ABSTRACT

The rapid increase of polymyxin-resistant MDR K. pneumoniae isolates has become a major global concern. This study aimed to investigate lipid A profiles and metabolomes of PB^S and PB^R MDR K. pneumoniae. Three paired of clinical isolates (Kp AHT 8 [PB MIC 64mg/L] vs AHT 7 [0.25mg/L], Kp AHT 16 [32mg/L] vs AHT 15 [0.5mg/L], and Kp AHT 18 [64mg/L] vs AHT 17 [1mg/L] were examined using liquid chromatography mass spectrometry and differences in the lipid A profiles and metabolomes were identified through multivariate and univariate statistics. The predominate forms of lipid A in these paired isolates were hexa-acylated, and lipid A species from PB^R isolates were mostly modified with 4-amino-4-deoxy-L-arabinose. The metabolomic profiles of PB^S and PB^R isolates were significantly different. In detail, UDP-N-acetyl-D-glucosamine, UDP-N-acetyl-D-mannosaminuronate associated with lipid A biosynthesis were significantly depleted in all PB^R isolates (>1.5 FC, p < 0.05), compared to their parent isolates. The intermediate metabolites in carbohydrate metabolic pathway, particularly pentose phosphate pathway (PPP) and tricarboxylic acid (TCA) cycle, were significantly lower in all PB^R isolates (approximately >1.5 FC, p < 0.05). Most nucleotide metabolites were also lower in abundance in PB^R isolates. Two important metabolites associated with the glycerophospholipid (GPL) metabolism, sn-glycerol-3-phosphate and sn-glycero-3-phosphoethanolamine were significantly lower in abundance in all PB^R isolates (> 2 FC, p < 0.05). Remarkably lower GPL levels were evident in PB^R AHT 16 and AHT 18 (approximately >1.5 FC), compared to their parent isolates, while no significant GLP changes were observed in PB^R Kp AHT 8. This study is the first to reveal that polymyxin resistance causes different metabolism in PB^R MDR K. pneumoniae and provided valuable mechanistic information for the development of rational polymyxin combinations against PB^RK. pneumoniae.