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Molecular epidemiology and variants of the multidrug-resistant Streptococcus pneumoniae Spain14-5 international clone among Spanish clinical isolates.

OBJECTIVE
To analyse the molecular structure of several antimicrobial resistance determinants in isolates of the Spain(14)-5 clone to better understand its emergence and spread.


METHODS
The distinct genes and mechanism of resistance to penicillin, erythromycin, clindamycin, tetracycline, chloramphenicol and trimethoprim were studied in an apparently homogeneous group of 117 isolates of the multidrug-resistant Spain(14)-5 major clone isolated in Spain between 1981 and 2004.


RESULTS
Several genotyping techniques such as PFGE, BOX-PCR and multilocus sequence typing (MLST) revealed a high degree of homogeneity among these isolates over time. Nevertheless, distinct variants of the clone could be established according to the restriction fragment length polymorphism (RFLP) patterns of the penicillin-binding protein (pbp) genes and the sequences of the dihydrofolate reductase (dhfr) gene. In addition, an association between the pbp2b RFLP patterns, the ddl alleles identified by MLST and the dhfr alleles was found. The emergence of variants of the Spain(14)-5 clone, which had lost macrolide and tetracycline resistance, while harbouring the ins and xis genes of the Tn916-Tn1545 family of conjugative transposons, was documented. Two different tet(M) alleles were detected in isolates of the clone, one of them with a mosaic structure.


CONCLUSIONS
The finding of different patterns or alleles of the genes responsible for antibiotic resistance among isolates of the Spain(14)-5 clone from different Spanish cities indicates different evolutionary events within isolates of a unique Streptococcus pneumoniae clone.