Overproduction of Efflux Pumps as a Mechanism of Metal and Antibiotic Cross-Resistance in the Natural Environment

Abstract

Antibiotic and metal resistance can occur together in the environment and can be linked by the same detoxication mechanism (cross-resistance). The understanding of this linkage may be a key to further study of the spread of antibiotic resistance in the non-hospital environment worldwide. In our study, we examined the overproduction of efflux pumps as a possible mechanism of the cross-resistance of isolates originating from industrial and mine tailings. Resistance to metals (Cu, Ni, Zn and Pb) and antibiotics (ampicillin, chloramphenicol, tetracycline and kanamycin) was observed at all the sampling sites and ranged from 16 to 75%. Multiresistance (MAR index > 0.38) was recorded in 26% of the isolates and was associated with the metal selective pressure duration. Overproduction of efflux pumps has mainly been observed in multiresistant isolates. Our results may indicate that the overproduction of efflux pumps could be the mechanism of cross-resistance between metals and therefore related to metal and antibiotic multiresistance. The results also show that the importance of sustainably storing metal-containing waste lies not only in its environmental impact but also in human health via antibiotic resistance proliferation.