ABSTRACT
Nosocomial infections caused by gram-negative opportunistic pathogens, including Acinetobacter baumannii ( A. baumannii) and Klebsiella pneumoniae ( K. pneumoniae), pose a great challenge to health care management and human health. New treatment strategies are urgently needed to tackle with the spread of multi-drug resistant strains and the increase in bacterial virulence. Type Ⅵ secretion system (T6SS), a conservative secretory apparatus encoded in a variety of gram-negative bacteria, can inject effectors into other prokaryotic or eukaryotic cells in a contact-dependent manner to achieve antibacterial and anti-host properties. It is closely related to the environmental adaptability, competitiveness and colonization ability of bacteria in hosts. The T6SS gene cluster is composed of core genes, effector genes and associated genes, and the effectors encoded by it are highly diverse and play an important role in pathogen infection. This review summarized the advances in A. baumannii and K. pneumoniae T6SS in terms of competition, host colonization, interaction between conjugative plasmids and expression regulation, aiming to provide reference for future study on T6SS-related antimicrobial activity, virulence and resistance.