Seasonal Dynamics of Microbial Contamination and Antibiotic Resistance in the Water at the Tietê Ecological Park, Brazil

The quality of water resources can be altered by human activities carried out in watersheds. These changes can lead to the occurrence of antibiotic-resistant bacteria and compromise public health. The aim of the present study was to evaluate the presence and concentration of total coliforms and Escherichia coli in the water at the Ecological Park Tietê in São Paulo, the antibiotics resistance of isolated E. coli, and the interaction between season, collection points, and water quality variables. Sample localities were georeferenced and identified as P1—drinking water from the distribution system (23°29′33.46″S, 46°31′16.12″O); P2—main lagoon of the park (23°29′37.59″S, 46°31′28.22″O); and P3—connection between the main lagoon and the Tietê River (23°29′14.66″S, 46°31′26.57″O). Physical–chemical and microbiological variables were measured. Data were subjected to analysis of variance. The isolated effect or the interaction between season, collection points, and variables had the means compared to each other by the Scott-Knott test. The microbiological analysis was performed by inoculating the samples in 3 M™ Petrifilm™ E. coli/Coliform Count Plates (containing agar medium with Violet Red Bile nutrients), incubated at 37 °C for 48 h and the E. coli isolated had their antibiotic resistance profile tested by the disk diffusion technique using Mueller–Hinton agar. Total coliforms and E. coli were not identified at P1. Total coliforms were identified in 64% of the samples and E. coli was identified in 36% of the samples. The microbial contamination of the surface waters of the park presents seasonal variation with higher concentrations of E. coli in the hottest and rainiest seasons (spring and summer). The isolated E. coli showed greater resistance to erythromycin (82%) and amoxicillin (55%) in P2 and to erythromycin (82%) and amoxicillin (27%) in P3, with the presence of multiresistant isolates at both points. No strain showed resistance to amikacin. The high rate of resistance of E. coli to the antibiotics frequently used in human and veterinary medicine demonstrates that the contribution of these substances in aquatic ecosystems over the years has exerted a selection pressure on microorganisms, assisting the appearance and spread of resistant bacteria, changing the environmental biota, and turning these locations in possible reservoirs of antibiotic resistance.