With regard to Martin Blaser's concerns about the collateral damage to commensal bacteria caused by overuse of broad-spectrum antibiotics (Nature 476, 393–394; 2011), there are some potent alternatives in the pipeline.

Bacteriocins are peptide antimicrobials that could be harnessed to control a variety of problematic pathogens. Many bacteriocins act only on a narrow range of targets and are active at very low (nanomolar) concentrations. For example, we found that thuricin CD specifically eliminates Clostridium difficile bacteria from among the trillions of bacteria in a model gut system (M. C. Rea et al. Proc. Natl Acad. Sci. USA 108, S4639–S4644; 2011). Diarrhoea associated with C. difficile infection is an often-fatal disease resulting from the growth of antibiotic-resistant spores after disruption of the gut microbiota by antibiotics.

Researchers are beginning to identify microbes and human microbial populations that are associated with conditions as wide-ranging as liver, coeliac and inflammatory bowel diseases, obesity, diabetes, irritable bowel syndrome, colon cancer, pouchitis and even mental health. We believe that bacteriocins could be used in the future to design and shape 'healthy' bacterial communities.