M.V. Baviskar, R.B. Barjibhe and A.B. Chaudhari*

Department of Microbiology,
School of Life Sciences, North Maharashtra University,
P.B. 80, Jalgaon-425001(M.S.), India
Phone : 91-0257-252193, 252187 (Extn. 411)
Fax : 91-0257-252 183
E-mail : abchaudhari@hotmail.com

* Corresponding author

Microbial examination of water from recreational zone, upstream of Tapi river near Bhusawal revealed (i) total heterotrophs in 1.8 x 10⁵ to 5.5. x 10⁷ CFU/ml range, (ii) total coliforms more than 1.9 x 10⁴ per L and (iii) fecal coliforms 1.5 ± 0.4 x 10³ per L. From these coliforms, 5 thermotolerant E. coli strains were identified, exhibiting prevalence of broad spectrum antibiotics resistance and metal tolerance. They showed resistance to lincomycin (2 m g/ml), methicillin (5 m g/ml), trimethoprim (5 m g/ml), ampicillin (10 m g/ml), penicillin (10 units/ml), norfloxacin (10 m g/ml), chloramphenicol (30 m g/ml) and kanamycin (30 m g/ml). MIC of these five E. coli strains to chloramphenicol and nalidixic acid (MIC > 500 m g/ml) as well as penicillin, lincomycin and trimethoprim (MIC > 1000 m g/ml) confirmed multiple antibiotics resistance (MAR). Their further probing exhibited tolerance to mercury (MIC > 20 m g/ml), cadmium (MIC > 800 m g/ml), aluminium (MIC > 1600 m g/ml) and copper as well as zinc (MIC >2000 m g/ml), suggested prevalence of plasmid mediated resistance. Curing experiments confirmed the resistance to antibiotics and metals being plasmid borne. Transmissibility of antibiotic resistance in these MAR isolates showed highest level of R plasmid transfer. All five E. coli strains remained relatively unaffected in drinking water, suggesting that maintenance of a free residual chlorine level in a distribution system was not enough as it provided only a false sense of safety.

Keywords : Thermo-tolerant, antibiotic resistant, metal tolerant coliform