What is a common drawback of relying solely on PCR for pathogen detection?

Relying solely on PCR (Polymerase Chain Reaction) for pathogen detection has a common drawback in that it only detects pathogen DNA. This limitation means that if a pathogen does not have detectable DNA in the sample being tested, or if the target sequences of DNA are degraded or mutated, then the PCR will not detect the presence of the pathogen, even if it is there. This can lead to false-negative results, which can be critical in research and clinical settings where prompt and accurate pathogen identification is essential for diagnosis and treatment.

Other options present misconceptions regarding PCR's capabilities. The assertion that PCR does not require special protocols overlooks the fact that PCR requires specific primers, thermal cycling protocols, and often handling of samples in a sterile and controlled environment to prevent contamination. The claim that PCR is always accurate is misleading; while PCR is highly sensitive, it is not infallible and can yield false positives or negatives based on sample quality and assay conditions. Finally, stating that PCR can detect all known pathogens disregards the specificity of the technique; PCR can only amplify DNA of specific sequences for particular pathogens, thus it does not have the capability to detect every known pathogen unless the assay is specifically designed for them.