Detection of Morganella morganii, a Prolific Histamine Former, by the Polymerase Chain Reaction Assay with 16S rDNA–Targeted Primers

A polymerase chain reaction (PCR) assay for the rapid and sensitive detection of the most prolific histamine former, Morganella morganii, was developed.16S rDNA targeted PCR primers were designed, and the primer specificity and sensitivity of the PCR assay were evaluated. The 16S rDNA sequence (1,503 bp) for M. morganiishowed 95% identity to those for enteric bacteria, i.e., Enterobacterspp., Klebsiellaspp., Citrobacterspp., Hafnia alvei, Proteusspp., and Providenciaspp. The unique primers for M. morganiiwere designed on the basis of the variable regions in the 16S rDNA sequence. The primers showed positive reactions with all M. morganiistrains tested. However, PCR amplification was not detected when the primers were tested with other enteric or marine bacteria. When the sensitivity of the assay was evaluated, M. morganiiwas detected at levels ranging from 106to 108CFU/ml in albacore homogenate after the PCR amplification. The sensitivity of the assay was greatly improved with the enrichment of samples, and 9 CFU of M. morganiiper ml of albacore homogenate was detected after 6 h of enrichment at 37°C.