Distribution and antibiotic resistance among aerobic heterotrophic bacteria from rivers in relation to pollution

Abstract
A total of 490 isolates of aerobic heterotrophs from the river Indus at Leh and the Gomati at Lucknow were identified into 16 genera. There were 213, 105 and 172 isolates from the river Indus, upstream and downstream of the river Gomati, respectively. Bacteriological and physicochemical analyses showed the increased values with riverine pollution. Gram negative bacilli were dominant and ranged between 79–93%. Aeromonas spp. was the commenst among the genera isolated from the Indus (51%) and downstream (30%) of the river Gomati. Spore‐forming Bacillus spp. was recovered in higher numbers from the river Indus (14%) and upstream (13%) of the river Gomati, while Micrococcus spp. were found in increased numbers from downstream (13%) of the river Gomati. The incidence of resistance for four antibiotics was determined among these isolates. Total and multiple antibiotic resistances were found to be highest among the isolates from downstream, while they were lowest among the isolates from upstream of the river Gomati. Ampicillin resistance was observed in 80% of aeromonads from the river Indus. Sewage contamination was considered to be responsible for predominance of some genera and antibiotic resistant isolates from downstream of the river Gomati. The increased resistance among isolates from the river Indus may be attributed to less pollution with low nutrient level.