Genotype and phenotype correlation of biofilm formation among Acinetobacter Baumannii isolated from clinical samples

Acinetobacter baumannii is an important nosocomial pathogen responsible for various human diseases. Recently, the exponential increase of antibiotic resistance in A. baumannii has emerged as a major public health concern. The capacity to form biofilms plays an important role in facilitating the survival and transmission of Acinetobacter in the hospital setting. This study was conducted to isolate and diagnose Acinetobacter baumani by collecting 200 samples from different clinical sites (urine, ear infection, throat swab, blood, skin lesion) from patients of different gender and age admitted to various hospitals in Babylon/Iraq between November 2021 and May 2022. Bacterial isolates were isolated and identified using MacConkey agar and biochemical tests in addition to antibiotic resistance pattern and conformational identification were performed using automated VITEK-2 system devices. The biofilm-forming capacity of bacterial isolates was determined using the microtiter plate method; biofilm-associated genes were also detected using conventional polymerase chain reaction (PCR). Only 59 out of 200 clinical samples yielded positive cultures for A. baumannii. According to age, the minimum age of the patients was 9 years, and the maximum age was 78 years, with a mean age of 35.69±18.05 years. The frequency of females was 31 (52.54%), which was 28 (47.46%) higher than the frequency of males. Among the 59 samples positive for A. baumannii isolates, ear pus samples had the highest number with 19 (32.20%), followed by blood samples with 14 (23.78%), urine samples with 10 (16.95%) and skin lesion samples with 9 (15.25%), while throat swab samples had the lowest number with 7 (11.86%). All A. baumannii isolate colonies were medium-sized, non-mucoid, non-pigmented and had late lactose fermentation on MacConkey agar. Of the 59 isolates, 53 were capable of producing biofilms. These were classified as strong 26 (44.1%), moderate 17 (28.8%) and weak 10 (16.9%), with only 6 (10.2%) isolates not associated with biofilm production. Among the bacterial isolates, the frequency of cruF gene was the highest with 76.3%, followed by bap bla PER-1 gene with 69.5% and bap gene with 62.7%, while the frequency of OmpA gene was 44.1%. The highest antibiotic resistance was to trimethoprim-sulfamethoxazole (57.6%), followed by gentamicin and imipenem (55.9%), ceftazidime (52.5%), amikacin (50.8%), streptomycin (47.5%), tigecycline (44.1%), cefepime (39%), carbenicillin (37.3%) and piperacillin (25.4%). The lowest level of resistance was determined as ticarcillin (23.7%).