Abstract:
Salmonella spp. is classified as human pathogenic bacteria that cause disease in the gastrointestinal tract or Gastroenteritis. This study aims to develop a rapid process for determining Salmonella serotypes (Salmonella typing) using various molecular techniques, HRM-PCR, CRISPR 2 and virulotype analysis and CRISPER 1 and CRISPR 2 for the study of the characteristics of Salmonella distribution in northern Thailand especially phayao province. This study performed and assessed the efficiency of three rapid Salmonella typing processes. HRM-PCR process using triplex primer (fljB, gyrB, ycfQ) to evaluate Salmonella serotype of 43 clinical samples were able to determine the most salmonella prevalence as S. 4,5, 12:i:- (n=16), S. Enteritidis (n=5) and S. Stanley (n= 3). To identify Salmonella serotypes, the HRM method needs the standard control (identified Salmonella serotypes by conventional serotyping) to generate unique HRM patterns for each Salmonella serotype. Moreover, eight samples showing unique HRM patterns characterized as unknown, but five samples could not be analyzed because they produced similar HRM patterns. The second method, CRISPR 2 and virulotype analysis, was performed to evaluate the differences in CRISPR 2 combined with MLVA (5 genes) and Virulence genes (7 genes) in agarose gel patterns. The method was performed to characterize 59 samples which were from 43 clinical patients and 16 from an animal origin. The analyzation based on specific DNA band pattern of MLVA (n=5) and one fragment of CRISPR 2 (500-2,000 bps) on agarose gel electrophoresis. Results showed S. 4,5, 12:i:-, S. Typhimurium, S. Enteritidis and S. Derby generated quite a similar MLVA pattern with a specific CRISPR 2 size, but S. Weltevraden and S. Stanley generated different CRISPR 2 DNA fragment sizes. Then eight unknowns from HRM-PCR method were characterized by identifying CRISPR 2 sequences and compared the size of CRISPR 2 fragments with WGS data from known Salmonella serotypes as well as with conventional method. Using CRISPR 2 with Virulence genes (7 genes), two subtypes of S. 4,5, 12:i:- were analyzed with the differences in acquisitions of sopE1 gene as with sopE1 (n=8) and without sopE1(n=10). The third method is to evaluate the differences between CRISPER 1 and CRISPR 2 using agarose gel electrophoresis to predict Salmonella serotypes. The positive controls or the predicted sizes of DNA fragments of CRISPER 1 and CRISPR 2 (In silico analysis) were obtained using the WGS program (Mega 6) along with the CRISPR Cas Finder program. Results showed that CRISPER 1 and 2 method could identify Salmonella serotypes based on the unique DNA band patterns of CRISPER 1 and 2 loci. Moreover, experimental data from CRISPR 1 and 2 fragments in agarose gel CRISPR 1 and 2 fragments were corresponded to those from analyzed data from WGS obtained from public database (enterobase.com). Finally, CRISPER 1 and 2 method was the best candidate for Salmonella serotyping because this method is simple and cost a little.