Mechanisms involved in the inhibition mediated by Klebsiella pneumoniae of neutrophil extracelular traps released by human neutrophils

BIRNBERG WEISS, FEDERICO; CASTILLO, LUIS A.; PITTALUGA, JOSÉ R.; MARTIRE-GRECO, DAIANA; LANDONI, VERONICA I.; FERNANDEZ, GABRIELA C.

San Miguel de Tucumán

Congreso; LXVII Reunión Anual de la Sociedad Argentina de Inmunología 2019; 2019

Sociedad Argentina de Inmunología (SAI)

Klebsiella pneumoniae (Kp) carbapenemase (KPC)-producing bacteria are associated with significant mortality in immunocompromised patients. We have previously reported that neutrophils (PMN) failed to release neutrophil-extracellular-traps (NET) when challenged with Kp-KPC, whereas Escherichia coli (Eco) was a high NET inducer. Moreover, Kp-KPC was able to inhibit NETosis induced by Eco. Our aim was to study the mechanisms involved in this phenomenon. NET released by purified human PMN were observed and quantified after 3 h using confocal microscopy after DNA and Elastase staining. NET-associated Myeloperoxidase (MPO) and DNA released by nuclease treatment were measured in the supernatants.To assess if the inhibition of NETosis was mediated by a soluble Kp-KPC factor, the supernatant (SN) of a log-phase bacterial culture was used. We found that the SN-Kp-KPC was not able to decrease NET induced by Eco (NET area, μM2: Ctrl=667±250, Eco=22406±5161*, SN-Kp-KPC+Eco=19721±6918*; Released-DNA, ng/mL: Ctrl=147±11, Eco=265±61*, SN-Kp-KPC+Eco=298±63*; Released-MPO, O.D: Ctrl=0.34±0.02, Eco=0.99±0.19*, SN-Kp-KPC+Eco=0.93±0.19*, *p