The K95 capsular polysaccharide produced by Acinetobacter baumannii isolate MAR18-2212 includes a rarely encountered 3-acetamido-3,6-dideoxy-D-glucose (D-Qui3NAc) sugar

The whole genome sequence from Acinetobacter baumannii MAR18-2212, an isolate recovered in 2018 from a human respiratory tract specimen in Russia, was obtained and found to carry KL95 at the capsular polysaccharide (CPS) biosynthesis K locus. KL95 includes a module of four genes (rmlB-rmlA-qdtE-qdtB) predicting synthesis of 3-acetamido-3,6-dideoxy-d-glucose (d-Quip3NAc). The structure of the K95 CPS isolated from MAR18-2212 was established using ¹H and ¹³C NMR spectroscopy, including two-dimensional ¹Н,¹Н COSY, ¹Н,¹Н TOCSY, ¹Н,¹Н ROESY, ¹Н,¹³C HSQC, and ¹Н,¹³C HMBC experiments, and was confirmed by Smith degradation. K95 is composed of branched hexasaccharide K-units containing three d-GalpNAc residues, two d-Galp residues and one residue of d-Quip3NAc. Assignment of the enzymes encoded by KL95 established the role of rmlB-rmlA-qdtE-qdtB in the synthesis of d-Quip3NAc. Five encoded glycosyltransferases and the Wzy polymerase were also assigned to the glycosidic linkages in K95.