Characterization of antibiotic resistance in Enterobacteriaceae isolates from the Mhlathuze River

A dissertation submitted in fulfillment of the requirements for the degree of Master of Science in the Department of Biochemistry and Microbiology, Faculty of Science and Agriculture, University of Zululand, South Africa, 2003.

The wide and indiscriminate use of antibiotics often results in the establishment of a pool of antibiotic resistance in the environment. In order to establish the state of bacterial resistance to antibiotics in the Mhlathuze River, 114 enteric bacteria were isolated from water samples collected from this river over a period of two years. The isolates were identified using the culture methods and confirmed by the API 20E system. The isolates were then tested for their susceptibility or resistance to a battery of 15 antibiotics. Those that showed multiple antibiotic resistance, 43 in total were screened for the presence of classl integrons and the associated antibiotic resistance genes using the polymerase chain reaction (PCR). The resistance of the enteric bacteria isolated over a period of one year showed that resistance to the older classes of antibiotics was high (94.7 % resistance to one antibiotic and 80.8 % resistance to two antibiotics). Furthermore, antibiotic resistance data of the environmental isolates showed a strong correlation (r= 0.97) with data obtained from diarrhea patients. PCR based methods demonstrated that class 1 integrons were present in more than 50% of the environmental bacterial isolates that were resistant to multiple antibiotics. This class of integrons is capable of transferring genes responsible for resistance to beta-lactam, aminoglycoside, sulfonamide and quaternary ammonium antimicrobial agents. Conjugate plasmids were also isolated, but from a small percentage of isolates. This study showed that the Mhlathuze River (i) is a medium for the spread of bacterial antibiotic resistance genes (ii) acts as a reservoir for these genes and (iii) due to socio-economic pressures may play a role in the development and evolution of these genes along this river system.

National Research Foundation (NRF) and Water Research Commission (WRC).