Appearance of ciprofloxacin/chlortetracycline-resistant bacteria in waters of Québec City in Canada.

Most of the waterborne fecal pathogens belong to the family of Gram-negative bacteria. Hence, minimal inhibitory concentrations of chlortetracycline and ciprofloxacin antibiotics towards Gram-negative representative, Enterobacter aerogenes were estimated, which were 7 μg/ml and 0.125 μg/ml, respectively. The combined antimicrobial effect of chlortetracycline and ciprofloxacin against E. aerogenes was also investigated to establish their potential interaction towards the pathogens present in water. Eventually, the water samples obtained from various drinking water treatment plants from Québec municipality were tested for the occurrence of chlortetracycline-, ciprofloxacin- and chlortetracycline/ciprofloxacin-resistant strains.