Investigation of antibiotic resistance profile and TEM-type β-lactamase gene carriage of ampicillin-resistant Escherichia coli strains isolated from drinking water

Abstract

Fifty-five ampicillin-resistant (Ampr) Escherichia coli strains were isolated from 51 drinking water points in Rize region containing abundant fresh water sources in Turkey during the years 2000 to 2002 and from January to February 2004. The large number of organisms (nearly 57%) exhibited resistance to three or more antibiotics commonly used in human and veterinary medicine. These strains displayed a multiresistant phenotype. Nearly half of the strains (27%) expressed resistance to ceftazidime, but these strains were not an extended-spectrum ?-lactamase-producer according to the results of double-disk synergy test. All isolates were then screened for the carriage of TEM-type ?-lactamase gene (blaTEM) by polymerase chain reaction. TEM-type ?-lactamase genes were found in six (11%) isolates. Sequence analysis showed TEM-1 type genes. However, isoelectric focusing analysis did not confirm the production of TEM-1 type ?-lactamase except for one strain. Conjugation experiments showed that resistance to ampicillin, tetracycline or trimethoprim/sulfamethoxazole was transferable in six (11%) isolates. Emergence of transferable antibiotic resistance and blaTEM-1 gene in E. coli strains from public drinking waters possesses a significant public health risk.