Quantitative Recovery of Aeromonas hydrophila from Nsukka Sewage

Sewage samples were analyzed for the recovery of Aeromonas hydrophila. The pH of the samples ranged from 8.2 - 9.6 and the temperature from 20.0 – 28.7. Samples were enriched in alkaline peptone water medium (pH 8.4) before plating on different selective media. Media tested for the recovery of Aeromonas hydrophila from the sewage did not restrict the growth of other Aeromonas colonies, Vibrio spp and Pseudomonas spp. A. hydrophila had a recovery rate of 35.3%, 44.4%, 10.7% and 9.6% on starchampicillin agar, sheep blood-ampicillin agar, trypticase soy agar and thiosulphate citrate bile-sucrose agar respectively. Seasonal variations in temperature affected the rate of isolation of Aeromonas hydrophila from the sewage with higher microbial numbers occurring during the warmer months. Incorporation of ampicillin to a concentration of 10μg/mL in both starch-ampicillin agar and sheep bloodampicillin agar improved the selectivity and sensitivity of A. hydrophila on these media. Media without ampicillin did not give good selectivity and specificity for A. hydrophila and were therefore not recommended for preliminary isolation of this organism from sewage samples.

 O Nwokoro, C.S Ubani, G.N Okpala