Carpenter et al.’s recent study adds to the growing body of evidence showing that antibiotic use can be harmful to the human microbiome.1 We recently introduced the term “microbiotoxicity” to describe unintended harms of antibiotic therapy to the microbiome, proposing a framework for prescribers to weigh these bystander effects against intended therapeutic benefits.2 However, it is becoming increasingly clear that microbiotoxicity extends far beyond antibiotics, encompassing non-antibiotic pharmaceuticals,3 dietary additives,4 and biocide-containing consumer products.5 Indeed, antibiotics are only one of a panoply of commonly used antimicrobials. The distinction between antibiotics, antiseptics, disinfectants, and sterilising agents lies primarily in the substrate to which they are applied: internal aspects of bodies, external aspects of bodies, surfaces, and inert substances, respectively (Fig. 1). Thus, all products with antimicrobial properties may cause unintended microbiotoxicity.
Apart from antibiotics, other pharmaceutical agents have been clearly shown to impact the microbiome, including proton pump inhibitors, metformin, selective serotonin reuptake inhibitors, statins and laxatives.3 These drugs alter microbial diversity and function, often promoting blooms of pathobionts and antimicrobial resistant organisms. Further, dietary additives such as emulsifiers, sweeteners, colours, and nanoparticles are associated with altered gut microbiota and permeability in both animal and human studies; for instance, germ-free mouse models indicate that emulsifiers contribute causally to transgenerational metabolic syndrome and colitis.4 Importantly, biocides are widely present in consumer products, including antiseptic soaps, chlorhexidine mouthwashes, and silver nanoparticles in clothing; these have been linked to altered microbiome and antimicrobial resistance profiles in end-users and even in treated wastewater.5 Finally, One Health research has highlighted that antimicrobial products not only directly impact the human microbiome, but also soil, plant, and animal microbiomes, potentiating the downstream impact on human health.6
