IDENTIFICATION OF 3 MAJOR CLONES OF MULTIPLY ANTIBIOTIC-RESISTANT STREPTOCOCCUS-PNEUMONIAE IN TAIWANESE HOSPITALS BY MULTILOCUS SEQUENCE TYPING

In this paper we demonstrate the advantages of a new molecular typing procedure, multilocus sequence typing, for the unambiguous characteriz ation of penicillin-resistant pneumococci. The sequences of similar to 450-bp fragments of seven housekeeping genes were determined for 74 p enicillin-resistant Taiwanese isolates of Streptococcus pneumoniae (MI C of penicillin > 0.5 mu g/ml). The combination of alleles at the seve n loci defined an allelic profile for each strain, and a dendrogram, b ased on the pairwise mismatches in allelic profiles, grouped 86% of th e isolates into one of three penicillin-resistant clones for which the MICs of penicillin were 1 to 2 mu g/ml. Isolates within each clone ha d identical alleles at all seven loci or differed at only a single loc us, and the fingerprints of their pbp1A, pbp2B, and php2X genes were u niform. Isolates of the Taiwan-19F clone and the Taiwan-23F clone were resistant to penicillin, tetracycline, and erythromycin but were susc eptible to chloramphenicol. A second serotype 23F clone and serotype 1 9F variants of this clone were resistant to penicillin, tetracycline, chloramphenicol, and, in some cases, erythromycin, Comparisons of the allelic profiles of the three major clones with those of reference iso lates of the known penicillin-resistant clones showed that the Taiwan- 19F and Taiwan-23F clones were previously undescribed, whereas the sec ond serotype 23F clone was indistinguishable from the Spanish multidru g-resistant serotype 23F clone. Single isolates of the Spanish penicil lin-resistant serotype 9V clone and the Spanish multidrug-resistant se rotype 6B clone were also identified in the collection.