Klebsiella pneumoniae is mostly responsible for nosocomial infections in immunocompromised patients, but can also cause severe community-acquired infections. The clinical scenario has worsened in recent years, with the global emergence and dissemination of K. pneumoniae strains resistant to carbapenems (CR-Kp). The major carbapenem resistance mechanism among CR-Kp is the production of carbapenemase, i.e. KPC. The most successful and widespread disseminated clonal group (CG) of KPC-producing K. pneumoniae (KPC-Kp) is CG258, which can be further differentiated in two clades characterized by the production of distinct capsular polysaccharides. Infections caused by KPC-Kp strains are challenging in healthcare settings, where they spread rapidly and are associated with significant morbidity and mortality .
Genotyping of the cps207-2 gene cluster with the wzc-based method showed that it is a new K-type, while the wzi-based method associated it to the already known K41 K-type.
Therefore, the primary structure of the capsular polysaccharide produced by K. pneumoniae KK207-2 , a member of the clade I of CG258, was determined by using GLC-MS of appropriate carbohydrate derivatives, ESI-MS of both partial hydrolysis and Smith degradation derived oligosaccharides, and NMR spectroscopy of oligosaccharides, lithium degraded CPS, and the native and de-O-acetylated CPS. The results showed that the repeating unit of KK207-2 capsular polysaccharide (Fig. 1a) is a novel one among the Klebsiella K-types. Moreover, each glycosyltransferase in the sequenced cps207-2 gene cluster was assigned to the corresponding catalyzed reaction (Fig. 1b, 1c).
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