OBJECTIVETo establish a method for diagnosis of freshwater drowning by amplifying gyrB and 16S rRNA genes of Aeromonas hydrophila using PCR coupled with capillary electrophoresis (CE).

METHODSDNA samples were extracted from human, 18 planktons (including Candida albicans, Aeromonas hydrophila, and 16 species of algae), and 30 cases of tissue samples (including the lung, liver, and kidney, all examined with microwave digestion-vacuum filtration-automated scanning electron microscopy) from human cadavers, including 28 freshwater drowning victims and 2 with natural death. The DNA samples were amplified with the primer AH (for gyrB gene) and primer Ah (for 16S rRNA gene), and the products were analyzed with CE.

RESULTSPCR amplification followed by CE yielded negative results for DNA of human, Candida albicans and 16 species of algae, whereas a positive result was found for Aeromonas hydrophila DNA with PCR products of 195 bp (with primer AH) and 350 bp (with primer Ah). In the 28 drowning cases, the detection rates of Aeromonas hydrophila using primer AH were 96.4% in the lung tissue, 71.4% in the liver tissue, and 60.7% in the kidney, as compared with the rates of 75.0%, 42.9%, and 32.1% using primer Ah, respectively. The positive rates for Aeromonas hydrophila in the organs of the drowning victims were 82.1% and 53.6% with primer AH and primer Ah, respectively. The detection showed negative results in the 2 cases of natural deaths. The two primers produced significantly different detection rates of Aeromonas hydrophila (P<0.05).

CONCLUSIONPCR coupled with CE for detecting gyrB gene of Aeromonas hydrophila has a high sensitivity in assisting a diagnosis of freshwater drowning. Detection of both the gyrB gene and 16S rRNA gene of Aeromonas hydrophila can yield more convincing evidence of the diagnosis of freshwater drowning.