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A multidrug resistance plasmid contains the molecular switch for type VI secretion in Acinetobacter baumannii

Weber, Brent S., Ly, Pek Man, Irwin, Joshua N., Pukatzki, Stefan, Feldman, Mario F.
Proceedings of the National Academy of Sciences of the United States of America 2015 v.112 no.30 pp. 9442-9447
Acinetobacter baumannii, antibiotic resistance, bacteria, health services, multiple drug resistance, pathogens, plasmids, regulator genes, type VI secretion system
Although the multidrug-resistant (MDR) bacterium Acinetobacter baumannii is a serious threat for health care systems worldwide, very little is known about the mechanisms that have facilitated its rise as a successful pathogen. Our work demonstrates that multiple MDR A. baumannii strains regulate the expression of their type VI secretion system (T6SS), an antibacterial apparatus used to kill other bacteria, by harboring a large, self-transmissible resistance plasmid containing T6SS regulatory genes. Through spontaneous plasmid loss, A. baumannii activates its T6SS and is able to outcompete other bacteria. However, this comes at a cost, as these strains lose resistance to antibiotics. This mechanism constitutes an apparent survival strategy by A. baumannii and provides insights into the pathobiology of this important pathogen.