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Pneumococci resistant to erythromycin
Abstract:
Susceptibility to erythromycin was determined for all pneumococci isolated in one laboratory from clinical specimens between 1969 and 1977. All 4724 isolates examined prior to October 1973 were susceptible to erythromycin. From October 1973 to December 1977, 64 (0.71%) of 8995 pneumococcus isolates were resistant to erythromycin. The resistant strains were isolated from 38 patients living in six widely separated communities in Alberta. The erythromycin-resistant strains were of nine capsular types, including six that often cause bacteremic disease and five for which resistance to erythromycin has not been reported hitherto. Certain strains of type 33 and of type 15 were highly resistant, the minimum inhibitory concentration (MIC) of erythromycin being 2000 microgram/mL; these strains were also highly resistant to lincomycin and clindamycin. Resistance in strains of other types was much lower, the MIC of erythromycin being 0.6 to 20 microgram/mL, and all but one of these strains were susceptible to lincomycin and clindamycin. All the erythromycin-resistant pneumococci were suspectible to penicillin.
Insights
Erythromycin resistance in pneumococci emerged in Alberta after October 1973, affecting 0.71% of isolates. These resistant strains, including novel types, remained susceptible to penicillin.
Area of Science:
- Microbiology
- Infectious Diseases
- Antimicrobial Resistance
Background:
- Streptococcus pneumoniae (pneumococci) are a leading cause of bacterial infections.
- Erythromycin is a crucial antibiotic for treating pneumococcal infections.
- Monitoring antibiotic resistance is vital for public health.
Purpose of the Study:
- To determine the prevalence and characteristics of erythromycin-resistant pneumococci.
- To track the emergence and spread of erythromycin resistance in pneumococci.
- To assess the susceptibility of resistant strains to other antibiotics.
Main Methods:
- Isolation and susceptibility testing of pneumococci from clinical specimens.
- Monitoring erythromycin resistance from 1969 to 1977.
- Characterization of resistant strains, including capsular typing and MIC determination.
- Testing resistance to lincomycin, clindamycin, and penicillin.
Main Results:
- Erythromycin resistance emerged in pneumococci isolates after October 1973.
- 0.71% (64/8995) of isolates were resistant between October 1973 and December 1977.
- Resistant strains were found in multiple communities and represented nine capsular types.
- Some strains showed high-level resistance (MIC 2000 µg/mL) to erythromycin, lincomycin, and clindamycin.
- All resistant strains remained susceptible to penicillin.
Conclusions:
- Erythromycin resistance in pneumococci emerged in Alberta during the study period.
- The emergence of resistance involved diverse capsular types, some previously unreported.
- High-level resistance to erythromycin, lincomycin, and clindamycin was observed in specific strains.
- Penicillin remains an effective treatment option for erythromycin-resistant pneumococcal infections.