Study of Streptococcus pneumoniae serotype 19A blood isolates from Thailand by enterobacterial repetitive intergenic consensus (ERIC)-PCR typing

Streptococcus pneumoniae serotype 19A is frequently isolated worldwide. In this study, the clonal relationships among 62 isolates from different patients from 21 hospitals between 2008 and 2018 were characterized using enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). The different band patterns that appeared upon agarose gel electrophoresis were used to construct an unweighted pair group method with an arithmetic mean (UPGMA) dendrogram. There were 23 different ERIC types (E1-E23). The most prevalent type was E9, accounting for 19.36% of all isolates, followed by E6 at 16.13%, E5 at 11.30%, and 13 ERIC types present in only one isolate or at 1.61% each. Using an additional study to determine the clonal relationships, we compared our ERIC-PCR results to the corresponding multilocus sequence types (MLSTs) from our recent study with the same 62 S. pneumoniae serotype 19A isolates. The results showed there were 20 different MLST types and that ERIC-PCR was comparable to MLST as a valuable complementary tool for the investigation of S. pneumoniae serotype 19A isolates. Furthermore, ERIC-PCR is very fast, affordable, and easy to perform compared to MLST. However, there is less concordance between these two methods. These results suggest a high diversity of different ERIC-PCR and MLST patterns. Overall, the combination of results from both methods can add greater discrimination and complementary information for the differentiation of S. pneumoniae strains in Thailand.