. Studies of single colony isolates from the individuals with doubly resistant strains showed that a majority (15 of the 22 patients) carried streptococci resistant to 100 µg of erythromycin and 10 µg of lincomycin per milliliter. Clinical implications of these results are discussed.