Infections with -Hemolytic Streptococcus Resistant to Lincomycin and Erythromycin and Observations on Zonal-Pattern Resistance to Lincomycin

Abstract

The incidence of group A hemolytic Streptococcus resistant to lincomycin and erythromycin increased markedly during 1971 and 1972 in Alberta and adjacent parts of northern Canada. In 1972, 126 of 9,110 strains of Streptococcus pyogenes (1.38%) isolated from clinical specimens were resistant. Many of the strains showed a zonal pattern of resistance when tested with lincomycin. The zone phenomenon was seen in some tests with clindamycin, to which many of the strains were also resistant. Outbreaks in two communities of infections due to the resistant group A strains were recorded. It was shown by serotyping that many distinct foci of epidemiologically unrelated resistant strains had developed. Among 2,442 strains of group B Streptococcus isolated in the two-year period, 15 (0.6%) were resistant to both antibiotics; 18 of 1,561 group C strains (1.2%) were resistant; and 23 of 1,839 group G strains (1.3%) were resistant. Strains resistant to both erythromycin and lincomycin (including zonally resistant strains) were readily detected by use of a 2-µg erythromycin disk.