Bacteria become antibiotic-resistant over time as a result of

Antibiotic resistance is the ability of microbes to resist the effects of an antibiotic. Antibiotic resistance in the microbes or bacteria occurs when bacteria change in a way that the effectiveness of drugs, chemicals, or other agents designed to cure or prevent infections is reduced or eliminated. The bacteria survive and continue to multiply causing more harm.

poor water quality affects most estuarine organisms, including commercially important fish and shellfish. the pollutants that have the greatest impact on the health of estuaries include toxic substances like chemicals and heavy metals, nutrient pollution (or eutrophication), and pathogens such as bacteria or viruses.