Abstract
The outbreak of certain bacteria can trigger severe diseases, even posing a threat to public safety, leading to significant social panic and economic losses. Thus, tracing the origin of bacteria is of great significance. Stable isotope analysis technology offers a new way to determine the geographical information of bacteria, yet related research still fails to meet the application requirements of this technology in practical cases of bacterial traceability. In this study, a systematic stable isotope analysis method for bacteria and their culture conditions, based on practical geographical environments, was established for the first time. Escherichia coli and Staphylococcus aureus were cultured with water from five regions and different culture media, and the stable isotope ratios of H/O/C/N in the two bacteria and the culture media were measured to explore the relationship between bacteria and their cultivation site. The results showed that there were linear relationships between the hydrogen and oxygen stable isotopes of the two bacteria and the culture water. The combined discriminant model constructed using multi-isotope (H/O/C/N) characteristics achieved a 100% accuracy rate in identifying the types of culture media. These results indicate that research on the isotope association between bacteria and their culture water can be used to infer the cultivation region, and the specific source of bacteria can be further inferred through the multi-isotope combination discriminant model. This study can provide a relatively complete research idea for bacterial geographical traceability research, and improve the efficiency and accuracy of bacterial traceability work in practical investigations. KEY POINTS: Established a systematic stable isotope analysis method for bacteria. E. coli and S. aureus have linear H/O isotope correlations with culture water. Multi-isotope discriminant model achieves 100% accuracy in identifying culture media.