Comparative Study Of Three Different Genotyping Methods In Library Pathogenic Microbial Source Tracking

Various bacteriosises continue to do harm to public health and the heathy development of stock farming. Strain typing methods can evaluate the relationship of strains isolated from different resources, depending on their biochemical traits or genomic characteristics. Therefore, we can trace back the source of the infection. During the past decades, an expansion of genotyping methods based on DNA has emerged. The genotyping approaches have several advantages over traditional typing methods. All of these methods must meet several criteria in order to be broadly useful, including discriminatory power, stability, easy to use, easy to interpretation and so on. The objective of this study was to explore the method suitable to use widely based on the comparison of the utility of pulsed field gel electrophoresis (PFGE), Sau-PCR and ERIC-PCR in microbial source tracing.Three different genotyping methods were used together to trace the source of infections on a Shigella flexneri outbreak. According to the fingerprinting of ERIC-PCR, Sau-PCR and PFGE, 5 Shigella flexneri strains exhibited the same patterns, indicating that Shigella flexneri-infectioned food from the restaurant were the cause of this outbreak. Therefore, the department in charge of food surveillance and healthy quarantine should enhance the supervision and regulation to this restaurant. The order of the time and cost spent to these three techniques was PFGE first, Sau-PCR second and then ERIC-PCR. So, it's recommended that the primary organization could select ERIC-PCR or Sau-PCR as the initial rapid and inexpensive approach for the tracing analysis.To further examine the stability of the profiles of PFGE, Sau-PCR and ERIC-PCR, one Shigella flexneri strain was subcultured repeatedly or stored at room temperature over a 30-day period. And then three genotyping approaches were performed to the cultures after 10, 20, and 30 days. There's no appreciable variation in their PFGE fragment patterns to be observed, demonstrating perfect reproducibility. While ERIC-PCR exhibited obvious variations, which could offer incorrect epidemiological information. The fragment patterns of Sau-PCR were stable after subculturing repeatedly and prolonging the storage term, which enabled the communication between different laboratories and the establishment of large databases of characterized organisms. This further verified the feasibility of Sau-PCR method.Furthermore, 9 Strains of methicillin-resistant Staphylococcus aureus (MRSA) of different staphylococcal cassette chromosome mec (SCCmec) types were used to evaluate the suitability of Sau-PCR and ERIC-PCR. The Sau-PCR procedure showed a good correlation to SCCmec typing method for MRSA. Sau-PCR method overcame the limitation of prior sequence knowledge for PCR analysis, didn't need special equipment, and was easy to implement, suggesting that it could significantly contribute to rapid detection and epidemiological trace-back analysis.In this study,we compared the convenience, stability and the discriminatory power in microbial source tracking study of three different typing methods successively, finding that the newly-developed Sau-PCR approach was easier to implement than PFGE, and more stable and powerful than ERIC-PCR. This study offered a further empirical and theoretical evidence for the application of Sau-PCR in primary organization.