Screening of strong biofilm phenotype-associated core genes in Acinetobacter baumannii based on genomics

OBJECTIVE To characterize the core genomic features associated with the strong biofilm-forming phenotypes of Acinetobacter baumannii. METHODS The biofilm-forming capacities of 20 clinical isolates (from cerebrospinal fluid of hospitalized patients of neurosurgery department) and 2 standard strains were assessed by the crystal violet staining method. The difference in the biofilm-forming capacities of the strains was analyzed. The core genes of the strong biofilm-forming group were screened based on whole-genome sequencing and comparative genomics, and the dynamic expressions of these core genes were subsequently analyzed. RESULTS Among the 22 isolates, there were 4 strong biofilm isolates, 13 moderate biofilm isolates and 5 weak biofilm isolates that were obtained through the screening. Totally 5 core genes, both common and unique to the strong biofilm-forming group, were identified: the efflux pump gene czcA, virulence factor wzb, drug resistance gene craA and amino acid transporter encoding genes rhtB and aroP. The real-time quantitative polymerase chain reaction (qRT-PCR) dynamic analysis showed that the above genes were remarkably upregulated during the initial stage of biofilm formation as compared with the planktonic state, with an average upregulated margin 4.52-fold. The expressions of czcA, craA, rhtB and aroP further rose till the maturation period of biofilm, reaching up to 7.94-fold, while the expression of wzb decreased. CONCLUSIONS It is reveal the conservation of czcA-wzb-craA-rhtB-aroP gene module in the strong biofilm-forming strains in the study. The dynamic expression pattern of these core genes indicates a functional shift from early biofilm construction to mature defense in strong biofilms, providing insights for intervention strategies targeting early-stage biofilm infections.