Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı 2

Investigation of Some Virulence Factors of Salmonella Strains Isolated From Different Sources
The genus Salmonella, which is a member of Enterobacteriaceae family, includes facultative aerobic and Gram-negative bacteria that cause food- borne diseases in the gut such as typhoid fever and diarrheal diseases. These bacteria are transmitted from food, water sources and fecal contaminations. For the formation of virulence degree among Salmonellas, antigenic factors are need to be known in order to investigate the patogenicity of these bacteria. Although there are studies to determine the virulence of Salmonellas which were isolated from clinical samples, any comparison about the patogenesis of Salmonellas among the isolates of food samples, environmental sources and wild type strains has not been found. For this reason, the aim of the study is to evaluate the patogenicity of the members in genus Salmonella to compare virulence between wild type (ATCC) standards and bacteria which are isolated from minced meat samples, water and clinical sources.
In scope of the study, we aimed to investigate the antigenic surface structures which play role for resistance to the antimicrobial activity of host serum, antibiotic resistance via altered metabolic pathways, hemolysine activity with toxins and hemagglutination capabilities due to the type I, II, III and type IV secretory systems, lipopolysaccharides and flagella mediated invasion and intracellular multiplication that regulates attachment for biofilm structures and capability of siderophore production to chelate iron from the environment.
When the results are evaluated, serum resistance was shown by standard Salmonella enterica serovar Typhimurium ATCC 14028 strain and most of the minced meat isolates (11 of isolates) of Salmonella except the bacteria isolated from water samples (3 of isolates) that were less resistant to the effects of serum and standard Salmonella enterica serovar Enteritidis ATCC 13076 strain was serum sensitive. Further multiple resistance to the antibiotics has been investigated by Salmonella strains isolated from minced meat (16 of isolates) and rare of the water sampled (11 of isolates) and clinical isolates (0 of isolates) or standard bacteria (0 of strains) have been shown resistance. A few bacteria (3 of meat isolates) were capable of producing -hemolysins, whereas all Salmonella isolates (35 isolates) and standard bacteria (2 strains) produce -hemolysins and were capable of showing mannose resistant hemagglutination due to the presence of type IV fimbriae. Moreover, Salmonellas isolated from water (13 of isolates), clinical samples (3 isolates) and standard Salmonella strains have been occured mannose resistant Klebsiella-like hemagglutination by their type III fimbriae. Low and moderate attachment and biofilm formation have been shown by the Salmonella bacteria isolated from minced meat (13 of isolates) , water (10 of isolates) and clinical samples (3 isolates), while standard Salmonella strains were capable of forming moderate (1 strain) and high level (1 strain) biofilm structures. Additionally, standard Salmonella Typhimurium ATCC 14028, most of the isolates from minced meat, all clinical isolates and less of the isolates from water samples (8 of isolates) were detected siderophore production on Chrome Azurol S (CAS) Agar plates, although 6 of the isolates have been determined as catechol-productive bacteria by thin layer chromatography (TLC).
Considering all the results of the experiments, Salmonella isolates from minced meat samples were found out as the most pathogen bacteria, but the ZS-4 isolate from water samples has been the most virulent of all.
When the virulence factors in our study were considered it has been determined that the bacteria have different virulence properties according to their sources of isolation. Generally, nine of the 35 isolates were found to be more virulent than the standard Salmonella Typhimurium ATCC 14028 and 33 of the 35 isolates were much more virulent than the standard Salmonella Enteritidis ATCC 13076 strain.
According to the results of the thesis we evaluated, it was determined that the serum and antibiotic resistance, production of hemolysins, capability of hemagglutination, biofilm formation and siderophore production of the Salmonella bacteria have differences depending on their source of isolation and difference of the strains.
This thesis, which performed in our country, is the first study comparing some virulence factors of Salmonella bacteria isolated from different sources and standard Salmonella bacteria. The study may create a step for the future definitions of the patogenicity of the members of genus Salmonella.