High inflammatory potential and reduced regulatory T cells differentiation of selected KPC-Klebsiella pneumoniae (Kp) strains compared to non KPC-producing Kp

Introduction In the last years, strains of Klebsiella pneumoniae (Kp) producing KPC-type carbapenemases (KPC-Kp) belonging in sequence type (ST) 258 have undergone a global dissemination. Infections by these strains represent a major healthcare threat given their extensively drug resistant phenotypes and ability to rapidly disseminate in healthcare settings. The ability to escape pathogen recognition and host-immune response represent an important virulence factor in Kp infections, easily reproducible in animal models. In contrast, KPC-Kp isolates were reported as less virulent than Kp in experimental infections, and no data are available about their interactions with the human immune system. In this work we studied four strains of KPC-Kp (KKBO-1, KKBO-4, KK207-1, KK207-2), representative of colistin-susceptible and colistin-resistant isogenic mutants of the two different sublineages of ST-258, for their ability to activate cells of innate and adaptive immunity in comparison with a Kp reference strain (Kp52.145) of capsular serotype K2.