Co-selection of antibiotic resistance caused by a legacy of PTE pollution in Gram-negative bacteria

Antimicrobial resistant bacteria can become harboured in sediments of post-industrial estuaries. Subsequently, their resistance traits could be enriched by pollutants deposited in the sediments. Recent evidence strongly suggests this may pose hazards that not only affects the health care sector, but could also impact tourism and the aquaculture industries. The River Clyde, UK was chosen for this study due to its extensive industrial history, and three sites were chosen to sample from representing different levels and types of industrial activities—two highly polluted and one relatively ‘pristine’ site. We extracted and analysed for metal pollutants (or ‘potentially toxic elements’, PTE), and other geochemical characteristics for all sediment cores. Gram-negative, enteric bacteria were isolated from all sediment cores from the three sites. Their susceptibilities to antibiotics and metals were assayed—determining minimum inhibitory concentrations (MIC) and minimum bactericidal concentrations (MBC). The results indicate that co-selection of PTEs and antibiotic resistance does occur, and this impacts bacteria that are potential human pathogens. Higher concentrations of metals in the environment correlated to antibiotic resistance and higher MICs to metals than among bacteria found in less polluted sites. To continue to protect human health, the interactions between environmental and human health must be fully understood. This study provides critical information behind the specific causes of antibiotic resistance due to a legacy of pollution.