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High rate of tetracycline resistance in Streptococcus pyogenes in Iran: an epidemiological study
1Department of Infectious Diseases and Medical Microbiology, University of Lund, Lund, Sweden.
Abstract:
Streptococcus pyogenes, a major human pathogen, is still considered susceptible to beta-lactams, but for other relevant antibiotics, highly variable resistance rates have been reported. Since no data were available from Iran, we tested 1,335 throat isolates from two different regions of the country for their antibiotic susceptibilities and, for comparison, a collection of 80 strains isolated from 1989 to 1991. Erythromycin resistance was uncommon (0.6%), whereas an overall high rate of tetracycline resistance was found, increasing between 1989-1991 and 1995-1997 from 23 to 42%. The tetracycline-resistant strains belonged to more than 10 different T types, the majority being types 4, 11, and B3264. By conventional M typing of 406 tetracycline-resistant isolates, more than 20 different M types were found. Approximately 50% of the strains were nontypeable by T agglutination as well as serological M typing; however, by genotyping by a combined PCR-capture-enzyme-linked immunosorbent assay, many of these strains were successfully emm typed. We conclude that the high rate of tetracycline resistance among Iranian S. pyogenes isolates is due to multiclonal dissemination of resistance within the streptococcal population rather than epidemic spread of single clones.
Insights
High tetracycline resistance in Streptococcus pyogenes was observed in Iran, increasing significantly from 1989-1997. This resistance is attributed to diverse bacterial clones, not a single dominant strain.
Area of Science:
- Microbiology
- Infectious Diseases
- Public Health
Background:
- Streptococcus pyogenes is a significant human pathogen with variable antibiotic resistance rates.
- Limited data existed on antibiotic resistance patterns of S. pyogenes in Iran.
- Tetracycline resistance is a growing concern in bacterial pathogens globally.
Purpose of the Study:
- To determine the antibiotic susceptibility patterns of S. pyogenes isolates from Iran.
- To investigate the prevalence and trends of tetracycline resistance in Iranian S. pyogenes.
- To characterize the genetic diversity of tetracycline-resistant S. pyogenes strains.
Main Methods:
- Antibiotic susceptibility testing was performed on 1,335 throat isolates and 80 historical strains.
- Conventional T typing and M typing were used for strain characterization.
- Genotyping using a combined PCR-capture-enzyme-linked immunosorbent assay was employed for emm typing.
Main Results:
- Erythromycin resistance was rare (0.6%).
- Tetracycline resistance rates increased from 23% (1989-1991) to 42% (1995-1997).
- Tetracycline resistance was associated with multiple T and M types, indicating multiclonal dissemination.
Conclusions:
- The high rate of tetracycline resistance in Iranian S. pyogenes is driven by the spread of resistance across various bacterial clones.
- Genotyping methods improved the characterization of non-typeable strains.
- Continuous surveillance of antibiotic resistance in S. pyogenes is crucial.