The role of Type VI Secretion System in resistance and pathogenicity of Acinetobacter baumannii

The Type VI secretion system (T6SS) is a multi-component transmembrane apparatus that is crucial for substance acquisition and pathogenicity of bacteria. In this study we investigated Acinetobacter baumannii , a causative agent of bacteremia, to explore the mechanisms of T6SS in drug resistance and pathogenicity by contrasting virulence, drug sensitivity, conjugation, transformation, competition, and cell adhesion capacities. A total of 136 non-repetitive A. baumannii strains were collected, and 80.1% of patients received treatment in intensive care unit. Forty (29.4%) were classified as hypervirulent A. baumannii (hvAB), which exhibited a higher prevalence of the virulence gene abaI , a reduced capacity for biofilm formation, and a lower prevalence of the outer membrane protein gene carO . T6SS-positive strains exhibited enhanced antimicrobial resistance, elevated frequencies of resistance genes ( bla _{OXA−23−like} , bla _TEM , adeB , adeR , adeS ) and the virulence gene csuE . Differences were observed between strains with T6SS deletion and those with an intact T6SS concerning the HigAB toxin-antitoxin system and the RSF1010-like IncQ plasmid. T6SS may down-regulate the expression of effector genes due to the insertion sequence IS Aba13 . The critical role of the T6SS in the drug resistance and pathogenicity of A. baumannii necessitates strengthened surveillance and the prompt implementation of effective measures.