Comparison of Antibiotic Resistance and Plasmid Bands between Two Identical Sets of Raw Sewage Enterobacterial Strains

Abstract

AbstractA total of 300 enterobacterial strains were collected from raw sewage effluent from the wastewater treatment: a first set of 150 strains collected through 1983 and a second set of 150 identical genera and species composition strains through 1986. The rates of incidence of antibiotic resistance by MICs determinations to eleven betalactamic antibiotics were compared between isolates from both sets. It was determined that there was no increase in the total percentage of resistance (set 1 : 86%0 : set 2 : 90%); however there was an increase in terms of the number and kind of antibiotics that bacteria were resistant to. Screening for the presence of plasmid DNA by alkaline lysis and agarose gel techniques were also compared between antibiotic resistant isolates from both sets. It was found that 27% of antibiotic resistant isolates from set 1 carried plasmid bands and 74% of those from set 2. More of half the plasmid carrying isolates showed multiple bands, and the sizes of classes of the plasmids were higher than 20 MDa in nearly two thirds of plasmid carrying isolates from both sets.