Retrospective diagnosis of diphtheria by detection of the Corynebacterium diphtheriae tox gene in a formaldehyde-fixed throat swab using PCR and sequencing analysis

The tox gene of Corynebacterium diphtheriae was detected in a formaldehyde- fixed throat swab taken from a 68-year-old man who was reported to have die d of suffocation due to a pharyngeal tumor. DNA templates prepared from bac terial cells fixed with 10% formaldehyde were subjected to a PCR analysis w ith tox gene-specific PCR primers. The resultant 112-nucleotide-long PCR pr oduct was sequenced using a dye terminator method, and an expected 57-nucle otide-long internal sequence of the tox gene was detected. This method is a pplicable for retrospective diagnosis in diphtheria cases in which only a f ormaldehyde-fixed clinical sample is available.