© 2020 Ankara Microbiology Society. All rights reserved.Acinetobacter baumannii is a multi-drug resistant (MDR) gram-negative pathogen leading to nosocomial infections. Hospital-acquired infections due to A.baumannii occur especially in patients hospitalized in intensive care units. Important infections related to this bacterium are pneumonia, bacteremia, endocarditis, skin and soft tissue, urinary tract infections and meningitis. Human transmission is usually through the hospital environment or through medical personnel. A.baumannii isolates increases their virulence not only being multiple resistance to antibiotics but as well as the ability to form biofilm. The biofilm formation of A.baumannii isolates were mostly related with genes encoding curli fiber (csgA), the chaperone-usher fimbria (csuE) and the outer membrane (ompA). The aim of this study was to demonstrate biofilm production and virulence genes in MDR invasive A.baumannii isolates. MDR and similarity status previously known invasive A.baumannii (n= 156) isolates were included in the study. Biofilm production was determined by quantitative microplate biofilm method. Virulence genes csgA, csuE, fimH, ompA and blaPER-1 were investigated by polymerase chain reaction (PCR). It was determined that 60.3% (94/156) of all the isolates formed biofilm. Of these 94 isolates, 17 were weak, 33 were medium and 44 were strong. The mean biomass forming capacity of the isolates was found to be 2.23 ± 0.0033. Among the isolates included in the study (n= 156) the frequency of csgA, csuE, ompA, fimH and blaPER-1 genes were 71.2%, 32.1%, 21.8%, 7.1% and 3.2% respectively. The frequency of csgA, ompA, bap, csuE, fimH virulence genes were found to be 41.5%, 24.5%, 20.2% and 5.3% among biofilm positive isolates respectively. Biofilm-forming isolates were most commonly found in pulsotype II 19.1% (18/94), pulsotype IX 17.0% (16/94) and pulsotype VI 12.8% (12/94). In this study, when the distribution of virulence genes were compared with the isolates that have weak, medium and strong biofilm, all of the studied genes were found to be more abundant in isolates with strong and medium positive biofilm production. This has shown that excluding imH gene, csgA, csuE and ompA genes have contributed to the biofilm formation in invasive A.baumannii isolates, respectively.