Consumer-driven demand for products that inhibit the growth of disease-causing bacteria has often superseded scientific studies that raise concerns regarding the continuous use of antimicrobials. One such chemical, triclosan, has been added to common personal hygiene products for decades in spite of its effectiveness being called into question by the U.S. Food and Drug Administration in 1974. This study directly links triclosan exposure to immediate reduction in sensitivity to this antimicrobial for five different Gram-negative bacteria species and further characterizes the derived strains, noting alterations in MIC50/90 values as compared with those of initial strains. These findings are contrasted to parallel studies with three Gram-positive species, which showed little to no change in triclosan susceptibility. In spite of its use being restricted in January 2017, decades of consumer overuse of triclosan has led to an accumulation of this compound in the environment, and this study raises concerns regarding long-term alterations to resident bacteria.