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Capsular Serotyping of Streptococcus pneumoniae Using the Quellung Reaction
Published on: February 24, 2014
Serotype Distribution and Multi Locus Sequence Type (MLST) of Erythromycin-Resistant Streptococcus Pneumoniae
Mohammad Azarsa1, Mehrdad Mosadegh2, Soheila Habibi Ghahfarokhi2
1Department of Microbiology, Khoy University of Medical Sciences, Khoy, Iran.
Background:
The number of erythromycin-resistant Streptococcus pneumoniae has significantly increased around the world. The present study aimed to determine the serotype distribution and molecular epidemiology of the erythromycin-resistant Streptococcus pneumoniae (ERSP) isolated from patients with invasive disease.
Methods:
A total of 44 Streptococcus pneumoniae isolates were tested for susceptibility to several antimicrobial agents. Additionally, the polymerase chain reaction (PCR) was applied to evaluate ERSP isolates in terms of the presence of erythromycin resistance genes (e.g., ermB and mefA). The isolates were serotyped using the sequential multiplex-PCR method, and molecular epidemiology was assessed through the multilocus sequence typing (MLST) analysis.
Results:
The results represented multidrug resistance (MDR) in approximately half of the pneumococcal isolates. Among 22 ERSP isolates, 20 (90.9%) and 12 (56%) ones contained ermB and mefA, respectively. Further, 14 (31.8%), 3 (22.7%), and 19A (18.1%) were the common serotypes among the isolates. No significant correlation was observed between serotypes and erythromycin resistance genes. Furthermore, the MLST results revealed 18 different sequence types (STs), the top ones of which were ST3130 (3 isolates) and ST166 (3 isolates). Population genetic analysis disclosed that CC63 (32%), CC156 (18%), and CC320 (18%) were identified as the predominant clonal complexes.
Conclusions:
The ERSP isolates exhibited high genetic diversity. The large frequency of MDR isolates suggests the emergence of high resistant strains, as well as the need to implement vaccination in the immunization schedule of Iran. These accumulating evidences indicate that 13-valent pneumococcal conjugate vaccines provided higher serotype coverage in the ERSP isolates.
Insights
Erythromycin-resistant Streptococcus pneumoniae (ERSP) isolates show high genetic diversity and multidrug resistance. Vaccination strategies, particularly using 13-valent pneumococcal conjugate vaccines, are recommended to address emerging resistant strains.
Area of Science:
- Microbiology
- Epidemiology
- Genetics
Background:
- Increasing global prevalence of erythromycin-resistant Streptococcus pneumoniae (ERSP).
- Need to understand serotype distribution and molecular epidemiology of ERSP in invasive diseases.
Purpose of the Study:
- Determine serotype distribution of ERSP.
- Investigate molecular epidemiology of ERSP.
- Identify erythromycin resistance genes in ERSP.
Main Methods:
- Antimicrobial susceptibility testing on 44 Streptococcus pneumoniae isolates.
- Polymerase chain reaction (PCR) for ermB and mefA genes.
- Serotyping via multiplex-PCR and molecular epidemiology using multilocus sequence typing (MLST).
Main Results:
- Multidrug resistance observed in approximately 50% of isolates.
- ermB and mefA genes detected in 90.9% and 56% of ERSP isolates, respectively.
- Common serotypes included 14, 3, and 19A; 18 sequence types (STs) identified, with CC63, CC156, and CC320 being predominant clonal complexes.
Conclusions:
- ERSP isolates display significant genetic diversity and multidrug resistance.
- Emergence of highly resistant strains necessitates updated vaccination strategies.
- 13-valent pneumococcal conjugate vaccines show promising serotype coverage for ERSP.
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