Vibriosis in penaeid species cultured in the Philippines results in massive mortalities and consequently in severe economic losses in the shrimp industry. Rapid and accurate detection of the causative agent of the disease is imperative. In this study,
toxR gene sequence analysis of ten
Vibrio isolates (from several provinces of the Philippines) implicated in disease affecting the penaeid shrimp (
Penaeus monodon) was performed in order to develop a
toxR-targeted PCR detection of similar strains of shrimp pathogens. Analysis of the partial
toxR gene revealed 97–100% sequence similarity among the ten Philippine
Vibrio isolates. Distinct sequence variation of the
toxR gene, however, was observed between the Philippine
Vibrio isolates and the type strains, with the Philippine isolates exhibiting only 92–93% and 74–75% sequence similarity with the type strain
V. campbellii (NBRC 15631
T) and
V. harveyi (NBRC 15634
T), respectively. The use of a PCR primer set that was designed based on
toxR sequences of the Philippine
Vibrio isolates amplified the expected 226-bp
toxR fragment using templates from all ten Philippine
Vibrio isolates. No amplified product was observed in PCR using templates from type strains of
V. harveyi,
V. campbellii, and other non-target bacteria, suggesting that the primers were specific for the Philippine
Vibrio isolates. The
toxR-targeted PCR primers reported in this study could be useful in the detection of Philippine
Vibrio isolates associated with mortalities in the shrimp industry, which could not be detected in PCR using primers designed for type strains of
V. harveyi and
V. campbellii.
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