Virulence Characteristics of Biofilm-Forming in Clinical Isolates Using a Model.

is a Gram-negative coccobacillus responsible for severe hospital-acquired infections, particularly in intensive care units (ICUs). The current study was designed to characterize the virulence traits of biofilm-forming carbapenem-resistant causing pneumonia in ICU patients using a model. Two hundred and thirty patients with hospital-acquired or ventilator-associated pneumonia were included in our study. Among the total isolates, was the most frequently isolated etiological agent in ICU patients with pneumonia (54/165, 32.7%). All isolates were subjected to antimicrobial susceptibility testing by the Kirby-Bauer disk diffusion method, while the minimum inhibitory concentrations of imipenem and colistin were estimated using the broth microdilution technique. The biofilm formation activity of the isolates was tested using the microtiter plate technique. Biofilm quantification showed that 61.1% (33/54) of the isolates were strong biofilm producers, while 27.7% (15/54) and 11.1% (6/54) showed moderate or weak biofilm production. By studying the prevalence of carbapenemases-encoding genes among isolates, - was positive in 88.9% of the isolates (48/54). The gene was found in 27.7% of the isolates (15/54 isolates). - and genes coexisted in 25.9% (14/54 isolates). and genes, the biofilm-associated genes, coexisted in 5.6% (3/54) of the isolates. For in vivo assessment of pathogenicity, a survival assay was used. survival was statistically different between moderate and poor biofilm producers ( < 0.0001). The killing effect of the strong biofilm-producing group was significantly higher than that of the moderate and poor biofilm producers ( < 0.0001 for each comparison). These findings highlight the role of biofilm formation as a powerful virulence factor for carbapenem-resistant that causes pneumonia in the ICU.