AUTHOR=Mayer Celia , Muras Andrea , Romero Manuel , López María , Tomás María , Otero Ana 

TITLE=Multiple Quorum Quenching Enzymes Are Active in the Nosocomial Pathogen Acinetobacter baumannii ATCC17978

JOURNAL=Frontiers in Cellular and Infection Microbiology

VOLUME=8

YEAR=2018

URL=https://www.frontiersin.org/journals/cellular-and-infection-microbiology/articles/10.3389/fcimb.2018.00310

DOI=10.3389/fcimb.2018.00310

ISSN=2235-2988

ABSTRACT=<p><italic>Acinetobacter baumannii</italic> presents a typical <italic>lux</italic>I/<italic>lux</italic>R quorum sensing (QS) system (<italic>abaI</italic>/<italic>abaR</italic>) but the acyl-homoserine lactone (AHL) signal profile and factors controlling the production of QS signals in this species have not been determined yet. A very complex AHL profile was identified for <italic>A. baumannii</italic> ATCC17978 as well as for <italic>A. nosocomialis</italic> M2, but only when cultivated under static conditions, suggesting that surface or cell-to-cell contact is involved in the activation of the QS genes. The analysis of <italic>A. baumanni</italic> clinical isolates revealed a strain-specific AHL profile that was also affected by nutrient availability. The concentration of OHC12-HSL, the major AHL found in <italic>A. baumannii</italic> ATCC17978, peaked upon stationary-phase establishment and decreases steeply afterwards. Quorum quenching (QQ) activity was found in the cell extracts of <italic>A. baumannii</italic> ATCC17978, correlating with the disappearance of the AHLs from the culture media, indicating that AHL concentration may be self-regulated in this pathogen. Since QQ activity was observed in strains in which AidA, a novel α/β-hydrolase recently identified in <italic>A. baumannii</italic>, is not present, we have searched for additional QQ enzymes in <italic>A. baumannii</italic> ATCC17978. Seven putative AHL-lactonase sequences could be identified in the genome and the QQ activity of 3 of them could be confirmed. At least six of these lactonase sequences are also present in all clinical isolates as well as in <italic>A. nosocomialis</italic> M2. Surface-associated motility and biofilm formation could be blocked by the exogenous addition of the wide spectrum QQ enzyme Aii20J. The differential regulation of the QQ enzymes in <italic>A. baumannii</italic> ATCC17978 and the full dependence of important virulence factors on the QS system provides a strong evidence of the importance of the AHL-mediated QS/QQ network in this species.</p>