Antimicrobial susceptibility of aeromonads and coliforms before and after municipal wastewater treatment by activated sludge under arid climate

Two hundred and twenty four-strains of motile Aeromonas species and E. coli were isolated from three sampling points (influent, oxidation pond and effluent) in an activated sludge wastewater treatment plant in Nouakchott, Mauritania. Antimicrobial susceptibility tests were performed in accordance with the diffusion technique and fifteen of the most frequently used antibiotics in the antibiotic treatment at the national level were tested on these isolates. The statistical analysis showed insignificant differences (P>0.05) in the resistance patterns between influent and effluent isolates. All strains were found to be monoresistant, primarily to Vancomycin. Nearly 4.5 % of A. hydrophila and 3.1 % A. caviae were resistant to Cefoperazone, while greater than 97.1 % of A. sobria were found to be susceptible to this drug. The overall resistance rates to Amikacin and Chloramphenicol did not exceed 4.6 and 10.6 % respectively. The results indicate that despite the important removal rate given by the treatment process, antimicrobial resistance incidence among pathogenic aeromonads has not been decreased and remains significant to potentially compromise the reclaim of the treated effluent in urban agricultural practices in the wastewater spreading area of Nouakchott where water reclaim permits to the urban agriculture to survive water scarcity.