PFGE is still being used for subtyping most pathogens in surveillance except?

• A. Listeria monocytogenes
• B. Staphylococcus aureus
• C. Salmonella enterica
• D. Escherichia coli O157:H7

Answer: (A)

PFGE provides a DNA fingerprint for subtyping by cutting the genome with rare restriction enzymes and separating the large fragments to produce a pattern that can be compared across labs. It has been the backbone of surveillance networks, offering shareable, interpretable results that help link cases and trace outbreaks. For several major pathogens, this method remains standard because the patterns it generates are reproducible enough to be compared widely and the technique fits well into established workflows. However, Listeria monocytogenes is not typically subtyped by PFGE in current surveillance. Its genome can yield PFGE patterns with limited discriminatory power across diverse isolates, and laboratories have shifted toward higher-resolution approaches, particularly whole-genome sequencing, along with other typing methods. In contrast, organisms like Salmonella enterica, Escherichia coli O157:H7, and Staphylococcus aureus continue to rely on PFGE as a core subtyping tool in surveillance.