5. Does biocide use contribute to the development of antibiotic resistant bacteria?
Exposure to biocides can affect bacterial populations so that only the resistant strains survive, and this has been associated with increasing resistance to antibiotics. This could be relevant for biocides used in consumer goods because a small number of biocides are used widely in many different household and personal hygiene products. As a result, the bacteria on human skin and in homes are repeatedly exposed to certain antimicrobial products. However, it is not clear whether this type of bacterial exposure to biocides will lead to antibiotic resistance.
Data are scarce but there is some evidence of a link between using biocides in veterinary products, and increased resistance to antibiotics. This emphasizes the need to develop research and surveillance programmes in the area of animal husbandry.
Measuring the effect of biocides on the way that bacteria react to antibiotics is far from straightforward. In experiments, a group of bacteria are first treated with a biocide and those that survive are then tested to see to what extent they are affected by antibiotics. This latter stage is complicated and the results are often hard to interpret because several mechanisms may modulate antibiotic susceptibility. Recent data clearly demonstrate that some biocides activate genetic controls that are involved in triggering resistance mechanisms that alter both biocide and antibiotic activity.
Some studies on bacteria that grow as biofilms have investigated whether using biocides can lead to the emergence of more resistant strains, and the results vary depending on the species of bacteria and on the biocide used. Some studies showed that biocide use had no effect on the development of resistance. Other studies found that using biocides made some strains of bacteria grow at the expense of others, and that successful bacteria were less easily affected by biocides. More...