Research Information System
Thesis Type: Postgraduate
Institution Of The Thesis: Gazi Üniversitesi, Sağlık Bilimleri Enstitüsü, Turkey
Approval Date: 2014
Student: TÜRKAN ÖZDEMİR
Supervisor: AYŞE MELTEM YALINAY
Abstract:This study is intended to analyze the ability of the S.aureus strains isolated from wounds to make biofilm, to assess the presence of the genes related to the biofilm formation and the genes related to surface proteins, and to compare the phenotypic and genotypic characters of the biofilm positive and negative strains at the Microbiology and Clinical Microbiology Laboratory of Gazi University Faculty of Medicine. A total of 50 S.aureus bacteria isolated from wounds were included to the study. In the study, Congo Red Agar and microplate assay method were used to compare the biofilm formation. According to the phenotypic assessment of colony morphology of 50 strains at Congo Red Agar, which was conducted after they were incubated at 37 oC for one night and then at room temperature for 48 hours, the biofilm production of 16 (32%) of the strains was found negative, while that of 34 (68%) strains was found positive. In microplate method, after the 24-hour incubation at 37 oC, absorbance measurements were evaluated after they were painted by using crystal violet, and then the biofilm production of all the strains was assessed. According to the absorbance measurements related to using crystal violet, 17 (34%) strains were negative, 21 (42%) were moderate and 12 (24%) were strong in terms of biofilm production. There was found no statistical relationship between microplate method and Congo Red Agar in terms of biofilm formation, upon their comparison. In the molecular evaluation of the biofilm formation of S.aureus bacteria, the existence of surface proteins genes (fnbA, clfA ve ebpS) that has role in the first step of biofilm formation was analyzed as well as the icaA and icaD genes that has role in the cell-cell adhesion and multi-layered biofilm formation. In our study, fnbA and clfA genes were detected in 44 (88%) of 50 S.aureus bacteria isolated from wounds while fnbA and clfA genes were not detected in 6 (12%) strains. Also ebpS genes were detected in 23 (46%) strains and were not detected in 17 (34%) strains. There was a normal-to-moderate relation between fnbA and clfA genes and the biofilm formation examined on Congo Red Agar (r=0.274, p<0.001). There was a poor relationship between the biofilm formation and ebpS gene (r=0.031 p>0.001). Moreover, there was a poor relation between fnbA gene and biofilm formation examined with the microplate method (r=0.039, p>0.001). There was a poor relation between the biofilm formation and clfA gene (r=0.028, p>0.001) and a negative relation between the biofilm formation and ebpS gene (r=0.148, p>0.001). In our study, both icaA and icaD genes were determined in 42 (84%) strains of 50 S.aureus bacteria isolated from wounds and in S.aureus ATCC 43300 used positively. Neither icaA nor icaD genes were determined in 7 (14%) strains of 50 S.aureus bacteria included in the study and in S.aureus ATCC 43300 used negatively. In one strain (2%) included in the study, icaA gene was found as positive and icaD gene was found as negative. There was a normal-to-moderate relationship between icaA and icaD genes and the biofilm formation examined on Congo Red Agar (r=0.285, p=0.001). However, a poor correlation was determined between biofilm formation with the microplate method and icaA and icaD genes existence (r=0.088, p>0.001). 81 As a result, no standardization was determined among the conventional methods used in the evaluation of S. aureus biofilm formation. The result of molecular evaluations showed that the genes (fnbA, clfA, icaA ve icaD) was found to be responsible for the biofilm formation of S.aureus have something to do with the biofilm and have a negative relationship with ebpS gene. These results also indicate that biofilm formation does not depend only on genotypic features, but its mechanisms are also affected by the environmental features.