What limitations do Koch's postulates have for pathogens that cannot be grown in laboratory cultures?

Robert Koch developed his four postulates as a foundational framework in microbiology to establish a causal link between a specific microorganism and a disease.12

The second postulate specifically requires that the microorganism be isolated from a diseased host and grown in pure culture in a laboratory setting. A primary limitation of these criteria is that they cannot be easily applied to pathogens that are difficult or impossible to cultivate using standard laboratory techniques. Because these organisms cannot be grown in isolation, researchers are unable to fulfill the requirement of producing a pure culture to demonstrate that the agent alone causes the disease in a healthy host.132

Furthermore, these principles face challenges regarding pathogens that cause asymptomatic infections, as the presence of the organism does not always correlate with the presence of clinical symptoms. To address such limitations, modern science has increasingly relied on advanced diagnostic tools, including molecular biology and serological tests, to identify pathogens that traditional culture methods cannot detect.24