Biochemical identification and assessment of virulence in fecal isolates aeromonas spp

ABSTRACT

One hundred sixteen fecal isolates of Aeromonas spp. were identified to the species level on the basis of phenotypic characteristics. The three species of Aeromonas recognized were A. hydrophila [n = 59], A. sobria [n = 18], and A. caviae [n = 39]. Of the 18 strains of A. sobria, 100% were cytotoxic for Vero cells and positive [titer >/= 18] in the hemolysin assay. Fifty-one percent of the A. hydrophila strains and 18% of the A. caviae were positive for both cytotoxic and hemolysin activities. A positive lysine decarboxylase phenotype had the highest positive predictive value [PPV = 81%] for producing both cytotoxin and hemolysin. It was followed by negative arabi-nose fermentation phenotype [PPV = 75%], positive Voges-Proskauer phenotype [PPV = 74%] and positive gas production from D-glucose phenotype [PPV = 69%]. A combination of positive Voges-Proskauer, positive lysine decarboxylase and negative arabinose fermentation reactions increased the PPV to 85%. We conclude that the virulence of Aeromonas spp. may reliably be based on these three biochemical reactions considered in combination