ABSTRACT
Objective To understand the genetic polymorphism of Salmonella and Staphylococcus aureus in Guangdong province, as well as to explore methods for identifying and tracing the source of these two foodbome pathogens. Methods Using the automated ribotyping system, two foodbome pathogens were tested with either EcoR Ⅰ or Pvu Ⅱ restriction enzymes. BioNumerics software was then applied for image analysis, database establishment and other corresponding analysis. Results Digestion of 32 Salmonella isolates with Pvu Ⅱ yielded 19 different ribotypes,and digestion of 14 Salmonella isolates with EcoR Ⅰ yielded 2 different ribotypes. Staphyloccus aureus isolates showed greater genetic diversity, whereas EcoR Ⅰ digestion of 49 different isolates yielded 31 different ribotypes. Conclusion Unique Salmonella and Staphylococcus aureus isolates could be identified through ribotyping. Although Salmonella serotyping and ribotyping were not strongly correlated, the combination of both restriction enzymes could be used to more effectively identify the genetic relationship among different strains as well as the source of food poisoning. Thus, not only could the genetic relationships amongst the different strains be inferred through ribotyping skills, the source of food poisoning and mode of transmission could also be determined under the use of this method.
ABSTRACT
<p><b>OBJECTIVE</b>To establish molecular typing of Listeria monocytogenes isolates by pulsed-field gel electrophoresis (PFGE) for studying the epidemiologic characteristics of Listeria monocytogenes isolated from foodstuff in Guangdong province and to build up PFGE typing database of Listeria monocytogenes isolates for identifying the infectious resource of the outbreaks and other epidemiologic investigation.</p><p><b>METHODS</b>"Standardized Protocol for Molecular Subtyping of Listeria monocytogenes by PFGE" was followed. BioNumerics software was applied on image analysis, database establishment, comparative and corresponding analysis.</p><p><b>RESULTS</b>107 Listeria monocytogenes isolates were typed by PFGE, 41 PFGE types were observed among the isolates. The PFGE types were dispersive among these isolates. Listeria monocytogenes isolates were most frequently isolated in raw chicken while the most PFGE types were found in this type of food. The positive rate was relatively high in cold and iced foods. Only 1-2 DNA fragment difference occurred in 26 Listeria monocytogenes isolates by PFGE, so high degree of relatedness remained among these isolates. There were unique PFGE patterns in the regions of Shaoguan and Huizhou. From time to time, a number of isolates remained close relationship.</p><p><b>CONCLUSION</b>PFGE typing of the 107 Guangdong Listeria monocytogenes isolates demonstrated relative genetic diversity but a number of the isolates showed close relatedness.</p>