Epidemiological typing of Streptococcus pneumoniae from various sources in India & Korea using Box A PCR fingerprinting.

ABSTRACT

BACKGROUND & OBJECTIVES: Epidemiological typing of Streptococcus pneumoniae is necessary to study genetic relatedness among strains. The Box A PCR assay, a good epidemiological tool for high resolution typing of pneumococcal isolates, was used for comparison of strains of S. pneumoniae from Korea, an area of high penicillin resistance and India with low resistance to penicillin. METHODS: The pneumococcal strains from Indian and Korean sources included in the study belonged to serotypes 19F, 23F, 6A & 6B. The penicillin susceptibility of the strains was confirmed by determination of minimum inhibitory concentration values. The strains were then fingerprinted using the Box A PCR protocol and the results were further analysed by Molecular Analyst Software. RESULTS: The Box fingerprinting technique produced sharp, clear and reproducible banding patterns for strains of S. pneumoniae included in the study. There was no similarity between Indian and Korean strains at the genetic level. Among the Korean strains with similar serotypes, the level of similarity varied. Except for one pair (serotype 23F), that showed a level of homology of about 90 per cent, almost all the others showed less than 80 per cent homology. It was also seen that there was a high percentage of homology (> 90% in nasopharyngeal isolates from India belonging to serotype 19F) between isolates from similar source. Comparison of the Indian and Korean isolates of similar serotype showed low homology, except for one cluster of two strains with serotype 6B which showed 84 per cent homology (blood isolates from India and Korea). INTERPRETATION & CONCLUSION: Box A PCR is a highly discriminatory and useful method for typing S. pneumoniae. The results of the study have shown low levels of homology between strains from within India and also between two geographically distinct areas.