Table 1 Factors favouring the emergence of antibiotic resistance in the water environment

Residual antibiotics (RAbs)

Bacterial exposure to sublethal concentration of RAbs leads to the emergence of resistance, post exposure resistance via selection for specific antibiotic-resistant genes (ARGs) or resistance determinants, bacterial mutation as a form of adaptation to the antibiotics in water habitat

β-Lactams by mutations in PBP5 and PBP2 among aquatic Enterococcus faecium and Proteus mirabilis

Adegoke et al. (2017); Li et al. (2009); Sosa et al. (2006)

Metals

Co-selection of resistance genes against antibiotics in which exposure/selection for metal resistance leads to antibiotic resistance

merA and KPC beta-lactamase. This may affect a wide range of β-lactam antibiotics including the carbapenems

Romero et al. (2017); Pal et al. (2015); Baker-Austin et al. (2006); Fang et al. (2016)

Copper and silver may develop co-occurrence of resistance to beta-lactam and fluoroquinolone

Fang et al. (2016)

Copper, mercury and silver

Colistin may develop co-occurrence of resistance to ampicillin, sulfonamide, tetracycline, streptomycin and chloramphenicol

Li et al. (2016); Campos et al. (2016)

Biocide

Co-selection of resistance genes against antibiotics in which exposure/selection for biocide resistance leads to antibiotic resistance

Acriflavine, chlorhexidine and ethidium bromide may develop co-occurrence of resistance to gentamicin and amikacin

Wales and Davies (2015)

Water-borne mutagens

Alteration of drug target by mutagenesis

Bromoacetamide (BAcAm), trichloroacetonitrile (TCAN) or tribromonitromethane (TBNM) increased the resistance of Pseudomonas aeruginosa PAO1 to both individual and multiple antibiotics (ciprofloxacin, gentamicin, polymyxin B, rifampin, tetracycline, ciprofloxacin + gentamicin and ciprofloxacin + tetracycline)

Lv et al. (2014); Lv et al. (2015); Watanabe et al. (2006)