Impact of microbial multi-metal and broad spectrum antibiotic tolerance in urban SW (Adi Ganga, Kolkata) on adjacent groundwater: A future threat

Abstract

One hundred and sixty six bacterial strains were isolated from a highly polluted location of Adi Ganga surface water (SW, n = 144), groundwater (GW, n = 22) system for their multi metal and antibiotic resistance study. A BOD(5) of 45 mg/L and ORP of −368 mV with faecal coliform contamination (>1800/100 ml) was noted for SW along with elevated levels of Zn (228 μg/L) and Mn (396 μg/L). However, no faecal coliform could be detected in GW sample. Multi-metal tolerance was observed to be a common property among the strains isolated. Resistance to seven or more heavy metals was prevalent among 70% of the SW bacterial population. Remaining 30% comprised isolates from both SW and GW resistant to 2–6 metals. Bacterial resistance to metals was highest for Pb followed by Cr, Mo, Ni, Hg, Cd, As, Cu, Co, Zn. Muti antibiotic resistance profiling indicated very high resistance towards ampicillin, chloramphenicol, aerosporin and streptomycin whereas the population was considerably sensitive to ciprofloxacin and gentamycin. High MAR index of 0.8 (SW) and 0.3 (GW) is a threat to the health of mankind and a possible indication of origin of multidrug resistant bacterial infections. Correlation in heavy metal and antibiotic resistance suggested their natural co-selection. Acquisition of such genetic elements by disease causing pathogenic microbes might confer resistance to a broad spectrum of antibiotics. Contamination of GW with such multi-metal and antibiotic resistant strains may spread the resistance property to human microflora.