Coselection for microbial resistance to metals and antibiotics in freshwater microcosms

Abstract

Bacterial resistances to diverse metals and antibiotics are often genetically linked, suggesting that exposure to toxic metals may select for strains resistant to antibiotics and vice versa. To test the hypothesis that resistances to metals and antibiotics are coselected for in environmental microbial assemblages, we investigated the frequency of diverse resistances in freshwater microcosms amended with Cd, Ni, ampicillin or tetracycline. We found that all four toxicants significantly increased the frequency of bacterioplankton resistance to multiple, chemically unrelated metals and antibiotics. An ampicillin-resistant strain of the opportunistic human pathogen Ralstonia mannitolilytica was enriched in microcosms amended with Cd. Frequencies of antibiotic resistance were elevated in microcosms with metal concentrations representative of industry and mining-impacted environments (0.01-1 mM). Metal but not antibiotic amendments decreased microbial diversity, and a weeklong exposure to high concentrations of ampicillin (0.01-10 mg l-1) and tetracycline (0.03-30 mg l-1) decreased microbial abundance only slightly, implying a large reservoir of antibiotic resistance in the studied environment. Our results provide first experimental evidence that the exposure of freshwater environments to individual metals and antibiotics selects for multiresistant microorganisms, including opportunistic human pathogens.

Fluoroquinolone (FQ) Contamination Does Not Correlate with Occurrence of FQ-Resistant Bacteria in Aquatic Environments of Vietnam and Thailand

“…The second is that other selective pressures play a role in inducing FQ r bacteria. This is supported by findings that some heavy metals cause drugresistance in bacteria (2,54). A combination of the two possibilities may also apply.…”

High Occurrence Rate of Tetracycline (TC)-Resistant Bacteria and TC Resistance Genes Relates to Microbial Diversity in Sediment of Mekong River Main Waterway

“…In the case of TC resistance, it is known that treatment with a single drug leads to resistance of that drug and cross-resistance to other drugs 4) . Furthermore, a recent study reported that resistance to metals and TC are linked 16) . In our study, chemicals other than TC/OTC or TBT might have presented selective pressure to environmental bacteria, which may have resulted in cross-resistance to TC as well as to TBT.…”

Macrolide resistance mechanisms inEnterobacteriaceae: Focus on azithromycin

“…Besides, indirect selection may also be made, because some TMMR are present in genetic structures that also include other antibiotic resistance determinants such as dfrA genes, involved in resistance to trimethoprim, aacA or aadA genes, involved in aminoglycoside resistance or b-lactamase genes, involved in b-lactam resistance, among others (Dolejska et al, 2013;Du et al, 2012;Ho et al, 2011;Pons et al, 2015;S aenz et al, 2010). Thus, the TMMR may be fixed in the bacterial genetic background by the use of unrelated antimicrobial agents, or by the presence of heavy metals or antibiotic traces in the environment as has been described in other cases (Stepanauskas et al, 2006;Vien et al, 2012).…”