TY  - INPR
A1  - Rubio, Tristan
A1  - Gagné, Stéphanie
A1  - Debruyne, Charline
A1  - Dias, Chloé
A1  - Cluzel, Caroline
A1  - Mongellaz, Doriane
A1  - Rousselle, Patricia
A1  - Göttig, Stephan
A1  - Seifert, Harald
A1  - Higgins, Paul G.
A1  - Salcedo, Suzana P.
T1  - Incidence of an intracellular multiplication niche amongst Acinetobacter baumannii clinical isolates
T2  - bioRxiv
N2  - The spread of antibiotic resistant Acinetobacter baumannii poses a significant threat to public health worldwide. This nosocomial bacterial pathogen can be associated with life-threatening infections, particularly in intensive care units. A. baumannii is mainly described as an extracellular pathogen with restricted survival within cells. This study shows that a subset of A. baumannii clinical isolates extensively multiply within non-phagocytic immortalized and primary cells, without the induction of apoptosis, and with bacterial clusters visible up to 48 hours after infection. This phenotype was observed for the A. baumannii C4 strain associated with high mortality in a hospital outbreak, and the A. baumannii ABC141 strain which wasn’t isolated from an infection site but was found to be hyperinvasive. Intracellular multiplication of these A. baumannii strains occurred within spacious single membrane-bound vacuoles, labeled with the lysosomal associate membrane protein (LAMP1). However, these compartments excluded lysotracker, an indicator of acidic pH, suggesting that A. baumannii can divert its trafficking away from the lysosomal degradative pathway. These compartments were also devoid of autophagy features. A high-content microscopy screen of 43 additional A. baumannii clinical strains highlighted various phenotypes: (1) the majority of strains remained extracellular, (2) a significant proportion was capable of invasion and limited persistence, and (3) two strains efficiently multiplied within LAMP1-positive vacuoles, one of which was also hyperinvasive. These data identify an intracellular niche for specific A. baumannii clinical strains that enables extensive multiplication in an environment protected from host immune responses and out of reach from many antibiotics.

Importance Multidrug resistant Acinetobacter baumannii strains are associated with significant morbidity and mortality in hospitals world-wide. Understanding their pathogenicity is critical for improving therapeutics. Although A. baumannii can steadily adhere to surfaces and host cells, most bacteria remain extracellular. Recent studies have shown that a small proportion of bacteria can invade cells but present limited survival. We have found that some A. baumannii clinical isolates can establish a specialized intracellular niche that sustains extensive intracellular multiplication for a prolonged time without induction of cell death. We propose that this intracellular compartment allows A. baumannii to escape the cell’s normal degradative pathway, protecting bacteria from host immune responses and potentially hindering antibiotic accessibility. This may contribute to A. baumannii persistence, relapsing infections and enhanced mortality in susceptible patients. A high-content microscopy-based screen confirmed this pathogenicity trait is present in other clinical isolates. There is an urgent need for new antibiotics or alternative antimicrobial approaches, particularly to combat carbapenem-resistant A. baumannii. The discovery of an intracellular niche for this pathogen as well as hyperinvasive isolates may help guide the development of antimicrobial therapies and diagnostics in the future.
KW  - Acinetobacter baumannii
KW  - intracellular
KW  - trafficking
KW  - clinical isolates
Y1  - 2021
UR  - http://publikationen.ub.uni-frankfurt.de/frontdoor/index/index/docId/72881
UR  - https://nbn-resolving.org/urn:nbn:de:hebis:30:3-728813
IS  - 2021.04.15.439986
ER  -