The role of iron uptake systems in the pathogenesis of colistin-resistant hypervirulent K. pneumoniae infections

Here we proposed the hypothesis that hypervirulent colistin resistant K.pneumoniae (ColR-Kp) exhibit high number of virulence factors and have enhanced survival capacity against neutrophil activity.\n\nWe studied virulence genes of ColR-Kp isolates and neutrophil response in 142 patients with invasive infections.\n\nThe patients infected with hypervirulent ST101 and ST395 ColR-Kp had higher 30-day mortality (58%, p=0.005 and 75%, p=0.003, respectively. The yersiniabactin biosynthesis gene (ybtS) and ferric uptake operon associated gene (kfu) were significantly higher in ST101 (99%, p=<0.001) and in ST395 (94%, p<0.012). Being in ICU (OR: 7.9; CI: 1.43-55.98; p=0.024), kfu (OR:27.0; CI:5.67-179.65; p<0.001) and ST101 (OR: 17.2; CI: 2.45-350.40; p=0.01) were found to be predictors of 30-day mortality. The uptake of kfu+-ybtS+ ColR-Kp by neutrophils was significantly higher than kfu--ybtS- ColR-Kp (78% vs 65%, p<0.001). However, kfu+-ybtS+ ColR-Kp were more resistant to the killing activity of neutrophils than negative ones (7.90 vs 4.22; p=0.001). The kfu+-ybtS+ ColR-Kp stimulated excessive NET formation while the NETs against kfu--ybtS- ColR-Kp were weak and rare.\n\nIron uptake systems enhance successful survival of K.pneumoniae against neutrophil phagocytic defense, and stimulate excessive NET formation. The drugs targeted to iron uptake systems would be a promising approach for treatment of hypervirulent K.pneumoniae infections.