ANTIBIOTIC-RESISTANT ESCHERICHIA-COLI FROM WASTE-WATER BEFORE AND AFTER TREATMENT IN STABILIZATION PONDS IN THE ARID REGION OF MARRAKECH, MOROCCO

A total of 693 Escherichia coli strains isolated from raw wastewater and two successive stabilization pond effluents were tested for their resistance to 10 antibiotics. Of the total isolates examined, approximately 21% of the raw sewage strains, 32% of the first basin isolates and 34% of the final effluent strains were resistant to one or more antibiotics. It was also determined that there was an increase in the percentage of antibiotic-resistant E. coli populations in the effluents. Similarly, the mean frequency of multiple antibiotic resistance was significantly higher in the populations from treated waters than it was in the raw sewage. This clearly shows that sewage treatment in stabilization ponds directly affects the selection of antibiotic-resistant E. coli strains.